mpc.c 6.54 KB
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/*
 * Musepack demuxer
 * Copyright (c) 2006 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 St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "avformat.h"
#include "bitstream.h"

#define MPC_FRAMESIZE  1152
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#define DELAY_FRAMES   32
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static const int mpc_rate[4] = { 44100, 48000, 37800, 32000 };
typedef struct {
    int64_t pos;
    int size, skip;
}MPCFrame;

typedef struct {
    int ver;
    uint32_t curframe, lastframe;
    uint32_t fcount;
    MPCFrame *frames;
    int curbits;
    int frames_noted;
} MPCContext;

static int mpc_probe(AVProbeData *p)
{
    const uint8_t *d = p->buf;
    if (d[0] == 'M' && d[1] == 'P' && d[2] == '+' && (d[3] == 0x17 || d[3] == 0x7))
        return AVPROBE_SCORE_MAX;
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    if (d[0] == 'I' && d[1] == 'D' && d[2] == '3')
        return AVPROBE_SCORE_MAX / 2;
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    return 0;
}

static int mpc_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    MPCContext *c = s->priv_data;
    AVStream *st;
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    int t;
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    t = get_le24(&s->pb);
    if(t != MKTAG('M', 'P', '+', 0)){
        if(t != MKTAG('I', 'D', '3', 0)){
            av_log(s, AV_LOG_ERROR, "Not a Musepack file\n");
            return -1;
        }
        /* skip ID3 tags and try again */
        url_fskip(&s->pb, 3);
        t  = get_byte(&s->pb) << 21;
        t |= get_byte(&s->pb) << 14;
        t |= get_byte(&s->pb) <<  7;
        t |= get_byte(&s->pb);
        av_log(s, AV_LOG_DEBUG, "Skipping %d(%X) bytes of ID3 data\n", t, t);
        url_fskip(&s->pb, t);
        if(get_le24(&s->pb) != MKTAG('M', 'P', '+', 0)){
            av_log(s, AV_LOG_ERROR, "Not a Musepack file\n");
            return -1;
        }
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    }
    c->ver = get_byte(&s->pb);
    if(c->ver != 0x07 && c->ver != 0x17){
        av_log(s, AV_LOG_ERROR, "Can demux Musepack SV7, got version %02X\n", c->ver);
        return -1;
    }
    c->fcount = get_le32(&s->pb);
    if((int64_t)c->fcount * sizeof(MPCFrame) >= UINT_MAX){
        av_log(s, AV_LOG_ERROR, "Too many frames, seeking is not possible\n");
        return -1;
    }
    c->frames = av_malloc(c->fcount * sizeof(MPCFrame));
    c->curframe = 0;
    c->lastframe = -1;
    c->curbits = 8;
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    c->frames_noted = 0;
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    st = av_new_stream(s, 0);
    if (!st)
        return AVERROR_NOMEM;
    st->codec->codec_type = CODEC_TYPE_AUDIO;
    st->codec->codec_id = CODEC_ID_MUSEPACK7;
    st->codec->channels = 2;
    st->codec->bits_per_sample = 16;

    st->codec->extradata_size = 16;
    st->codec->extradata = av_mallocz(st->codec->extradata_size+FF_INPUT_BUFFER_PADDING_SIZE);
    get_buffer(&s->pb, st->codec->extradata, 16);
    st->codec->sample_rate = mpc_rate[st->codec->extradata[2] & 3];
    av_set_pts_info(st, 32, MPC_FRAMESIZE, st->codec->sample_rate);
    /* scan for seekpoints */
    s->start_time = 0;
    s->duration = (int64_t)c->fcount * MPC_FRAMESIZE * AV_TIME_BASE / st->codec->sample_rate;

    return 0;
}

static int mpc_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    MPCContext *c = s->priv_data;
    int ret, size, size2, curbits, cur = c->curframe;
    int64_t tmp, pos;

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    if (c->curframe >= c->fcount)
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        return -1;

    if(c->curframe != c->lastframe + 1){
        url_fseek(&s->pb, c->frames[c->curframe].pos, SEEK_SET);
        c->curbits = c->frames[c->curframe].skip;
    }
    c->lastframe = c->curframe;
    c->curframe++;
    curbits = c->curbits;
    pos = url_ftell(&s->pb);
    tmp = get_le32(&s->pb);
    if(curbits <= 12){
        size2 = (tmp >> (12 - curbits)) & 0xFFFFF;
    }else{
        tmp = (tmp << 32) | get_le32(&s->pb);
        size2 = (tmp >> (44 - curbits)) & 0xFFFFF;
    }
    curbits += 20;
    url_fseek(&s->pb, pos, SEEK_SET);

    size = ((size2 + curbits + 31) & ~31) >> 3;
    if(cur == c->frames_noted){
        c->frames[cur].pos = pos;
        c->frames[cur].size = size;
        c->frames[cur].skip = curbits - 20;
        av_add_index_entry(s->streams[0], cur, cur, size, 0, AVINDEX_KEYFRAME);
        c->frames_noted++;
    }
    c->curbits = (curbits + size2) & 0x1F;

    if (av_new_packet(pkt, size) < 0)
        return AVERROR_IO;

    pkt->data[0] = curbits;
    pkt->data[1] = (c->curframe > c->fcount);

    pkt->stream_index = 0;
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    pkt->pts = cur;
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    ret = get_buffer(&s->pb, pkt->data + 4, size);
    if(c->curbits)
        url_fseek(&s->pb, -4, SEEK_CUR);
    if(ret < size){
        av_free_packet(pkt);
        return AVERROR_IO;
    }
    pkt->size = ret + 4;

    return 0;
}

static int mpc_read_close(AVFormatContext *s)
{
    MPCContext *c = s->priv_data;

    av_freep(&c->frames);
    return 0;
}

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/**
 * Seek to the given position
 * If position is unknown but is within the limits of file
 * then packets are skipped unless desired position is reached
 *
 * Also this function makes use of the fact that timestamp == frameno
 */
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static int mpc_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
{
    AVStream *st = s->streams[stream_index];
    MPCContext *c = s->priv_data;
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    AVPacket pkt1, *pkt = &pkt1;
    int ret;
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    int index = av_index_search_timestamp(st, timestamp - DELAY_FRAMES, flags);
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    uint32_t lastframe;
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    /* if found, seek there */
    if (index >= 0){
        c->curframe = st->index_entries[index].pos;
        return 0;
    }
    /* if timestamp is out of bounds, return error */
    if(timestamp < 0 || timestamp >= c->fcount)
        return -1;
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    timestamp -= DELAY_FRAMES;
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    /* seek to the furthest known position and read packets until
       we reach desired position */
    lastframe = c->curframe;
    if(c->frames_noted) c->curframe = c->frames_noted - 1;
    while(c->curframe < timestamp){
        ret = av_read_frame(s, pkt);
        if (ret < 0){
            c->curframe = lastframe;
            return -1;
        }
        av_free_packet(pkt);
    }
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    return 0;
}


AVInputFormat mpc_demuxer = {
    "mpc",
    "musepack",
    sizeof(MPCContext),
    mpc_probe,
    mpc_read_header,
    mpc_read_packet,
    mpc_read_close,
    mpc_read_seek,
    .extensions = "mpc",
};