audio sync... only on HD/Clear QAM files

[JohnInSJ]

I'm still fighting audio sync on these recordings, with the latest GBPVR.

Plain old mpeg-2s from the hauppauge hvr-1600 (analog) play back in perfect sync no matter how long the recording.

HD recordings - clear QAM, 5.1 surround audio... seem to start out ok, but over time drift so the video is WELL ahead [1-2+ seconds] of the audio. No amount of stopping/restarting changes it - it stays exactly out of sync further out.

Tried different muxes (TS, MS, etc) tried differed audio decoders, nada... no difference.

Any suggestions welcome. I am going to check the file itself in a different player (say, VLC) and on different machines (Plex on a mac) to see if the file itself is ok.

[JohnInSJ]

Well, I guess I will have another dialog with myself here

More debugging. Played with various settings for audio and video decoding. No changes.
On a hunch, tried playing with VLC (which would get rid of *all* directshow stuff and directly render with internal codecs.) And here's the interesting thing... it does maintain audio sync, but after about 4GB (ie, the file is 6.5GB since it is a 720p 1 hour HD program) the video gets amazingly choppy and I can hear the disk seeking a lot more.

So is it just a "playing back large files" problem after all? And if it is, what the heck can I do about it? I can't wait to see what I come up with :p

[sub]

In case you've got your audio renderer set to something else, it'd be worth setting it back to 'system default'. Having it set to something else is a common cause of sync issues.

[ilovejedd]

Sounds more like a heavily fragmented hard drive problem to me...

[sub]

Yep, that could certainly be a factor.

[JohnInSJ]

Hm. Pulled the file over to the mac mini (copied it over) and under vlc and Plex it is having serious issues at the halfway or better point.

So, the recording itself is borked. That's odd, since it should just be a direct capture of the clear QAM stream, right? Is it because the file is "too big" or is it a bad happaugh driver (I am current) or is it Comcast (the provider) or ???

Any debugging I can do here, just let me know.

[ilovejedd]

It's also quite possible that your PC was already having problems writing to hard drive during recording because of heavy fragmentation. I'd say defrag first and do a couple of hour long test recordings before you start changing settings in your system. Better yet, if you have an empty hard drive, format with NTFS with block size 32k or 64k and use it as your recording directory.

[sub]

So, the recording itself is borked. That's odd, since it should just be a direct capture of the clear QAM stream, right?

If you're using the 'TS Mux' optionm then yes its pretty much a direct capture. If it was using one of the other muxes, its possible that mux encountered a problem in the stream and wasnt able to deal to it gracefully. Alternatively it could have been caused by something else you were doing on the machine at that time in the recording that used either a lot of CPU or I/O.

[JohnInSJ]

Thank iLove, the disk is already set up for recording (fast SATA drive, NTFS, 64k blocks, only gbpvr is using it, for recordings) and is already defragged.

Sub, the TS Mux option is new (for the current version) no? Let me look at that, I don't believe I've set it up to use that. The machine is core 2 duo 64 bit 2.4ghz 2gb ram, and it just runs gbpvr... I would hope it could handle one recording - I think that's about a 4% load

Ugh.... looking at the MFT - 79% in use. Might need to bump that puppy up a bit!

Lemme poke at this some more.

[sub]

Sub, the TS Mux option is new (for the current version) no?

Correct, and I wasnt suggesting you use it instead. I was just trying to say that the mux filter you used could have been the cause of the problem.

Sub, the TS Mux option is new (for the current version) no? Let me look at that, I don't believe I've set it up to use that. The machine is core 2 duo 64 bit 2.4ghz 2gb ram, and it just runs gbpvr... I would hope it could handle one recording - I think that's about a 4% load

I'm sure it can handle your recordings on very little load. Thats not to say you can be doing something else on your machine (even for a short time) that couldnt saturate the I/O, or consume large amounts of CPU. gaming or copying lots of files etc.