ffmpeg / libavcodec / ac3enc.c @ 660ab0e6
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/*


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* The simplest AC3 encoder

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* Copyright (c) 2000 Fabrice Bellard

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* Copyright (c) 20062010 Justin Ruggles <justin.ruggles@gmail.com>

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* Copyright (c) 20062010 Prakash Punnoor <prakash@punnoor.de>

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*

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* This file is part of FFmpeg.

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*

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* FFmpeg is free software; you can redistribute it and/or

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* modify it under the terms of the GNU Lesser General Public

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* License as published by the Free Software Foundation; either

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* version 2.1 of the License, or (at your option) any later version.

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*

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* FFmpeg is distributed in the hope that it will be useful,

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* but WITHOUT ANY WARRANTY; without even the implied warranty of

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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

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* Lesser General Public License for more details.

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*

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* You should have received a copy of the GNU Lesser General Public

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* License along with FFmpeg; if not, write to the Free Software

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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 021101301 USA

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*/

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/**

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* @file

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* The simplest AC3 encoder.

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*/

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//#define DEBUG

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#include "libavutil/audioconvert.h" 
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#include "libavutil/crc.h" 
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#include "avcodec.h" 
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#include "put_bits.h" 
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#include "dsputil.h" 
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#include "ac3dsp.h" 
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#include "ac3.h" 
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#include "audioconvert.h" 
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40  
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#ifndef CONFIG_AC3ENC_FLOAT

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#define CONFIG_AC3ENC_FLOAT 0 
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#endif

44  
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/** Maximum number of exponent groups. +1 for separate DC exponent. */

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#define AC3_MAX_EXP_GROUPS 85 
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/* stereo rematrixing algorithms */

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#define AC3_REMATRIXING_IS_STATIC 0x1 
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#define AC3_REMATRIXING_SUMS 0 
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#define AC3_REMATRIXING_NONE 1 
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#define AC3_REMATRIXING_ALWAYS 3 
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/** Scale a float value by 2^bits and convert to an integer. */

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#define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits))) 
57  
58  
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#if CONFIG_AC3ENC_FLOAT

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#include "ac3enc_float.h" 
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#else

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#include "ac3enc_fixed.h" 
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#endif

64  
65  
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/**

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* Data for a single audio block.

68 
*/

69 
typedef struct AC3Block { 
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uint8_t **bap; ///< bit allocation pointers (bap)

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CoefType **mdct_coef; ///< MDCT coefficients

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int32_t **fixed_coef; ///< fixedpoint MDCT coefficients

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uint8_t **exp; ///< original exponents

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uint8_t **grouped_exp; ///< grouped exponents

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int16_t **psd; ///< psd per frequency bin

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int16_t **band_psd; ///< psd per critical band

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int16_t **mask; ///< masking curve

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uint16_t **qmant; ///< quantized mantissas

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int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values

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uint8_t new_rematrixing_strategy; ///< send new rematrixing flags in this block

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uint8_t rematrixing_flags[4]; ///< rematrixing flags 
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} AC3Block; 
83  
84 
/**

85 
* AC3 encoder private context.

86 
*/

87 
typedef struct AC3EncodeContext { 
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PutBitContext pb; ///< bitstream writer context

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DSPContext dsp; 
90 
AC3DSPContext ac3dsp; ///< AC3 optimized functions

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AC3MDCTContext mdct; ///< MDCT context

92  
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AC3Block blocks[AC3_MAX_BLOCKS]; ///< perblock info

94  
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int bitstream_id; ///< bitstream id (bsid) 
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int bitstream_mode; ///< bitstream mode (bsmod) 
97  
98 
int bit_rate; ///< target bit rate, in bitspersecond 
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int sample_rate; ///< sampling frequency, in Hz 
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101 
int frame_size_min; ///< minimum frame size in case rounding is necessary 
102 
int frame_size; ///< current frame size in bytes 
103 
int frame_size_code; ///< frame size code (frmsizecod) 
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uint16_t crc_inv[2];

105 
int bits_written; ///< bit count (used to avg. bitrate) 
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int samples_written; ///< sample count (used to avg. bitrate) 
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108 
int fbw_channels; ///< number of fullbandwidth channels (nfchans) 
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int channels; ///< total number of channels (nchans) 
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int lfe_on; ///< indicates if there is an LFE channel (lfeon) 
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int lfe_channel; ///< channel index of the LFE channel 
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int channel_mode; ///< channel mode (acmod) 
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const uint8_t *channel_map; ///< channel map used to reorder channels 
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int cutoff; ///< userspecified cutoff frequency, in Hz 
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int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod) 
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int nb_coefs[AC3_MAX_CHANNELS];

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119 
int rematrixing; ///< determines how rematrixing strategy is calculated 
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/* bitrate allocation control */

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int slow_gain_code; ///< slow gain code (sgaincod) 
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int slow_decay_code; ///< slow decay code (sdcycod) 
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int fast_decay_code; ///< fast decay code (fdcycod) 
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int db_per_bit_code; ///< dB/bit code (dbpbcod) 
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int floor_code; ///< floor code (floorcod) 
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AC3BitAllocParameters bit_alloc; ///< bit allocation parameters

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int coarse_snr_offset; ///< coarse SNR offsets (csnroffst) 
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int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signaltomask ratio) (fgaincod) 
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int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst) 
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int frame_bits_fixed; ///< number of noncoefficient bits for fixed parameters 
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int frame_bits; ///< all frame bits except exponents and mantissas 
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int exponent_bits; ///< number of bits used for exponents 
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135 
/* mantissa encoding */

136 
int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4 
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uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4

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139 
SampleType **planar_samples; 
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uint8_t *bap_buffer; 
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uint8_t *bap1_buffer; 
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CoefType *mdct_coef_buffer; 
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int32_t *fixed_coef_buffer; 
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uint8_t *exp_buffer; 
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uint8_t *grouped_exp_buffer; 
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int16_t *psd_buffer; 
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int16_t *band_psd_buffer; 
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int16_t *mask_buffer; 
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uint16_t *qmant_buffer; 
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uint8_t exp_strategy[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; ///< exponent strategies

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DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];

154 
} AC3EncodeContext; 
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/* prototypes for functions in ac3enc_fixed.c and ac3enc_float.c */

158  
159 
static av_cold void mdct_end(AC3MDCTContext *mdct); 
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161 
static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct, 
162 
int nbits);

163  
164 
static void mdct512(AC3MDCTContext *mdct, CoefType *out, SampleType *in); 
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166 
static void apply_window(DSPContext *dsp, SampleType *output, const SampleType *input, 
167 
const SampleType *window, int n); 
168  
169 
static int normalize_samples(AC3EncodeContext *s); 
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171 
static void scale_coefficients(AC3EncodeContext *s); 
172  
173  
174 
/**

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* LUT for number of exponent groups.

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* exponent_group_tab[exponent strategy1][number of coefficients]

177 
*/

178 
static uint8_t exponent_group_tab[3][256]; 
179  
180  
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/**

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* List of supported channel layouts.

183 
*/

184 
static const int64_t ac3_channel_layouts[] = { 
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AV_CH_LAYOUT_MONO, 
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AV_CH_LAYOUT_STEREO, 
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AV_CH_LAYOUT_2_1, 
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AV_CH_LAYOUT_SURROUND, 
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AV_CH_LAYOUT_2_2, 
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AV_CH_LAYOUT_QUAD, 
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AV_CH_LAYOUT_4POINT0, 
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AV_CH_LAYOUT_5POINT0, 
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AV_CH_LAYOUT_5POINT0_BACK, 
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(AV_CH_LAYOUT_MONO  AV_CH_LOW_FREQUENCY), 
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(AV_CH_LAYOUT_STEREO  AV_CH_LOW_FREQUENCY), 
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(AV_CH_LAYOUT_2_1  AV_CH_LOW_FREQUENCY), 
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(AV_CH_LAYOUT_SURROUND  AV_CH_LOW_FREQUENCY), 
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(AV_CH_LAYOUT_2_2  AV_CH_LOW_FREQUENCY), 
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(AV_CH_LAYOUT_QUAD  AV_CH_LOW_FREQUENCY), 
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(AV_CH_LAYOUT_4POINT0  AV_CH_LOW_FREQUENCY), 
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AV_CH_LAYOUT_5POINT1, 
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AV_CH_LAYOUT_5POINT1_BACK, 
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0

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}; 
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/**

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* Adjust the frame size to make the average bit rate match the target bit rate.

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* This is only needed for 11025, 22050, and 44100 sample rates.

210 
*/

211 
static void adjust_frame_size(AC3EncodeContext *s) 
212 
{ 
213 
while (s>bits_written >= s>bit_rate && s>samples_written >= s>sample_rate) {

214 
s>bits_written = s>bit_rate; 
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s>samples_written = s>sample_rate; 
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} 
217 
s>frame_size = s>frame_size_min + 
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2 * (s>bits_written * s>sample_rate < s>samples_written * s>bit_rate);

219 
s>bits_written += s>frame_size * 8;

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s>samples_written += AC3_FRAME_SIZE; 
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} 
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/**

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* Deinterleave input samples.

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* Channels are reordered from FFmpeg's default order to AC3 order.

