ogg2.c

ffmpeg源码分析

/*
 * Ogg bitstream support
 * Luca Barbato <[e-mail]>
 * Based on tcvp implementation
 *
 */

/**
    Copyright (C) 2005  Michael Ahlberg, Måns Rullgård

    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation
    files (the "Software"), to deal in the Software without
    restriction, including without limitation the rights to use, copy,
    modify, merge, publish, distribute, sublicense, and/or sell copies
    of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
    HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
    WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
**/


#include <stdio.h>
#include "ogg2.h"
#include "avformat.h"

#define MAX_PAGE_SIZE 65307
#define DECODER_BUFFER_SIZE MAX_PAGE_SIZE

static ogg_codec_t *ogg_codecs[] = {
    &vorbis_codec,
    &theora_codec,
    &flac_codec,
    NULL
};

#if 0                           // CONFIG_MUXERS
static int
ogg_write_header (AVFormatContext * avfcontext)
{
}

static int
ogg_write_packet (AVFormatContext * avfcontext, AVPacket * pkt)
{
}


static int
ogg_write_trailer (AVFormatContext * avfcontext)
{
}


static AVOutputFormat ogg_oformat = {
    "ogg",
    "Ogg Vorbis",
    "audio/x-vorbis",
    "ogg",
    sizeof (OggContext),
    CODEC_ID_VORBIS,
    0,
    ogg_write_header,
    ogg_write_packet,
    ogg_write_trailer,
};
#endif //CONFIG_MUXERS

//FIXME We could avoid some structure duplication
static int
ogg_save (AVFormatContext * s)
{
    ogg_t *ogg = s->priv_data;
    ogg_state_t *ost =
        av_malloc(sizeof (*ost) + (ogg->nstreams-1) * sizeof (*ogg->streams));
    int i;
    ost->pos = url_ftell (&s->pb);;
    ost->curidx = ogg->curidx;
    ost->next = ogg->state;
    memcpy(ost->streams, ogg->streams, ogg->nstreams * sizeof(*ogg->streams));

    for (i = 0; i < ogg->nstreams; i++){
        ogg_stream_t *os = ogg->streams + i;
        os->buf = av_malloc (os->bufsize);
        memset (os->buf, 0, os->bufsize);
        memcpy (os->buf, ost->streams[i].buf, os->bufpos);
    }

    ogg->state = ost;

    return 0;
}

static int
ogg_restore (AVFormatContext * s, int discard)
{
    ogg_t *ogg = s->priv_data;
    ByteIOContext *bc = &s->pb;
    ogg_state_t *ost = ogg->state;
    int i;

    if (!ost)
        return 0;

    ogg->state = ost->next;

    if (!discard){
        for (i = 0; i < ogg->nstreams; i++)
            av_free (ogg->streams[i].buf);

        url_fseek (bc, ost->pos, SEEK_SET);
        ogg->curidx = ost->curidx;
        memcpy (ogg->streams, ost->streams,
        ogg->nstreams * sizeof (*ogg->streams));
    }

    av_free (ost);

    return 0;
}

static int
ogg_reset (ogg_t * ogg)
{
    int i;

    for (i = 0; i < ogg->nstreams; i++){
        ogg_stream_t *os = ogg->streams + i;
        os->bufpos = 0;
        os->pstart = 0;
        os->psize = 0;
        os->granule = -1;
        os->lastgp = -1;
        os->nsegs = 0;
        os->segp = 0;
    }

    ogg->curidx = -1;

    return 0;
}

static ogg_codec_t *
ogg_find_codec (uint8_t * buf, int size)
{
    int i;

    for (i = 0; ogg_codecs[i]; i++)
        if (size >= ogg_codecs[i]->magicsize &&
            !memcmp (buf, ogg_codecs[i]->magic, ogg_codecs[i]->magicsize))
            return ogg_codecs[i];

    return NULL;
}

static int
ogg_find_stream (ogg_t * ogg, int serial)
{
    int i;

    for (i = 0; i < ogg->nstreams; i++)
        if (ogg->streams[i].serial == serial)
            return i;

