avidec.c

FFmpeg is an audio/video conversion tool. It includes libavcodec, the leading open source codec libr

    memset(d, -1, sizeof(int)*8);
   
    if (avi->dv_demux) {
        size = dv_get_packet(avi->dv_demux, pkt);
	if (size >= 0)
	    return size;
    }
        
    for(i=url_ftell(pb); !url_feof(pb); i++) {
        int j;

	if (i >= avi->movi_end) { /* Let's see if it's an OpenDML AVI */
	    uint32_t tag, size, tag2;
	    url_fskip(pb, avi->riff_end - url_ftell(pb));
	    if (get_riff(avi, pb) < 0)
	        return -1;
	    
	    tag = get_le32(pb);
	    size = get_le32(pb);
	    tag2 = get_le32(pb);
	    if (tag == MKTAG('L','I','S','T') && tag2 == MKTAG('m','o','v','i'))
	        avi->movi_end = url_ftell(pb) + size - 4; 
	    else
	        return -1;
	}

        for(j=0; j<7; j++)
            d[j]= d[j+1];
        d[7]= get_byte(pb);
        
        size= d[4] + (d[5]<<8) + (d[6]<<16) + (d[7]<<24);
        
        //parse ix##
        n= (d[2] - '0') * 10 + (d[3] - '0');
        if(    d[2] >= '0' && d[2] <= '9'
            && d[3] >= '0' && d[3] <= '9'
            && d[0] == 'i' && d[1] == 'x'
            && n < s->nb_streams
            && i + size <= avi->movi_end){
            
            url_fskip(pb, size);
        }
        
        //parse ##dc/##wb
        n= (d[0] - '0') * 10 + (d[1] - '0');
        if(    d[0] >= '0' && d[0] <= '9'
            && d[1] >= '0' && d[1] <= '9'
            && ((d[2] == 'd' && d[3] == 'c') || 
	        (d[2] == 'w' && d[3] == 'b') || 
		(d[2] == 'd' && d[3] == 'b') ||
		(d[2] == '_' && d[3] == '_'))
            && n < s->nb_streams
            && i + size <= avi->movi_end) {
        
            av_new_packet(pkt, size);
            get_buffer(pb, pkt->data, size);
            if (size & 1) {
                get_byte(pb);
		size++;
	    }
	
	    if (avi->dv_demux) {
	        dstr = pkt->destruct;
	        size = dv_produce_packet(avi->dv_demux, pkt,
		                         pkt->data, pkt->size);
		pkt->destruct = dstr;
                pkt->flags |= PKT_FLAG_KEY;
	    } else {
                AVStream *st;
                AVIStream *ast;
                st = s->streams[n];
                ast = st->priv_data;
                
                /* XXX: how to handle B frames in avi ? */
                pkt->dts = ast->frame_offset;
//                pkt->dts += ast->start;
                if(ast->sample_size)
                    pkt->dts /= ast->sample_size;
//av_log(NULL, AV_LOG_DEBUG, "dts:%Ld offset:%d %d/%d %d st:%d size:%d\n", pkt->dts, ast->frame_offset, ast->scale, ast->rate, AV_TIME_BASE, n, size);
                pkt->stream_index = n;
                /* FIXME: We really should read index for that */
                if (st->codec.codec_type == CODEC_TYPE_VIDEO) {
                    if (ast->frame_offset < ast->nb_index_entries) {
                        if (ast->index_entries[ast->frame_offset].flags & AVIIF_INDEX)
                            pkt->flags |= PKT_FLAG_KEY; 
                    } else {
                        /* if no index, better to say that all frames
                           are key frames */
                        pkt->flags |= PKT_FLAG_KEY;
                    }
                } else {
                    pkt->flags |= PKT_FLAG_KEY; 
                }
                if(ast->sample_size)
                    ast->frame_offset += pkt->size;
                else
                    ast->frame_offset++;
	    }
            return size;
        }
    }
    return -1;
}

/* XXX: we make the implicit supposition that the position are sorted
   for each stream */
static int avi_read_idx1(AVFormatContext *s, int size)
{
    ByteIOContext *pb = &s->pb;
    int nb_index_entries, i;
    AVStream *st;
    AVIStream *ast;
    AVIIndexEntry *ie, *entries;
    unsigned int index, tag, flags, pos, len;
    
    nb_index_entries = size / 16;
    if (nb_index_entries <= 0)
        return -1;

    /* read the entries and sort them in each stream component */
    for(i = 0; i < nb_index_entries; i++) {
        tag = get_le32(pb);
        flags = get_le32(pb);
        pos = get_le32(pb);
        len = get_le32(pb);
#if defined(DEBUG_SEEK) && 0
        printf("%d: tag=0x%x flags=0x%x pos=0x%x len=%d\n", 
               i, tag, flags, pos, len);
#endif
        index = ((tag & 0xff) - '0') * 10;
        index += ((tag >> 8) & 0xff) - '0';
        if (index >= s->nb_streams)
            continue;
        st = s->streams[index];
        ast = st->priv_data;
        
        entries = av_fast_realloc(ast->index_entries,
                                  &ast->index_entries_allocated_size,
                                  (ast->nb_index_entries + 1) * 
                                  sizeof(AVIIndexEntry));
        if (entries) {
            ast->index_entries = entries;
            ie = &entries[ast->nb_index_entries++];
            ie->flags = flags;
            ie->pos = pos;
            ie->cum_len = ast->cum_len;
            ast->cum_len += len;
        }
    }
    return 0;
}

static int avi_load_index(AVFormatContext *s)
{
    AVIContext *avi = s->priv_data;
    ByteIOContext *pb = &s->pb;
    uint32_t tag, size;
    offset_t pos= url_ftell(pb);
    
