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 RiceContext {

    int porder;

    int params[256];

} RiceContext;

typedef struct FlacSubframe {

    int type;

    int type_code;

    int obits;

    int order;

    RiceContext rc;

    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;

    AVCodecContext *avctx;

} 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

};

/**

 * 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 27

/**

 * 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 = flac_blocksizes[1];

    target = (samplerate * BLOCK_TIME_MS) / 1000;

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

        if(target >= flac_blocksizes[i] && flac_blocksizes[i] > blocksize) {

            blocksize = flac_blocksizes[i];

        }

    }

    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;

    s->avctx = avctx;

    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;

    /* set maximum encoded frame size in verbatim mode */

    if(s->channels == 2) {

        s->max_framesize = 14 + ((s->blocksize * 33 + 7) >> 3);

    } else {

        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 void 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;

    }

}

/**

 * 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];

        }

    }

}

#define rice_encode_count(sum, n, k) (((n)*((k)+1))+((sum-(n>>1))>>(k)))

static int find_optimal_param(uint32_t sum, int n)

{

    int k, k_opt;

    uint32_t nbits, nbits_opt;

    k_opt = 0;

    nbits_opt = rice_encode_count(sum, n, 0);

    for(k=1; k<=14; k++) {

        nbits = rice_encode_count(sum, n, k);

        if(nbits < nbits_opt) {

            nbits_opt = nbits;

            k_opt = k;

        }

    }

    return k_opt;

}

static uint32_t calc_optimal_rice_params(RiceContext *rc, int porder,

                                         uint32_t *sums, int n, int pred_order)

{

    int i;

    int k, cnt, part;

    uint32_t all_bits;

    part = (1 << porder);

    all_bits = 0;

    cnt = (n >> porder) - pred_order;

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

        if(i == 1) cnt = (n >> porder);

        k = find_optimal_param(sums[i], cnt);

        rc->params[i] = k;

        all_bits += rice_encode_count(sums[i], cnt, k);

    }

    all_bits += (4 * part);

    rc->porder = porder;

    return all_bits;

}

static void calc_sums(int pmax, uint32_t *data, int n, int pred_order,

                      uint32_t sums[][256])

{

    int i, j;

    int parts, cnt;

    uint32_t *res;

    /* sums for highest level */

    parts = (1 << pmax);

    res = &data[pred_order];

    cnt = (n >> pmax) - pred_order;

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

        if(i == 1) cnt = (n >> pmax);

        if(i > 0) res = &data[i*cnt];

        sums[pmax][i] = 0;

        for(j=0; j<cnt; j++) {

            sums[pmax][i] += res[j];

        }

    }

    /* sums for lower levels */

    for(i=pmax-1; i>=0; i--) {

        parts = (1 << i);

        for(j=0; j<parts; j++) {

            sums[i][j] = sums[i+1][2*j] + sums[i+1][2*j+1];

        }

    }

}

static uint32_t calc_rice_params(RiceContext *rc, int pmax, int32_t *data,

                                 int n, int pred_order)

{

    int i;

    uint32_t bits, opt_bits;

    int opt_porder;

    RiceContext opt_rc;

    uint32_t *udata;

    uint32_t sums[9][256];

    assert(pmax >= 0 && pmax <= 8);

    udata = av_malloc(n * sizeof(uint32_t));

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

        udata[i] = (2*data[i]) ^ (data[i]>>31);

    }

    calc_sums(pmax, udata, n, pred_order, sums);

    opt_porder = 0;

    opt_bits = UINT32_MAX;

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

        bits = calc_optimal_rice_params(rc, i, sums[i], n, pred_order);

        if(bits < opt_bits) {

            opt_bits = bits;

            opt_porder = i;

            memcpy(&opt_rc, rc, sizeof(RiceContext));

        }

    }

    if(opt_porder != pmax) {

        memcpy(rc, &opt_rc, sizeof(RiceContext));

    }

    av_freep(&udata);

    return opt_bits;

}

static uint32_t calc_rice_params_fixed(RiceContext *rc, int pmax, int32_t *data,

                                       int n, int pred_order, int bps)

{

    uint32_t bits;

    bits = pred_order*bps + 6;

    bits += calc_rice_params(rc, pmax, data, n, pred_order);

    return bits;

