A/V out of sync - Audio 25fps stretch to fit video 23.976fps

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A/V out of sync - Audio 25fps stretch to fit video 23.976fps

Postby ExSport » Sun Aug 02, 2009 6:33 pm

Hello all and mainly Shagrath 8-)
I tried to play with files where video part(MKV) has 23.976fps and audio part has 25fps so audio is stretched to fit video fps.
When these kind of files are played on PC, A/V is synced but not on PS3 with PMS.

My test results with A/V Sync alternative method disabled:
- when -noskip and -mc 0 is avoided and -ofps 24000/1001 is changed with -ofps 25 video plays without shuttering/skipping and SYNCED
- when -noskip remains with forced 25fps, video is shuttering/skipping
- when -mc 0 remains with forced 25fps, video is not synced without skipping
The best paramteres which I found are -mc .05 -ofps 25.

But files which don't use timestretching are skipping with these parameters due to forced 25fps but both Audio&Video use 23.976 :(
Shagrath, please exists some technique how to detect timestretching in MKV so it can be used only for these files?
Or it is possible to add virtual option to use this technique in #TRANSCODE# folder available directly from same folder where file is shown so no need to browse through 7 folders back to enable/disable it?
I think something like virtual file=option e.g. FIX A/V fps mismatch which will enable it only for files in currently browsed #TRANSCODE# folder but when you left this folder, option will be reseted again?
It will be cool to have this kind of feature. 8-)
I know there are more people with same problems when they mux native PAL audio with english only BLU-RAY 24p video so this option could solve all A/V issues.
Many thanks for your opinion ;)
ExSport
 
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Re: A/V out of sync - Audio 25fps stretch to fit video 23.976fps

Postby Parker77 » Mon Aug 03, 2009 8:16 am

I tried to play with files where video part(MKV) has 23.976fps and audio part has 25fps so audio is stretched to fit video fps.

I would believe that audio is actually SLOWED down to fit to video 23.976 fps. Correct?!

Have you seen any differences comparing PS3MS with PC when playing these files? I'm just asking since your options for PS3MS would lead to a FASTEN UP video (25 fps) wheras the PC would still play them with 23.976 fps.

The next thing is what happens to not mismatched MKV files, i.e. untouched PAL-Blurays with native 23,976 fps for video and audio? Are your options maintaining that speed or would they also speed up the video?

Regards
Parker77
 
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Re: A/V out of sync - Audio 25fps stretch to fit video 23.976fps

Postby ExSport » Mon Aug 03, 2009 3:57 pm

No, Video framerate is changed from 23.976 to fit 25fps of audio. Not audio. Audio is AC3 which is not recoded and only muxed with video stream so video needs to be fixed.
There is no possibility to change audio framerate only via PMS (it is possible to do it manually - recode audio stream and mux with video again) so I need to recode video from 23.976 to 25 to fit with audio stream which has 25fps. It is only solution how to fix A/V sync which I found.
As I wrote, software players can fix timings of audio and interleave it to fix with video (used timestretching) but not when you do it via PMS (or I don't know how)
So yes, video fps is modified to 25fps but I didn't saw any difference when comparing with original video in 23.976. And audio is in sync then without manual recoding of audio stream!!!!
Parker77 wrote:The next thing is what happens to not mismatched MKV files, i.e. untouched PAL-Blurays with native 23,976 fps for video and audio? Are your options maintaining that speed or would they also speed up the video?

I bought quite a lot PAL BLU-RAY medias (documentary or movies) with missing my native language. So I taked native audio from PAL DVD which use 25fps and added it to MKV file which is recoded from BLU-RAY with 23.976. For these files it is working.
As I asked Shagrath:
ExSport wrote:But files which don't use timestretching are skipping with these parameters due to forced 25fps but both Audio&Video use 23.976
Shagrath, please exists some technique how to detect timestretching in MKV so it can be used only for these files?

it has side effect for "correct" files and because that I need to find solution how to detect it in stream or temporarily enable it on PS3 to fix these "bad" files for one folder until it is left when browsing ;)
All your questions were described already in first post 8-)
ExSport
 
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Re: A/V out of sync - Audio 25fps stretch to fit video 23.976fps

Postby ExSport » Wed Aug 05, 2009 4:00 pm

So I suppose no interest from Shagrath side :cry:
ExSport
 
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Re: A/V out of sync - Audio 25fps stretch to fit video 23.976fps

Postby ExSport » Wed Aug 12, 2009 8:53 am

Some of my own tryouts:
viewtopic.php?f=2&t=3336&start=0
ExSport
 
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