227 
*/

228 
static void deinterleave_input_samples(AC3EncodeContext *s, 
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const SampleType *samples)

230 
{ 
231 
int ch, i;

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233 
/* deinterleave and remap input samples */

234 
for (ch = 0; ch < s>channels; ch++) { 
235 
const SampleType *sptr;

236 
int sinc;

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238 
/* copy last 256 samples of previous frame to the start of the current frame */

239 
memcpy(&s>planar_samples[ch][0], &s>planar_samples[ch][AC3_FRAME_SIZE],

240 
AC3_BLOCK_SIZE * sizeof(s>planar_samples[0][0])); 
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242 
/* deinterleave */

243 
sinc = s>channels; 
244 
sptr = samples + s>channel_map[ch]; 
245 
for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {

246 
s>planar_samples[ch][i] = *sptr; 
247 
sptr += sinc; 
248 
} 
249 
} 
250 
} 
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252  
253 
/**

254 
* Apply the MDCT to input samples to generate frequency coefficients.

255 
* This applies the KBD window and normalizes the input to reduce precision

256 
* loss due to fixedpoint calculations.

257 
*/

258 
static void apply_mdct(AC3EncodeContext *s) 
259 
{ 
260 
int blk, ch;

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262 
for (ch = 0; ch < s>channels; ch++) { 
263 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
264 
AC3Block *block = &s>blocks[blk]; 
265 
const SampleType *input_samples = &s>planar_samples[ch][blk * AC3_BLOCK_SIZE];

266  
267 
apply_window(&s>dsp, s>windowed_samples, input_samples, s>mdct.window, AC3_WINDOW_SIZE); 
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269 
block>exp_shift[ch] = normalize_samples(s); 
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271 
mdct512(&s>mdct, block>mdct_coef[ch], s>windowed_samples); 
272 
} 
273 
} 
274 
} 
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276  
277 
/**

278 
* Initialize stereo rematrixing.

279 
* If the strategy does not change for each frame, set the rematrixing flags.

280 
*/

281 
static void rematrixing_init(AC3EncodeContext *s) 
282 
{ 
283 
if (s>channel_mode == AC3_CHMODE_STEREO)

284 
s>rematrixing = AC3_REMATRIXING_SUMS; 
285 
else

286 
s>rematrixing = AC3_REMATRIXING_NONE; 
287 
/* NOTE: AC3_REMATRIXING_ALWAYS might be used in

288 
the future in conjunction with channel coupling. */

289  
290 
if (s>rematrixing & AC3_REMATRIXING_IS_STATIC) {

291 
int flag = (s>rematrixing == AC3_REMATRIXING_ALWAYS);

292 
s>blocks[0].new_rematrixing_strategy = 1; 
293 
memset(s>blocks[0].rematrixing_flags, flag,

294 
sizeof(s>blocks[0].rematrixing_flags)); 
295 
} 
296 
} 
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298  
299 
/**

300 
* Determine rematrixing flags for each block and band.

301 
*/

302 
static void compute_rematrixing_strategy(AC3EncodeContext *s) 
303 
{ 
304 
int nb_coefs;

305 
int blk, bnd, i;

306 
AC3Block *block, *block0; 
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308 
if (s>rematrixing & AC3_REMATRIXING_IS_STATIC)

309 
return;

310  
311 
nb_coefs = FFMIN(s>nb_coefs[0], s>nb_coefs[1]); 
312  
313 
s>blocks[0].new_rematrixing_strategy = 1; 
314 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
315 
block = &s>blocks[blk]; 
316 
for (bnd = 0; bnd < 4; bnd++) { 
317 
/* calculate calculate sum of squared coeffs for one band in one block */

318 
int start = ff_ac3_rematrix_band_tab[bnd];

319 
int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]); 
320 
CoefSumType sum[4] = {0,}; 
321 
for (i = start; i < end; i++) {

322 
CoefType lt = block>mdct_coef[0][i];

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CoefType rt = block>mdct_coef[1][i];

324 
CoefType md = lt + rt; 
325 
CoefType sd = lt  rt; 
326 
sum[0] += lt * lt;

327 
sum[1] += rt * rt;

328 
sum[2] += md * md;

329 
sum[3] += sd * sd;

330 
} 
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/* compare sums to determine if rematrixing will be used for this band */

333 
if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1])) 
334 
block>rematrixing_flags[bnd] = 1;

335 
else

336 
block>rematrixing_flags[bnd] = 0;

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338 
/* determine if new rematrixing flags will be sent */

339 
if (blk &&

340 
!block>new_rematrixing_strategy && 
341 
block>rematrixing_flags[bnd] != block0>rematrixing_flags[bnd]) { 
342 
block>new_rematrixing_strategy = 1;

343 
} 
344 
} 
345 
block0 = block; 
346 
} 
347 
} 
348  
349  
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/**

351 
* Apply stereo rematrixing to coefficients based on rematrixing flags.

352 
*/

353 
static void apply_rematrixing(AC3EncodeContext *s) 
354 
{ 
355 
int nb_coefs;

356 
int blk, bnd, i;

357 
int start, end;

358 
uint8_t *flags; 
359  
360 
if (s>rematrixing == AC3_REMATRIXING_NONE)

361 
return;

362  
363 
nb_coefs = FFMIN(s>nb_coefs[0], s>nb_coefs[1]); 
364  
365 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
366 
AC3Block *block = &s>blocks[blk]; 
367 
if (block>new_rematrixing_strategy)

368 
flags = block>rematrixing_flags; 
369 
for (bnd = 0; bnd < 4; bnd++) { 
370 
if (flags[bnd]) {

371 
start = ff_ac3_rematrix_band_tab[bnd]; 
372 
end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);

373 
for (i = start; i < end; i++) {

374 
int32_t lt = block>fixed_coef[0][i];

375 
int32_t rt = block>fixed_coef[1][i];

376 
block>fixed_coef[0][i] = (lt + rt) >> 1; 
377 
block>fixed_coef[1][i] = (lt  rt) >> 1; 
378 
} 
379 
} 
380 
} 
381 
} 
382 
} 
383  
384  
385 
/**

386 
* Initialize exponent tables.

387 
*/

388 
static av_cold void exponent_init(AC3EncodeContext *s) 
389 
{ 
390 
int i;

391 
for (i = 73; i < 256; i++) { 
392 
exponent_group_tab[0][i] = (i  1) / 3; 
393 
exponent_group_tab[1][i] = (i + 2) / 6; 
394 
exponent_group_tab[2][i] = (i + 8) / 12; 
395 
} 
396 
/* LFE */

397 
exponent_group_tab[0][7] = 2; 
398 
} 
399  
400  
401 
/**

402 
* Extract exponents from the MDCT coefficients.

403 
* This takes into account the normalization that was done to the input samples

404 
* by adjusting the exponents by the exponent shift values.

405 
*/

406 
static void extract_exponents(AC3EncodeContext *s) 
407 
{ 
408 
int blk, ch, i;

409  
410 
for (ch = 0; ch < s>channels; ch++) { 
411 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
412 
AC3Block *block = &s>blocks[blk]; 
413 
uint8_t *exp = block>exp[ch]; 
414 
int32_t *coef = block>fixed_coef[ch]; 
415 
int exp_shift = block>exp_shift[ch];

416 
for (i = 0; i < AC3_MAX_COEFS; i++) { 
417 
int e;

418 
int v = abs(coef[i]);

419 
if (v == 0) 
420 
e = 24;

421 
else {

422 
e = 23  av_log2(v) + exp_shift;

423 
if (e >= 24) { 
424 
e = 24;

425 
coef[i] = 0;

426 
} 
427 
} 
428 
exp[i] = e; 
429 
} 
430 
} 
431 
} 
432 
} 
433  
434  
435 
/**

436 
* Exponent Difference Threshold.

437 
* New exponents are sent if their SAD exceed this number.

438 
*/

439 
#define EXP_DIFF_THRESHOLD 500 
440  
441  
442 
/**

443 
* Calculate exponent strategies for all blocks in a single channel.

444 
*/

445 
static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy, 
446 
uint8_t *exp) 
447 
{ 
448 
int blk, blk1;

449 
int exp_diff;

450  
451 
/* estimate if the exponent variation & decide if they should be

452 
reused in the next frame */

453 
exp_strategy[0] = EXP_NEW;

454 
exp += AC3_MAX_COEFS; 
455 
for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) { 
456 
exp_diff = s>dsp.sad[0](NULL, exp, exp  AC3_MAX_COEFS, 16, 16); 
457 
if (exp_diff > EXP_DIFF_THRESHOLD)

458 
exp_strategy[blk] = EXP_NEW; 
459 
else

460 
exp_strategy[blk] = EXP_REUSE; 
461 
exp += AC3_MAX_COEFS; 
462 
} 
463  
464 
/* now select the encoding strategy type : if exponents are often

465 
recoded, we use a coarse encoding */

466 
blk = 0;

467 
while (blk < AC3_MAX_BLOCKS) {

468 
blk1 = blk + 1;

469 
while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)

470 
blk1++; 
471 
switch (blk1  blk) {

472 
case 1: exp_strategy[blk] = EXP_D45; break; 
473 
case 2: 
474 
case 3: exp_strategy[blk] = EXP_D25; break; 
475 
default: exp_strategy[blk] = EXP_D15; break; 
476 
} 
477 
blk = blk1; 
478 
} 
479 
} 
480  
481  
482 
/**

483 
* Calculate exponent strategies for all channels.

