ogg.c

ffmpeg源码分析

/*
 * Ogg bitstream support
 * Mark Hills <[e-mail]>
 *
 * Uses libogg, but requires libvorbisenc to construct correct headers
 * when containing Vorbis stream -- currently the only format supported
 */

#include <stdio.h>

#include <ogg/ogg.h>

#include "avformat.h"

#undef NDEBUG
#include <assert.h>

#define DECODER_BUFFER_SIZE 4096


typedef struct OggContext {
    /* output */
    ogg_stream_state os ;
    int header_handled ;
    ogg_packet op;

    /* input */
    ogg_sync_state oy ;
} OggContext ;


#ifdef CONFIG_MUXERS
static int ogg_write_header(AVFormatContext *avfcontext)
{
    OggContext *context = avfcontext->priv_data;
    ogg_packet *op= &context->op;
    int n;

    ogg_stream_init(&context->os, 31415);

    for(n = 0 ; n < avfcontext->nb_streams ; n++) {
        AVCodecContext *codec = avfcontext->streams[n]->codec;
        uint8_t *headers = codec->extradata;
        int headers_len = codec->extradata_size;
        uint8_t *header_start[3];
        int header_len[3];
        int i, j;

        av_set_pts_info(avfcontext->streams[n], 60, 1, AV_TIME_BASE);

        for(j=1,i=0;i<2;++i, ++j) {
            header_len[i]=0;
            while(j<headers_len && headers[j]==0xff) {
                header_len[i]+=0xff;
                ++j;
            }
            header_len[i]+=headers[j];
        }
        header_len[2]=headers_len-header_len[0]-header_len[1]-j;
        headers+=j;
        header_start[0] = headers;
        header_start[1] = header_start[0] + header_len[0];
        header_start[2] = header_start[1] + header_len[1];

        for(i=0; i < 3; ++i){
            op->bytes = header_len[i];

            op->packet= header_start[i];
            op->b_o_s= op->packetno==0;

            ogg_stream_packetin(&context->os, op);

            op->packetno++; //FIXME multiple streams
        }

        context->header_handled = 0 ;
    }

    return 0 ;
}

static int ogg_write_packet(AVFormatContext *avfcontext, AVPacket *pkt)
{
    OggContext *context = avfcontext->priv_data ;
    AVCodecContext *avctx= avfcontext->streams[pkt->stream_index]->codec;
    ogg_packet *op= &context->op;
    ogg_page og ;
    int64_t pts;

    pts= av_rescale(pkt->pts, avctx->sample_rate, AV_TIME_BASE);

//    av_log(avfcontext, AV_LOG_DEBUG, "M%d\n", size);

    /* flush header packets so audio starts on a new page */

    if(!context->header_handled) {
        while(ogg_stream_flush(&context->os, &og)) {
            put_buffer(&avfcontext->pb, og.header, og.header_len) ;
            put_buffer(&avfcontext->pb, og.body, og.body_len) ;
            put_flush_packet(&avfcontext->pb);
        }
        context->header_handled = 1 ;
    }

    op->packet = (uint8_t*) pkt->data;
    op->bytes  = pkt->size;
    op->b_o_s  = op->packetno == 0;
    op->granulepos= pts;

    /* correct the fields in the packet -- essential for streaming */

    ogg_stream_packetin(&context->os, op);

    while(ogg_stream_pageout(&context->os, &og)) {
        put_buffer(&avfcontext->pb, og.header, og.header_len);
        put_buffer(&avfcontext->pb, og.body, og.body_len);
        put_flush_packet(&avfcontext->pb);
    }
    op->packetno++;

    return 0;
}


static int ogg_write_trailer(AVFormatContext *avfcontext) {
    OggContext *context = avfcontext->priv_data ;
    ogg_page og ;

    while(ogg_stream_flush(&context->os, &og)) {
        put_buffer(&avfcontext->pb, og.header, og.header_len) ;
        put_buffer(&avfcontext->pb, og.body, og.body_len) ;
        put_flush_packet(&avfcontext->pb);
    }

    ogg_stream_clear(&context->os) ;
    return 0 ;
}


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

#if 0
static int next_packet(AVFormatContext *avfcontext, ogg_packet *op) {
    OggContext *context = avfcontext->priv_data ;
    ogg_page og ;
    char *buf ;

    while(ogg_stream_packetout(&context->os, op) != 1) {

        /* while no pages are available, read in more data to the sync */
        while(ogg_sync_pageout(&context->oy, &og) != 1) {
            buf = ogg_sync_buffer(&context->oy, DECODER_BUFFER_SIZE) ;
            if(get_buffer(&avfcontext->pb, buf, DECODER_BUFFER_SIZE) <= 0)
                return 1 ;
            ogg_sync_wrote(&context->oy, DECODER_BUFFER_SIZE) ;
        }

