[mythtv-users] Re: Getting good audio sync in nuvexport/transcodings w/cutlist?

Neil neil-on-mythtv at restricted.dyndns.org
Tue May 31 21:46:31 UTC 2005

Likewise, I'm on the same boat you guys are. :) The Audio/video sync issue 
happens gradually in my situation. Video gets delayed .5 secs, 1 sec, 1.5 
secs, then 2 secs. This is for a 1 hour recorded program. 

However, I spoke to someone last night on mythtv-users(Agrajag). He pointed 
me to a thread here which was similar to our audio/video sync issues. 
Unfortunately, I couldn't remember the link. However, I do remember the tool 
that was mentioned as the a/v issue life saver. It's called ProjectX. I ran 
it last night. Once I reach home later, I will convert the files generated 
by ProjectX into DVD format. I will let you know if audio/video sync is 
gone. Oh btw, I'm taking the same source .nuv file. This would compare both 
approach as apples to apples comparison. 

I'll let you know guys! 



>Re: audio sync: Welcome to my world. It's incredibly frustrating, and
>only happens with 720p material. After transcode, my audio loses step
>with video at about the rate of 850ms/hour of programming. Very
>consistent, very repeatable. I have absolutely no solution. Sorry to
>respond with a 'meee toooo' but I'd love to hear if somebody has an
>Re: transcode speed: What transcode paramaters are you using? Are you
>resizing? I get very acceptable transcode speeds with 720p material
>using ffmpeg (from transcode). I can't remember the fps off the top
>of my head, but I think it's roughly 30fps. 
>John Sturgeon <><
>On 5/28/05, Brad Templeton <brad+myth at templetons.com> wrote:
>> Well, I've seen a number of threads about this but no clear resolution. 
>> Recently I've been trying to transocde a 720p MP2 file to MP4 with
>> a cutlist. The file is 4 hours long -- 22 gigabytes, and it has
>> a whopping 76 minutes of "cuttable material", so use of a cutlist
>> is pretty important. 
>> However, the result had steadily worsening audio sync, getting over
>> a second off eventually. I used divx bucause xvid was so slow
>> (4fps on a 60fps recording) that it would take at least 33 hours
>> to transocde even on a fast machine. That's with ffmpeg, should I
>> try transcode? (mencoder does not work yet). 
>> Even dvix took over 8 hours to transcode, but that's a touch more
>> tolerable. Worse, while this is 60fps, it's really 24fps underneath,
>> most frames are duplicates. Alas the mythtransocde | ffmpeg approach
>> presumably doesn't allow the encoder access to the knowledge it's just
>> been handed an exactly duplicate frame and shouldn't waste its time. 
>> To my surprise, also, while I asked for a bitrate of 7200, which should
>> have generated a file in the range of 9 gigabytes, I got one that
>> was 4 gigabytes. It is actually pretty good, video wise, though
>> with some obvious artifacts in smooth surfaces and a little blurring.
>> But I felt I was willing to spend more space on it and hopefully be
>> rid of those.

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