Audio Compression and then some...

[jongjungbu]

So, I don't want AV Sync problems, and I'm not sure if what I'm doing is creating a VBR audio in my DivX movie. I remember someone mentioning that PocketDivX does not support VBR audio. At any rate, I am using VirtualDub and upon selecting audio compression...I have 3 choices.
- DivX Audio
- MP3
- MPEG Layer-3

All of them containing the desired compression I want
- 24 or 32kbps, 22,050 Hz, Mono

My question then is, does it matter which of those 3 choices I make? Is one of them VBR? The one I typically have been using is MPEG Layer-3.

When it comes to AV Sync issues, I have the one sometimes where it's fine on PC but may not be on PPC. Although I've really only tested this out by fastforwarding about an hour into the movie. Perhaps doing that can mess with AV sync. I don't usually do lengthy movie files, so I have yet to test running one persisently for an hours time to see if AV is still in sync into the movie.

I am having to use PocketDivX 0.8 as for some reason PocketMVP 0. seems to lockup whenever loading a file or even selecting File-Open or when pressing play. I figure if it sets there for 15 minutes and it still hasn't started playing or responding, then its a no go.

JJB

[jonw]

I think it's more a case that .avi should not contain vbr mp3 than PocketMVP not supporting it. PMVP will support vbr audio in the form of ogg vorbis which can be muxed with divx video using oggmux. Voila, end of a/v sync probs.

Plus ogg is much better than mp3 at lower bitrates. Try q1, 22kHz mono (nominal bitrate around 30kbps); as good or better than mp3 at 48kbps.

But answering your question none of the codecs will be vbr. The first is the hacked mp3 that installs with divx3.11. Gives you greater choice than standard windows version which will be one of the others (can't remember which is which) The final one could have been installed with your sound card (do you have Creative for example) or another mp3 encoder.

Suggest you avoid divx audio and use one of the others. Or better still try vorbis

[jongjungbu]

Thanks for the reply!
As to Creative, yeah, I use a Creative SB Live, so that would coincide with that last codec appearing.

As for using ogg..I want to use it but I have not..as of yet...been able to make PocketMVP work on my Asus Zayo. If any of you with this device have been successful, please send me a PM. Instead, I am having to use the ProjectMayo's original PocketDivX 0.8. Fortunately, it's a great program and thusly works really well even if it's not the latest player to use.

For a/v sync. My only solution so far has been to split my video files in half. What I had been doing was creating one large movie file to copy over and play. This worked great at first. But playing it on PPC resulted in slight a/v sync probs after a while. PC did not have this problem playing it. I finally tested by playing the movie straight on without fastforwarding. The a/v sync wasn't nearly as bad then. And it wasn't a problem until well over an hour's time.

So in the end, I'm splitting the movie files in half. Which I suppose is what most folks do anyway, especially those who have 2 64MB CF cards or some such, for instance. Not that I do, but just thinking those folks don't seem to complain of A/V sync problems either.

Later,
JJB

[jonw]

Sorry, to hear that you cannot use latest PMVP. Hope it gets sorted soon 'cos it's looking better and better!

As for your sync problem it might be due to audio being slightly shorter than video. Way to check is to extract the audio from your encoded movie as a wav using virtualdub. Open the wav with windows sound recorder and note length of the audio track to the fraction of a second. Then in virtualdub open the movie file and click Video ->Select Range and check length of video. If it's different than the figure you noted for the audio set range to the exact same length. Then set video and audio to direct stream copy and save as new avi. This has worked for some people