Workaround buggy flv files (#2590).

 It seems that (a lot of?) flv files does not correctly set PTS,
so ignore them, with luck the decoder (avcodec) will recreate
them.
 It might break some valid files, so report any regression.

(It needs the AVCodecContext::ticks_per_frame change).
(cherry picked from commit d1bf1bcf)
Signed-off-by: Derk-Jan Hartman <hartman@videolan.org>

modules/demux/avformat/demux.c

@@ -395,6 +395,8 @@ static int Demux( demux_t *p_demux )
         av_free_packet( &pkt );
         return 1;
     }
+    const AVStream *p_stream = p_sys->ic->streams[pkt.stream_index];
+
     if( ( p_frame = block_New( p_demux, pkt.size ) ) == NULL )
     {
         return 0;
@@ -410,17 +412,24 @@ static int Demux( demux_t *p_demux )
 
     p_frame->i_dts = ( pkt.dts == (int64_t)AV_NOPTS_VALUE ) ?
         0 : (pkt.dts) * 1000000 *
-        p_sys->ic->streams[pkt.stream_index]->time_base.num /
-        p_sys->ic->streams[pkt.stream_index]->time_base.den - i_start_time;
+        p_stream->time_base.num /
+        p_stream->time_base.den - i_start_time;
     p_frame->i_pts = ( pkt.pts == (int64_t)AV_NOPTS_VALUE ) ?
         0 : (pkt.pts) * 1000000 *
-        p_sys->ic->streams[pkt.stream_index]->time_base.num /
-        p_sys->ic->streams[pkt.stream_index]->time_base.den - i_start_time;
+        p_stream->time_base.num /
+        p_stream->time_base.den - i_start_time;
     if( pkt.duration > 0 )
         p_frame->i_length = pkt.duration * 1000000 *
-            p_sys->ic->streams[pkt.stream_index]->time_base.num /
-            p_sys->ic->streams[pkt.stream_index]->time_base.den - i_start_time;
+            p_stream->time_base.num /
+            p_stream->time_base.den - i_start_time;
 
+    if( pkt.dts != AV_NOPTS_VALUE && pkt.dts == pkt.pts &&
+        p_stream->codec->codec_type == CODEC_TYPE_VIDEO )
+    {
+        /* Add here notoriously bugged file formats/samples regarding PTS */
+        if( !strcmp( p_sys->fmt->name, "flv" ) )
+            p_frame->i_pts = 0;
+    }
 #ifdef AVFORMAT_DEBUG
     msg_Dbg( p_demux, "tk[%d] dts=%"PRId64" pts=%"PRId64,
              pkt.stream_index, p_frame->i_dts, p_frame->i_pts );