PeerStreamer

/*

 * Wmapro compatible decoder

 * Copyright (c) 2007 Baptiste Coudurier, Benjamin Larsson, Ulion

 * Copyright (c) 2008 - 2011 Sascha Sommer, Benjamin Larsson

 *

 * This file is part of FFmpeg.

 *

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

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

 * License as published by the Free Software Foundation; either

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

 *

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

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

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

 * Lesser General Public License for more details.

 *

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

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

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

/**

 * @file

 * @brief wmapro decoder implementation

 * Wmapro is an MDCT based codec comparable to wma standard or AAC.

 * The decoding therefore consists of the following steps:

 * - bitstream decoding

 * - reconstruction of per-channel data

 * - rescaling and inverse quantization

 * - IMDCT

 * - windowing and overlapp-add

 *

 * The compressed wmapro bitstream is split into individual packets.

 * Every such packet contains one or more wma frames.

 * The compressed frames may have a variable length and frames may

 * cross packet boundaries.

 * Common to all wmapro frames is the number of samples that are stored in

 * a frame.

 * The number of samples and a few other decode flags are stored

 * as extradata that has to be passed to the decoder.

 *

 * The wmapro frames themselves are again split into a variable number of

 * subframes. Every subframe contains the data for 2^N time domain samples

 * where N varies between 7 and 12.

 *

 * Example wmapro bitstream (in samples):

 *

 * ||   packet 0           || packet 1 || packet 2      packets

 * ---------------------------------------------------

 * || frame 0      || frame 1       || frame 2    ||    frames

 * ---------------------------------------------------

 * ||   |      |   ||   |   |   |   ||            ||    subframes of channel 0

 * ---------------------------------------------------

 * ||      |   |   ||   |   |   |   ||            ||    subframes of channel 1

 * ---------------------------------------------------

 *

 * The frame layouts for the individual channels of a wma frame does not need

 * to be the same.

 *

 * However, if the offsets and lengths of several subframes of a frame are the

 * same, the subframes of the channels can be grouped.

 * Every group may then use special coding techniques like M/S stereo coding

 * to improve the compression ratio. These channel transformations do not

 * need to be applied to a whole subframe. Instead, they can also work on

 * individual scale factor bands (see below).

 * The coefficients that carry the audio signal in the frequency domain

 * are transmitted as huffman-coded vectors with 4, 2 and 1 elements.

 * In addition to that, the encoder can switch to a runlevel coding scheme

 * by transmitting subframe_length / 128 zero coefficients.

 *

 * Before the audio signal can be converted to the time domain, the

 * coefficients have to be rescaled and inverse quantized.

 * A subframe is therefore split into several scale factor bands that get

 * scaled individually.

 * Scale factors are submitted for every frame but they might be shared

 * between the subframes of a channel. Scale factors are initially DPCM-coded.

 * Once scale factors are shared, the differences are transmitted as runlevel

 * codes.

 * Every subframe length and offset combination in the frame layout shares a

 * common quantization factor that can be adjusted for every channel by a

 * modifier.

 * After the inverse quantization, the coefficients get processed by an IMDCT.

 * The resulting values are then windowed with a sine window and the first half

 * of the values are added to the second half of the output from the previous

 * subframe in order to reconstruct the output samples.

 */

#include "avcodec.h"

#include "internal.h"

#include "get_bits.h"

#include "put_bits.h"

#include "wmaprodata.h"

#include "dsputil.h"

#include "wma.h"

/** current decoder limitations */

#define WMAPRO_MAX_CHANNELS    8                             ///< max number of handled channels

#define MAX_SUBFRAMES  32                                    ///< max number of subframes per channel

#define MAX_BANDS      29                                    ///< max number of scale factor bands

#define MAX_FRAMESIZE  32768                                 ///< maximum compressed frame size

#define WMAPRO_BLOCK_MIN_BITS  6                                           ///< log2 of min block size

#define WMAPRO_BLOCK_MAX_BITS 12                                           ///< log2 of max block size

#define WMAPRO_BLOCK_MAX_SIZE (1 << WMAPRO_BLOCK_MAX_BITS)                 ///< maximum block size

#define WMAPRO_BLOCK_SIZES    (WMAPRO_BLOCK_MAX_BITS - WMAPRO_BLOCK_MIN_BITS + 1) ///< possible block sizes

#define VLCBITS            9

#define SCALEVLCBITS       8

#define VEC4MAXDEPTH    ((HUFF_VEC4_MAXBITS+VLCBITS-1)/VLCBITS)

#define VEC2MAXDEPTH    ((HUFF_VEC2_MAXBITS+VLCBITS-1)/VLCBITS)

#define VEC1MAXDEPTH    ((HUFF_VEC1_MAXBITS+VLCBITS-1)/VLCBITS)

#define SCALEMAXDEPTH   ((HUFF_SCALE_MAXBITS+SCALEVLCBITS-1)/SCALEVLCBITS)

#define SCALERLMAXDEPTH ((HUFF_SCALE_RL_MAXBITS+VLCBITS-1)/VLCBITS)

static VLC              sf_vlc;           ///< scale factor DPCM vlc

static VLC              sf_rl_vlc;        ///< scale factor run length vlc

static VLC              vec4_vlc;         ///< 4 coefficients per symbol

static VLC              vec2_vlc;         ///< 2 coefficients per symbol

static VLC              vec1_vlc;         ///< 1 coefficient per symbol

static VLC              coef_vlc[2];      ///< coefficient run length vlc codes

static float            sin64[33];        ///< sinus table for decorrelation

/**

 * @brief frame specific decoder context for a single channel

 */

typedef struct {

    int16_t  prev_block_len;                          ///< length of the previous block

    uint8_t  transmit_coefs;

    uint8_t  num_subframes;

    uint16_t subframe_len[MAX_SUBFRAMES];             ///< subframe length in samples

    uint16_t subframe_offset[MAX_SUBFRAMES];          ///< subframe positions in the current frame

    uint8_t  cur_subframe;                            ///< current subframe number

    uint16_t decoded_samples;                         ///< number of already processed samples

    uint8_t  grouped;                                 ///< channel is part of a group

    int      quant_step;                              ///< quantization step for the current subframe

    int8_t   reuse_sf;                                ///< share scale factors between subframes

    int8_t   scale_factor_step;                       ///< scaling step for the current subframe

    int      max_scale_factor;                        ///< maximum scale factor for the current subframe

    int      saved_scale_factors[2][MAX_BANDS];       ///< resampled and (previously) transmitted scale factor values

    int8_t   scale_factor_idx;                        ///< index for the transmitted scale factor values (used for resampling)

    int*     scale_factors;                           ///< pointer to the scale factor values used for decoding

    uint8_t  table_idx;                               ///< index in sf_offsets for the scale factor reference block

    float*   coeffs;                                  ///< pointer to the subframe decode buffer