    url_fseek(pb, avi->movi_end, SEEK_SET);
#ifdef DEBUG_SEEK
    printf("movi_end=0x%llx\n", avi->movi_end);
#endif
    for(;;) {
        if (url_feof(pb))
            break;
        tag = get_le32(pb);
        size = get_le32(pb);
#ifdef DEBUG_SEEK
        printf("tag=%c%c%c%c size=0x%x\n",
               tag & 0xff,
               (tag >> 8) & 0xff,
               (tag >> 16) & 0xff,
               (tag >> 24) & 0xff,
               size);
#endif
        switch(tag) {
        case MKTAG('i', 'd', 'x', '1'):
            if (avi_read_idx1(s, size) < 0)
                goto skip;
            else
                goto the_end;
            break;
        default:
        skip:
            size += (size & 1);
            url_fskip(pb, size);
            break;
        }
    }
 the_end:
    url_fseek(pb, pos, SEEK_SET);
    return 0;
}

/* return the index entry whose position is immediately >= 'wanted_pos' */
static int locate_frame_in_index(AVIIndexEntry *entries, 
                                 int nb_entries, int wanted_pos)
{
    int a, b, m, pos;
    
    a = 0;
    b = nb_entries - 1;
    while (a <= b) {
        m = (a + b) >> 1;
        pos = entries[m].pos;
        if (pos == wanted_pos)
            goto found;
        else if (pos > wanted_pos) {
            b = m - 1;
        } else {
            a = m + 1;
        }
    }
    m = a;
    if (m > 0)
        m--;
 found:
    return m;
}

static int avi_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp)
{
    AVIContext *avi = s->priv_data;
    AVStream *st;
    AVIStream *ast;
    int frame_number, i;
    int64_t pos;

    if (!avi->index_loaded) {
        /* we only load the index on demand */
        avi_load_index(s);
        avi->index_loaded = 1;
    }
    if (stream_index < 0) {
        for(i = 0; i < s->nb_streams; i++) {
            st = s->streams[i];
            if (st->codec.codec_type == CODEC_TYPE_VIDEO)
                goto found;
        }
        return -1;
    found:
        stream_index = i;
    }

    st = s->streams[stream_index];
    if (st->codec.codec_type != CODEC_TYPE_VIDEO)
        return -1;
    ast = st->priv_data;
    /* compute the frame number */
    frame_number = timestamp;
#ifdef DEBUG_SEEK
    printf("timestamp=%0.3f nb_indexes=%d frame_number=%d\n", 
           (double)timestamp / AV_TIME_BASE,
           ast->nb_index_entries, frame_number);
#endif
    /* find a closest key frame before */
    if (frame_number >= ast->nb_index_entries)
        return -1;
    while (frame_number >= 0 &&
           !(ast->index_entries[frame_number].flags & AVIIF_INDEX))
        frame_number--;
    if (frame_number < 0)
        return -1;
    ast->new_frame_offset = frame_number;

    /* find the position */
    pos = ast->index_entries[frame_number].pos;

#ifdef DEBUG_SEEK
    printf("key_frame_number=%d pos=0x%llx\n", 
           frame_number, pos);
#endif
    
    /* update the frame counters for all the other stream by looking
       at the positions just after the one found */
    for(i = 0; i < s->nb_streams; i++) {
        int j;
        if (i != stream_index) {
            st = s->streams[i];
            ast = st->priv_data;
            if (ast->nb_index_entries <= 0)
                return -1;
            j = locate_frame_in_index(ast->index_entries,
                                      ast->nb_index_entries,
                                      pos);
            /* get next frame */
            if ((j  + 1) < ast->nb_index_entries)
                j++;
            /* extract the current frame number */
            if (ast->sample_size==0)
                ast->new_frame_offset = j;
            else
                ast->new_frame_offset = ast->index_entries[j].cum_len;
        }
    }
    
    /* everything is OK now. We can update the frame offsets */
    for(i = 0; i < s->nb_streams; i++) {
        st = s->streams[i];
        ast = st->priv_data;
        ast->frame_offset = ast->new_frame_offset;
#ifdef DEBUG_SEEK
        printf("%d: frame_offset=%d\n", i, 
               ast->frame_offset);
#endif
    }
    /* do the seek */
    pos += avi->movi_list;
    url_fseek(&s->pb, pos, SEEK_SET);
    return 0;
}

static int avi_read_close(AVFormatContext *s)
{
    int i;
    AVIContext *avi = s->priv_data;

    for(i=0;i<s->nb_streams;i++) {
        AVStream *st = s->streams[i];
        AVIStream *ast = st->priv_data;
        if(ast){
            av_free(ast->index_entries);
            av_free(ast);
        }
        av_free(st->codec.extradata);
        av_free(st->codec.palctrl);
    }

    if (avi->dv_demux)
        av_free(avi->dv_demux);

    return 0;
}

static int avi_probe(AVProbeData *p)
{
    /* check file header */
    if (p->buf_size <= 32)
        return 0;
    if (p->buf[0] == 'R' && p->buf[1] == 'I' &&
        p->buf[2] == 'F' && p->buf[3] == 'F' &&
        p->buf[8] == 'A' && p->buf[9] == 'V' &&
        p->buf[10] == 'I' && p->buf[11] == ' ')
        return AVPROBE_SCORE_MAX;
    else
        return 0;
}

static AVInputFormat avi_iformat = {
    "avi",
    "avi format",
    sizeof(AVIContext),
    avi_probe,
    avi_read_header,
    avi_read_packet,
    avi_read_close,
    avi_read_seek,
};

int avidec_init(void)
{
    av_register_input_format(&avi_iformat);
    return 0;
}