[mythtv] [PATCH] Add new MPEG4 encoding options

Edward Wildgoose Edward.Wildgoose at FRMHedge.com
Wed Apr 2 16:53:40 EST 2003


> On Tue, 1 Apr 2003 11:12:53 +0100, Edward Wildgoose said:
> > On my machine applying this patch causes some lipsync issues due to
> > slight sound delay.  It could just be because the machine is on the limit
> > (dual 1Ghz Pentium 3) and I haven't tried enabling the options in myth to
> > deal with this
> > 
> > Actually at first I thought it could simply have been something to do
> > with the extra processing required, however, thinking about it, I reckon
> > the sound was behind the video, not vice versa as you might expect..
> > 
> > I will assume that it is specific to my machine unless someone else has
> > seen this as well?
> 
> I can't duplicate this on my machine (1.6GHz P4), and haven't looked at
> how the threads are handled in myth(perhaps it has to do with your dual
> CPU setup?).  What kind of CPU load are you seeing?  My  understanding
> was that the libavcodec library took care of synchronizing, but I haven't
> looked into that too carefully.  Can you try booting in UP mode and see
> if you still have the problem?

So if you flick the new HQ and 4MV flags on you still see the voice in sync just as closely as with rtjpeg?  It is only slightly out, and I *think* that flicking the anti-jitter knob has reduced it significantly

My total CPU usage is around 70%+ so it will be difficult to boot in UP mode and still get a good picture I think

If others aren't seeing this, then it is likely to be something specific to my machine, probably because it is running at such high load.  From the archives it appears that Isaac has tweaked libavcodec so that most of the encoder is synchronised and hence doesn't benefit from SMP (apparently there were serious artifacts appearing in MPEG4 streams without this tweak).  However, I do obviously get the benefit of one processor to compress and one to view the resulting stream.  I hope soon to get a P4 2.8ghz or thereabouts.

Thanks



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