    DECLARE_ALIGNED(16, float, out)[WMAPRO_BLOCK_MAX_SIZE + WMAPRO_BLOCK_MAX_SIZE / 2]; ///< output buffer

} WMAProChannelCtx;

/**

 * @brief channel group for channel transformations

 */

typedef struct {

    uint8_t num_channels;                                     ///< number of channels in the group

    int8_t  transform;                                        ///< transform on / off

    int8_t  transform_band[MAX_BANDS];                        ///< controls if the transform is enabled for a certain band

    float   decorrelation_matrix[WMAPRO_MAX_CHANNELS*WMAPRO_MAX_CHANNELS];

    float*  channel_data[WMAPRO_MAX_CHANNELS];                ///< transformation coefficients

} WMAProChannelGrp;

/**

 * @brief main decoder context

 */

typedef struct WMAProDecodeCtx {

    /* generic decoder variables */

    AVCodecContext*  avctx;                         ///< codec context for av_log

    DSPContext       dsp;                           ///< accelerated DSP functions

    uint8_t          frame_data[MAX_FRAMESIZE +

                      FF_INPUT_BUFFER_PADDING_SIZE];///< compressed frame data

    PutBitContext    pb;                            ///< context for filling the frame_data buffer

    FFTContext       mdct_ctx[WMAPRO_BLOCK_SIZES];  ///< MDCT context per block size

    DECLARE_ALIGNED(16, float, tmp)[WMAPRO_BLOCK_MAX_SIZE]; ///< IMDCT output buffer

    float*           windows[WMAPRO_BLOCK_SIZES];   ///< windows for the different block sizes

    /* frame size dependent frame information (set during initialization) */

    uint32_t         decode_flags;                  ///< used compression features

    uint8_t          len_prefix;                    ///< frame is prefixed with its length

    uint8_t          dynamic_range_compression;     ///< frame contains DRC data

    uint8_t          bits_per_sample;               ///< integer audio sample size for the unscaled IMDCT output (used to scale to [-1.0, 1.0])

    uint16_t         samples_per_frame;             ///< number of samples to output

    uint16_t         log2_frame_size;

    int8_t           num_channels;                  ///< number of channels in the stream (same as AVCodecContext.num_channels)

    int8_t           lfe_channel;                   ///< lfe channel index

    uint8_t          max_num_subframes;

    uint8_t          subframe_len_bits;             ///< number of bits used for the subframe length

    uint8_t          max_subframe_len_bit;          ///< flag indicating that the subframe is of maximum size when the first subframe length bit is 1

    uint16_t         min_samples_per_subframe;

    int8_t           num_sfb[WMAPRO_BLOCK_SIZES];   ///< scale factor bands per block size

    int16_t          sfb_offsets[WMAPRO_BLOCK_SIZES][MAX_BANDS];                    ///< scale factor band offsets (multiples of 4)

    int8_t           sf_offsets[WMAPRO_BLOCK_SIZES][WMAPRO_BLOCK_SIZES][MAX_BANDS]; ///< scale factor resample matrix

    int16_t          subwoofer_cutoffs[WMAPRO_BLOCK_SIZES]; ///< subwoofer cutoff values

    /* packet decode state */

    GetBitContext    pgb;                           ///< bitstream reader context for the packet

    int              next_packet_start;             ///< start offset of the next wma packet in the demuxer packet

    uint8_t          packet_offset;                 ///< frame offset in the packet

    uint8_t          packet_sequence_number;        ///< current packet number

    int              num_saved_bits;                ///< saved number of bits

    int              frame_offset;                  ///< frame offset in the bit reservoir

    int              subframe_offset;               ///< subframe offset in the bit reservoir

    uint8_t          packet_loss;                   ///< set in case of bitstream error

    uint8_t          packet_done;                   ///< set when a packet is fully decoded

    /* frame decode state */

    uint32_t         frame_num;                     ///< current frame number (not used for decoding)

    GetBitContext    gb;                            ///< bitstream reader context

    int              buf_bit_size;                  ///< buffer size in bits

    float*           samples;                       ///< current samplebuffer pointer

    float*           samples_end;                   ///< maximum samplebuffer pointer

    uint8_t          drc_gain;                      ///< gain for the DRC tool

    int8_t           skip_frame;                    ///< skip output step

    int8_t           parsed_all_subframes;          ///< all subframes decoded?

    /* subframe/block decode state */

    int16_t          subframe_len;                  ///< current subframe length

    int8_t           channels_for_cur_subframe;     ///< number of channels that contain the subframe

    int8_t           channel_indexes_for_cur_subframe[WMAPRO_MAX_CHANNELS];

    int8_t           num_bands;                     ///< number of scale factor bands

    int16_t*         cur_sfb_offsets;               ///< sfb offsets for the current block

    uint8_t          table_idx;                     ///< index for the num_sfb, sfb_offsets, sf_offsets and subwoofer_cutoffs tables

    int8_t           esc_len;                       ///< length of escaped coefficients

    uint8_t          num_chgroups;                  ///< number of channel groups

    WMAProChannelGrp chgroup[WMAPRO_MAX_CHANNELS];  ///< channel group information

    WMAProChannelCtx channel[WMAPRO_MAX_CHANNELS];  ///< per channel data

} WMAProDecodeCtx;

/**

 *@brief helper function to print the most important members of the context

 *@param s context

 */

static void av_cold dump_context(WMAProDecodeCtx *s)

{

#define PRINT(a, b)     av_log(s->avctx, AV_LOG_DEBUG, " %s = %d\n", a, b);

#define PRINT_HEX(a, b) av_log(s->avctx, AV_LOG_DEBUG, " %s = %x\n", a, b);

    PRINT("ed sample bit depth", s->bits_per_sample);

    PRINT_HEX("ed decode flags", s->decode_flags);

    PRINT("samples per frame",   s->samples_per_frame);

    PRINT("log2 frame size",     s->log2_frame_size);

    PRINT("max num subframes",   s->max_num_subframes);

    PRINT("len prefix",          s->len_prefix);

    PRINT("num channels",        s->num_channels);

}

/**

 *@brief Uninitialize the decoder and free all resources.

 *@param avctx codec context

 *@return 0 on success, < 0 otherwise

 */

static av_cold int decode_end(AVCodecContext *avctx)

{

    WMAProDecodeCtx *s = avctx->priv_data;

    int i;

    for (i = 0; i < WMAPRO_BLOCK_SIZES; i++)

        ff_mdct_end(&s->mdct_ctx[i]);

    return 0;

}

/**

 *@brief Initialize the decoder.

