asf.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

            //printf("PacketLeftSize:%d  Pad:%d Pos:%"PRId64"\n", asf->packet_size_left, asf->packet_padsize, url_ftell(pb));
            assert(ret>=0);
            /* fail safe */
            url_fskip(pb, ret);

            asf->packet_pos= url_ftell(&s->pb);
            if (asf->data_object_size != (uint64_t)-1 &&
                (asf->packet_pos - asf->data_object_offset >= asf->data_object_size))
                return AVERROR(EIO); /* Do not exceed the size of the data object */
            ret = asf_get_packet(s);
            //printf("READ ASF PACKET  %d   r:%d   c:%d\n", ret, asf->packet_size_left, pc++);
            if (ret < 0)
                assert(asf->packet_size_left < FRAME_HEADER_SIZE || asf->packet_segments < 1);
            asf->packet_time_start = 0;
            continue;
        }
        if (asf->packet_time_start == 0) {
            if(asf_read_frame_header(s) < 0){
                asf->packet_segments= 0;
                continue;
            }
            if (asf->stream_index < 0
                || s->streams[asf->stream_index]->discard >= AVDISCARD_ALL
                || (!asf->packet_key_frame && s->streams[asf->stream_index]->discard >= AVDISCARD_NONKEY)
                ) {
                asf->packet_time_start = 0;
                /* unhandled packet (should not happen) */
                url_fskip(pb, asf->packet_frag_size);
                asf->packet_size_left -= asf->packet_frag_size;
                if(asf->stream_index < 0)
                    av_log(s, AV_LOG_ERROR, "ff asf skip %d (unknown stream)\n", asf->packet_frag_size);
                continue;
            }
            asf->asf_st = s->streams[asf->stream_index]->priv_data;
        }
        asf_st = asf->asf_st;

        if (asf->packet_replic_size == 1) {
            // frag_offset is here used as the begining timestamp
            asf->packet_frag_timestamp = asf->packet_time_start;
            asf->packet_time_start += asf->packet_time_delta;
            asf->packet_obj_size = asf->packet_frag_size = get_byte(pb);
            asf->packet_size_left--;
            asf->packet_multi_size--;
            if (asf->packet_multi_size < asf->packet_obj_size)
            {
                asf->packet_time_start = 0;
                url_fskip(pb, asf->packet_multi_size);
                asf->packet_size_left -= asf->packet_multi_size;
                continue;
            }
            asf->packet_multi_size -= asf->packet_obj_size;
            //printf("COMPRESS size  %d  %d  %d   ms:%d\n", asf->packet_obj_size, asf->packet_frag_timestamp, asf->packet_size_left, asf->packet_multi_size);
        }
        if(   /*asf->packet_frag_size == asf->packet_obj_size*/
              asf_st->frag_offset + asf->packet_frag_size <= asf_st->pkt.size
           && asf_st->frag_offset + asf->packet_frag_size > asf->packet_obj_size){
            av_log(s, AV_LOG_INFO, "ignoring invalid packet_obj_size (%d %d %d %d)\n",
                asf_st->frag_offset, asf->packet_frag_size,
                asf->packet_obj_size, asf_st->pkt.size);
            asf->packet_obj_size= asf_st->pkt.size;
        }

        if (   asf_st->pkt.size != asf->packet_obj_size
            || asf_st->frag_offset + asf->packet_frag_size > asf_st->pkt.size) { //FIXME is this condition sufficient?
            if(asf_st->pkt.data){
                av_log(s, AV_LOG_INFO, "freeing incomplete packet size %d, new %d\n", asf_st->pkt.size, asf->packet_obj_size);
                asf_st->frag_offset = 0;
                av_free_packet(&asf_st->pkt);
            }
            /* new packet */
            av_new_packet(&asf_st->pkt, asf->packet_obj_size);
            asf_st->seq = asf->packet_seq;
            asf_st->pkt.pts = asf->packet_frag_timestamp;
            asf_st->pkt.stream_index = asf->stream_index;
            asf_st->pkt.pos =
            asf_st->packet_pos= asf->packet_pos;
//printf("new packet: stream:%d key:%d packet_key:%d audio:%d size:%d\n",
//asf->stream_index, asf->packet_key_frame, asf_st->pkt.flags & PKT_FLAG_KEY,
//s->streams[asf->stream_index]->codec->codec_type == CODEC_TYPE_AUDIO, asf->packet_obj_size);
            if (s->streams[asf->stream_index]->codec->codec_type == CODEC_TYPE_AUDIO)
                asf->packet_key_frame = 1;
            if (asf->packet_key_frame)
                asf_st->pkt.flags |= PKT_FLAG_KEY;
        }