484 
* Array arrangement is reversed to simplify the perchannel calculation.

485 
*/

486 
static void compute_exp_strategy(AC3EncodeContext *s) 
487 
{ 
488 
int ch, blk;

489  
490 
for (ch = 0; ch < s>fbw_channels; ch++) { 
491 
compute_exp_strategy_ch(s, s>exp_strategy[ch], s>blocks[0].exp[ch]);

492 
} 
493 
if (s>lfe_on) {

494 
ch = s>lfe_channel; 
495 
s>exp_strategy[ch][0] = EXP_D15;

496 
for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) 
497 
s>exp_strategy[ch][blk] = EXP_REUSE; 
498 
} 
499 
} 
500  
501  
502 
/**

503 
* Update the exponents so that they are the ones the decoder will decode.

504 
*/

505 
static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy) 
506 
{ 
507 
int nb_groups, i, k;

508  
509 
nb_groups = exponent_group_tab[exp_strategy1][nb_exps] * 3; 
510  
511 
/* for each group, compute the minimum exponent */

512 
switch(exp_strategy) {

513 
case EXP_D25:

514 
for (i = 1, k = 1; i <= nb_groups; i++) { 
515 
uint8_t exp_min = exp[k]; 
516 
if (exp[k+1] < exp_min) 
517 
exp_min = exp[k+1];

518 
exp[i] = exp_min; 
519 
k += 2;

520 
} 
521 
break;

522 
case EXP_D45:

523 
for (i = 1, k = 1; i <= nb_groups; i++) { 
524 
uint8_t exp_min = exp[k]; 
525 
if (exp[k+1] < exp_min) 
526 
exp_min = exp[k+1];

527 
if (exp[k+2] < exp_min) 
528 
exp_min = exp[k+2];

529 
if (exp[k+3] < exp_min) 
530 
exp_min = exp[k+3];

531 
exp[i] = exp_min; 
532 
k += 4;

533 
} 
534 
break;

535 
} 
536  
537 
/* constraint for DC exponent */

538 
if (exp[0] > 15) 
539 
exp[0] = 15; 
540  
541 
/* decrease the delta between each groups to within 2 so that they can be

542 
differentially encoded */

543 
for (i = 1; i <= nb_groups; i++) 
544 
exp[i] = FFMIN(exp[i], exp[i1] + 2); 
545 
i; 
546 
while (i >= 0) 
547 
exp[i] = FFMIN(exp[i], exp[i+1] + 2); 
548  
549 
/* now we have the exponent values the decoder will see */

550 
switch (exp_strategy) {

551 
case EXP_D25:

552 
for (i = nb_groups, k = nb_groups * 2; i > 0; i) { 
553 
uint8_t exp1 = exp[i]; 
554 
exp[k] = exp1; 
555 
exp[k] = exp1; 
556 
} 
557 
break;

558 
case EXP_D45:

559 
for (i = nb_groups, k = nb_groups * 4; i > 0; i) { 
560 
exp[k] = exp[k1] = exp[k2] = exp[k3] = exp[i]; 
561 
k = 4;

562 
} 
563 
break;

564 
} 
565 
} 
566  
567  
568 
/**

569 
* Encode exponents from original extracted form to what the decoder will see.

570 
* This copies and groups exponents based on exponent strategy and reduces

571 
* deltas between adjacent exponent groups so that they can be differentially

572 
* encoded.

573 
*/

574 
static void encode_exponents(AC3EncodeContext *s) 
575 
{ 
576 
int blk, blk1, ch;

577 
uint8_t *exp, *exp1, *exp_strategy; 
578 
int nb_coefs, num_reuse_blocks;

579  
580 
for (ch = 0; ch < s>channels; ch++) { 
581 
exp = s>blocks[0].exp[ch];

582 
exp_strategy = s>exp_strategy[ch]; 
583 
nb_coefs = s>nb_coefs[ch]; 
584  
585 
blk = 0;

586 
while (blk < AC3_MAX_BLOCKS) {

587 
blk1 = blk + 1;

588  
589 
/* count the number of EXP_REUSE blocks after the current block */

590 
while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)

591 
blk1++; 
592 
num_reuse_blocks = blk1  blk  1;

593  
594 
/* for the EXP_REUSE case we select the min of the exponents */

595 
s>ac3dsp.ac3_exponent_min(exp, num_reuse_blocks, nb_coefs); 
596  
597 
encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk]); 
598  
599 
/* copy encoded exponents for reuse case */

600 
exp1 = exp + AC3_MAX_COEFS; 
601 
while (blk < blk11) { 
602 
memcpy(exp1, exp, nb_coefs * sizeof(*exp));

603 
exp1 += AC3_MAX_COEFS; 
604 
blk++; 
605 
} 
606 
blk = blk1; 
607 
exp = exp1; 
608 
} 
609 
} 
610 
} 
611  
612  
613 
/**

614 
* Group exponents.

615 
* 3 deltaencoded exponents are in each 7bit group. The number of groups

616 
* varies depending on exponent strategy and bandwidth.

617 
*/

618 
static void group_exponents(AC3EncodeContext *s) 
619 
{ 
620 
int blk, ch, i;

621 
int group_size, nb_groups, bit_count;

622 
uint8_t *p; 
623 
int delta0, delta1, delta2;

624 
int exp0, exp1;

625  
626 
bit_count = 0;

627 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
628 
AC3Block *block = &s>blocks[blk]; 
629 
for (ch = 0; ch < s>channels; ch++) { 
630 
int exp_strategy = s>exp_strategy[ch][blk];

631 
if (exp_strategy == EXP_REUSE)

632 
continue;

633 
group_size = exp_strategy + (exp_strategy == EXP_D45); 
634 
nb_groups = exponent_group_tab[exp_strategy1][s>nb_coefs[ch]];

635 
bit_count += 4 + (nb_groups * 7); 
636 
p = block>exp[ch]; 
637  
638 
/* DC exponent */

639 
exp1 = *p++; 
640 
block>grouped_exp[ch][0] = exp1;

641  
642 
/* remaining exponents are delta encoded */

643 
for (i = 1; i <= nb_groups; i++) { 
644 
/* merge three delta in one code */

645 
exp0 = exp1; 
646 
exp1 = p[0];

647 
p += group_size; 
648 
delta0 = exp1  exp0 + 2;

649  
650 
exp0 = exp1; 
651 
exp1 = p[0];

652 
p += group_size; 
653 
delta1 = exp1  exp0 + 2;

654  
655 
exp0 = exp1; 
656 
exp1 = p[0];

657 
p += group_size; 
658 
delta2 = exp1  exp0 + 2;

659  
660 
block>grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2; 
661 
} 
662 
} 
663 
} 
664  
665 
s>exponent_bits = bit_count; 
666 
} 
667  
668  
669 
/**

670 
* Calculate final exponents from the supplied MDCT coefficients and exponent shift.

671 
* Extract exponents from MDCT coefficients, calculate exponent strategies,

672 
* and encode final exponents.

673 
*/

674 
static void process_exponents(AC3EncodeContext *s) 
675 
{ 
676 
extract_exponents(s); 
677  
678 
compute_exp_strategy(s); 
679  
680 
encode_exponents(s); 
681  
682 
group_exponents(s); 
683  
684 
emms_c(); 
685 
} 
686  
687  
688 
/**

689 
* Count frame bits that are based solely on fixed parameters.

690 
* This only has to be run once when the encoder is initialized.

691 
*/

692 
static void count_frame_bits_fixed(AC3EncodeContext *s) 
693 
{ 
694 
static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; 
695 
int blk;

696 
int frame_bits;

697  
698 
/* assumptions:

699 
* no dynamic range codes

700 
* no channel coupling

701 
* bit allocation parameters do not change between blocks

702 
* SNR offsets do not change between blocks

703 
* no delta bit allocation

704 
* no skipped data

705 
* no auxilliary data

706 
*/

707  
708 
/* header size */

709 
frame_bits = 65;

710 
frame_bits += frame_bits_inc[s>channel_mode]; 
711  
712 
/* audio blocks */

713 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
714 
frame_bits += s>fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ 
715 
if (s>channel_mode == AC3_CHMODE_STEREO) {

716 
frame_bits++; /* rematstr */

717 
} 
718 
frame_bits += 2 * s>fbw_channels; /* chexpstr[2] * c */ 
719 
if (s>lfe_on)

720 
frame_bits++; /* lfeexpstr */

721 
frame_bits++; /* baie */

722 
frame_bits++; /* snr */

723 
frame_bits += 2; /* delta / skip */ 
724 
} 
725 
frame_bits++; /* cplinu for block 0 */

726 
/* bit alloc info */

727 
/* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */

728 
/* csnroffset[6] */

729 
/* (fsnoffset[4] + fgaincod[4]) * c */

730 
frame_bits += 2*4 + 3 + 6 + s>channels * (4 + 3); 
731  
732 
/* auxdatae, crcrsv */

733 
frame_bits += 2;

734  
735 
/* CRC */

736 
frame_bits += 16;

737  
738 
s>frame_bits_fixed = frame_bits; 
739 
} 
740  
741  
742 
/**

743 
* Initialize bit allocation.

744 
* Set default parameter codes and calculate parameter values.