 *@param avctx codec context

 *@return 0 on success, -1 otherwise

 */

static av_cold int decode_init(AVCodecContext *avctx)

{

    WMAProDecodeCtx *s = avctx->priv_data;

    uint8_t *edata_ptr = avctx->extradata;

    unsigned int channel_mask;

    int i;

    int log2_max_num_subframes;

    int num_possible_block_sizes;

    s->avctx = avctx;

    dsputil_init(&s->dsp, avctx);

    init_put_bits(&s->pb, s->frame_data, MAX_FRAMESIZE);

    avctx->sample_fmt = AV_SAMPLE_FMT_FLT;

    if (avctx->extradata_size >= 18) {

        s->decode_flags    = AV_RL16(edata_ptr+14);

        channel_mask       = AV_RL32(edata_ptr+2);

        s->bits_per_sample = AV_RL16(edata_ptr);

        /** dump the extradata */

        for (i = 0; i < avctx->extradata_size; i++)

            dprintf(avctx, "[%x] ", avctx->extradata[i]);

        dprintf(avctx, "\n");

    } else {

        av_log_ask_for_sample(avctx, "Unknown extradata size\n");

        return AVERROR_INVALIDDATA;

    }

    /** generic init */

    s->log2_frame_size = av_log2(avctx->block_align) + 4;

    /** frame info */

    s->skip_frame  = 1; /* skip first frame */

    s->packet_loss = 1;

    s->len_prefix  = (s->decode_flags & 0x40);

    /** get frame len */

    s->samples_per_frame = 1 << ff_wma_get_frame_len_bits(avctx->sample_rate,

                                                          3, s->decode_flags);

    /** init previous block len */

    for (i = 0; i < avctx->channels; i++)

        s->channel[i].prev_block_len = s->samples_per_frame;

    /** subframe info */

    log2_max_num_subframes       = ((s->decode_flags & 0x38) >> 3);

    s->max_num_subframes         = 1 << log2_max_num_subframes;

    if (s->max_num_subframes == 16 || s->max_num_subframes == 4)

        s->max_subframe_len_bit = 1;

    s->subframe_len_bits = av_log2(log2_max_num_subframes) + 1;

    num_possible_block_sizes     = log2_max_num_subframes + 1;

    s->min_samples_per_subframe  = s->samples_per_frame / s->max_num_subframes;

    s->dynamic_range_compression = (s->decode_flags & 0x80);

    if (s->max_num_subframes > MAX_SUBFRAMES) {

        av_log(avctx, AV_LOG_ERROR, "invalid number of subframes %i\n",

               s->max_num_subframes);

        return AVERROR_INVALIDDATA;

    }

    s->num_channels = avctx->channels;

    /** extract lfe channel position */

    s->lfe_channel = -1;

    if (channel_mask & 8) {

        unsigned int mask;

        for (mask = 1; mask < 16; mask <<= 1) {

            if (channel_mask & mask)

                ++s->lfe_channel;

        }

    }

    if (s->num_channels < 0) {

        av_log(avctx, AV_LOG_ERROR, "invalid number of channels %d\n", s->num_channels);

        return AVERROR_INVALIDDATA;

    } else if (s->num_channels > WMAPRO_MAX_CHANNELS) {

        av_log_ask_for_sample(avctx, "unsupported number of channels\n");

        return AVERROR_PATCHWELCOME;

    }

    INIT_VLC_STATIC(&sf_vlc, SCALEVLCBITS, HUFF_SCALE_SIZE,

                    scale_huffbits, 1, 1,

                    scale_huffcodes, 2, 2, 616);

    INIT_VLC_STATIC(&sf_rl_vlc, VLCBITS, HUFF_SCALE_RL_SIZE,

                    scale_rl_huffbits, 1, 1,

                    scale_rl_huffcodes, 4, 4, 1406);

    INIT_VLC_STATIC(&coef_vlc[0], VLCBITS, HUFF_COEF0_SIZE,

                    coef0_huffbits, 1, 1,

                    coef0_huffcodes, 4, 4, 2108);

    INIT_VLC_STATIC(&coef_vlc[1], VLCBITS, HUFF_COEF1_SIZE,

                    coef1_huffbits, 1, 1,

                    coef1_huffcodes, 4, 4, 3912);

    INIT_VLC_STATIC(&vec4_vlc, VLCBITS, HUFF_VEC4_SIZE,

                    vec4_huffbits, 1, 1,

                    vec4_huffcodes, 2, 2, 604);

    INIT_VLC_STATIC(&vec2_vlc, VLCBITS, HUFF_VEC2_SIZE,

                    vec2_huffbits, 1, 1,

                    vec2_huffcodes, 2, 2, 562);

    INIT_VLC_STATIC(&vec1_vlc, VLCBITS, HUFF_VEC1_SIZE,

                    vec1_huffbits, 1, 1,

                    vec1_huffcodes, 2, 2, 562);

    /** calculate number of scale factor bands and their offsets

        for every possible block size */

    for (i = 0; i < num_possible_block_sizes; i++) {

        int subframe_len = s->samples_per_frame >> i;

        int x;

        int band = 1;

        s->sfb_offsets[i][0] = 0;

        for (x = 0; x < MAX_BANDS-1 && s->sfb_offsets[i][band - 1] < subframe_len; x++) {

            int offset = (subframe_len * 2 * critical_freq[x])

                          / s->avctx->sample_rate + 2;

            offset &= ~3;

            if (offset > s->sfb_offsets[i][band - 1])

                s->sfb_offsets[i][band++] = offset;

        }

        s->sfb_offsets[i][band - 1] = subframe_len;

        s->num_sfb[i]               = band - 1;

    }

    /** Scale factors can be shared between blocks of different size

        as every block has a different scale factor band layout.

        The matrix sf_offsets is needed to find the correct scale factor.

     */

    for (i = 0; i < num_possible_block_sizes; i++) {

        int b;

        for (b = 0; b < s->num_sfb[i]; b++) {

            int x;

            int offset = ((s->sfb_offsets[i][b]

                           + s->sfb_offsets[i][b + 1] - 1) << i) >> 1;

            for (x = 0; x < num_possible_block_sizes; x++) {

                int v = 0;

                while (s->sfb_offsets[x][v + 1] << x < offset)

                    ++v;

                s->sf_offsets[i][x][b] = v;

            }

        }

    }

    /** init MDCT, FIXME: only init needed sizes */

    for (i = 0; i < WMAPRO_BLOCK_SIZES; i++)

        ff_mdct_init(&s->mdct_ctx[i], WMAPRO_BLOCK_MIN_BITS+1+i, 1,

                     1.0 / (1 << (WMAPRO_BLOCK_MIN_BITS + i - 1))

                     / (1 << (s->bits_per_sample - 1)));

