PeerStreamer

/**

 * FLAC audio encoder

 * Copyright (c) 2006  Justin Ruggles <jruggle@earthlink.net>

 *

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

 *

 * This library 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 this library; if not, write to the Free Software

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

 */

#include "avcodec.h"

#include "bitstream.h"

#include "crc.h"

#include "golomb.h"

#define FLAC_MAX_CH  8

#define FLAC_MIN_BLOCKSIZE  16

#define FLAC_MAX_BLOCKSIZE  65535

#define FLAC_SUBFRAME_CONSTANT  0

#define FLAC_SUBFRAME_VERBATIM  1

#define FLAC_SUBFRAME_FIXED     8

#define FLAC_SUBFRAME_LPC      32

#define FLAC_CHMODE_NOT_STEREO      0

#define FLAC_CHMODE_LEFT_RIGHT      1

#define FLAC_CHMODE_LEFT_SIDE       8

#define FLAC_CHMODE_RIGHT_SIDE      9

#define FLAC_CHMODE_MID_SIDE       10

#define FLAC_STREAMINFO_SIZE  34

typedef struct FlacSubframe {

    int type;

    int type_code;

    int obits;

    int order;

    int32_t samples[FLAC_MAX_BLOCKSIZE];

    int32_t residual[FLAC_MAX_BLOCKSIZE];

} FlacSubframe;

typedef struct FlacFrame {

    FlacSubframe subframes[FLAC_MAX_CH];

    int blocksize;

    int bs_code[2];

    uint8_t crc8;

    int ch_mode;

} FlacFrame;

typedef struct FlacEncodeContext {

    PutBitContext pb;

    int channels;

    int ch_code;

    int samplerate;

    int sr_code[2];

    int blocksize;

    int max_framesize;

    uint32_t frame_count;

    FlacFrame frame;

} FlacEncodeContext;

static const int flac_samplerates[16] = {

    0, 0, 0, 0,

    8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000,

    0, 0, 0, 0

};

static const int flac_blocksizes[16] = {

    0,

    192,

    576, 1152, 2304, 4608,

    0, 0,

    256, 512, 1024, 2048, 4096, 8192, 16384, 32768

};

static const int flac_blocksizes_ordered[14] = {

    0, 192, 256, 512, 576, 1024, 1152, 2048, 2304, 4096, 4608, 8192, 16384, 32768

};

/**

 * Writes streaminfo metadata block to byte array

 */

static void write_streaminfo(FlacEncodeContext *s, uint8_t *header)

{

    PutBitContext pb;

    memset(header, 0, FLAC_STREAMINFO_SIZE);

    init_put_bits(&pb, header, FLAC_STREAMINFO_SIZE);

    /* streaminfo metadata block */

    put_bits(&pb, 16, s->blocksize);

    put_bits(&pb, 16, s->blocksize);

    put_bits(&pb, 24, 0);

    put_bits(&pb, 24, s->max_framesize);

    put_bits(&pb, 20, s->samplerate);

    put_bits(&pb, 3, s->channels-1);

    put_bits(&pb, 5, 15);       /* bits per sample - 1 */

    flush_put_bits(&pb);

    /* total samples = 0 */

    /* MD5 signature = 0 */

}

#define BLOCK_TIME_MS 105

/**

 * Sets blocksize based on samplerate

 * Chooses the closest predefined blocksize >= BLOCK_TIME_MS milliseconds

 */

static int select_blocksize(int samplerate)

{

    int i;

    int target;

    int blocksize;

    assert(samplerate > 0);

    blocksize = 0;

    target = (samplerate * BLOCK_TIME_MS) / 1000;

    for(i=13; i>=0; i--) {

        if(target >= flac_blocksizes_ordered[i]) {

            blocksize = flac_blocksizes_ordered[i];

            break;

        }

    }

    if(blocksize == 0) {

        blocksize = flac_blocksizes_ordered[1];

    }

    return blocksize;

}

static int flac_encode_init(AVCodecContext *avctx)

{

    int freq = avctx->sample_rate;

    int channels = avctx->channels;

    FlacEncodeContext *s = avctx->priv_data;

    int i;

    uint8_t *streaminfo;

    if(s == NULL) {

        return -1;