    return -1;
}

static int
ogg_new_stream (AVFormatContext * s, uint32_t serial)
{

    ogg_t *ogg = s->priv_data;
    int idx = ogg->nstreams++;
    AVStream *st;
    ogg_stream_t *os;

    ogg->streams = av_realloc (ogg->streams,
                               ogg->nstreams * sizeof (*ogg->streams));
    memset (ogg->streams + idx, 0, sizeof (*ogg->streams));
    os = ogg->streams + idx;
    os->serial = serial;
    os->bufsize = DECODER_BUFFER_SIZE;
    os->buf = av_malloc (os->bufsize);
    memset (os->buf, 0, os->bufsize);
    os->header = -1;

    st = av_new_stream (s, idx);
    if (!st)
        return AVERROR_NOMEM;

    av_set_pts_info(st, 64, 1, 1000000);
    st->start_time = 0;

    return idx;
}

static int
ogg_read_page (AVFormatContext * s, int *str)
{
    ByteIOContext *bc = &s->pb;
    ogg_t *ogg = s->priv_data;
    ogg_stream_t *os;
    int i = 0;
    int flags, nsegs;
    uint64_t gp;
    uint32_t serial;
    uint32_t seq;
    uint32_t crc;
    int size, idx;
    char sync[4];
    int sp = 0;

    if (get_buffer (bc, sync, 4) < 4)
        return -1;

    do{
        int c;

        if (sync[sp & 3] == 'O' &&
            sync[(sp + 1) & 3] == 'g' &&
            sync[(sp + 2) & 3] == 'g' && sync[(sp + 3) & 3] == 'S')
            break;

        c = url_fgetc (bc);
        if (c < 0)
            return -1;
        sync[sp++ & 3] = c;
    }while (i++ < MAX_PAGE_SIZE);

    if (i >= MAX_PAGE_SIZE){
        av_log (s, AV_LOG_INFO, "ogg, can't find sync word\n");
        return -1;
    }

    if (url_fgetc (bc) != 0)      /* version */
        return -1;

    flags = url_fgetc (bc);
    gp = get_le64 (bc);
    serial = get_le32 (bc);
    seq = get_le32 (bc);
    crc = get_le32 (bc);
    nsegs = url_fgetc (bc);

    idx = ogg_find_stream (ogg, serial);
    if (idx < 0){
        idx = ogg_new_stream (s, serial);
        if (idx < 0)
            return -1;
    }

    os = ogg->streams + idx;

    if (get_buffer (bc, os->segments, nsegs) < nsegs)
        return -1;

    os->nsegs = nsegs;
    os->segp = 0;

    size = 0;
    for (i = 0; i < nsegs; i++)
        size += os->segments[i];

    if (flags & OGG_FLAG_CONT){
        if (!os->psize){
            while (os->segp < os->nsegs){
                int seg = os->segments[os->segp++];
                os->pstart += seg;
                if (seg < 255)
                  break;
            }
        }
    }else{
      os->psize = 0;
    }

    if (os->bufsize - os->bufpos < size){
        uint8_t *nb = av_malloc (os->bufsize *= 2);
        memset (nb, 0, os->bufsize);
        memcpy (nb, os->buf, os->bufpos);
        av_free (os->buf);
        os->buf = nb;
    }

    if (get_buffer (bc, os->buf + os->bufpos, size) < size)
        return -1;

    os->lastgp = os->granule;
    os->bufpos += size;
    os->granule = gp;
    os->flags = flags;

    if (str)
        *str = idx;

    return 0;
}

static int
ogg_packet (AVFormatContext * s, int *str)
{
    ogg_t *ogg = s->priv_data;
    int idx;
    ogg_stream_t *os;
    int complete = 0;
    int segp = 0, psize = 0;

#if 0
    av_log (s, AV_LOG_DEBUG, "ogg_packet: curidx=%i\n", ogg->curidx);
#endif

    do{
        idx = ogg->curidx;

        while (idx < 0){
            if (ogg_read_page (s, &idx) < 0)
                return -1;
        }

        os = ogg->streams + idx;