    /** init MDCT windows: simple sinus window */

    for (i = 0; i < WMAPRO_BLOCK_SIZES; i++) {

        const int win_idx = WMAPRO_BLOCK_MAX_BITS - i;

        ff_init_ff_sine_windows(win_idx);

        s->windows[WMAPRO_BLOCK_SIZES - i - 1] = ff_sine_windows[win_idx];

    }

    /** calculate subwoofer cutoff values */

    for (i = 0; i < num_possible_block_sizes; i++) {

        int block_size = s->samples_per_frame >> i;

        int cutoff = (440*block_size + 3 * (s->avctx->sample_rate >> 1) - 1)

                     / s->avctx->sample_rate;

        s->subwoofer_cutoffs[i] = av_clip(cutoff, 4, block_size);

    }

    /** calculate sine values for the decorrelation matrix */

    for (i = 0; i < 33; i++)

        sin64[i] = sin(i*M_PI / 64.0);

    if (avctx->debug & FF_DEBUG_BITSTREAM)

        dump_context(s);

    avctx->channel_layout = channel_mask;

    return 0;

}

/**

 *@brief Decode the subframe length.

 *@param s context

 *@param offset sample offset in the frame

 *@return decoded subframe length on success, < 0 in case of an error

 */

static int decode_subframe_length(WMAProDecodeCtx *s, int offset)

{

    int frame_len_shift = 0;

    int subframe_len;

    /** no need to read from the bitstream when only one length is possible */

    if (offset == s->samples_per_frame - s->min_samples_per_subframe)

        return s->min_samples_per_subframe;

    /** 1 bit indicates if the subframe is of maximum length */

    if (s->max_subframe_len_bit) {

        if (get_bits1(&s->gb))

            frame_len_shift = 1 + get_bits(&s->gb, s->subframe_len_bits-1);

    } else

        frame_len_shift = get_bits(&s->gb, s->subframe_len_bits);

    subframe_len = s->samples_per_frame >> frame_len_shift;

    /** sanity check the length */

    if (subframe_len < s->min_samples_per_subframe ||

        subframe_len > s->samples_per_frame) {

        av_log(s->avctx, AV_LOG_ERROR, "broken frame: subframe_len %i\n",

               subframe_len);

        return AVERROR_INVALIDDATA;

    }

    return subframe_len;

}

/**

 *@brief Decode how the data in the frame is split into subframes.

 *       Every WMA frame contains the encoded data for a fixed number of

 *       samples per channel. The data for every channel might be split

 *       into several subframes. This function will reconstruct the list of

 *       subframes for every channel.

 *

 *       If the subframes are not evenly split, the algorithm estimates the

 *       channels with the lowest number of total samples.

 *       Afterwards, for each of these channels a bit is read from the

 *       bitstream that indicates if the channel contains a subframe with the

 *       next subframe size that is going to be read from the bitstream or not.

 *       If a channel contains such a subframe, the subframe size gets added to

 *       the channel's subframe list.

 *       The algorithm repeats these steps until the frame is properly divided

 *       between the individual channels.

 *

 *@param s context

 *@return 0 on success, < 0 in case of an error

 */

static int decode_tilehdr(WMAProDecodeCtx *s)

{

    uint16_t num_samples[WMAPRO_MAX_CHANNELS];        /**< sum of samples for all currently known subframes of a channel */

    uint8_t  contains_subframe[WMAPRO_MAX_CHANNELS];  /**< flag indicating if a channel contains the current subframe */

    int channels_for_cur_subframe = s->num_channels;  /**< number of channels that contain the current subframe */

    int fixed_channel_layout = 0;                     /**< flag indicating that all channels use the same subframe offsets and sizes */

    int min_channel_len = 0;                          /**< smallest sum of samples (channels with this length will be processed first) */

    int c;

    /* Should never consume more than 3073 bits (256 iterations for the

     * while loop when always the minimum amount of 128 samples is substracted

     * from missing samples in the 8 channel case).

     * 1 + BLOCK_MAX_SIZE * MAX_CHANNELS / BLOCK_MIN_SIZE * (MAX_CHANNELS  + 4)

     */

    /** reset tiling information */

    for (c = 0; c < s->num_channels; c++)

        s->channel[c].num_subframes = 0;

    memset(num_samples, 0, sizeof(num_samples));

    if (s->max_num_subframes == 1 || get_bits1(&s->gb))

        fixed_channel_layout = 1;

    /** loop until the frame data is split between the subframes */

    do {

        int subframe_len;

        /** check which channels contain the subframe */

        for (c = 0; c < s->num_channels; c++) {

            if (num_samples[c] == min_channel_len) {

                if (fixed_channel_layout || channels_for_cur_subframe == 1 ||

                   (min_channel_len == s->samples_per_frame - s->min_samples_per_subframe))

                    contains_subframe[c] = 1;

                else

                    contains_subframe[c] = get_bits1(&s->gb);

            } else

                contains_subframe[c] = 0;

        }

        /** get subframe length, subframe_len == 0 is not allowed */

        if ((subframe_len = decode_subframe_length(s, min_channel_len)) <= 0)

            return AVERROR_INVALIDDATA;

        /** add subframes to the individual channels and find new min_channel_len */

        min_channel_len += subframe_len;

        for (c = 0; c < s->num_channels; c++) {

            WMAProChannelCtx* chan = &s->channel[c];

            if (contains_subframe[c]) {

                if (chan->num_subframes >= MAX_SUBFRAMES) {

                    av_log(s->avctx, AV_LOG_ERROR,

                           "broken frame: num subframes > 31\n");

                    return AVERROR_INVALIDDATA;

                }

                chan->subframe_len[chan->num_subframes] = subframe_len;

                num_samples[c] += subframe_len;

                ++chan->num_subframes;

                if (num_samples[c] > s->samples_per_frame) {

                    av_log(s->avctx, AV_LOG_ERROR, "broken frame: "

                           "channel len > samples_per_frame\n");

                    return AVERROR_INVALIDDATA;

                }

            } else if (num_samples[c] <= min_channel_len) {

                if (num_samples[c] < min_channel_len) {

                    channels_for_cur_subframe = 0;

                    min_channel_len = num_samples[c];

                }

                ++channels_for_cur_subframe;

            }

        }

    } while (min_channel_len < s->samples_per_frame);

    for (c = 0; c < s->num_channels; c++) {

        int i;

        int offset = 0;

        for (i = 0; i < s->channel[c].num_subframes; i++) {

            dprintf(s->avctx, "frame[%i] channel[%i] subframe[%i]"

                    " len %i\n", s->frame_num, c, i,

                    s->channel[c].subframe_len[i]);

            s->channel[c].subframe_offset[i] = offset;

            offset += s->channel[c].subframe_len[i];

        }

    }

    return 0;

}

/**

 *@brief Calculate a decorrelation matrix from the bitstream parameters.