    }

    if(avctx->sample_fmt != SAMPLE_FMT_S16) {

        return -1;

    }

    if(channels < 1 || channels > FLAC_MAX_CH) {

        return -1;

    }

    s->channels = channels;

    s->ch_code = s->channels-1;

    /* find samplerate in table */

    if(freq < 1)

        return -1;

    for(i=4; i<12; i++) {

        if(freq == flac_samplerates[i]) {

            s->samplerate = flac_samplerates[i];

            s->sr_code[0] = i;

            s->sr_code[1] = 0;

            break;

        }

    }

    /* if not in table, samplerate is non-standard */

    if(i == 12) {

        if(freq % 1000 == 0 && freq < 255000) {

            s->sr_code[0] = 12;

            s->sr_code[1] = freq / 1000;

        } else if(freq % 10 == 0 && freq < 655350) {

            s->sr_code[0] = 14;

            s->sr_code[1] = freq / 10;

        } else if(freq < 65535) {

            s->sr_code[0] = 13;

            s->sr_code[1] = freq;

        } else {

            return -1;

        }

        s->samplerate = freq;

    }

    s->blocksize = select_blocksize(s->samplerate);

    avctx->frame_size = s->blocksize;

    s->max_framesize = 14 + (s->blocksize * s->channels * 2);

    streaminfo = av_malloc(FLAC_STREAMINFO_SIZE);

    write_streaminfo(s, streaminfo);

    avctx->extradata = streaminfo;

    avctx->extradata_size = FLAC_STREAMINFO_SIZE;

    s->frame_count = 0;

    avctx->coded_frame = avcodec_alloc_frame();

    avctx->coded_frame->key_frame = 1;

    return 0;

}

static int init_frame(FlacEncodeContext *s)

{

    int i, ch;

    FlacFrame *frame;

    frame = &s->frame;

    for(i=0; i<16; i++) {

        if(s->blocksize == flac_blocksizes[i]) {

            frame->blocksize = flac_blocksizes[i];

            frame->bs_code[0] = i;

            frame->bs_code[1] = 0;

            break;

        }

    }

    if(i == 16) {

        frame->blocksize = s->blocksize;

        if(frame->blocksize <= 256) {

            frame->bs_code[0] = 6;

            frame->bs_code[1] = frame->blocksize-1;

        } else {

            frame->bs_code[0] = 7;

            frame->bs_code[1] = frame->blocksize-1;

        }

    }

    for(ch=0; ch<s->channels; ch++) {

        frame->subframes[ch].obits = 16;

    }

    if(s->channels == 2) {

        frame->ch_mode = FLAC_CHMODE_LEFT_RIGHT;

    } else {

        frame->ch_mode = FLAC_CHMODE_NOT_STEREO;

    }

    return 0;

}

/**

 * Copy channel-interleaved input samples into separate subframes

 */

static void copy_samples(FlacEncodeContext *s, int16_t *samples)

{

    int i, j, ch;

    FlacFrame *frame;

    frame = &s->frame;

    for(i=0,j=0; i<frame->blocksize; i++) {

        for(ch=0; ch<s->channels; ch++,j++) {

            frame->subframes[ch].samples[i] = samples[j];

        }

    }

}

static void encode_residual_verbatim(FlacEncodeContext *s, int ch)

{

    FlacFrame *frame;

    FlacSubframe *sub;

    int32_t *res;

    int32_t *smp;

    int n;

    frame = &s->frame;

    sub = &frame->subframes[ch];

    res = sub->residual;

    smp = sub->samples;

    n = frame->blocksize;

    sub->order = 0;

    sub->type = FLAC_SUBFRAME_VERBATIM;

    sub->type_code = sub->type;

    memcpy(res, smp, n * sizeof(int32_t));

}

static void encode_residual_fixed(int32_t *res, int32_t *smp, int n, int order)

{

    int i;

    int32_t pred;

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

        res[i] = smp[i];

