rmdec.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

 header_end:
    rm->nb_packets = get_be32(pb); /* number of packets */
    if (!rm->nb_packets && (flags & 4))
        rm->nb_packets = 3600 * 25;
    get_be32(pb); /* next data header */
    return 0;

 fail:
    for(i=0;i<s->nb_streams;i++) {
        av_free(s->streams[i]);
    }
    return AVERROR(EIO);
}

static int get_num(ByteIOContext *pb, int *len)
{
    int n, n1;

    n = get_be16(pb);
    (*len)-=2;
    if (n >= 0x4000) {
        return n - 0x4000;
    } else {
        n1 = get_be16(pb);
        (*len)-=2;
        return (n << 16) | n1;
    }
}

/* multiple of 20 bytes for ra144 (ugly) */
#define RAW_PACKET_SIZE 1000

static int sync(AVFormatContext *s, int64_t *timestamp, int *flags, int *stream_index, int64_t *pos){
    RMContext *rm = s->priv_data;
    ByteIOContext *pb = &s->pb;
    int len, num, res, i;
    AVStream *st;
    uint32_t state=0xFFFFFFFF;

    while(!url_feof(pb)){
        *pos= url_ftell(pb);
        if(rm->remaining_len > 0){
            num= rm->current_stream;
            len= rm->remaining_len;
            *timestamp = AV_NOPTS_VALUE;
            *flags= 0;
        }else{
            state= (state<<8) + get_byte(pb);

            if(state == MKBETAG('I', 'N', 'D', 'X')){
                len = get_be16(pb) - 6;
                if(len<0)
                    continue;
                goto skip;
            }

            if(state > (unsigned)0xFFFF || state < 12)
                continue;
            len=state;
            state= 0xFFFFFFFF;

            num = get_be16(pb);
            *timestamp = get_be32(pb);
            res= get_byte(pb); /* reserved */
            *flags = get_byte(pb); /* flags */


            len -= 12;
        }
        for(i=0;i<s->nb_streams;i++) {
            st = s->streams[i];
            if (num == st->id)
                break;
        }
        if (i == s->nb_streams) {
skip:
            /* skip packet if unknown number */
            url_fskip(pb, len);
            rm->remaining_len -= len;
            continue;
        }
        *stream_index= i;

        return len;
    }
    return -1;
}

static int rm_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    RMContext *rm = s->priv_data;
    ByteIOContext *pb = &s->pb;
    AVStream *st;
    int i, len, j;
    int64_t timestamp, pos;
    uint8_t *ptr;
    int flags;

    if (rm->audio_pkt_cnt) {
        // If there are queued audio packet return them first
        st = s->streams[rm->audio_stream_num];
        if (st->codec->codec_id == CODEC_ID_AAC)
            av_get_packet(pb, pkt, rm->sub_packet_lengths[rm->sub_packet_cnt - rm->audio_pkt_cnt]);
        else {
        av_new_packet(pkt, st->codec->block_align);
        memcpy(pkt->data, rm->audiobuf + st->codec->block_align *
               (rm->sub_packet_h * rm->audio_framesize / st->codec->block_align - rm->audio_pkt_cnt),
               st->codec->block_align);
        }
        rm->audio_pkt_cnt--;
        pkt->flags = 0;
        pkt->stream_index = rm->audio_stream_num;
    } else if (rm->old_format) {
        st = s->streams[0];
        if (st->codec->codec_id == CODEC_ID_RA_288) {
            int x, y;