 *@param s codec context

 *@param chgroup channel group for which the matrix needs to be calculated

 */

static void decode_decorrelation_matrix(WMAProDecodeCtx *s,

                                        WMAProChannelGrp *chgroup)

{

    int i;

    int offset = 0;

    int8_t rotation_offset[WMAPRO_MAX_CHANNELS * WMAPRO_MAX_CHANNELS];

    memset(chgroup->decorrelation_matrix, 0, s->num_channels *

           s->num_channels * sizeof(*chgroup->decorrelation_matrix));

    for (i = 0; i < chgroup->num_channels * (chgroup->num_channels - 1) >> 1; i++)

        rotation_offset[i] = get_bits(&s->gb, 6);

    for (i = 0; i < chgroup->num_channels; i++)

        chgroup->decorrelation_matrix[chgroup->num_channels * i + i] =

            get_bits1(&s->gb) ? 1.0 : -1.0;

    for (i = 1; i < chgroup->num_channels; i++) {

        int x;

        for (x = 0; x < i; x++) {

            int y;

            for (y = 0; y < i + 1; y++) {

                float v1 = chgroup->decorrelation_matrix[x * chgroup->num_channels + y];

                float v2 = chgroup->decorrelation_matrix[i * chgroup->num_channels + y];

                int n = rotation_offset[offset + x];

                float sinv;

                float cosv;

                if (n < 32) {

                    sinv = sin64[n];

                    cosv = sin64[32 - n];

                } else {

                    sinv =  sin64[64 -  n];

                    cosv = -sin64[n  - 32];

                }

                chgroup->decorrelation_matrix[y + x * chgroup->num_channels] =

                                               (v1 * sinv) - (v2 * cosv);

                chgroup->decorrelation_matrix[y + i * chgroup->num_channels] =

                                               (v1 * cosv) + (v2 * sinv);

            }

        }

        offset += i;

    }

}

/**

 *@brief Decode channel transformation parameters

 *@param s codec context

 *@return 0 in case of success, < 0 in case of bitstream errors

 */

static int decode_channel_transform(WMAProDecodeCtx* s)

{

    int i;

    /* should never consume more than 1921 bits for the 8 channel case

     * 1 + MAX_CHANNELS * (MAX_CHANNELS + 2 + 3 * MAX_CHANNELS * MAX_CHANNELS

     * + MAX_CHANNELS + MAX_BANDS + 1)

     */

    /** in the one channel case channel transforms are pointless */

    s->num_chgroups = 0;

    if (s->num_channels > 1) {

        int remaining_channels = s->channels_for_cur_subframe;

        if (get_bits1(&s->gb)) {

            av_log_ask_for_sample(s->avctx,

                                  "unsupported channel transform bit\n");

            return AVERROR_INVALIDDATA;

        }

        for (s->num_chgroups = 0; remaining_channels &&

             s->num_chgroups < s->channels_for_cur_subframe; s->num_chgroups++) {

            WMAProChannelGrp* chgroup = &s->chgroup[s->num_chgroups];

            float** channel_data = chgroup->channel_data;

            chgroup->num_channels = 0;

            chgroup->transform = 0;

            /** decode channel mask */

            if (remaining_channels > 2) {

                for (i = 0; i < s->channels_for_cur_subframe; i++) {

                    int channel_idx = s->channel_indexes_for_cur_subframe[i];

                    if (!s->channel[channel_idx].grouped

                        && get_bits1(&s->gb)) {

                        ++chgroup->num_channels;

                        s->channel[channel_idx].grouped = 1;

                        *channel_data++ = s->channel[channel_idx].coeffs;

                    }

                }

            } else {

                chgroup->num_channels = remaining_channels;

                for (i = 0; i < s->channels_for_cur_subframe; i++) {

                    int channel_idx = s->channel_indexes_for_cur_subframe[i];

                    if (!s->channel[channel_idx].grouped)

                        *channel_data++ = s->channel[channel_idx].coeffs;

                    s->channel[channel_idx].grouped = 1;

                }

            }

            /** decode transform type */

            if (chgroup->num_channels == 2) {

                if (get_bits1(&s->gb)) {

                    if (get_bits1(&s->gb)) {

                        av_log_ask_for_sample(s->avctx,

                                              "unsupported channel transform type\n");

                    }

                } else {

                    chgroup->transform = 1;

                    if (s->num_channels == 2) {

                        chgroup->decorrelation_matrix[0] =  1.0;

                        chgroup->decorrelation_matrix[1] = -1.0;

                        chgroup->decorrelation_matrix[2] =  1.0;

                        chgroup->decorrelation_matrix[3] =  1.0;

                    } else {

                        /** cos(pi/4) */

                        chgroup->decorrelation_matrix[0] =  0.70703125;

                        chgroup->decorrelation_matrix[1] = -0.70703125;

                        chgroup->decorrelation_matrix[2] =  0.70703125;

                        chgroup->decorrelation_matrix[3] =  0.70703125;

                    }

                }

            } else if (chgroup->num_channels > 2) {

                if (get_bits1(&s->gb)) {

                    chgroup->transform = 1;

                    if (get_bits1(&s->gb)) {

                        decode_decorrelation_matrix(s, chgroup);

                    } else {

                        /** FIXME: more than 6 coupled channels not supported */

                        if (chgroup->num_channels > 6) {

                            av_log_ask_for_sample(s->avctx,

                                                  "coupled channels > 6\n");

                        } else {

                            memcpy(chgroup->decorrelation_matrix,

                                   default_decorrelation[chgroup->num_channels],

                                   chgroup->num_channels * chgroup->num_channels *

                                   sizeof(*chgroup->decorrelation_matrix));

                        }

                    }

                }

            }

            /** decode transform on / off */

            if (chgroup->transform) {

                if (!get_bits1(&s->gb)) {

                    int i;

                    /** transform can be enabled for individual bands */

                    for (i = 0; i < s->num_bands; i++) {

                        chgroup->transform_band[i] = get_bits1(&s->gb);

                    }

                } else {

                    memset(chgroup->transform_band, 1, s->num_bands);

                }

            }

            remaining_channels -= chgroup->num_channels;

        }

    }

    return 0;

}

/**

 *@brief Extract the coefficients from the bitstream.