    }

    for(i=order; i<n; i++) {

        pred = 0;

        switch(order) {

            case 0: pred = 0;

                    break;

            case 1: pred = smp[i-1];

                    break;

            case 2: pred = 2*smp[i-1] - smp[i-2];

                    break;

            case 3: pred = 3*smp[i-1] - 3*smp[i-2] + smp[i-3];

                    break;

            case 4: pred = 4*smp[i-1] - 6*smp[i-2] + 4*smp[i-3] - smp[i-4];

                    break;

        }

        res[i] = smp[i] - pred;

    }

}

static void encode_residual(FlacEncodeContext *s, int ch)

{

    FlacFrame *frame;

    FlacSubframe *sub;

    int32_t *res;

    int32_t *smp;

    int n;

    frame = &s->frame;

    sub = &frame->subframes[ch];

    res = sub->residual;

    smp = sub->samples;

    n = frame->blocksize;

    sub->order = 2;

    sub->type = FLAC_SUBFRAME_FIXED;

    sub->type_code = sub->type | sub->order;

    encode_residual_fixed(res, smp, n, sub->order);

}

static void

put_sbits(PutBitContext *pb, int bits, int32_t val)

{

    uint32_t uval;

    assert(bits >= 0 && bits <= 31);

    uval = (val < 0) ? (1UL << bits) + val : val;

    put_bits(pb, bits, uval);

}

static void

write_utf8(PutBitContext *pb, uint32_t val)

{

    int i, bytes, mask, shift;

    bytes = 1;

    if(val >= 0x80)      bytes++;

    if(val >= 0x800)     bytes++;

    if(val >= 0x10000)   bytes++;

    if(val >= 0x200000)  bytes++;

    if(val >= 0x4000000) bytes++;

    if(bytes == 1) {

        put_bits(pb, 8, val);

        return;

    }

    shift = (bytes - 1) * 6;

    mask = 0x80 + ((1 << 7) - (1 << (8 - bytes)));

    put_bits(pb, 8, mask | (val >> shift));

    for(i=0; i<bytes-1; i++) {

        shift -= 6;

        put_bits(pb, 8, 0x80 | ((val >> shift) & 0x3F));

    }

}

static void

output_frame_header(FlacEncodeContext *s)

{

    FlacFrame *frame;

    int crc;

    frame = &s->frame;

    put_bits(&s->pb, 16, 0xFFF8);

    put_bits(&s->pb, 4, frame->bs_code[0]);

    put_bits(&s->pb, 4, s->sr_code[0]);

    if(frame->ch_mode == FLAC_CHMODE_NOT_STEREO) {

        put_bits(&s->pb, 4, s->ch_code);

    } else {

        put_bits(&s->pb, 4, frame->ch_mode);

    }

    put_bits(&s->pb, 3, 4); /* bits-per-sample code */

    put_bits(&s->pb, 1, 0);

    write_utf8(&s->pb, s->frame_count);

    if(frame->bs_code[1] > 0) {

        if(frame->bs_code[1] < 256) {

            put_bits(&s->pb, 8, frame->bs_code[1]);

        } else {

            put_bits(&s->pb, 16, frame->bs_code[1]);

        }

    }

    if(s->sr_code[1] > 0) {

        if(s->sr_code[1] < 256) {

            put_bits(&s->pb, 8, s->sr_code[1]);

        } else {

            put_bits(&s->pb, 16, s->sr_code[1]);

        }

    }

    flush_put_bits(&s->pb);

    crc = av_crc(av_crc07, 0, s->pb.buf, put_bits_count(&s->pb)>>3);

    put_bits(&s->pb, 8, crc);

}

static void output_subframe_verbatim(FlacEncodeContext *s, int ch)

{

    int i;

    FlacFrame *frame;

    FlacSubframe *sub;

    int32_t res;

    frame = &s->frame;

    sub = &frame->subframes[ch];

    for(i=0; i<frame->blocksize; i++) {

        res = sub->residual[i];

        put_sbits(&s->pb, sub->obits, res);

    }

}

static void

output_residual(FlacEncodeContext *ctx, int ch)

{

    int i, j, p;

    int k, porder, psize, res_cnt;

    FlacFrame *frame;

    FlacSubframe *sub;

    frame = &ctx->frame;

    sub = &frame->subframes[ch];