745 
*/

746 
static void bit_alloc_init(AC3EncodeContext *s) 
747 
{ 
748 
int ch;

749  
750 
/* init default parameters */

751 
s>slow_decay_code = 2;

752 
s>fast_decay_code = 1;

753 
s>slow_gain_code = 1;

754 
s>db_per_bit_code = 3;

755 
s>floor_code = 7;

756 
for (ch = 0; ch < s>channels; ch++) 
757 
s>fast_gain_code[ch] = 4;

758  
759 
/* initial snr offset */

760 
s>coarse_snr_offset = 40;

761  
762 
/* compute real values */

763 
/* currently none of these values change during encoding, so we can just

764 
set them once at initialization */

765 
s>bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s>slow_decay_code] >> s>bit_alloc.sr_shift; 
766 
s>bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s>fast_decay_code] >> s>bit_alloc.sr_shift; 
767 
s>bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s>slow_gain_code]; 
768 
s>bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s>db_per_bit_code]; 
769 
s>bit_alloc.floor = ff_ac3_floor_tab[s>floor_code]; 
770  
771 
count_frame_bits_fixed(s); 
772 
} 
773  
774  
775 
/**

776 
* Count the bits used to encode the frame, minus exponents and mantissas.

777 
* Bits based on fixed parameters have already been counted, so now we just

778 
* have to add the bits based on parameters that change during encoding.

779 
*/

780 
static void count_frame_bits(AC3EncodeContext *s) 
781 
{ 
782 
int blk, ch;

783 
int frame_bits = 0; 
784  
785 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
786 
/* stereo rematrixing */

787 
if (s>channel_mode == AC3_CHMODE_STEREO &&

788 
s>blocks[blk].new_rematrixing_strategy) { 
789 
frame_bits += 4;

790 
} 
791  
792 
for (ch = 0; ch < s>fbw_channels; ch++) { 
793 
if (s>exp_strategy[ch][blk] != EXP_REUSE)

794 
frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ 
795 
} 
796 
} 
797 
s>frame_bits = s>frame_bits_fixed + frame_bits; 
798 
} 
799  
800  
801 
/**

802 
* Calculate the number of bits needed to encode a set of mantissas.

803 
*/

804 
static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs) 
805 
{ 
806 
int bits, b, i;

807  
808 
bits = 0;

809 
for (i = 0; i < nb_coefs; i++) { 
810 
b = bap[i]; 
811 
if (b <= 4) { 
812 
// bap=1 to bap=4 will be counted in compute_mantissa_size_final

813 
mant_cnt[b]++; 
814 
} else if (b <= 13) { 
815 
// bap=5 to bap=13 use (bap1) bits

816 
bits += b  1;

817 
} else {

818 
// bap=14 uses 14 bits and bap=15 uses 16 bits

819 
bits += (b == 14) ? 14 : 16; 
820 
} 
821 
} 
822 
return bits;

823 
} 
824  
825  
826 
/**

827 
* Finalize the mantissa bit count by adding in the grouped mantissas.

828 
*/

829 
static int compute_mantissa_size_final(int mant_cnt[5]) 
830 
{ 
831 
// bap=1 : 3 mantissas in 5 bits

832 
int bits = (mant_cnt[1] / 3) * 5; 
833 
// bap=2 : 3 mantissas in 7 bits

834 
// bap=4 : 2 mantissas in 7 bits

835 
bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7; 
836 
// bap=3 : each mantissa is 3 bits

837 
bits += mant_cnt[3] * 3; 
838 
return bits;

839 
} 
840  
841  
842 
/**

843 
* Calculate masking curve based on the final exponents.

844 
* Also calculate the power spectral densities to use in future calculations.

845 
*/

846 
static void bit_alloc_masking(AC3EncodeContext *s) 
847 
{ 
848 
int blk, ch;

849  
850 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
851 
AC3Block *block = &s>blocks[blk]; 
852 
for (ch = 0; ch < s>channels; ch++) { 
853 
/* We only need psd and mask for calculating bap.

854 
Since we currently do not calculate bap when exponent

855 
strategy is EXP_REUSE we do not need to calculate psd or mask. */

856 
if (s>exp_strategy[ch][blk] != EXP_REUSE) {

857 
ff_ac3_bit_alloc_calc_psd(block>exp[ch], 0,

858 
s>nb_coefs[ch], 
859 
block>psd[ch], block>band_psd[ch]); 
860 
ff_ac3_bit_alloc_calc_mask(&s>bit_alloc, block>band_psd[ch], 
861 
0, s>nb_coefs[ch],

862 
ff_ac3_fast_gain_tab[s>fast_gain_code[ch]], 
863 
ch == s>lfe_channel, 
864 
DBA_NONE, 0, NULL, NULL, NULL, 
865 
block>mask[ch]); 
866 
} 
867 
} 
868 
} 
869 
} 
870  
871  
872 
/**

873 
* Ensure that bap for each block and channel point to the current bap_buffer.

874 
* They may have been switched during the bit allocation search.

875 
*/

876 
static void reset_block_bap(AC3EncodeContext *s) 
877 
{ 
878 
int blk, ch;

879 
if (s>blocks[0].bap[0] == s>bap_buffer) 
880 
return;

881 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
882 
for (ch = 0; ch < s>channels; ch++) { 
883 
s>blocks[blk].bap[ch] = &s>bap_buffer[AC3_MAX_COEFS * (blk * s>channels + ch)]; 
884 
} 
885 
} 
886 
} 
887  
888  
889 
/**

890 
* Run the bit allocation with a given SNR offset.

891 
* This calculates the bit allocation pointers that will be used to determine

892 
* the quantization of each mantissa.

893 
* @return the number of bits needed for mantissas if the given SNR offset is

894 
* is used.

895 
*/

896 
static int bit_alloc(AC3EncodeContext *s, int snr_offset) 
897 
{ 
898 
int blk, ch;

899 
int mantissa_bits;

900 
int mant_cnt[5]; 
901  
902 
snr_offset = (snr_offset  240) << 2; 
903  
904 
reset_block_bap(s); 
905 
mantissa_bits = 0;

906 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
907 
AC3Block *block = &s>blocks[blk]; 
908 
// initialize grouped mantissa counts. these are set so that they are

909 
// padded to the next whole group size when bits are counted in

910 
// compute_mantissa_size_final

911 
mant_cnt[0] = mant_cnt[3] = 0; 
912 
mant_cnt[1] = mant_cnt[2] = 2; 
913 
mant_cnt[4] = 1; 
914 
for (ch = 0; ch < s>channels; ch++) { 
915 
/* Currently the only bit allocation parameters which vary across

916 
blocks within a frame are the exponent values. We can take

917 
advantage of that by reusing the bit allocation pointers

918 
whenever we reuse exponents. */

919 
if (s>exp_strategy[ch][blk] == EXP_REUSE) {

920 
memcpy(block>bap[ch], s>blocks[blk1].bap[ch], AC3_MAX_COEFS);

921 
} else {

922 
ff_ac3_bit_alloc_calc_bap(block>mask[ch], block>psd[ch], 0,

923 
s>nb_coefs[ch], snr_offset, 
924 
s>bit_alloc.floor, ff_ac3_bap_tab, 
925 
block>bap[ch]); 
926 
} 
927 
mantissa_bits += compute_mantissa_size(mant_cnt, block>bap[ch], s>nb_coefs[ch]); 
928 
} 
929 
mantissa_bits += compute_mantissa_size_final(mant_cnt); 
930 
} 
931 
return mantissa_bits;

932 
} 
933  
934  
935 
/**

936 
* Constant bitrate bit allocation search.

937 
* Find the largest SNR offset that will allow data to fit in the frame.

938 
*/

939 
static int cbr_bit_allocation(AC3EncodeContext *s) 
940 
{ 
941 
int ch;

942 
int bits_left;

943 
int snr_offset, snr_incr;

944  
945 
bits_left = 8 * s>frame_size  (s>frame_bits + s>exponent_bits);

946  
947 
snr_offset = s>coarse_snr_offset << 4;

948  
949 
/* if previous frame SNR offset was 1023, check if current frame can also

950 
use SNR offset of 1023. if so, skip the search. */

951 
if ((snr_offset  s>fine_snr_offset[0]) == 1023) { 
952 
if (bit_alloc(s, 1023) <= bits_left) 
953 
return 0; 
954 
} 
955  
956 
while (snr_offset >= 0 && 
957 
bit_alloc(s, snr_offset) > bits_left) { 
958 
snr_offset = 64;

959 
} 
960 
if (snr_offset < 0) 
961 
return AVERROR(EINVAL);

962  
963 
FFSWAP(uint8_t *, s>bap_buffer, s>bap1_buffer); 
964 
for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) { 
965 
while (snr_offset + snr_incr <= 1023 && 
966 
bit_alloc(s, snr_offset + snr_incr) <= bits_left) { 
967 
snr_offset += snr_incr; 
968 
FFSWAP(uint8_t *, s>bap_buffer, s>bap1_buffer); 
969 
} 
970 
} 
971 
FFSWAP(uint8_t *, s>bap_buffer, s>bap1_buffer); 
972 
reset_block_bap(s); 
973  
974 
s>coarse_snr_offset = snr_offset >> 4;

975 
for (ch = 0; ch < s>channels; ch++) 
976 
s>fine_snr_offset[ch] = snr_offset & 0xF;

977  
978 
return 0; 
979 
} 
980  
981  
982 
/**

983 
* Downgrade exponent strategies to reduce the bits used by the exponents.