 *@param s codec context

 *@param c current channel number

 *@return 0 on success, < 0 in case of bitstream errors

 */

static int decode_coeffs(WMAProDecodeCtx *s, int c)

{

    /* Integers 0..15 as single-precision floats.  The table saves a

       costly int to float conversion, and storing the values as

       integers allows fast sign-flipping. */

    static const int fval_tab[16] = {

        0x00000000, 0x3f800000, 0x40000000, 0x40400000,

        0x40800000, 0x40a00000, 0x40c00000, 0x40e00000,

        0x41000000, 0x41100000, 0x41200000, 0x41300000,

        0x41400000, 0x41500000, 0x41600000, 0x41700000,

    };

    int vlctable;

    VLC* vlc;

    WMAProChannelCtx* ci = &s->channel[c];

    int rl_mode = 0;

    int cur_coeff = 0;

    int num_zeros = 0;

    const uint16_t* run;

    const float* level;

    dprintf(s->avctx, "decode coefficients for channel %i\n", c);

    vlctable = get_bits1(&s->gb);

    vlc = &coef_vlc[vlctable];

    if (vlctable) {

        run = coef1_run;

        level = coef1_level;

    } else {

        run = coef0_run;

        level = coef0_level;

    }

    /** decode vector coefficients (consumes up to 167 bits per iteration for

      4 vector coded large values) */

    while (!rl_mode && cur_coeff + 3 < s->subframe_len) {

        int vals[4];

        int i;

        unsigned int idx;

        idx = get_vlc2(&s->gb, vec4_vlc.table, VLCBITS, VEC4MAXDEPTH);

        if (idx == HUFF_VEC4_SIZE - 1) {

            for (i = 0; i < 4; i += 2) {

                idx = get_vlc2(&s->gb, vec2_vlc.table, VLCBITS, VEC2MAXDEPTH);

                if (idx == HUFF_VEC2_SIZE - 1) {

                    int v0, v1;

                    v0 = get_vlc2(&s->gb, vec1_vlc.table, VLCBITS, VEC1MAXDEPTH);

                    if (v0 == HUFF_VEC1_SIZE - 1)

                        v0 += ff_wma_get_large_val(&s->gb);

                    v1 = get_vlc2(&s->gb, vec1_vlc.table, VLCBITS, VEC1MAXDEPTH);

                    if (v1 == HUFF_VEC1_SIZE - 1)

                        v1 += ff_wma_get_large_val(&s->gb);

                    ((float*)vals)[i  ] = v0;

                    ((float*)vals)[i+1] = v1;

                } else {

                    vals[i]   = fval_tab[symbol_to_vec2[idx] >> 4 ];

                    vals[i+1] = fval_tab[symbol_to_vec2[idx] & 0xF];

                }

            }

        } else {

            vals[0] = fval_tab[ symbol_to_vec4[idx] >> 12      ];

            vals[1] = fval_tab[(symbol_to_vec4[idx] >> 8) & 0xF];

            vals[2] = fval_tab[(symbol_to_vec4[idx] >> 4) & 0xF];

            vals[3] = fval_tab[ symbol_to_vec4[idx]       & 0xF];

        }

        /** decode sign */

        for (i = 0; i < 4; i++) {

            if (vals[i]) {

                int sign = get_bits1(&s->gb) - 1;

                *(uint32_t*)&ci->coeffs[cur_coeff] = vals[i] ^ sign<<31;

                num_zeros = 0;

            } else {

                ci->coeffs[cur_coeff] = 0;

                /** switch to run level mode when subframe_len / 128 zeros

                    were found in a row */

                rl_mode |= (++num_zeros > s->subframe_len >> 8);

            }

            ++cur_coeff;

        }

    }

    /** decode run level coded coefficients */

    if (rl_mode) {

        memset(&ci->coeffs[cur_coeff], 0,

               sizeof(*ci->coeffs) * (s->subframe_len - cur_coeff));

        if (ff_wma_run_level_decode(s->avctx, &s->gb, vlc,

                                    level, run, 1, ci->coeffs,

                                    cur_coeff, s->subframe_len,

                                    s->subframe_len, s->esc_len, 0))

            return AVERROR_INVALIDDATA;

    }

    return 0;

}

/**

 *@brief Extract scale factors from the bitstream.

 *@param s codec context

 *@return 0 on success, < 0 in case of bitstream errors

 */

static int decode_scale_factors(WMAProDecodeCtx* s)

{

    int i;

    /** should never consume more than 5344 bits

     *  MAX_CHANNELS * (1 +  MAX_BANDS * 23)

     */

    for (i = 0; i < s->channels_for_cur_subframe; i++) {

        int c = s->channel_indexes_for_cur_subframe[i];

        int* sf;

        int* sf_end;

        s->channel[c].scale_factors = s->channel[c].saved_scale_factors[!s->channel[c].scale_factor_idx];

        sf_end = s->channel[c].scale_factors + s->num_bands;

        /** resample scale factors for the new block size

         *  as the scale factors might need to be resampled several times

         *  before some  new values are transmitted, a backup of the last

         *  transmitted scale factors is kept in saved_scale_factors

         */

        if (s->channel[c].reuse_sf) {

            const int8_t* sf_offsets = s->sf_offsets[s->table_idx][s->channel[c].table_idx];

            int b;

            for (b = 0; b < s->num_bands; b++)

                s->channel[c].scale_factors[b] =

                    s->channel[c].saved_scale_factors[s->channel[c].scale_factor_idx][*sf_offsets++];

        }

        if (!s->channel[c].cur_subframe || get_bits1(&s->gb)) {

            if (!s->channel[c].reuse_sf) {

                int val;

                /** decode DPCM coded scale factors */

                s->channel[c].scale_factor_step = get_bits(&s->gb, 2) + 1;

                val = 45 / s->channel[c].scale_factor_step;

                for (sf = s->channel[c].scale_factors; sf < sf_end; sf++) {

                    val += get_vlc2(&s->gb, sf_vlc.table, SCALEVLCBITS, SCALEMAXDEPTH) - 60;

                    *sf = val;

                }

            } else {

                int i;

                /** run level decode differences to the resampled factors */

                for (i = 0; i < s->num_bands; i++) {

                    int idx;

                    int skip;

                    int val;

                    int sign;

                    idx = get_vlc2(&s->gb, sf_rl_vlc.table, VLCBITS, SCALERLMAXDEPTH);

                    if (!idx) {

                        uint32_t code = get_bits(&s->gb, 14);

                        val  =  code >> 6;

                        sign = (code & 1) - 1;

                        skip = (code & 0x3f) >> 1;

                    } else if (idx == 1) {

                        break;

                    } else {

                        skip = scale_rl_run[idx];

                        val  = scale_rl_level[idx];

                        sign = get_bits1(&s->gb)-1;

                    }

                    i += skip;

                    if (i >= s->num_bands) {

                        av_log(s->avctx, AV_LOG_ERROR,

                               "invalid scale factor coding\n");

                        return AVERROR_INVALIDDATA;

                    }

                    s->channel[c].scale_factors[i] += (val ^ sign) - sign;

                }

            }

            /** swap buffers */

            s->channel[c].scale_factor_idx = !s->channel[c].scale_factor_idx;

            s->channel[c].table_idx = s->table_idx;

            s->channel[c].reuse_sf  = 1;

        }

        /** calculate new scale factor maximum */

        s->channel[c].max_scale_factor = s->channel[c].scale_factors[0];

        for (sf = s->channel[c].scale_factors + 1; sf < sf_end; sf++) {

            s->channel[c].max_scale_factor =

                FFMAX(s->channel[c].max_scale_factor, *sf);

        }

    }

    return 0;

}

/**

 *@brief Reconstruct the individual channel data.

