[mythtv] DVB

[Edward Wildgoose]

> Don't have much time right now, but I have a two tuner DVB setup in
> Australia (Sydney) and am experiencing the same problems as discussed in
> this thread. Ie, audio seems to lag video and when changing channels it
> sometimes goes all 'stuttery'. Going out of 'live tv' and back in seems
> to fix the stuttering, but not the lagging audio.
> All channels are QAM 64.

The lagging audio is a known problem with the current CVS.  There was some code in myth a while ago which tried to guess timestamps for the video, but as I understand it, Isaac removed this because it wasn't production quality.  Unfortunately it also means that DVB is pretty useless at the moment for a lot of people.  Seems that many channels are doing some unusual things to sync audio and video.

Kenneth has posted a patch recently which tries to guess timestamps by just counting forward at 1000/framerate and although this doesn't work at all for me, it may work better for you.

What I am using is the orig code (from Isaac I think?) which works well for me, but has some jitter.

In avformatdecoder.cpp around line 1120

                        long long newvpts = 0;
                        if (pkt->pts > 0)
                        {
                            validvpts = true;
                            newvpts = (long long)((double)pkt->pts *
                                                  ptsmultiplier);
                        }
+                       else
+                       {
+                           newvpts = lastapts + (int)(1000.0 / fps) * 3;
+                       }