        /* read data */
        //printf("READ PACKET s:%d  os:%d  o:%d,%d  l:%d   DATA:%p\n",
        //       asf->packet_size, asf_st->pkt.size, asf->packet_frag_offset,
        //       asf_st->frag_offset, asf->packet_frag_size, asf_st->pkt.data);
        asf->packet_size_left -= asf->packet_frag_size;
        if (asf->packet_size_left < 0)
            continue;

        if(   asf->packet_frag_offset >= asf_st->pkt.size
           || asf->packet_frag_size > asf_st->pkt.size - asf->packet_frag_offset){
            av_log(s, AV_LOG_ERROR, "packet fragment position invalid %u,%u not in %u\n",
                asf->packet_frag_offset, asf->packet_frag_size, asf_st->pkt.size);
            continue;
        }

        get_buffer(pb, asf_st->pkt.data + asf->packet_frag_offset,
                   asf->packet_frag_size);
        asf_st->frag_offset += asf->packet_frag_size;
        /* test if whole packet is read */
        if (asf_st->frag_offset == asf_st->pkt.size) {
            //workaround for macroshit radio DVR-MS files
            if(   s->streams[asf->stream_index]->codec->codec_id == CODEC_ID_MPEG2VIDEO
               && asf_st->pkt.size > 100){
                int i;
                for(i=0; i<asf_st->pkt.size && !asf_st->pkt.data[i]; i++);
                if(i == asf_st->pkt.size){
                    av_log(s, AV_LOG_DEBUG, "discarding ms fart\n");
                    asf_st->frag_offset = 0;
                    av_free_packet(&asf_st->pkt);
                    continue;
                }
            }

            /* return packet */
            if (asf_st->ds_span > 1) {
              if(asf_st->pkt.size != asf_st->ds_packet_size * asf_st->ds_span){
                    av_log(s, AV_LOG_ERROR, "pkt.size != ds_packet_size * ds_span (%d %d %d)\n", asf_st->pkt.size, asf_st->ds_packet_size, asf_st->ds_span);
              }else{
                /* packet descrambling */
                uint8_t *newdata = av_malloc(asf_st->pkt.size);
                if (newdata) {
                    int offset = 0;
                    while (offset < asf_st->pkt.size) {
                        int off = offset / asf_st->ds_chunk_size;
                        int row = off / asf_st->ds_span;
                        int col = off % asf_st->ds_span;
                        int idx = row + col * asf_st->ds_packet_size / asf_st->ds_chunk_size;
                        //printf("off:%d  row:%d  col:%d  idx:%d\n", off, row, col, idx);

                        assert(offset + asf_st->ds_chunk_size <= asf_st->pkt.size);
                        assert(idx+1 <= asf_st->pkt.size / asf_st->ds_chunk_size);
                        memcpy(newdata + offset,
                               asf_st->pkt.data + idx * asf_st->ds_chunk_size,
                               asf_st->ds_chunk_size);
                        offset += asf_st->ds_chunk_size;
                    }
                    av_free(asf_st->pkt.data);
                    asf_st->pkt.data = newdata;
                }
              }
            }
            asf_st->frag_offset = 0;
            *pkt= asf_st->pkt;
            //printf("packet %d %d\n", asf_st->pkt.size, asf->packet_frag_size);
            asf_st->pkt.size = 0;
            asf_st->pkt.data = 0;
            break; // packet completed
        }
    }
    return 0;
}

static int asf_read_close(AVFormatContext *s)
{
    int i;

    for(i=0;i<s->nb_streams;i++) {
        AVStream *st = s->streams[i];
        av_free(st->priv_data);
        av_free(st->codec->palctrl);
    }
    return 0;
}

// Added to support seeking after packets have been read
// If information is not reset, read_packet fails due to
// leftover information from previous reads
static void asf_reset_header(AVFormatContext *s)
{
    ASFContext *asf = s->priv_data;
    ASFStream *asf_st;
    int i;

    asf->packet_nb_frames = 0;
    asf->packet_size_left = 0;
    asf->packet_segments = 0;
    asf->packet_flags = 0;
    asf->packet_property = 0;
    asf->packet_timestamp = 0;
    asf->packet_segsizetype = 0;
    asf->packet_segments = 0;
    asf->packet_seq = 0;
    asf->packet_replic_size = 0;
    asf->packet_key_frame = 0;
    asf->packet_padsize = 0;
    asf->packet_frag_offset = 0;
    asf->packet_frag_size = 0;
    asf->packet_frag_timestamp = 0;
    asf->packet_multi_size = 0;
    asf->packet_obj_size = 0;
    asf->packet_time_delta = 0;
    asf->packet_time_start = 0;

    for(i=0; i<s->nb_streams; i++){
        asf_st= s->streams[i]->priv_data;
        av_free_packet(&asf_st->pkt);
        asf_st->frag_offset=0;
        asf_st->seq=0;
    }
    asf->asf_st= NULL;
}

static int64_t asf_read_pts(AVFormatContext *s, int stream_index, int64_t *ppos, int64_t pos_limit)
{
    ASFContext *asf = s->priv_data;
    AVPacket pkt1, *pkt = &pkt1;
    ASFStream *asf_st;
    int64_t pts;
    int64_t pos= *ppos;
    int i;
    int64_t start_pos[s->nb_streams];

    for(i=0; i<s->nb_streams; i++){
        start_pos[i]= pos;
    }

    pos= (pos+asf->packet_size-1-s->data_offset)/asf->packet_size*asf->packet_size+ s->data_offset;
    *ppos= pos;
    url_fseek(&s->pb, pos, SEEK_SET);

