I worked around my sync issues, but still curious

[mrtristan]

I've been experiencing some audio/video sync issues that I think are related to the PICvideo mjpeg codec.

Up until recently, I've been using Virtualdub to capture, since it's one of the few programs that I can run on my system. I updated the ATI drivers, because Warcraft was bogging down when lots of little guys were running around on screen. After that, my computer started to drop more frames than usual. I would lose about 1 frame per minute. It's liveable, but really got on my nerves. Anyway, Warcraft still bogs down and I don't remember which set of drivers captured well with Virtualdub.

So short of going through each set of ATI drivers and running tests, I switched to iuvcr. I've always been able to capture with no frame loss with this program, no matter how long I let it run. I avoided iuvcr, because Virtualdub has an integrated noise reduction filter for capturing.

Now on to the problems. With Virtualdub, I would compress with huffyuv and capture at a resolution of 640X480. I opened up the files with Virtualdub, clipped out the commercials and frameserved to Tmpgenc. As far as I can remember, I didn't experience any audio/video sync issues.

Since switching to iuvcr, I've been using PICvideo's mjpeg. Huffyuv works too, but the PICvideo is available as a WDM codec. I figured that it would be better to use a compression coded that's native to the capture drivers. With iuvcr, I go through the same process as with Virtualdub, but I use mjpeg to compress, instead.

That's where I'm unsure. I haven't capped in a few months, so my memory isn't fresh. As far as I can remember, I haven't experienced sync issues when using huffyuv. I'm pretty sure I had some problems with mjpeg in the past, though. Aside from changing the capture drivers, the compression codec seems to the the only variable that I altered. No matter what I capture and convert, I stick to the same basic process.

I tried clipping out in both Virtualdub and Tmpgenc, but both ways still give me video that's out of sync. The only way that I've been able to maintain perfect syncronization is to encode each clip separately, then clip and join the mpeg files. It works, but it's also more work.

I'm going to try and capture with huffyuv on Monday. That's when the show will air again. Until then, if anyone has any ideas about this issue, I would appreciate your input.

[DJRumpy]

Depending on the quality of your MJPEG compression, you may be pushing your CPU too hard. The more compression you select, the harder the CPU has to work, and as a result, the more dropped frames. VirtualDub handles these dropped frames seemlessly, by keeping the audio in sync, regardless of the dropped frames (assuming you have this setting turned on). I'm guessing iuVCR does not. I would keep capturing with Huffman. Less work. You can still capture in VirtualDub. I'd suggest Huffman as the codec. Predict Left for the YUY2 compression method, and Convert To YUY2 for the RGB Compression method. You can also enable the checkbox for 'Always suggest RGB format for output'. If your still experiencing dropped frames, ensure you have no unecessary background programs running. Things like Virus Scanners can cause a big hit on performance. Also ensure the drive your capturing to is defragmented. Last but not least, consider dropping the frame size if necessary. This can also reduce the CPU overhead, and eliminate dropped frames.

[Gazorgan]

IUVCR , by default for my installation, syncs video to audio. That is, it lays down the audio track and forces the video to sync. I had problems until I made the video the master track and let the audio sync to it. It's just a setting change.

[mrtristan]

DJRumpy

That's the strange part. I don't drop a single frame with iuvcr, and the avi files are perfectly in sync. It's only when I edit and encode that the problem occurs.

I'll try those settings with Virtualdub, though. I really would rather use Virtualdub, since I can save on encoding time by filtering most of the noise while capturing.

I think altering the default codec settings will make a difference in the dropped frames. At a resolution of 640X480, compressing with huffyuv, and enabling noise reduction, the single cpu usage never goes above 60%. I doubt that it's a hard drive problem, since the other program can capture flawlessly.

Gazorgon

If I can't get Virtualdub to work, I'll try that. I changed the setting so that there's no master stream. I really don't know why, other than the fact that I like to push buttons that don't need to be pushed and I like to fiddle around with settings that I don't understand.

[DJRumpy]

That is strange. CPU below or around 60% shouldn't be dropping frames. You don't have any timed software running in the background do you? Something like a Virus Scanner, or a screen saver?

Other than that, the only thing I can think of is a fragmented hard drive. I suppose if it was bad enough, it could cause a dropped frame during a seek/write operation.

[mrtristan]

I really don't know what it is. I don't run any background applications, other than the ones that come with the installation of windows 2000. I stopped installing Norton's and other crap, since it only slows down the system and I've never gotten a virus.

I tried using those settings and my cpu usage is actually 30-40%. I use a dedicated 120Gig, 7,200 ATA100 drive for capping, but it still drops frames. I experimented with the chunk size settings which I thought helped, but really didn't. I'm pretty sure there's just a line of computer code or two that's different between the drivers that work and don't. That one little error probably causes a frame to be dropped when it glitches the system.

Or the damn Matrix is acting up again. Couldn't resist. I just saw Reloaded.

To get back on track, I isolated the problem to a setting in iuvcr... I think. Yesterday's capture with huffyuv and identical settings gave me the same result. I missed capturing today, because I was too busy watching Ocean's Eleven on a different channel. I ended up realizing that the show was on, when my wife came out of the shower. Anyway, I'm pretty sure enabling a master stream of either audio or video will solve my problem. Virtualdub does this automatically, from what I understand, but you have the option of selecting either or none, with iuvcr.

Thanks for the help.

[DJRumpy]

I might suggest you try the Direct Draw options in VirtualDub. Also, make sure you capping at 29.97 fps. If change any options under the Video/Frame Rate menu, it will artificially drop frames to meet your settings. Last but not least, make sure your capturing using overlay mode. You can always disable the display on capture too. This could possibly affect the capture/driver issue you seem to be experiencing.

[mrtristan]

Thanks again. I tried experimenting with those settings in the past. The only thing that helps is disabling the preview display, which is kind of hard, since I moved my computer to a room without a tv.

I think it may be motherboard related, since I was able to capture with less dropped frames on my older slower system, using the same card and guts.

[DJRumpy]

The only time I've ever seen such a drastic slowdown, was using SDRAM on a Pentium IV. The old interfaces were horrible for performance when you weren't using RDRAM, or DDR. I don't know if they still experience this problem or not, as I quickly upgraded to DDR memory.