#if 0
        av_log (s, AV_LOG_DEBUG,
                "ogg_packet: idx=%d pstart=%d psize=%d segp=%d nsegs=%d\n",
                idx, os->pstart, os->psize, os->segp, os->nsegs);
#endif

        if (!os->codec){
            if (os->header < 0){
                os->codec = ogg_find_codec (os->buf, os->bufpos);
                if (!os->codec){
                    os->header = 0;
                    return 0;
                }
            }else{
                return 0;
            }
        }

        segp = os->segp;
        psize = os->psize;

        while (os->segp < os->nsegs){
            int ss = os->segments[os->segp++];
            os->psize += ss;
            if (ss < 255){
                complete = 1;
                break;
            }
        }

        if (!complete && os->segp == os->nsegs){
            uint8_t *nb = av_malloc (os->bufsize);
            int size = os->bufpos - os->pstart;
            memset (nb, 0, os->bufsize);
            memcpy (nb, os->buf + os->pstart, size);
            av_free (os->buf);
            os->buf = nb;
            os->bufpos = size;
            os->pstart = 0;
            ogg->curidx = -1;
        }
    }while (!complete);

#if 0
    av_log (s, AV_LOG_DEBUG,
            "ogg_packet: idx %i, frame size %i, start %i\n",
            idx, os->psize, os->pstart);
#endif

    ogg->curidx = idx;

    if (os->header < 0){
        int hdr = os->codec->header (s, idx);
        if (!hdr){
          os->header = os->seq;
          os->segp = segp;
          os->psize = psize;
          ogg->headers = 1;
        }else{
          os->pstart += os->psize;
          os->psize = 0;
        }
    }

    if (os->header > -1 && os->seq > os->header){
        if (os->codec && os->codec->packet)
            os->codec->packet (s, idx);
        if (str)
            *str = idx;
    }

    os->seq++;
    if (os->segp == os->nsegs)
        ogg->curidx = -1;

    return 0;
}

static int
ogg_get_headers (AVFormatContext * s)
{
    ogg_t *ogg = s->priv_data;

    do{
        if (ogg_packet (s, NULL) < 0)
            return -1;
    }while (!ogg->headers);

#if 0
    av_log (s, AV_LOG_DEBUG, "found headers\n");
#endif

    return 0;
}

static uint64_t
ogg_gptopts (AVFormatContext * s, int i, uint64_t gp)
{
    ogg_t *ogg = s->priv_data;
    ogg_stream_t *os = ogg->streams + i;
    AVStream *st = s->streams[i];
    AVCodecContext *codec = st->codec;
    uint64_t pts = AV_NOPTS_VALUE;

    if(os->codec->gptopts){
        pts = os->codec->gptopts(s, i, gp);
    } else if (codec->codec_type == CODEC_TYPE_AUDIO){
        pts = gp * 1000000LL / codec->sample_rate;
    }else if (codec->codec_type == CODEC_TYPE_VIDEO){
        pts = gp;
    }

    return pts;
}


static int
ogg_get_length (AVFormatContext * s)
{
    ogg_t *ogg = s->priv_data;
    int idx = -1, i;

    if(s->pb.is_streamed)
        return 0;

// already set
    if (s->duration != AV_NOPTS_VALUE)
        return 0;

    ogg_save (s);
    url_fseek (&s->pb, -MAX_PAGE_SIZE, SEEK_END);

    while (!ogg_read_page (s, &i)){
        if (ogg->streams[i].granule != -1 && ogg->streams[i].granule != 0)
            idx = i;
    }

    if (idx != -1){
        s->streams[idx]->duration =
            ogg_gptopts (s, idx, ogg->streams[idx].granule);
    }

    ogg->size = url_fsize(&s->pb);
    ogg_restore (s, 0);

    return 0;
}


static int
ogg_read_header (AVFormatContext * s, AVFormatParameters * ap)
{
    ogg_t *ogg = s->priv_data;
    ogg->curidx = -1;
    //linear headers seek from start
    if (ogg_get_headers (s) < 0){
      return -1;
    }

    //linear granulepos seek from end
    ogg_get_length (s);

