PeerStreamer

/*

 * Musepack SV8 demuxer

 * Copyright (c) 2007 Konstantin Shishkov

 *

 * 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

 */

#include "libavcodec/get_bits.h"

#include "libavcodec/unary.h"

#include "avformat.h"

/// Two-byte MPC tag

#define MKMPCTAG(a, b) (a | (b << 8))

#define TAG_MPCK MKTAG('M','P','C','K')

/// Reserved MPC tags

enum MPCPacketTags{

    TAG_STREAMHDR   = MKMPCTAG('S','H'),

    TAG_STREAMEND   = MKMPCTAG('S','E'),

    TAG_AUDIOPACKET = MKMPCTAG('A','P'),

    TAG_SEEKTBLOFF  = MKMPCTAG('S','O'),

    TAG_SEEKTABLE   = MKMPCTAG('S','T'),

    TAG_REPLAYGAIN  = MKMPCTAG('R','G'),

    TAG_ENCINFO     = MKMPCTAG('E','I'),

};

static const int mpc8_rate[8] = { 44100, 48000, 37800, 32000, -1, -1, -1, -1 };

typedef struct {

    int ver;

    int frame;

    int64_t header_pos;

    int64_t samples;

} MPCContext;

static inline int64_t bs_get_v(uint8_t **bs)

{

    int64_t v = 0;

    int br = 0;

    int c;

    do {

        c = **bs; (*bs)++;

        v <<= 7;

        v |= c & 0x7F;

        br++;

        if (br > 10)

            return -1;

    } while (c & 0x80);

    return v - br;

}

static int mpc8_probe(AVProbeData *p)

{

    uint8_t *bs = p->buf + 4;

    uint8_t *bs_end = bs + p->buf_size;

    int64_t size;

    if (p->buf_size < 16)

        return 0;

    if (AV_RL32(p->buf) != TAG_MPCK)

        return 0;

    while (bs < bs_end + 3) {

        int header_found = (bs[0] == 'S' && bs[1] == 'H');

        if (bs[0] < 'A' || bs[0] > 'Z' || bs[1] < 'A' || bs[1] > 'Z')

            return 0;

        bs += 2;

        size = bs_get_v(&bs);

        if (size < 2)

            return 0;

        if (bs + size - 2 >= bs_end)

            return AVPROBE_SCORE_MAX / 4 - 1; //seems to be valid MPC but no header yet

        if (header_found) {

            if (size < 11 || size > 28)

                return 0;

            if (!AV_RL32(bs)) //zero CRC is invalid

                return 0;

            return AVPROBE_SCORE_MAX;

        } else {

            bs += size - 2;

        }

    }

    return 0;

}

static inline int64_t gb_get_v(GetBitContext *gb)

{

    int64_t v = 0;

    int bits = 0;

    while(get_bits1(gb) && bits < 64-7){

        v <<= 7;

        v |= get_bits(gb, 7);

        bits += 7;

    }

    v <<= 7;

    v |= get_bits(gb, 7);

    return v;

}

static void mpc8_get_chunk_header(AVIOContext *pb, int *tag, int64_t *size)

{

    int64_t pos;

    pos = avio_tell(pb);

    *tag = avio_rl16(pb);

    *size = ff_get_v(pb);

    *size -= avio_tell(pb) - pos;

}

static void mpc8_parse_seektable(AVFormatContext *s, int64_t off)

{

    MPCContext *c = s->priv_data;

    int tag;

    int64_t size, pos, ppos[2];

    uint8_t *buf;

    int i, t, seekd;

    GetBitContext gb;

    avio_seek(s->pb, off, SEEK_SET);

    mpc8_get_chunk_header(s->pb, &tag, &size);

    if(tag != TAG_SEEKTABLE){

        av_log(s, AV_LOG_ERROR, "No seek table at given position\n");

        return;

    }

    if(!(buf = av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE)))

        return;

    avio_read(s->pb, buf, size);

    init_get_bits(&gb, buf, size * 8);

    size = gb_get_v(&gb);

    if(size > UINT_MAX/4 || size > c->samples/1152){

        av_log(s, AV_LOG_ERROR, "Seek table is too big\n");

        return;

    }

    seekd = get_bits(&gb, 4);

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

        pos = gb_get_v(&gb) + c->header_pos;

        ppos[1 - i] = pos;

        av_add_index_entry(s->streams[0], pos, i, 0, 0, AVINDEX_KEYFRAME);

