[mythtv-users] [Bulk] lossless cut question

Dan Wilga mythtv-users2 at dwilga-linux1.amherst.edu
Fri May 17 12:44:44 UTC 2013


On 5/16/13 9:06 PM, Doug Vaughan wrote:
> Although I use 0.26 fixes I do remember that the majority of v0.25 
> hdpvr recordings had a time sync issue of 300-340ms. Back then Iwas 
> manually cutting commercials with Avidemux2.5xand had to use mkvgui to 
> correct the sync issue. I never experienced majoraudio sync drift 
> issues as you described.
>
> My own experience with Lossless_cut and hdpvr 0.26 recordings over the 
> last severalmonths has been that some cut recordings have aconsistent 
> audio sync issue of 150ms (audio needs to be delayed). It is 
> infrequent but happens. I correct the cut video with mkvgui to apply 
> an audio delay.
>
> The only gradual audio drift I've noticed was with cut recordings 
> longer than 2hrs where the original recording duration was 3hrs+. 
> Therefore many cuts are required to pare it down to ~2hrs.The drift 
> was slight enough that it was tolarable. There is a special mkvmerge 
> command line variable you can use to compensate for gradual drift but 
> Inever tired is myself. From what I remember it is only meantfor 
> slight drift over a long time not forwhat you describe.
>
> I certainly cannot guarantee that upgrading to MythTV v0.26 fixes will 
> resolve this issue but that version includes a number of 
> improvements/fixes related to h264 encoded videos.
Based on my experience, I don't think it will help. I have a couple of 
HDPVR recordings of 2-hour movies made with 0.26 that, when cut, 
experience a very big lag (about an entire second) toward the end. In my 
case, the problem doesn't seem to get progressively worse; it's as 
though a magical point is hit and the sync goes off. Most movies are 
fine when lossless cut, though. Fortunately, the kiddies haven't noticed 
the problem in these few yet.

-- 
Dan Wilga                                                        "Ook."



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