            for (y = 0; y < rm->sub_packet_h; y++)
                for (x = 0; x < rm->sub_packet_h/2; x++)
                    if (get_buffer(pb, rm->audiobuf+x*2*rm->audio_framesize+y*rm->coded_framesize, rm->coded_framesize) <= 0)
                        return AVERROR(EIO);
            rm->audio_stream_num = 0;
            rm->audio_pkt_cnt = rm->sub_packet_h * rm->audio_framesize / st->codec->block_align - 1;
            // Release first audio packet
            av_new_packet(pkt, st->codec->block_align);
            memcpy(pkt->data, rm->audiobuf, st->codec->block_align);
            pkt->flags |= PKT_FLAG_KEY; // Mark first packet as keyframe
            pkt->stream_index = 0;
        } else {
            /* just read raw bytes */
            len = RAW_PACKET_SIZE;
            len= av_get_packet(pb, pkt, len);
            pkt->stream_index = 0;
            if (len <= 0) {
                return AVERROR(EIO);
            }
            pkt->size = len;
        }
    } else {
        int seq=1;
resync:
        len=sync(s, &timestamp, &flags, &i, &pos);
        if(len<0)
            return AVERROR(EIO);
        st = s->streams[i];

        if (st->codec->codec_type == CODEC_TYPE_VIDEO) {
            int h, pic_num, len2, pos;

            h= get_byte(pb); len--;
            if(!(h & 0x40)){
                seq = get_byte(pb); len--;
            }

            if((h & 0xc0) == 0x40){
                len2= pos= 0;
            }else{
                len2 = get_num(pb, &len);
                pos = get_num(pb, &len);
            }
            /* picture number */
            pic_num= get_byte(pb); len--;
            rm->remaining_len= len;
            rm->current_stream= st->id;

//            av_log(NULL, AV_LOG_DEBUG, "%X len:%d pos:%d len2:%d pic_num:%d\n",h, len, pos, len2, pic_num);
            if((h & 0xc0) == 0x80)
                len=pos;
            if(len2 && len2<len)
                len=len2;
            rm->remaining_len-= len;
            av_get_packet(pb, pkt, len);

        } else if (st->codec->codec_type == CODEC_TYPE_AUDIO) {
            if ((st->codec->codec_id == CODEC_ID_RA_288) ||
                (st->codec->codec_id == CODEC_ID_COOK) ||
                (st->codec->codec_id == CODEC_ID_ATRAC3)) {
                int x;
                int sps = rm->sub_packet_size;
                int cfs = rm->coded_framesize;
                int h = rm->sub_packet_h;
                int y = rm->sub_packet_cnt;
                int w = rm->audio_framesize;

                if (flags & 2)
                    y = rm->sub_packet_cnt = 0;
                if (!y)
                    rm->audiotimestamp = timestamp;

                switch(st->codec->codec_id) {
                    case CODEC_ID_RA_288:
                        for (x = 0; x < h/2; x++)
                            get_buffer(pb, rm->audiobuf+x*2*w+y*cfs, cfs);
                        break;
                    case CODEC_ID_ATRAC3:
                    case CODEC_ID_COOK:
                        for (x = 0; x < w/sps; x++)
                            get_buffer(pb, rm->audiobuf+sps*(h*x+((h+1)/2)*(y&1)+(y>>1)), sps);
                        break;
                }

                if (++(rm->sub_packet_cnt) < h)
                    goto resync;
                else {
                    rm->sub_packet_cnt = 0;
                    rm->audio_stream_num = i;
                    rm->audio_pkt_cnt = h * w / st->codec->block_align - 1;
                    // Release first audio packet
                    av_new_packet(pkt, st->codec->block_align);
                    memcpy(pkt->data, rm->audiobuf, st->codec->block_align);
                    timestamp = rm->audiotimestamp;
                    flags = 2; // Mark first packet as keyframe
                }
            } else if (st->codec->codec_id == CODEC_ID_AAC) {
                int x;
                rm->audio_stream_num = i;
                rm->sub_packet_cnt = (get_be16(pb) & 0xf0) >> 4;
                if (rm->sub_packet_cnt) {
                    for (x = 0; x < rm->sub_packet_cnt; x++)
                        rm->sub_packet_lengths[x] = get_be16(pb);
                    // Release first audio packet
                    rm->audio_pkt_cnt = rm->sub_packet_cnt - 1;
                    av_get_packet(pb, pkt, rm->sub_packet_lengths[0]);
                    flags = 2; // Mark first packet as keyframe
                }
            } else
                av_get_packet(pb, pkt, len);