 *@param s codec context

 */

static void inverse_channel_transform(WMAProDecodeCtx *s)

{

    int i;

    for (i = 0; i < s->num_chgroups; i++) {

        if (s->chgroup[i].transform) {

            float data[WMAPRO_MAX_CHANNELS];

            const int num_channels = s->chgroup[i].num_channels;

            float** ch_data = s->chgroup[i].channel_data;

            float** ch_end = ch_data + num_channels;

            const int8_t* tb = s->chgroup[i].transform_band;

            int16_t* sfb;

            /** multichannel decorrelation */

            for (sfb = s->cur_sfb_offsets;

                 sfb < s->cur_sfb_offsets + s->num_bands; sfb++) {

                int y;

                if (*tb++ == 1) {

                    /** multiply values with the decorrelation_matrix */

                    for (y = sfb[0]; y < FFMIN(sfb[1], s->subframe_len); y++) {

                        const float* mat = s->chgroup[i].decorrelation_matrix;

                        const float* data_end = data + num_channels;

                        float* data_ptr = data;

                        float** ch;

                        for (ch = ch_data; ch < ch_end; ch++)

                            *data_ptr++ = (*ch)[y];

                        for (ch = ch_data; ch < ch_end; ch++) {

                            float sum = 0;

                            data_ptr = data;

                            while (data_ptr < data_end)

                                sum += *data_ptr++ * *mat++;

                            (*ch)[y] = sum;

                        }

                    }

                } else if (s->num_channels == 2) {

                    int len = FFMIN(sfb[1], s->subframe_len) - sfb[0];

                    s->dsp.vector_fmul_scalar(ch_data[0] + sfb[0],

                                              ch_data[0] + sfb[0],

                                              181.0 / 128, len);

                    s->dsp.vector_fmul_scalar(ch_data[1] + sfb[0],

                                              ch_data[1] + sfb[0],

                                              181.0 / 128, len);

                }

            }

        }

    }

}

/**

 *@brief Apply sine window and reconstruct the output buffer.

 *@param s codec context

 */

static void wmapro_window(WMAProDecodeCtx *s)

{

    int i;

    for (i = 0; i < s->channels_for_cur_subframe; i++) {

        int c = s->channel_indexes_for_cur_subframe[i];

        float* window;

        int winlen = s->channel[c].prev_block_len;

        float* start = s->channel[c].coeffs - (winlen >> 1);

        if (s->subframe_len < winlen) {

            start += (winlen - s->subframe_len) >> 1;

            winlen = s->subframe_len;

        }

        window = s->windows[av_log2(winlen) - WMAPRO_BLOCK_MIN_BITS];

        winlen >>= 1;

        s->dsp.vector_fmul_window(start, start, start + winlen,

                                  window, 0, winlen);

        s->channel[c].prev_block_len = s->subframe_len;

    }

}

/**

 *@brief Decode a single subframe (block).

 *@param s codec context

 *@return 0 on success, < 0 when decoding failed

 */

static int decode_subframe(WMAProDecodeCtx *s)

{

    int offset = s->samples_per_frame;

    int subframe_len = s->samples_per_frame;

    int i;

    int total_samples   = s->samples_per_frame * s->num_channels;

    int transmit_coeffs = 0;

    int cur_subwoofer_cutoff;

    s->subframe_offset = get_bits_count(&s->gb);

    /** reset channel context and find the next block offset and size

        == the next block of the channel with the smallest number of

        decoded samples

    */

    for (i = 0; i < s->num_channels; i++) {

        s->channel[i].grouped = 0;

        if (offset > s->channel[i].decoded_samples) {

            offset = s->channel[i].decoded_samples;

            subframe_len =

                s->channel[i].subframe_len[s->channel[i].cur_subframe];

        }

    }

    dprintf(s->avctx,

            "processing subframe with offset %i len %i\n", offset, subframe_len);

    /** get a list of all channels that contain the estimated block */

    s->channels_for_cur_subframe = 0;

    for (i = 0; i < s->num_channels; i++) {

        const int cur_subframe = s->channel[i].cur_subframe;

        /** substract already processed samples */

        total_samples -= s->channel[i].decoded_samples;

        /** and count if there are multiple subframes that match our profile */

        if (offset == s->channel[i].decoded_samples &&

            subframe_len == s->channel[i].subframe_len[cur_subframe]) {

            total_samples -= s->channel[i].subframe_len[cur_subframe];

            s->channel[i].decoded_samples +=

                s->channel[i].subframe_len[cur_subframe];

            s->channel_indexes_for_cur_subframe[s->channels_for_cur_subframe] = i;

            ++s->channels_for_cur_subframe;

        }

    }

    /** check if the frame will be complete after processing the

        estimated block */

    if (!total_samples)

        s->parsed_all_subframes = 1;

    dprintf(s->avctx, "subframe is part of %i channels\n",

            s->channels_for_cur_subframe);

    /** calculate number of scale factor bands and their offsets */

    s->table_idx         = av_log2(s->samples_per_frame/subframe_len);

    s->num_bands         = s->num_sfb[s->table_idx];

    s->cur_sfb_offsets   = s->sfb_offsets[s->table_idx];

    cur_subwoofer_cutoff = s->subwoofer_cutoffs[s->table_idx];

    /** configure the decoder for the current subframe */

    for (i = 0; i < s->channels_for_cur_subframe; i++) {

        int c = s->channel_indexes_for_cur_subframe[i];

        s->channel[c].coeffs = &s->channel[c].out[(s->samples_per_frame >> 1)

                                                  + offset];

    }

    s->subframe_len = subframe_len;

    s->esc_len = av_log2(s->subframe_len - 1) + 1;

    /** skip extended header if any */

    if (get_bits1(&s->gb)) {

        int num_fill_bits;

        if (!(num_fill_bits = get_bits(&s->gb, 2))) {

            int len = get_bits(&s->gb, 4);

            num_fill_bits = get_bits(&s->gb, len) + 1;

        }

        if (num_fill_bits >= 0) {

            if (get_bits_count(&s->gb) + num_fill_bits > s->num_saved_bits) {

                av_log(s->avctx, AV_LOG_ERROR, "invalid number of fill bits\n");

                return AVERROR_INVALIDDATA;

            }

            skip_bits_long(&s->gb, num_fill_bits);