}

static void encode_residual_verbatim(int32_t *res, int32_t *smp, int n)

{

    assert(n > 0);

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

}

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

{

    int i;

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

        res[i] = smp[i];

    }

    if(order==0){

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

            res[i]= smp[i];

    }else if(order==1){

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

            res[i]= smp[i] - smp[i-1];

    }else if(order==2){

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

            res[i]= smp[i] - 2*smp[i-1] + smp[i-2];

    }else if(order==3){

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

            res[i]= smp[i] - 3*smp[i-1] + 3*smp[i-2] - smp[i-3];

    }else{

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

            res[i]= smp[i] - 4*smp[i-1] + 6*smp[i-2] - 4*smp[i-3] + smp[i-4];

    }

}

static int get_max_p_order(int max_porder, int n, int order)

{

    int porder, max_parts;

    porder = max_porder;

    while(porder > 0) {

        max_parts = (1 << porder);

        if(!(n % max_parts) && (n > max_parts*order)) {

            break;

        }

        porder--;

    }

    return porder;

}

static int encode_residual(FlacEncodeContext *ctx, int ch)

{

    int i, opt_order, porder, max_porder, n;

    FlacFrame *frame;

    FlacSubframe *sub;

    uint32_t bits[5];

    int32_t *res, *smp;

    frame = &ctx->frame;

    sub = &frame->subframes[ch];

    res = sub->residual;

    smp = sub->samples;

    n = frame->blocksize;

    /* CONSTANT */

    for(i=1; i<n; i++) {

        if(smp[i] != smp[0]) break;

    }

    if(i == n) {

        sub->type = sub->type_code = FLAC_SUBFRAME_CONSTANT;

        res[0] = smp[0];

        return sub->obits;

    }

    /* VERBATIM */

    if(n < 5) {

        sub->type = sub->type_code = FLAC_SUBFRAME_VERBATIM;

        encode_residual_verbatim(res, smp, n);

        return sub->obits * n;

    }

    max_porder = 3;

    /* FIXED */

    opt_order = 0;

    bits[0] = UINT32_MAX;

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

        encode_residual_fixed(res, smp, n, i);

        porder = get_max_p_order(max_porder, n, i);

        bits[i] = calc_rice_params_fixed(&sub->rc, porder, res, n, i, sub->obits);

        if(bits[i] < bits[opt_order]) {

            opt_order = i;

        }

    }

    sub->order = opt_order;

    sub->type = FLAC_SUBFRAME_FIXED;

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

    if(sub->order != 4) {

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

        porder = get_max_p_order(max_porder, n, sub->order);

        calc_rice_params_fixed(&sub->rc, porder, res, n, sub->order, sub->obits);

    }

    return bits[sub->order];

}

static int encode_residual_v(FlacEncodeContext *ctx, int ch)

{

    int i, n;

    FlacFrame *frame;

    FlacSubframe *sub;

    int32_t *res, *smp;

    frame = &ctx->frame;

    sub = &frame->subframes[ch];

    res = sub->residual;

    smp = sub->samples;

    n = frame->blocksize;

    /* CONSTANT */

    for(i=1; i<n; i++) {

        if(smp[i] != smp[0]) break;

    }

    if(i == n) {

        sub->type = sub->type_code = FLAC_SUBFRAME_CONSTANT;

        res[0] = smp[0];

        return sub->obits;

    }

    /* VERBATIM */

    sub->type = sub->type_code = FLAC_SUBFRAME_VERBATIM;

    encode_residual_verbatim(res, smp, n);

    return sub->obits * n;

}

static int estimate_stereo_mode(int32_t *left_ch, int32_t *right_ch, int n)

{

    int i, best;

    int32_t lt, rt;

    uint64_t sum[4];

    uint64_t score[4];

    int k;

    /* calculate sum of squares for each channel */

    sum[0] = sum[1] = sum[2] = sum[3] = 0;

    for(i=2; i<n; i++) {

        lt = left_ch[i] - 2*left_ch[i-1] + left_ch[i-2];

        rt = right_ch[i] - 2*right_ch[i-1] + right_ch[i-2];

        sum[2] += ABS((lt + rt) >> 1);

        sum[3] += ABS(lt - rt);

        sum[0] += ABS(lt);

        sum[1] += ABS(rt);

