[FFmpeg-devel] [PATCH] fix generic seek with MTV format

[Reimar Döffinger]

Hello,
currently mtv demuxer can not handle generic seeking code since it has
some internal state (audio_packet_count) that is incorrect afterwards.
There are certainly a lot more, maybe even better ways to fix this, but
attached is one possibility.
The pkt->pos fix (at least I think it should be changed like this)
probably should be applied separately though.

Greetings,
Reimar D?ffinger
-------------- next part --------------
Index: libavformat/mtv.c
===================================================================
--- libavformat/mtv.c	(revision 13372)
+++ libavformat/mtv.c	(working copy)
@@ -46,10 +46,8 @@
     unsigned int        img_height;        //
     unsigned int        img_segment_size;  ///< size of image segment
     unsigned int        video_fps;         //
-    unsigned int        audio_subsegments; ///< audio subsegments on one segment
+    unsigned int        full_segment_size;
 
-    uint8_t             audio_packet_count;
-
 } MTVDemuxContext;
 
 static int mtv_probe(AVProbeData *p)
@@ -67,6 +65,7 @@
     MTVDemuxContext    *mtv = s->priv_data;
     ByteIOContext      *pb  = s->pb;
     AVStream           *st;
+    unsigned int        audio_subsegments;
 
 
     url_fskip(pb, 3);
@@ -81,15 +80,14 @@
     mtv->img_height        = get_le16(pb);
     mtv->img_segment_size  = get_le16(pb);
     url_fskip(pb, 4);
-    mtv->audio_subsegments = get_le16(pb);
-    mtv->video_fps         = (mtv->audio_br / 4) / mtv->audio_subsegments;
+    audio_subsegments = get_le16(pb);
+    mtv->full_segment_size =
+        audio_subsegments * (MTV_AUDIO_PADDING_SIZE + MTV_ASUBCHUNK_DATA_SIZE) +
+        mtv->img_segment_size;
+    mtv->video_fps         = (mtv->audio_br / 4) / audio_subsegments;
 
     /* FIXME Add sanity check here */
 
-    /* first packet is always audio*/
-
-    mtv->audio_packet_count = 1;
-
     /* all systems go! init decoders */
 
     /* video - raw rgb565 */
@@ -139,7 +137,7 @@
 
     ret = 0;
 
-    if(mtv->audio_subsegments >= mtv->audio_packet_count)
+    if((url_ftell(pb) - s->data_offset + mtv->img_segment_size) % mtv->full_segment_size)
     {
         url_fskip(pb, MTV_AUDIO_PADDING_SIZE);
 
@@ -147,7 +145,7 @@
         if(ret != MTV_ASUBCHUNK_DATA_SIZE)
             return AVERROR(EIO);
 
-        mtv->audio_packet_count++;
+        pkt->pos -= MTV_AUDIO_PADDING_SIZE;
         pkt->stream_index = AUDIO_SID;
 
     }else
@@ -167,7 +165,6 @@
         for(i=0;i<mtv->img_segment_size/2;i++)
             *((uint16_t *)pkt->data+i) = bswap_16(*((uint16_t *)pkt->data+i));
 #endif
-        mtv->audio_packet_count = 1;
         pkt->stream_index = VIDEO_SID;
     }