    /* rice-encoded block */

    put_bits(&ctx->pb, 2, 0);

    /* partition order */

    porder = 0;

    psize = frame->blocksize;

    //porder = sub->rc.porder;

    //psize = frame->blocksize >> porder;

    put_bits(&ctx->pb, 4, porder);

    res_cnt = psize - sub->order;

    /* residual */

    j = sub->order;

    for(p=0; p<(1 << porder); p++) {

        //k = sub->rc.params[p];

        k = 9;

        put_bits(&ctx->pb, 4, k);

        if(p == 1) res_cnt = psize;

        for(i=0; i<res_cnt && j<frame->blocksize; i++, j++) {

            set_sr_golomb_flac(&ctx->pb, sub->residual[j], k, INT32_MAX, 0);

        }

    }

}

static void

output_subframe_fixed(FlacEncodeContext *ctx, int ch)

{

    int i;

    FlacFrame *frame;

    FlacSubframe *sub;

    frame = &ctx->frame;

    sub = &frame->subframes[ch];

    /* warm-up samples */

    for(i=0; i<sub->order; i++) {

        put_sbits(&ctx->pb, sub->obits, sub->residual[i]);

    }

    /* residual */

    output_residual(ctx, ch);

}

static void output_subframes(FlacEncodeContext *s)

{

    FlacFrame *frame;

    FlacSubframe *sub;

    int ch;

    frame = &s->frame;

    for(ch=0; ch<s->channels; ch++) {

        sub = &frame->subframes[ch];

        /* subframe header */

        put_bits(&s->pb, 1, 0);

        put_bits(&s->pb, 6, sub->type_code);

        put_bits(&s->pb, 1, 0); /* no wasted bits */

        /* subframe */

        if(sub->type == FLAC_SUBFRAME_VERBATIM) {

            output_subframe_verbatim(s, ch);

        } else {

            output_subframe_fixed(s, ch);

        }

    }

}

static void output_frame_footer(FlacEncodeContext *s)

{

    int crc;

    flush_put_bits(&s->pb);

    crc = bswap_16(av_crc(av_crc8005, 0, s->pb.buf, put_bits_count(&s->pb)>>3));

    put_bits(&s->pb, 16, crc);

    flush_put_bits(&s->pb);

}

static int flac_encode_frame(AVCodecContext *avctx, uint8_t *frame,

                             int buf_size, void *data)

{

    int ch;

    FlacEncodeContext *s;

    int16_t *samples = data;

    int out_bytes;

    s = avctx->priv_data;

    s->blocksize = avctx->frame_size;

    if(init_frame(s)) {

        return 0;

    }

    copy_samples(s, samples);

    for(ch=0; ch<s->channels; ch++) {

        encode_residual(s, ch);

    }

    init_put_bits(&s->pb, frame, buf_size);

    output_frame_header(s);

    output_subframes(s);

    output_frame_footer(s);

    out_bytes = put_bits_count(&s->pb) >> 3;

    if(out_bytes > s->max_framesize || out_bytes >= buf_size) {

        /* frame too large. use verbatim mode */

        for(ch=0; ch<s->channels; ch++) {

            encode_residual_verbatim(s, ch);

        }

        init_put_bits(&s->pb, frame, buf_size);

        output_frame_header(s);

        output_subframes(s);

        output_frame_footer(s);

        out_bytes = put_bits_count(&s->pb) >> 3;

        if(out_bytes > s->max_framesize || out_bytes >= buf_size) {

            /* still too large. must be an error. */

            av_log(avctx, AV_LOG_ERROR, "error encoding frame\n");

            return -1;

        }

    }

    s->frame_count++;

    return out_bytes;

}

static int flac_encode_close(AVCodecContext *avctx)

{

    av_freep(&avctx->coded_frame);

    return 0;

}

AVCodec flac_encoder = {

    "flac",

    CODEC_TYPE_AUDIO,

    CODEC_ID_FLAC,

    sizeof(FlacEncodeContext),

    flac_encode_init,

    flac_encode_frame,

    flac_encode_close,

    NULL,

    .capabilities = CODEC_CAP_SMALL_LAST_FRAME,

};