    }

    for(; i < size; i++){

        t = get_unary(&gb, 1, 33) << 12;

        t += get_bits(&gb, 12);

        if(t & 1)

            t = -(t & ~1);

        pos = (t >> 1) + ppos[0]*2 - ppos[1];

        av_add_index_entry(s->streams[0], pos, i << seekd, 0, 0, AVINDEX_KEYFRAME);

        ppos[1] = ppos[0];

        ppos[0] = pos;

    }

    av_free(buf);

}

static void mpc8_handle_chunk(AVFormatContext *s, int tag, int64_t chunk_pos, int64_t size)

{

    AVIOContext *pb = s->pb;

    int64_t pos, off;

    switch(tag){

    case TAG_SEEKTBLOFF:

        pos = avio_tell(pb) + size;

        off = ff_get_v(pb);

        mpc8_parse_seektable(s, chunk_pos + off);

        avio_seek(pb, pos, SEEK_SET);

        break;

    default:

        avio_seek(pb, size, SEEK_CUR);

    }

}

static int mpc8_read_header(AVFormatContext *s, AVFormatParameters *ap)

{

    MPCContext *c = s->priv_data;

    AVIOContext *pb = s->pb;

    AVStream *st;

    int tag = 0;

    int64_t size, pos;

    c->header_pos = avio_tell(pb);

    if(avio_rl32(pb) != TAG_MPCK){

        av_log(s, AV_LOG_ERROR, "Not a Musepack8 file\n");

        return -1;

    }

    while(!url_feof(pb)){

        pos = avio_tell(pb);

        mpc8_get_chunk_header(pb, &tag, &size);

        if(tag == TAG_STREAMHDR)

            break;

        mpc8_handle_chunk(s, tag, pos, size);

    }

    if(tag != TAG_STREAMHDR){

        av_log(s, AV_LOG_ERROR, "Stream header not found\n");

        return -1;

    }

    pos = avio_tell(pb);

    avio_seek(pb, 4, SEEK_CUR); //CRC

    c->ver = avio_r8(pb);

    if(c->ver != 8){

        av_log(s, AV_LOG_ERROR, "Unknown stream version %d\n", c->ver);

        return -1;

    }

    c->samples = ff_get_v(pb);

    ff_get_v(pb); //silence samples at the beginning

    st = av_new_stream(s, 0);

    if (!st)

        return AVERROR(ENOMEM);

    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;

    st->codec->codec_id = CODEC_ID_MUSEPACK8;

    st->codec->bits_per_coded_sample = 16;

    st->codec->extradata_size = 2;

    st->codec->extradata = av_mallocz(st->codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);

    avio_read(pb, st->codec->extradata, st->codec->extradata_size);

    st->codec->channels = (st->codec->extradata[1] >> 4) + 1;

    st->codec->sample_rate = mpc8_rate[st->codec->extradata[0] >> 5];

    av_set_pts_info(st, 32, 1152  << (st->codec->extradata[1]&3)*2, st->codec->sample_rate);

    st->duration = c->samples / (1152 << (st->codec->extradata[1]&3)*2);

    size -= avio_tell(pb) - pos;

    return 0;

}

static int mpc8_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    MPCContext *c = s->priv_data;

    int tag;

    int64_t pos, size;

    while(!url_feof(s->pb)){

        pos = avio_tell(s->pb);

        mpc8_get_chunk_header(s->pb, &tag, &size);

        if (size < 0)

            return -1;

        if(tag == TAG_AUDIOPACKET){

            if(av_get_packet(s->pb, pkt, size) < 0)

                return AVERROR(ENOMEM);

            pkt->stream_index = 0;

            pkt->pts = c->frame;

            return 0;

        }

        if(tag == TAG_STREAMEND)

            return AVERROR(EIO);

        mpc8_handle_chunk(s, tag, pos, size);

    }

    return 0;

}

static int mpc8_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)

{

    AVStream *st = s->streams[stream_index];

    MPCContext *c = s->priv_data;

    int index = av_index_search_timestamp(st, timestamp, flags);

    if(index < 0) return -1;

    avio_seek(s->pb, st->index_entries[index].pos, SEEK_SET);

    c->frame = st->index_entries[index].timestamp;

    return 0;

}

AVInputFormat ff_mpc8_demuxer = {

    "mpc8",

    NULL_IF_CONFIG_SMALL("Musepack SV8"),

    sizeof(MPCContext),

    mpc8_probe,

    mpc8_read_header,

    mpc8_read_packet,

    NULL,

    mpc8_read_seek,

};