        }

    }

    /** no idea for what the following bit is used */

    if (get_bits1(&s->gb)) {

        av_log_ask_for_sample(s->avctx, "reserved bit set\n");

        return AVERROR_INVALIDDATA;

    }

    if (decode_channel_transform(s) < 0)

        return AVERROR_INVALIDDATA;

    for (i = 0; i < s->channels_for_cur_subframe; i++) {

        int c = s->channel_indexes_for_cur_subframe[i];

        if ((s->channel[c].transmit_coefs = get_bits1(&s->gb)))

            transmit_coeffs = 1;

    }

    if (transmit_coeffs) {

        int step;

        int quant_step = 90 * s->bits_per_sample >> 4;

        if ((get_bits1(&s->gb))) {

            /** FIXME: might change run level mode decision */

            av_log_ask_for_sample(s->avctx, "unsupported quant step coding\n");

            return AVERROR_INVALIDDATA;

        }

        /** decode quantization step */

        step = get_sbits(&s->gb, 6);

        quant_step += step;

        if (step == -32 || step == 31) {

            const int sign = (step == 31) - 1;

            int quant = 0;

            while (get_bits_count(&s->gb) + 5 < s->num_saved_bits &&

                   (step = get_bits(&s->gb, 5)) == 31) {

                quant += 31;

            }

            quant_step += ((quant + step) ^ sign) - sign;

        }

        if (quant_step < 0) {

            av_log(s->avctx, AV_LOG_DEBUG, "negative quant step\n");

        }

        /** decode quantization step modifiers for every channel */

        if (s->channels_for_cur_subframe == 1) {

            s->channel[s->channel_indexes_for_cur_subframe[0]].quant_step = quant_step;

        } else {

            int modifier_len = get_bits(&s->gb, 3);

            for (i = 0; i < s->channels_for_cur_subframe; i++) {

                int c = s->channel_indexes_for_cur_subframe[i];

                s->channel[c].quant_step = quant_step;

                if (get_bits1(&s->gb)) {

                    if (modifier_len) {

                        s->channel[c].quant_step += get_bits(&s->gb, modifier_len) + 1;

                    } else

                        ++s->channel[c].quant_step;

                }

            }

        }

        /** decode scale factors */

        if (decode_scale_factors(s) < 0)

            return AVERROR_INVALIDDATA;

    }

    dprintf(s->avctx, "BITSTREAM: subframe header length was %i\n",

            get_bits_count(&s->gb) - s->subframe_offset);

    /** parse coefficients */

    for (i = 0; i < s->channels_for_cur_subframe; i++) {

        int c = s->channel_indexes_for_cur_subframe[i];

        if (s->channel[c].transmit_coefs &&

            get_bits_count(&s->gb) < s->num_saved_bits) {

            decode_coeffs(s, c);

        } else

            memset(s->channel[c].coeffs, 0,

                   sizeof(*s->channel[c].coeffs) * subframe_len);

    }

    dprintf(s->avctx, "BITSTREAM: subframe length was %i\n",

            get_bits_count(&s->gb) - s->subframe_offset);

    if (transmit_coeffs) {

        /** reconstruct the per channel data */

        inverse_channel_transform(s);

        for (i = 0; i < s->channels_for_cur_subframe; i++) {

            int c = s->channel_indexes_for_cur_subframe[i];

            const int* sf = s->channel[c].scale_factors;

            int b;

            if (c == s->lfe_channel)

                memset(&s->tmp[cur_subwoofer_cutoff], 0, sizeof(*s->tmp) *

                       (subframe_len - cur_subwoofer_cutoff));

            /** inverse quantization and rescaling */

            for (b = 0; b < s->num_bands; b++) {

                const int end = FFMIN(s->cur_sfb_offsets[b+1], s->subframe_len);

                const int exp = s->channel[c].quant_step -

                            (s->channel[c].max_scale_factor - *sf++) *

                            s->channel[c].scale_factor_step;

                const float quant = pow(10.0, exp / 20.0);

                int start = s->cur_sfb_offsets[b];

                s->dsp.vector_fmul_scalar(s->tmp + start,

                                          s->channel[c].coeffs + start,

                                          quant, end - start);

            }

            /** apply imdct (ff_imdct_half == DCTIV with reverse) */

            ff_imdct_half(&s->mdct_ctx[av_log2(subframe_len) - WMAPRO_BLOCK_MIN_BITS],

                          s->channel[c].coeffs, s->tmp);

        }

    }

    /** window and overlapp-add */

    wmapro_window(s);

    /** handled one subframe */

    for (i = 0; i < s->channels_for_cur_subframe; i++) {

        int c = s->channel_indexes_for_cur_subframe[i];

        if (s->channel[c].cur_subframe >= s->channel[c].num_subframes) {

            av_log(s->avctx, AV_LOG_ERROR, "broken subframe\n");

            return AVERROR_INVALIDDATA;

        }

        ++s->channel[c].cur_subframe;

    }

    return 0;

}

/**

 *@brief Decode one WMA frame.

 *@param s codec context

 *@return 0 if the trailer bit indicates that this is the last frame,

 *        1 if there are additional frames

 */

static int decode_frame(WMAProDecodeCtx *s)

{

    GetBitContext* gb = &s->gb;

    int more_frames = 0;

    int len = 0;

    int i;

    /** check for potential output buffer overflow */

    if (s->num_channels * s->samples_per_frame > s->samples_end - s->samples) {

        /** return an error if no frame could be decoded at all */

        av_log(s->avctx, AV_LOG_ERROR,

               "not enough space for the output samples\n");

        s->packet_loss = 1;

        return 0;

    }

    /** get frame length */

    if (s->len_prefix)

        len = get_bits(gb, s->log2_frame_size);

    dprintf(s->avctx, "decoding frame with length %x\n", len);

    /** decode tile information */

    if (decode_tilehdr(s)) {

        s->packet_loss = 1;

        return 0;

    }

    /** read postproc transform */

    if (s->num_channels > 1 && get_bits1(gb)) {

        if (get_bits1(gb)) {

            for (i = 0; i < s->num_channels * s->num_channels; i++)

                skip_bits(gb, 4);

        }

    }

    /** read drc info */

    if (s->dynamic_range_compression) {

        s->drc_gain = get_bits(gb, 8);

        dprintf(s->avctx, "drc_gain %i\n", s->drc_gain);

    }

    /** no idea what these are for, might be the number of samples

        that need to be skipped at the beginning or end of a stream */

    if (get_bits1(gb)) {

        int skip;

        /** usually true for the first frame */

        if (get_bits1(gb)) {

            skip = get_bits(gb, av_log2(s->samples_per_frame * 2));

            dprintf(s->avctx, "start skip: %i\n", skip);

        }