        /* got a page. Feed it into the stream and get the packet */
        if(ogg_stream_pagein(&context->os, &og) != 0)
            return 1 ;
    }

    return 0 ;
}


static int ogg_read_header(AVFormatContext *avfcontext, AVFormatParameters *ap)
{
    OggContext *context = avfcontext->priv_data;
    ogg_packet op ;
    char *buf ;
    ogg_page og ;
    AVStream *ast ;
    AVCodecContext *codec;
    uint8_t *p;
    int i;

    ogg_sync_init(&context->oy) ;
    buf = ogg_sync_buffer(&context->oy, DECODER_BUFFER_SIZE) ;

    if(get_buffer(&avfcontext->pb, buf, DECODER_BUFFER_SIZE) <= 0)
        return AVERROR_IO ;

    ogg_sync_wrote(&context->oy, DECODER_BUFFER_SIZE) ;
    ogg_sync_pageout(&context->oy, &og) ;
    ogg_stream_init(&context->os, ogg_page_serialno(&og)) ;
    ogg_stream_pagein(&context->os, &og) ;

    /* currently only one vorbis stream supported */

    ast = av_new_stream(avfcontext, 0) ;
    if(!ast)
        return AVERROR_NOMEM ;
    av_set_pts_info(ast, 60, 1, AV_TIME_BASE);

    codec= &ast->codec;
    codec->codec_type = CODEC_TYPE_AUDIO;
    codec->codec_id = CODEC_ID_VORBIS;
    for(i=0; i<3; i++){
        if(next_packet(avfcontext, &op)){
            return -1;
        }
        if(op.bytes >= (1<<16) || op.bytes < 0)
            return -1;
        codec->extradata_size+= 2 + op.bytes;
        codec->extradata= av_realloc(codec->extradata, codec->extradata_size + FF_INPUT_BUFFER_PADDING_SIZE);
        memset(codec->extradata + codec->extradata_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
        p= codec->extradata + codec->extradata_size - 2 - op.bytes;
        *(p++)= op.bytes>>8;
        *(p++)= op.bytes&0xFF;
        memcpy(p, op.packet, op.bytes);
    }

    return 0 ;
}


static int ogg_read_packet(AVFormatContext *avfcontext, AVPacket *pkt) {
    ogg_packet op ;

    if(next_packet(avfcontext, &op))
        return AVERROR_IO ;
    if(av_new_packet(pkt, op.bytes) < 0)
        return AVERROR_IO ;
    pkt->stream_index = 0 ;
    memcpy(pkt->data, op.packet, op.bytes);
    if(avfcontext->streams[0]->codec.sample_rate && op.granulepos!=-1)
        pkt->pts= av_rescale(op.granulepos, AV_TIME_BASE, avfcontext->streams[0]->codec.sample_rate);
//    printf("%lld %d %d\n", pkt->pts, (int)op.granulepos, avfcontext->streams[0]->codec.sample_rate);

    return op.bytes;
}


static int ogg_read_close(AVFormatContext *avfcontext) {
    OggContext *context = avfcontext->priv_data ;

    ogg_stream_clear(&context->os) ;
    ogg_sync_clear(&context->oy) ;
    av_freep(&avfcontext->streams[0]->codec.extradata);

    return 0 ;
}


static AVInputFormat ogg_iformat = {
    "ogg",
    "Ogg Vorbis",
    sizeof(OggContext),
    NULL,
    ogg_read_header,
    ogg_read_packet,
    ogg_read_close,
    .extensions = "ogg",
} ;
#endif

int libogg_init(void) {
#ifdef CONFIG_MUXERS
    av_register_output_format(&ogg_oformat) ;
#endif
/*     av_register_input_format(&ogg_iformat); */
    return 0 ;
}