smjpegdec: implement seeking

Signed-off-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavformat/smjpegdec.c

@@ -136,9 +136,11 @@ static int smjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
 {
     SMJPEGContext *sc = s->priv_data;
     uint32_t dtype, ret, size, timestamp;
+    int64_t pos;
 
     if (s->pb->eof_reached)
         return AVERROR_EOF;
+    pos   = avio_tell(s->pb);
     dtype = avio_rl32(s->pb);
     switch (dtype) {
     case SMJPEG_SNDD:
@@ -147,6 +149,7 @@ static int smjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
         ret = av_get_packet(s->pb, pkt, size);
         pkt->stream_index = sc->audio_stream_index;
         pkt->pts = timestamp;
+        pkt->pos = pos;
         break;
     case SMJPEG_VIDD:
         timestamp = avio_rb32(s->pb);
@@ -154,6 +157,7 @@ static int smjpeg_read_packet(AVFormatContext *s, AVPacket *pkt)
         ret = av_get_packet(s->pb, pkt, size);
         pkt->stream_index = sc->video_stream_index;
         pkt->pts = timestamp;
+        pkt->pos = pos;
         break;
     case SMJPEG_DONE:
         ret = AVERROR_EOF;
@@ -174,4 +178,5 @@ AVInputFormat ff_smjpeg_demuxer = {
     .read_header    = smjpeg_read_header,
     .read_packet    = smjpeg_read_packet,
     .extensions     = "mjpg",
+    .flags          = AVFMT_GENERIC_INDEX,
 };