984 
* This is a fallback for when bit allocation fails with the normal exponent

985 
* strategies. Each time this function is run it only downgrades the

986 
* strategy in 1 channel of 1 block.

987 
* @return nonzero if downgrade was unsuccessful

988 
*/

989 
static int downgrade_exponents(AC3EncodeContext *s) 
990 
{ 
991 
int ch, blk;

992  
993 
for (ch = 0; ch < s>fbw_channels; ch++) { 
994 
for (blk = AC3_MAX_BLOCKS1; blk >= 0; blk) { 
995 
if (s>exp_strategy[ch][blk] == EXP_D15) {

996 
s>exp_strategy[ch][blk] = EXP_D25; 
997 
return 0; 
998 
} 
999 
} 
1000 
} 
1001 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1002 
for (blk = AC3_MAX_BLOCKS1; blk >= 0; blk) { 
1003 
if (s>exp_strategy[ch][blk] == EXP_D25) {

1004 
s>exp_strategy[ch][blk] = EXP_D45; 
1005 
return 0; 
1006 
} 
1007 
} 
1008 
} 
1009 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1010 
/* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if

1011 
the block number > 0 */

1012 
for (blk = AC3_MAX_BLOCKS1; blk > 0; blk) { 
1013 
if (s>exp_strategy[ch][blk] > EXP_REUSE) {

1014 
s>exp_strategy[ch][blk] = EXP_REUSE; 
1015 
return 0; 
1016 
} 
1017 
} 
1018 
} 
1019 
return 1; 
1020 
} 
1021  
1022  
1023 
/**

1024 
* Reduce the bandwidth to reduce the number of bits used for a given SNR offset.

1025 
* This is a second fallback for when bit allocation still fails after exponents

1026 
* have been downgraded.

1027 
* @return nonzero if bandwidth reduction was unsuccessful

1028 
*/

1029 
static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code) 
1030 
{ 
1031 
int ch;

1032  
1033 
if (s>bandwidth_code[0] > min_bw_code) { 
1034 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1035 
s>bandwidth_code[ch]; 
1036 
s>nb_coefs[ch] = s>bandwidth_code[ch] * 3 + 73; 
1037 
} 
1038 
return 0; 
1039 
} 
1040 
return 1; 
1041 
} 
1042  
1043  
1044 
/**

1045 
* Perform bit allocation search.

1046 
* Finds the SNR offset value that maximizes quality and fits in the specified

1047 
* frame size. Output is the SNR offset and a set of bit allocation pointers

1048 
* used to quantize the mantissas.

1049 
*/

1050 
static int compute_bit_allocation(AC3EncodeContext *s) 
1051 
{ 
1052 
int ret;

1053  
1054 
count_frame_bits(s); 
1055  
1056 
bit_alloc_masking(s); 
1057  
1058 
ret = cbr_bit_allocation(s); 
1059 
while (ret) {

1060 
/* fallback 1: downgrade exponents */

1061 
if (!downgrade_exponents(s)) {

1062 
extract_exponents(s); 
1063 
encode_exponents(s); 
1064 
group_exponents(s); 
1065 
ret = compute_bit_allocation(s); 
1066 
continue;

1067 
} 
1068  
1069 
/* fallback 2: reduce bandwidth */

1070 
/* only do this if the user has not specified a specific cutoff

1071 
frequency */

1072 
if (!s>cutoff && !reduce_bandwidth(s, 0)) { 
1073 
process_exponents(s); 
1074 
ret = compute_bit_allocation(s); 
1075 
continue;

1076 
} 
1077  
1078 
/* fallbacks were not enough... */

1079 
break;

1080 
} 
1081  
1082 
return ret;

1083 
} 
1084  
1085  
1086 
/**

1087 
* Symmetric quantization on 'levels' levels.

1088 
*/

1089 
static inline int sym_quant(int c, int e, int levels) 
1090 
{ 
1091 
int v;

1092  
1093 
if (c >= 0) { 
1094 
v = (levels * (c << e)) >> 24;

1095 
v = (v + 1) >> 1; 
1096 
v = (levels >> 1) + v;

1097 
} else {

1098 
v = (levels * ((c) << e)) >> 24;

1099 
v = (v + 1) >> 1; 
1100 
v = (levels >> 1)  v;

1101 
} 
1102 
assert(v >= 0 && v < levels);

1103 
return v;

1104 
} 
1105  
1106  
1107 
/**

1108 
* Asymmetric quantization on 2^qbits levels.

1109 
*/

1110 
static inline int asym_quant(int c, int e, int qbits) 
1111 
{ 
1112 
int lshift, m, v;

1113  
1114 
lshift = e + qbits  24;

1115 
if (lshift >= 0) 
1116 
v = c << lshift; 
1117 
else

1118 
v = c >> (lshift); 
1119 
/* rounding */

1120 
v = (v + 1) >> 1; 
1121 
m = (1 << (qbits1)); 
1122 
if (v >= m)

1123 
v = m  1;

1124 
assert(v >= m); 
1125 
return v & ((1 << qbits)1); 
1126 
} 
1127  
1128  
1129 
/**

1130 
* Quantize a set of mantissas for a single channel in a single block.

1131 
*/

1132 
static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef, 
1133 
int8_t exp_shift, uint8_t *exp, 
1134 
uint8_t *bap, uint16_t *qmant, int n)

1135 
{ 
1136 
int i;

1137  
1138 
for (i = 0; i < n; i++) { 
1139 
int v;

1140 
int c = fixed_coef[i];

1141 
int e = exp[i]  exp_shift;

1142 
int b = bap[i];

1143 
switch (b) {

1144 
case 0: 
1145 
v = 0;

1146 
break;

1147 
case 1: 
1148 
v = sym_quant(c, e, 3);

1149 
switch (s>mant1_cnt) {

1150 
case 0: 
1151 
s>qmant1_ptr = &qmant[i]; 
1152 
v = 9 * v;

1153 
s>mant1_cnt = 1;

1154 
break;

1155 
case 1: 
1156 
*s>qmant1_ptr += 3 * v;

1157 
s>mant1_cnt = 2;

1158 
v = 128;

1159 
break;

1160 
default:

1161 
*s>qmant1_ptr += v; 
1162 
s>mant1_cnt = 0;

1163 
v = 128;

1164 
break;

1165 
} 
1166 
break;

1167 
case 2: 
1168 
v = sym_quant(c, e, 5);

1169 
switch (s>mant2_cnt) {

1170 
case 0: 
1171 
s>qmant2_ptr = &qmant[i]; 
1172 
v = 25 * v;

1173 
s>mant2_cnt = 1;

1174 
break;

1175 
case 1: 
1176 
*s>qmant2_ptr += 5 * v;

1177 
s>mant2_cnt = 2;

1178 
v = 128;

1179 
break;

1180 
default:

1181 
*s>qmant2_ptr += v; 
1182 
s>mant2_cnt = 0;

1183 
v = 128;

1184 
break;

1185 
} 
1186 
break;

1187 
case 3: 
1188 
v = sym_quant(c, e, 7);

1189 
break;

1190 
case 4: 
1191 
v = sym_quant(c, e, 11);

1192 
switch (s>mant4_cnt) {

1193 
case 0: 
1194 
s>qmant4_ptr = &qmant[i]; 
1195 
v = 11 * v;

1196 
s>mant4_cnt = 1;

1197 
break;

1198 
default:

1199 
*s>qmant4_ptr += v; 
1200 
s>mant4_cnt = 0;

1201 
v = 128;

1202 
break;

1203 
} 
1204 
break;

1205 
case 5: 
1206 
v = sym_quant(c, e, 15);

1207 
break;

1208 
case 14: 
1209 
v = asym_quant(c, e, 14);

1210 
break;

1211 
case 15: 
1212 
v = asym_quant(c, e, 16);

1213 
break;

1214 
default:

1215 
v = asym_quant(c, e, b  1);

1216 
break;

1217 
} 
1218 
qmant[i] = v; 
1219 
} 
1220 
} 
1221  
1222  
1223 
/**

1224 
* Quantize mantissas using coefficients, exponents, and bit allocation pointers.

1225 
*/

1226 
static void quantize_mantissas(AC3EncodeContext *s) 
1227 
{ 
1228 
int blk, ch;

1229  
1230  
1231 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1232 
AC3Block *block = &s>blocks[blk]; 
1233 
s>mant1_cnt = s>mant2_cnt = s>mant4_cnt = 0;

1234 
s>qmant1_ptr = s>qmant2_ptr = s>qmant4_ptr = NULL;

1235  
1236 
for (ch = 0; ch < s>channels; ch++) { 
1237 
quantize_mantissas_blk_ch(s, block>fixed_coef[ch], block>exp_shift[ch], 
1238 
block>exp[ch], block>bap[ch], 
1239 
block>qmant[ch], s>nb_coefs[ch]); 
1240 
} 
1241 
} 
1242 
} 
1243  
1244  
1245 
/**

1246 
* Write the AC3 frame header to the output bitstream.

