[FFmpeg-devel] [PATCH] rmdec.c: parse INDX chunk
Kostya
kostya.shishkov
Wed Mar 11 06:40:42 CET 2009
On Wed, Mar 11, 2009 at 01:00:45AM -0400, Ronald S. Bultje wrote:
> Hi,
>
> attached patch adds support for index parsing.
>
> Ronald
> Index: ffmpeg-svn/libavformat/rmdec.c
> ===================================================================
> --- ffmpeg-svn.orig/libavformat/rmdec.c 2009-03-09 23:22:13.000000000 -0400
> +++ ffmpeg-svn/libavformat/rmdec.c 2009-03-09 23:24:22.000000000 -0400
> @@ -292,6 +292,51 @@
> return 0;
> }
>
> +/** this function assumes that the demuxer has already seeked to the start
> + * of the INDX chunk, and will bail out if not. */
> +static int rm_read_index(AVFormatContext *s)
> +{
> + ByteIOContext *pb = s->pb;
> + unsigned int size, n_pkts, str_id, next_off, n, pos, pts;
> + AVStream *st;
> +
> + do {
> + if (get_le32(pb) != MKTAG('I','N','D','X'))
> + return -1;
> + size = get_be32(pb);
> + if (size < 20)
> + return -1;
> + url_fskip(pb, 2);
> + n_pkts = get_be32(pb);
> + str_id = get_be16(pb);
> + next_off = get_be32(pb);
> + if (size > 20)
> + url_fskip(pb, size - 20);
err, what happens when somebody decides to follow spec and include size of index
entries into header size?
> + for (n = 0; n < s->nb_streams; n++)
> + if (s->streams[n]->id == str_id) {
> + st = s->streams[n];
> + break;
> + }
> + if (n == s->nb_streams)
> + goto skip;
> + for (n = 0; n < n_pkts; n++) {
> + url_fskip(pb, 2);
> + pts = get_be32(pb);
> + pos = get_be32(pb);
> + url_fskip(pb, 4); /* packet no. */
> +
> + av_add_index_entry(st, pos, pts, 0, 0, AVINDEX_KEYFRAME);
> + }
> +
> +skip:
> + if (url_ftell(pb) != next_off &&
> + url_fseek(pb, next_off, SEEK_SET) < 0)
> + return -1;
this condition should be changed since it does not take into account streamed
data, for which we should read or skip only this index chunk
> + } while (next_off);
> +
> + return 0;
> +}
>
> static int rm_read_header_old(AVFormatContext *s, AVFormatParameters *ap)
> {
> @@ -314,6 +359,7 @@
> unsigned int tag;
> int tag_size;
> unsigned int start_time, duration;
> + unsigned int data_off = 0, indx_off = 0;
> char buf[128];
> int flags = 0;
>
> @@ -357,8 +403,8 @@
> get_be32(pb); /* nb packets */
> get_be32(pb); /* duration */
> get_be32(pb); /* preroll */
> - get_be32(pb); /* index offset */
> - get_be32(pb); /* data offset */
> + indx_off = get_be32(pb); /* index offset */
> + data_off = get_be32(pb); /* data offset */
> get_be16(pb); /* nb streams */
> flags = get_be16(pb); /* flags */
> break;
> @@ -400,6 +446,14 @@
> if (!rm->nb_packets && (flags & 4))
> rm->nb_packets = 3600 * 25;
> get_be32(pb); /* next data header */
> +
> + if (!data_off)
> + data_off = url_ftell(pb) - 14;
> + if (indx_off && url_fseek(pb, indx_off, SEEK_SET) >= 0) {
> + rm_read_index(s);
> + url_fseek(pb, data_off + 14, SEEK_SET);
> + }
> +
> return 0;
> }
after that someone has to write rm_read_seek() ;)
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