//printf("asf_read_pts\n");
    asf_reset_header(s);
    for(;;){
        if (av_read_frame(s, pkt) < 0){
            av_log(s, AV_LOG_INFO, "asf_read_pts failed\n");
            return AV_NOPTS_VALUE;
        }

        pts= pkt->pts;

        av_free_packet(pkt);
        if(pkt->flags&PKT_FLAG_KEY){
            i= pkt->stream_index;

            asf_st= s->streams[i]->priv_data;

//            assert((asf_st->packet_pos - s->data_offset) % asf->packet_size == 0);
            pos= asf_st->packet_pos;

            av_add_index_entry(s->streams[i], pos, pts, pkt->size, pos - start_pos[i] + 1, AVINDEX_KEYFRAME);
            start_pos[i]= asf_st->packet_pos + 1;

            if(pkt->stream_index == stream_index)
               break;
        }
    }

    *ppos= pos;
//printf("found keyframe at %"PRId64" stream %d stamp:%"PRId64"\n", *ppos, stream_index, pts);

    return pts;
}

static void asf_build_simple_index(AVFormatContext *s, int stream_index)
{
    GUID g;
    ASFContext *asf = s->priv_data;
    int64_t gsize, itime;
    int64_t pos, current_pos, index_pts;
    int i;
    int pct,ict;

    current_pos = url_ftell(&s->pb);

    url_fseek(&s->pb, asf->data_object_offset + asf->data_object_size, SEEK_SET);
    get_guid(&s->pb, &g);
    if (!memcmp(&g, &index_guid, sizeof(GUID))) {
        gsize = get_le64(&s->pb);
        get_guid(&s->pb, &g);
        itime=get_le64(&s->pb);
        pct=get_le32(&s->pb);
        ict=get_le32(&s->pb);
        av_log(NULL, AV_LOG_DEBUG, "itime:0x%"PRIx64", pct:%d, ict:%d\n",itime,pct,ict);

        for (i=0;i<ict;i++){
            int pktnum=get_le32(&s->pb);
            int pktct =get_le16(&s->pb);
            av_log(NULL, AV_LOG_DEBUG, "pktnum:%d, pktct:%d\n", pktnum, pktct);

            pos=s->data_offset + asf->packet_size*(int64_t)pktnum;
            index_pts=av_rescale(itime, i, 10000);

            av_add_index_entry(s->streams[stream_index], pos, index_pts, asf->packet_size, 0, AVINDEX_KEYFRAME);
        }
        asf->index_read= 1;
    }
    url_fseek(&s->pb, current_pos, SEEK_SET);
}

static int asf_read_seek(AVFormatContext *s, int stream_index, int64_t pts, int flags)
{
    ASFContext *asf = s->priv_data;
    AVStream *st = s->streams[stream_index];
    int64_t pos;
    int index;

    if (asf->packet_size <= 0)
        return -1;

    if (!asf->index_read)
        asf_build_simple_index(s, stream_index);

    if(!(asf->index_read && st->index_entries)){
        if(av_seek_frame_binary(s, stream_index, pts, flags)<0)
            return -1;
    }else{
        index= av_index_search_timestamp(st, pts, flags);
        if(index<0)
            return -1;

        /* find the position */
        pos = st->index_entries[index].pos;
        pts = st->index_entries[index].timestamp;

    // various attempts to find key frame have failed so far
    //    asf_reset_header(s);
    //    url_fseek(&s->pb, pos, SEEK_SET);
    //    key_pos = pos;
    //     for(i=0;i<16;i++){
    //         pos = url_ftell(&s->pb);
    //         if (av_read_frame(s, &pkt) < 0){
    //             av_log(s, AV_LOG_INFO, "seek failed\n");
    //             return -1;
    //         }
    //         asf_st = s->streams[stream_index]->priv_data;
    //         pos += st->parser->frame_offset;
    //
    //         if (pkt.size > b) {
    //             b = pkt.size;
    //             key_pos = pos;
    //         }
    //
    //         av_free_packet(&pkt);
    //     }

        /* do the seek */
        av_log(NULL, AV_LOG_DEBUG, "SEEKTO: %"PRId64"\n", pos);
        url_fseek(&s->pb, pos, SEEK_SET);
    }
    asf_reset_header(s);
    return 0;
}

AVInputFormat asf_demuxer = {
    "asf",
    "asf format",
    sizeof(ASFContext),
    asf_probe,
    asf_read_header,
    asf_read_packet,
    asf_read_close,
    asf_read_seek,
    asf_read_pts,
};