1247 
*/

1248 
static void output_frame_header(AC3EncodeContext *s) 
1249 
{ 
1250 
put_bits(&s>pb, 16, 0x0b77); /* frame header */ 
1251 
put_bits(&s>pb, 16, 0); /* crc1: will be filled later */ 
1252 
put_bits(&s>pb, 2, s>bit_alloc.sr_code);

1253 
put_bits(&s>pb, 6, s>frame_size_code + (s>frame_size  s>frame_size_min) / 2); 
1254 
put_bits(&s>pb, 5, s>bitstream_id);

1255 
put_bits(&s>pb, 3, s>bitstream_mode);

1256 
put_bits(&s>pb, 3, s>channel_mode);

1257 
if ((s>channel_mode & 0x01) && s>channel_mode != AC3_CHMODE_MONO) 
1258 
put_bits(&s>pb, 2, 1); /* XXX 4.5 dB */ 
1259 
if (s>channel_mode & 0x04) 
1260 
put_bits(&s>pb, 2, 1); /* XXX 6 dB */ 
1261 
if (s>channel_mode == AC3_CHMODE_STEREO)

1262 
put_bits(&s>pb, 2, 0); /* surround not indicated */ 
1263 
put_bits(&s>pb, 1, s>lfe_on); /* LFE */ 
1264 
put_bits(&s>pb, 5, 31); /* dialog norm: 31 db */ 
1265 
put_bits(&s>pb, 1, 0); /* no compression control word */ 
1266 
put_bits(&s>pb, 1, 0); /* no lang code */ 
1267 
put_bits(&s>pb, 1, 0); /* no audio production info */ 
1268 
put_bits(&s>pb, 1, 0); /* no copyright */ 
1269 
put_bits(&s>pb, 1, 1); /* original bitstream */ 
1270 
put_bits(&s>pb, 1, 0); /* no time code 1 */ 
1271 
put_bits(&s>pb, 1, 0); /* no time code 2 */ 
1272 
put_bits(&s>pb, 1, 0); /* no additional bit stream info */ 
1273 
} 
1274  
1275  
1276 
/**

1277 
* Write one audio block to the output bitstream.

1278 
*/

1279 
static void output_audio_block(AC3EncodeContext *s, int blk) 
1280 
{ 
1281 
int ch, i, baie, rbnd;

1282 
AC3Block *block = &s>blocks[blk]; 
1283  
1284 
/* block switching */

1285 
for (ch = 0; ch < s>fbw_channels; ch++) 
1286 
put_bits(&s>pb, 1, 0); 
1287  
1288 
/* dither flags */

1289 
for (ch = 0; ch < s>fbw_channels; ch++) 
1290 
put_bits(&s>pb, 1, 1); 
1291  
1292 
/* dynamic range codes */

1293 
put_bits(&s>pb, 1, 0); 
1294  
1295 
/* channel coupling */

1296 
if (!blk) {

1297 
put_bits(&s>pb, 1, 1); /* coupling strategy present */ 
1298 
put_bits(&s>pb, 1, 0); /* no coupling strategy */ 
1299 
} else {

1300 
put_bits(&s>pb, 1, 0); /* no new coupling strategy */ 
1301 
} 
1302  
1303 
/* stereo rematrixing */

1304 
if (s>channel_mode == AC3_CHMODE_STEREO) {

1305 
put_bits(&s>pb, 1, block>new_rematrixing_strategy);

1306 
if (block>new_rematrixing_strategy) {

1307 
/* rematrixing flags */

1308 
for (rbnd = 0; rbnd < 4; rbnd++) 
1309 
put_bits(&s>pb, 1, block>rematrixing_flags[rbnd]);

1310 
} 
1311 
} 
1312  
1313 
/* exponent strategy */

1314 
for (ch = 0; ch < s>fbw_channels; ch++) 
1315 
put_bits(&s>pb, 2, s>exp_strategy[ch][blk]);

1316 
if (s>lfe_on)

1317 
put_bits(&s>pb, 1, s>exp_strategy[s>lfe_channel][blk]);

1318  
1319 
/* bandwidth */

1320 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1321 
if (s>exp_strategy[ch][blk] != EXP_REUSE)

1322 
put_bits(&s>pb, 6, s>bandwidth_code[ch]);

1323 
} 
1324  
1325 
/* exponents */

1326 
for (ch = 0; ch < s>channels; ch++) { 
1327 
int nb_groups;

1328  
1329 
if (s>exp_strategy[ch][blk] == EXP_REUSE)

1330 
continue;

1331  
1332 
/* DC exponent */

1333 
put_bits(&s>pb, 4, block>grouped_exp[ch][0]); 
1334  
1335 
/* exponent groups */

1336 
nb_groups = exponent_group_tab[s>exp_strategy[ch][blk]1][s>nb_coefs[ch]];

1337 
for (i = 1; i <= nb_groups; i++) 
1338 
put_bits(&s>pb, 7, block>grouped_exp[ch][i]);

1339  
1340 
/* gain range info */

1341 
if (ch != s>lfe_channel)

1342 
put_bits(&s>pb, 2, 0); 
1343 
} 
1344  
1345 
/* bit allocation info */

1346 
baie = (blk == 0);

1347 
put_bits(&s>pb, 1, baie);

1348 
if (baie) {

1349 
put_bits(&s>pb, 2, s>slow_decay_code);

1350 
put_bits(&s>pb, 2, s>fast_decay_code);

1351 
put_bits(&s>pb, 2, s>slow_gain_code);

1352 
put_bits(&s>pb, 2, s>db_per_bit_code);

1353 
put_bits(&s>pb, 3, s>floor_code);

1354 
} 
1355  
1356 
/* snr offset */

1357 
put_bits(&s>pb, 1, baie);

1358 
if (baie) {

1359 
put_bits(&s>pb, 6, s>coarse_snr_offset);

1360 
for (ch = 0; ch < s>channels; ch++) { 
1361 
put_bits(&s>pb, 4, s>fine_snr_offset[ch]);

1362 
put_bits(&s>pb, 3, s>fast_gain_code[ch]);

1363 
} 
1364 
} 
1365  
1366 
put_bits(&s>pb, 1, 0); /* no delta bit allocation */ 
1367 
put_bits(&s>pb, 1, 0); /* no data to skip */ 
1368  
1369 
/* mantissas */

1370 
for (ch = 0; ch < s>channels; ch++) { 
1371 
int b, q;

1372 
for (i = 0; i < s>nb_coefs[ch]; i++) { 
1373 
q = block>qmant[ch][i]; 
1374 
b = block>bap[ch][i]; 
1375 
switch (b) {

1376 
case 0: break; 
1377 
case 1: if (q != 128) put_bits(&s>pb, 5, q); break; 
1378 
case 2: if (q != 128) put_bits(&s>pb, 7, q); break; 
1379 
case 3: put_bits(&s>pb, 3, q); break; 
1380 
case 4: if (q != 128) put_bits(&s>pb, 7, q); break; 
1381 
case 14: put_bits(&s>pb, 14, q); break; 
1382 
case 15: put_bits(&s>pb, 16, q); break; 
1383 
default: put_bits(&s>pb, b1, q); break; 
1384 
} 
1385 
} 
1386 
} 
1387 
} 
1388  
1389  
1390 
/** CRC16 Polynomial */

1391 
#define CRC16_POLY ((1 << 0)  (1 << 2)  (1 << 15)  (1 << 16)) 
1392  
1393  
1394 
static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) 
1395 
{ 
1396 
unsigned int c; 
1397  
1398 
c = 0;

1399 
while (a) {

1400 
if (a & 1) 
1401 
c ^= b; 
1402 
a = a >> 1;

1403 
b = b << 1;

1404 
if (b & (1 << 16)) 
1405 
b ^= poly; 
1406 
} 
1407 
return c;

1408 
} 
1409  
1410  
1411 
static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) 
1412 
{ 
1413 
unsigned int r; 
1414 
r = 1;

1415 
while (n) {

1416 
if (n & 1) 
1417 
r = mul_poly(r, a, poly); 
1418 
a = mul_poly(a, a, poly); 
1419 
n >>= 1;

1420 
} 
1421 
return r;

1422 
} 
1423  
1424  
1425 
/**

1426 
* Fill the end of the frame with 0's and compute the two CRCs.

1427 
*/

1428 
static void output_frame_end(AC3EncodeContext *s) 
1429 
{ 
1430 
const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);

1431 
int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;

1432 
uint8_t *frame; 
1433  
1434 
frame_size_58 = ((s>frame_size >> 2) + (s>frame_size >> 4)) << 1; 
1435  
1436 
/* pad the remainder of the frame with zeros */

1437 
flush_put_bits(&s>pb); 
1438 
frame = s>pb.buf; 
1439 
pad_bytes = s>frame_size  (put_bits_ptr(&s>pb)  frame)  2;

1440 
assert(pad_bytes >= 0);

1441 
if (pad_bytes > 0) 
1442 
memset(put_bits_ptr(&s>pb), 0, pad_bytes);

1443  
1444 
/* compute crc1 */

1445 
/* this is not so easy because it is at the beginning of the data... */

1446 
crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58  4)); 
1447 
crc_inv = s>crc_inv[s>frame_size > s>frame_size_min]; 
1448 
crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); 
1449 
AV_WB16(frame + 2, crc1);

1450  
1451 
/* compute crc2 */

1452 
crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,

1453 
s>frame_size  frame_size_58  3);

1454 
crc2 = av_crc(crc_ctx, crc2_partial, frame + s>frame_size  3, 1); 
1455 
/* ensure crc2 does not match sync word by flipping crcrsv bit if needed */

1456 
if (crc2 == 0x770B) { 
1457 
frame[s>frame_size  3] ^= 0x1; 
1458 
crc2 = av_crc(crc_ctx, crc2_partial, frame + s>frame_size  3, 1); 
1459 
} 
1460 
crc2 = av_bswap16(crc2); 
1461 
AV_WB16(frame + s>frame_size  2, crc2);

1462 
} 
1463  
1464  
1465 
/**

1466 
* Write the frame to the output bitstream.