        } else
            av_get_packet(pb, pkt, len);

        if(  (st->discard >= AVDISCARD_NONKEY && !(flags&2))
           || st->discard >= AVDISCARD_ALL){
            av_free_packet(pkt);
            goto resync;
        }

        pkt->stream_index = i;

#if 0
        if (st->codec->codec_type == CODEC_TYPE_VIDEO) {
            if(st->codec->codec_id == CODEC_ID_RV20){
                int seq= 128*(pkt->data[2]&0x7F) + (pkt->data[3]>>1);
                av_log(NULL, AV_LOG_DEBUG, "%d %"PRId64" %d\n", timestamp, timestamp*512LL/25, seq);

                seq |= (timestamp&~0x3FFF);
                if(seq - timestamp >  0x2000) seq -= 0x4000;
                if(seq - timestamp < -0x2000) seq += 0x4000;
            }
        }
#endif
        pkt->pts= timestamp;
        if(flags&2){
            pkt->flags |= PKT_FLAG_KEY;
            if((seq&0x7F) == 1)
                av_add_index_entry(st, pos, timestamp, 0, 0, AVINDEX_KEYFRAME);
        }
    }

    /* for AC3, needs to swap bytes */
    if (st->codec->codec_id == CODEC_ID_AC3) {
        ptr = pkt->data;
        for(j=0;j<pkt->size;j+=2) {
            FFSWAP(int, ptr[0], ptr[1]);
            ptr += 2;
        }
    }
    return 0;
}

static int rm_read_close(AVFormatContext *s)
{
    RMContext *rm = s->priv_data;

    av_free(rm->audiobuf);
    return 0;
}

static int rm_probe(AVProbeData *p)
{
    /* check file header */
    if ((p->buf[0] == '.' && p->buf[1] == 'R' &&
         p->buf[2] == 'M' && p->buf[3] == 'F' &&
         p->buf[4] == 0 && p->buf[5] == 0) ||
        (p->buf[0] == '.' && p->buf[1] == 'r' &&
         p->buf[2] == 'a' && p->buf[3] == 0xfd))
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

static int64_t rm_read_dts(AVFormatContext *s, int stream_index,
                               int64_t *ppos, int64_t pos_limit)
{
    RMContext *rm = s->priv_data;
    int64_t pos, dts;
    int stream_index2, flags, len, h;

    pos = *ppos;

    if(rm->old_format)
        return AV_NOPTS_VALUE;

    url_fseek(&s->pb, pos, SEEK_SET);
    rm->remaining_len=0;
    for(;;){
        int seq=1;
        AVStream *st;

        len=sync(s, &dts, &flags, &stream_index2, &pos);
        if(len<0)
            return AV_NOPTS_VALUE;

        st = s->streams[stream_index2];
        if (st->codec->codec_type == CODEC_TYPE_VIDEO) {
            h= get_byte(&s->pb); len--;
            if(!(h & 0x40)){
                seq = get_byte(&s->pb); len--;
            }
        }

        if((flags&2) && (seq&0x7F) == 1){
//            av_log(s, AV_LOG_DEBUG, "%d %d-%d %"PRId64" %d\n", flags, stream_index2, stream_index, dts, seq);
            av_add_index_entry(st, pos, dts, 0, 0, AVINDEX_KEYFRAME);
            if(stream_index2 == stream_index)
                break;
        }

        url_fskip(&s->pb, len);
    }
    *ppos = pos;
    return dts;
}

AVInputFormat rm_demuxer = {
    "rm",
    "rm format",
    sizeof(RMContext),
    rm_probe,
    rm_read_header,
    rm_read_packet,
    rm_read_close,
    NULL,
    rm_read_dts,
};