    //fill the extradata in the per codec callbacks
    return 0;
}


static int
ogg_read_packet (AVFormatContext * s, AVPacket * pkt)
{
    ogg_t *ogg;
    ogg_stream_t *os;
    int idx = -1;

    //Get an ogg packet
    do{
        if (ogg_packet (s, &idx) < 0)
            return AVERROR_IO;
    }while (idx < 0 || !s->streams[idx]);

    ogg = s->priv_data;
    os = ogg->streams + idx;

    //Alloc a pkt
    if (av_new_packet (pkt, os->psize) < 0)
        return AVERROR_IO;
    pkt->stream_index = idx;
    memcpy (pkt->data, os->buf + os->pstart, os->psize);
    if (os->lastgp != -1LL){
        pkt->pts = ogg_gptopts (s, idx, os->lastgp);
        os->lastgp = -1;
    }
    //next
    os->pstart += os->psize;
    os->psize = 0;
    return os->psize;
}


static int
ogg_read_close (AVFormatContext * s)
{
    ogg_t *ogg = s->priv_data;
    int i;

    for (i = 0; i < ogg->nstreams; i++){
        av_free (ogg->streams[i].buf);
        av_free (ogg->streams[i].private);
        av_freep (&s->streams[i]->codec->extradata);
    }
    av_free (ogg->streams);
    return 0;
}


static int
ogg_read_seek (AVFormatContext * s, int stream_index, int64_t target_ts,
               int flags)
{
    ogg_t *ogg = s->priv_data;
    ByteIOContext *bc = &s->pb;
    uint64_t min = 0, max = ogg->size;
    uint64_t tmin = 0, tmax = s->duration;
    int64_t pts = AV_NOPTS_VALUE;

    ogg_save (s);

    while (min <= max){
        uint64_t p = min + (max - min) * (target_ts - tmin) / (tmax - tmin);
        int i = -1;

        url_fseek (bc, p, SEEK_SET);

        while (!ogg_read_page (s, &i)){
            if (ogg->streams[i].granule != 0 && ogg->streams[i].granule != -1)
                break;
        }

        if (i == -1)
            break;

        pts = ogg_gptopts (s, i, ogg->streams[i].granule);
        p = url_ftell (bc);

        if (ABS (pts - target_ts) < 1000000LL)
            break;

        if (pts > target_ts){
            max = p;
            tmax = pts;
        }else{
            min = p;
            tmin = pts;
        }
    }

    if (ABS (pts - target_ts) < 1000000LL){
        ogg_restore (s, 1);
        ogg_reset (ogg);
    }else{
        ogg_restore (s, 0);
        pts = AV_NOPTS_VALUE;
    }

    return pts;

#if 0
    //later...
    int64_t pos;
    if (av_seek_frame_binary (s, stream_index, target_ts, flags) < 0)
        return -1;
    pos = url_ftell (&s->pb);
    ogg_read_timestamp (s, stream_index, &pos, pos - 1);
#endif

}

#if 0
static int64_t
ogg_read_timestamp (AVFormatContext * s, int stream_index, int64_t * pos_arg,
                    int64_t pos_limit)
{
    ogg_t *ogg = s->priv_data;
    ByteIOContext *bc = &s->pb;
    int64_t pos, pts;

    if (*pos_arg < 0)
        return AV_NOPTS_VALUE;

    pos = *pos_arg;
}
#endif

static int ogg_probe(AVProbeData *p)
{
    if (p->buf_size < 6)
        return 0;
    if (p->buf[0] == 'O' && p->buf[1] == 'g' &&
        p->buf[2] == 'g' && p->buf[3] == 'S' &&
        p->buf[4] == 0x0 && p->buf[5] <= 0x7 )
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

static AVInputFormat ogg_iformat = {
    "ogg",
    "Ogg",
    sizeof (ogg_t),
    ogg_probe,
    ogg_read_header,
    ogg_read_packet,
    ogg_read_close,
    ogg_read_seek,
// ogg_read_timestamp,
    .extensions = "ogg",
};

int
ogg_init (void)
{
#if 0 // CONFIG_MUXERS
    av_register_output_format (&ogg_oformat);
#endif
    av_register_input_format (&ogg_iformat);
    return 0;
}