1467 
*/

1468 
static void output_frame(AC3EncodeContext *s, unsigned char *frame) 
1469 
{ 
1470 
int blk;

1471  
1472 
init_put_bits(&s>pb, frame, AC3_MAX_CODED_FRAME_SIZE); 
1473  
1474 
output_frame_header(s); 
1475  
1476 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) 
1477 
output_audio_block(s, blk); 
1478  
1479 
output_frame_end(s); 
1480 
} 
1481  
1482  
1483 
/**

1484 
* Encode a single AC3 frame.

1485 
*/

1486 
static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame, 
1487 
int buf_size, void *data) 
1488 
{ 
1489 
AC3EncodeContext *s = avctx>priv_data; 
1490 
const SampleType *samples = data;

1491 
int ret;

1492  
1493 
if (s>bit_alloc.sr_code == 1) 
1494 
adjust_frame_size(s); 
1495  
1496 
deinterleave_input_samples(s, samples); 
1497  
1498 
apply_mdct(s); 
1499  
1500 
compute_rematrixing_strategy(s); 
1501  
1502 
scale_coefficients(s); 
1503  
1504 
apply_rematrixing(s); 
1505  
1506 
process_exponents(s); 
1507  
1508 
ret = compute_bit_allocation(s); 
1509 
if (ret) {

1510 
av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");

1511 
return ret;

1512 
} 
1513  
1514 
quantize_mantissas(s); 
1515  
1516 
output_frame(s, frame); 
1517  
1518 
return s>frame_size;

1519 
} 
1520  
1521  
1522 
/**

1523 
* Finalize encoding and free any memory allocated by the encoder.

1524 
*/

1525 
static av_cold int ac3_encode_close(AVCodecContext *avctx) 
1526 
{ 
1527 
int blk, ch;

1528 
AC3EncodeContext *s = avctx>priv_data; 
1529  
1530 
for (ch = 0; ch < s>channels; ch++) 
1531 
av_freep(&s>planar_samples[ch]); 
1532 
av_freep(&s>planar_samples); 
1533 
av_freep(&s>bap_buffer); 
1534 
av_freep(&s>bap1_buffer); 
1535 
av_freep(&s>mdct_coef_buffer); 
1536 
av_freep(&s>fixed_coef_buffer); 
1537 
av_freep(&s>exp_buffer); 
1538 
av_freep(&s>grouped_exp_buffer); 
1539 
av_freep(&s>psd_buffer); 
1540 
av_freep(&s>band_psd_buffer); 
1541 
av_freep(&s>mask_buffer); 
1542 
av_freep(&s>qmant_buffer); 
1543 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1544 
AC3Block *block = &s>blocks[blk]; 
1545 
av_freep(&block>bap); 
1546 
av_freep(&block>mdct_coef); 
1547 
av_freep(&block>fixed_coef); 
1548 
av_freep(&block>exp); 
1549 
av_freep(&block>grouped_exp); 
1550 
av_freep(&block>psd); 
1551 
av_freep(&block>band_psd); 
1552 
av_freep(&block>mask); 
1553 
av_freep(&block>qmant); 
1554 
} 
1555  
1556 
mdct_end(&s>mdct); 
1557  
1558 
av_freep(&avctx>coded_frame); 
1559 
return 0; 
1560 
} 
1561  
1562  
1563 
/**

1564 
* Set channel information during initialization.

1565 
*/

1566 
static av_cold int set_channel_info(AC3EncodeContext *s, int channels, 
1567 
int64_t *channel_layout) 
1568 
{ 
1569 
int ch_layout;

1570  
1571 
if (channels < 1  channels > AC3_MAX_CHANNELS) 
1572 
return AVERROR(EINVAL);

1573 
if ((uint64_t)*channel_layout > 0x7FF) 
1574 
return AVERROR(EINVAL);

1575 
ch_layout = *channel_layout; 
1576 
if (!ch_layout)

1577 
ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);

1578 
if (av_get_channel_layout_nb_channels(ch_layout) != channels)

1579 
return AVERROR(EINVAL);

1580  
1581 
s>lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY); 
1582 
s>channels = channels; 
1583 
s>fbw_channels = channels  s>lfe_on; 
1584 
s>lfe_channel = s>lfe_on ? s>fbw_channels : 1;

1585 
if (s>lfe_on)

1586 
ch_layout = AV_CH_LOW_FREQUENCY; 
1587  
1588 
switch (ch_layout) {

1589 
case AV_CH_LAYOUT_MONO: s>channel_mode = AC3_CHMODE_MONO; break; 
1590 
case AV_CH_LAYOUT_STEREO: s>channel_mode = AC3_CHMODE_STEREO; break; 
1591 
case AV_CH_LAYOUT_SURROUND: s>channel_mode = AC3_CHMODE_3F; break; 
1592 
case AV_CH_LAYOUT_2_1: s>channel_mode = AC3_CHMODE_2F1R; break; 
1593 
case AV_CH_LAYOUT_4POINT0: s>channel_mode = AC3_CHMODE_3F1R; break; 
1594 
case AV_CH_LAYOUT_QUAD:

1595 
case AV_CH_LAYOUT_2_2: s>channel_mode = AC3_CHMODE_2F2R; break; 
1596 
case AV_CH_LAYOUT_5POINT0:

1597 
case AV_CH_LAYOUT_5POINT0_BACK: s>channel_mode = AC3_CHMODE_3F2R; break; 
1598 
default:

1599 
return AVERROR(EINVAL);

1600 
} 
1601  
1602 
s>channel_map = ff_ac3_enc_channel_map[s>channel_mode][s>lfe_on]; 
1603 
*channel_layout = ch_layout; 
1604 
if (s>lfe_on)

1605 
*channel_layout = AV_CH_LOW_FREQUENCY; 
1606  
1607 
return 0; 
1608 
} 
1609  
1610  
1611 
static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s) 
1612 
{ 
1613 
int i, ret;

1614  
1615 
/* validate channel layout */

1616 
if (!avctx>channel_layout) {

1617 
av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "

1618 
"encoder will guess the layout, but it "

1619 
"might be incorrect.\n");

1620 
} 
1621 
ret = set_channel_info(s, avctx>channels, &avctx>channel_layout); 
1622 
if (ret) {

1623 
av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");

1624 
return ret;

1625 
} 
1626  
1627 
/* validate sample rate */

1628 
for (i = 0; i < 9; i++) { 
1629 
if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx>sample_rate) 
1630 
break;

1631 
} 
1632 
if (i == 9) { 
1633 
av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");

1634 
return AVERROR(EINVAL);

1635 
} 
1636 
s>sample_rate = avctx>sample_rate; 
1637 
s>bit_alloc.sr_shift = i % 3;

1638 
s>bit_alloc.sr_code = i / 3;

1639  
1640 
/* validate bit rate */

1641 
for (i = 0; i < 19; i++) { 
1642 
if ((ff_ac3_bitrate_tab[i] >> s>bit_alloc.sr_shift)*1000 == avctx>bit_rate) 
1643 
break;

1644 
} 
1645 
if (i == 19) { 
1646 
av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");

1647 
return AVERROR(EINVAL);

1648 
} 
1649 
s>bit_rate = avctx>bit_rate; 
1650 
s>frame_size_code = i << 1;

1651  
1652 
/* validate cutoff */

1653 
if (avctx>cutoff < 0) { 
1654 
av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");

1655 
return AVERROR(EINVAL);

1656 
} 
1657 
s>cutoff = avctx>cutoff; 
1658 
if (s>cutoff > (s>sample_rate >> 1)) 
1659 
s>cutoff = s>sample_rate >> 1;

1660  
1661 
return 0; 
1662 
} 
1663  
1664  
1665 
/**

1666 
* Set bandwidth for all channels.

1667 
* The user can optionally supply a cutoff frequency. Otherwise an appropriate

1668 
* default value will be used.