    }

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

        k = find_optimal_param(2*sum[i], n);

        sum[i] = rice_encode_count(2*sum[i], n, k);

    }

    /* calculate score for each mode */

    score[0] = sum[0] + sum[1];

    score[1] = sum[0] + sum[3];

    score[2] = sum[1] + sum[3];

    score[3] = sum[2] + sum[3];

    /* return mode with lowest score */

    best = 0;

    for(i=1; i<4; i++) {

        if(score[i] < score[best]) {

            best = i;

        }

    }

    if(best == 0) {

        return FLAC_CHMODE_LEFT_RIGHT;

    } else if(best == 1) {

        return FLAC_CHMODE_LEFT_SIDE;

    } else if(best == 2) {

        return FLAC_CHMODE_RIGHT_SIDE;

    } else {

        return FLAC_CHMODE_MID_SIDE;

    }

}

/**

 * Perform stereo channel decorrelation

 */

static void channel_decorrelation(FlacEncodeContext *ctx)

{

    FlacFrame *frame;

    int32_t *left, *right;

    int i, n;

    frame = &ctx->frame;

    n = frame->blocksize;

    left  = frame->subframes[0].samples;

    right = frame->subframes[1].samples;

    if(ctx->channels != 2) {

        frame->ch_mode = FLAC_CHMODE_NOT_STEREO;

        return;

    }

    frame->ch_mode = estimate_stereo_mode(left, right, n);

    /* perform decorrelation and adjust bits-per-sample */

    if(frame->ch_mode == FLAC_CHMODE_LEFT_RIGHT) {

        return;

    }

    if(frame->ch_mode == FLAC_CHMODE_MID_SIDE) {

        int32_t tmp;

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

            tmp = left[i];

            left[i] = (tmp + right[i]) >> 1;

            right[i] = tmp - right[i];

        }

        frame->subframes[1].obits++;

    } else if(frame->ch_mode == FLAC_CHMODE_LEFT_SIDE) {

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

            right[i] = left[i] - right[i];

        }

        frame->subframes[1].obits++;

    } else {

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

            left[i] -= right[i];

        }

        frame->subframes[0].obits++;

    }

}

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

{

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

    put_bits(pb, bits, val & ((1<<bits)-1));

}

static void write_utf8(PutBitContext *pb, uint32_t val)

{

    int bytes, shift;

    if(val < 0x80){

        put_bits(pb, 8, val);

        return;

    }

    bytes= (av_log2(val)+4) / 5;

    shift = (bytes - 1) * 6;

    put_bits(pb, 8, (256 - (256>>bytes)) | (val >> shift));

    while(shift >= 6){

        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[0] == 6) {

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

    } else if(frame->bs_code[0] == 7) {

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

    }

    if(s->sr_code[0] == 12) {

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

    } else if(s->sr_code[0] > 12) {

        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_constant(FlacEncodeContext *s, int ch)

{

    FlacSubframe *sub;

    int32_t res;

    sub = &s->frame.subframes[ch];

    res = sub->residual[0];

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

}

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, n, parts;

    int k, porder, psize, res_cnt;

    FlacFrame *frame;

    FlacSubframe *sub;

    int32_t *res;

    frame = &ctx->frame;

    sub = &frame->subframes[ch];

    res = sub->residual;

    n = frame->blocksize;

    /* rice-encoded block */

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

    /* partition order */

    porder = sub->rc.porder;

    psize = n >> porder;

    parts = (1 << porder);

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

    res_cnt = psize - sub->order;

    /* residual */

    j = sub->order;

    for(p=0; p<parts; p++) {

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

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

        if(p == 1) res_cnt = psize;

        for(i=0; i<res_cnt && j<n; i++, j++) {

            set_sr_golomb_flac(&ctx->pb, res[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_CONSTANT) {

            output_subframe_constant(s, ch);

        } else if(sub->type == FLAC_SUBFRAME_VERBATIM) {

            output_subframe_verbatim(s, ch);

        } else if(sub->type == FLAC_SUBFRAME_FIXED) {

            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;

    init_frame(s);

    copy_samples(s, samples);

    channel_decorrelation(s);

    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_v(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->extradata);

    avctx->extradata_size = 0;

    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,

};