1669 
*/

1670 
static av_cold void set_bandwidth(AC3EncodeContext *s) 
1671 
{ 
1672 
int ch, bw_code;

1673  
1674 
if (s>cutoff) {

1675 
/* calculate bandwidth based on userspecified cutoff frequency */

1676 
int fbw_coeffs;

1677 
fbw_coeffs = s>cutoff * 2 * AC3_MAX_COEFS / s>sample_rate;

1678 
bw_code = av_clip((fbw_coeffs  73) / 3, 0, 60); 
1679 
} else {

1680 
/* use default bandwidth setting */

1681 
/* XXX: should compute the bandwidth according to the frame

1682 
size, so that we avoid annoying high frequency artifacts */

1683 
bw_code = 50;

1684 
} 
1685  
1686 
/* set number of coefficients for each channel */

1687 
for (ch = 0; ch < s>fbw_channels; ch++) { 
1688 
s>bandwidth_code[ch] = bw_code; 
1689 
s>nb_coefs[ch] = bw_code * 3 + 73; 
1690 
} 
1691 
if (s>lfe_on)

1692 
s>nb_coefs[s>lfe_channel] = 7; /* LFE channel always has 7 coefs */ 
1693 
} 
1694  
1695  
1696 
static av_cold int allocate_buffers(AVCodecContext *avctx) 
1697 
{ 
1698 
int blk, ch;

1699 
AC3EncodeContext *s = avctx>priv_data; 
1700  
1701 
FF_ALLOC_OR_GOTO(avctx, s>planar_samples, s>channels * sizeof(*s>planar_samples),

1702 
alloc_fail); 
1703 
for (ch = 0; ch < s>channels; ch++) { 
1704 
FF_ALLOCZ_OR_GOTO(avctx, s>planar_samples[ch], 
1705 
(AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s>planar_samples),

1706 
alloc_fail); 
1707 
} 
1708 
FF_ALLOC_OR_GOTO(avctx, s>bap_buffer, AC3_MAX_BLOCKS * s>channels * 
1709 
AC3_MAX_COEFS * sizeof(*s>bap_buffer), alloc_fail);

1710 
FF_ALLOC_OR_GOTO(avctx, s>bap1_buffer, AC3_MAX_BLOCKS * s>channels * 
1711 
AC3_MAX_COEFS * sizeof(*s>bap1_buffer), alloc_fail);

1712 
FF_ALLOC_OR_GOTO(avctx, s>mdct_coef_buffer, AC3_MAX_BLOCKS * s>channels * 
1713 
AC3_MAX_COEFS * sizeof(*s>mdct_coef_buffer), alloc_fail);

1714 
FF_ALLOC_OR_GOTO(avctx, s>exp_buffer, AC3_MAX_BLOCKS * s>channels * 
1715 
AC3_MAX_COEFS * sizeof(*s>exp_buffer), alloc_fail);

1716 
FF_ALLOC_OR_GOTO(avctx, s>grouped_exp_buffer, AC3_MAX_BLOCKS * s>channels * 
1717 
128 * sizeof(*s>grouped_exp_buffer), alloc_fail); 
1718 
FF_ALLOC_OR_GOTO(avctx, s>psd_buffer, AC3_MAX_BLOCKS * s>channels * 
1719 
AC3_MAX_COEFS * sizeof(*s>psd_buffer), alloc_fail);

1720 
FF_ALLOC_OR_GOTO(avctx, s>band_psd_buffer, AC3_MAX_BLOCKS * s>channels * 
1721 
64 * sizeof(*s>band_psd_buffer), alloc_fail); 
1722 
FF_ALLOC_OR_GOTO(avctx, s>mask_buffer, AC3_MAX_BLOCKS * s>channels * 
1723 
64 * sizeof(*s>mask_buffer), alloc_fail); 
1724 
FF_ALLOC_OR_GOTO(avctx, s>qmant_buffer, AC3_MAX_BLOCKS * s>channels * 
1725 
AC3_MAX_COEFS * sizeof(*s>qmant_buffer), alloc_fail);

1726 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1727 
AC3Block *block = &s>blocks[blk]; 
1728 
FF_ALLOC_OR_GOTO(avctx, block>bap, s>channels * sizeof(*block>bap),

1729 
alloc_fail); 
1730 
FF_ALLOCZ_OR_GOTO(avctx, block>mdct_coef, s>channels * sizeof(*block>mdct_coef),

1731 
alloc_fail); 
1732 
FF_ALLOCZ_OR_GOTO(avctx, block>exp, s>channels * sizeof(*block>exp),

1733 
alloc_fail); 
1734 
FF_ALLOCZ_OR_GOTO(avctx, block>grouped_exp, s>channels * sizeof(*block>grouped_exp),

1735 
alloc_fail); 
1736 
FF_ALLOCZ_OR_GOTO(avctx, block>psd, s>channels * sizeof(*block>psd),

1737 
alloc_fail); 
1738 
FF_ALLOCZ_OR_GOTO(avctx, block>band_psd, s>channels * sizeof(*block>band_psd),

1739 
alloc_fail); 
1740 
FF_ALLOCZ_OR_GOTO(avctx, block>mask, s>channels * sizeof(*block>mask),

1741 
alloc_fail); 
1742 
FF_ALLOCZ_OR_GOTO(avctx, block>qmant, s>channels * sizeof(*block>qmant),

1743 
alloc_fail); 
1744  
1745 
for (ch = 0; ch < s>channels; ch++) { 
1746 
/* arrangement: block, channel, coeff */

1747 
block>bap[ch] = &s>bap_buffer [AC3_MAX_COEFS * (blk * s>channels + ch)]; 
1748 
block>mdct_coef[ch] = &s>mdct_coef_buffer [AC3_MAX_COEFS * (blk * s>channels + ch)]; 
1749 
block>grouped_exp[ch] = &s>grouped_exp_buffer[128 * (blk * s>channels + ch)];

1750 
block>psd[ch] = &s>psd_buffer [AC3_MAX_COEFS * (blk * s>channels + ch)]; 
1751 
block>band_psd[ch] = &s>band_psd_buffer [64 * (blk * s>channels + ch)];

1752 
block>mask[ch] = &s>mask_buffer [64 * (blk * s>channels + ch)];

1753 
block>qmant[ch] = &s>qmant_buffer [AC3_MAX_COEFS * (blk * s>channels + ch)]; 
1754  
1755 
/* arrangement: channel, block, coeff */

1756 
block>exp[ch] = &s>exp_buffer [AC3_MAX_COEFS * (AC3_MAX_BLOCKS * ch + blk)]; 
1757 
} 
1758 
} 
1759  
1760 
if (CONFIG_AC3ENC_FLOAT) {

1761 
FF_ALLOC_OR_GOTO(avctx, s>fixed_coef_buffer, AC3_MAX_BLOCKS * s>channels * 
1762 
AC3_MAX_COEFS * sizeof(*s>fixed_coef_buffer), alloc_fail);

1763 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1764 
AC3Block *block = &s>blocks[blk]; 
1765 
FF_ALLOCZ_OR_GOTO(avctx, block>fixed_coef, s>channels * 
1766 
sizeof(*block>fixed_coef), alloc_fail);

1767 
for (ch = 0; ch < s>channels; ch++) 
1768 
block>fixed_coef[ch] = &s>fixed_coef_buffer[AC3_MAX_COEFS * (blk * s>channels + ch)]; 
1769 
} 
1770 
} else {

1771 
for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { 
1772 
AC3Block *block = &s>blocks[blk]; 
1773 
FF_ALLOCZ_OR_GOTO(avctx, block>fixed_coef, s>channels * 
1774 
sizeof(*block>fixed_coef), alloc_fail);

1775 
for (ch = 0; ch < s>channels; ch++) 
1776 
block>fixed_coef[ch] = (int32_t *)block>mdct_coef[ch]; 
1777 
} 
1778 
} 
1779  
1780 
return 0; 
1781 
alloc_fail:

1782 
return AVERROR(ENOMEM);

1783 
} 
1784  
1785  
1786 
/**

1787 
* Initialize the encoder.

1788 
*/

1789 
static av_cold int ac3_encode_init(AVCodecContext *avctx) 
1790 
{ 
1791 
AC3EncodeContext *s = avctx>priv_data; 
1792 
int ret, frame_size_58;

1793  
1794 
avctx>frame_size = AC3_FRAME_SIZE; 
1795  
1796 
ff_ac3_common_init(); 
1797  
1798 
ret = validate_options(avctx, s); 
1799 
if (ret)

1800 
return ret;

1801  
1802 
s>bitstream_id = 8 + s>bit_alloc.sr_shift;

1803 
s>bitstream_mode = 0; /* complete main audio service */ 
1804  
1805 
s>frame_size_min = 2 * ff_ac3_frame_size_tab[s>frame_size_code][s>bit_alloc.sr_code];

1806 
s>bits_written = 0;

1807 
s>samples_written = 0;

1808 
s>frame_size = s>frame_size_min; 
1809  
1810 
/* calculate crc_inv for both possible frame sizes */

1811 
frame_size_58 = (( s>frame_size >> 2) + ( s>frame_size >> 4)) << 1; 
1812 
s>crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58)  16, CRC16_POLY); 
1813 
if (s>bit_alloc.sr_code == 1) { 
1814 
frame_size_58 = (((s>frame_size+2) >> 2) + ((s>frame_size+2) >> 4)) << 1; 
1815 
s>crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58)  16, CRC16_POLY); 
1816 
} 
1817  
1818 
set_bandwidth(s); 
1819  
1820 
rematrixing_init(s); 
1821  
1822 
exponent_init(s); 
1823  
1824 
bit_alloc_init(s); 
1825  
1826 
ret = mdct_init(avctx, &s>mdct, 9);

1827 
if (ret)

1828 
goto init_fail;

1829  
1830 
ret = allocate_buffers(avctx); 
1831 
if (ret)

1832 
goto init_fail;

1833  
1834 
avctx>coded_frame= avcodec_alloc_frame(); 
1835  
1836 
dsputil_init(&s>dsp, avctx); 
1837 
ff_ac3dsp_init(&s>ac3dsp); 
1838  
1839 
return 0; 
1840 
init_fail:

1841 
ac3_encode_close(avctx); 
1842 
return ret;

1843 
} 