Audio Sync Issues? Please report

fibrizo · 05-21-03, 12:13 PM

If you are having issues with audio syncing with your movie files in pocketMVP, Did virtual dub give you the VBR audio stream warning when you loaded the file?

If not, does pocketMVP report alot of dropped frames with your video?

05-21-03, 10:34 PM

So far every divx I have encoded has audio sync problems, but only when played on the Pocket PC. Playing the same file on the desktop is just fine. I'm wondering if perhaps I'm going too light on the audio, so it's playing fast while the video is using more CPU so it's lagged? Typically the audio plays roughly 1 second faster than the video does.

I'm going to try some higher bitrates on the audio and see if that helps even things out or not.

SimonCrux · 05-21-03, 11:06 PM

I am having an audio sync problem as well. Possibly it is because I have audio in stereo instead of mono... the sync problem is nonexistent when viewed on my comp but manifests on my Ax. As the clip goes on, the gap between audio and video grows larger. I've fast forwarded to the end scenes and renewed the cache but the gap is always larger towards the end of the file.

geezer · 05-22-03, 05:21 AM

I captured and encoded the final Buffy episode into 3 parts on a freshly formatted drive. After trimming commercials, the pre-encoded video seems to play fine. During Axim playback the first section freezes for a second about 3 minutes in, then I get slow video for about a minute or two. Afterwards A/V resyncs and the rest of the file plays fine.

I blame this on a Vud "hiccup" during the process and not on the Axim. I will reprocess to see if I can replicate the fault or see if I can find a problem in the DV capture. Audio was compressed to mp3 - 24kHz - 24kbps - mono.

A hint I found in the Vdub help file - ALWAYS cut at KEY FRAMES when trimming video. Sync issues can crop up due to the software expecting the next key frame and not finding it.

LFNNS · 05-22-03, 05:54 AM

Matrix has been giving me problems. The wav file is about 2 seconds shorter than the movie. This is directly from the DVD rip. It starts out OK but half way through the movie it starts to drift out of sync.

I found a guide on fixing sync issues but haven't had the time to try it yet. Not sure if the Matirx dvd layer break is causing some problems on dvd ripping?

I did Van Wilder with no problems so I know the process works. I may try dvd2one to get the full movie to my HD and start the process from there instead of ripping.

LFNNS

shadowfox777 · 05-22-03, 07:15 AM

I usually don't have audio sync problems when I use the 2-pass mode (at 160kps) but when I use 1-pass Quality, boy do I get audio sync problems from the middle of the video onwards. It plays fine on my computer.

I'm wondering if the kps rate is too high for the Axim (kps rate of both audio & video) when using 1-pass Quality.

thewisteron · 05-22-03, 09:42 AM

I have audio sync problems about half way through my video too. So in laymen's terms, can someone direct me what to do?

05-22-03, 11:45 AM

I haven't even gotten around to doing full movies yet. I'd rather get it right on something I can encode quickly before I waste hours encoding a whole movie only to find out it's screwed up.

I think the longest running time of anything I've encoded so far is approximately 7 minutes. Usually it's just trailers or animated shorts so far, and everything is slightly out of sync (audio plays ~ 1 sec before the video) almost from the start, it seems.

red-i · 05-22-03, 06:38 PM

count me in also...

i've done some tests grabbing video from my tv tuner card (which is a leadtek winfast deluxe).. i capture to mpg1 at 320x240.. this video plays flawlessly on pc..

so then i bring it into vdub.. i use divx 5.05 at 150kbps 2 pass. i encode every other frame, and use rotate 90 degrees for filter. as for audio it's mp3 24kbps mono. with anything i encode.. after about 1 or 2 mins the audio starts laggin behind the video.. what gives?? i'm using the latest pocketmvp and vdub (might be one version behind teh latest but it's current)..

this sucks cuz at 320x240 it looks nice

if i encode using wma i don't get sync issues.. however i cant play wma at 320x240 cuz i cant' encode it rotated, and it gets choppy when playing back .. i think partly cuz wmp is rotating the video as it's being played. is there anything other than media encoder to encode wmv??? media encoder is good but doesnt' have any filters to do rotation...

grrr... is there anyone with a 300mhz axim that's getting sync'd fullscreen playback? i don't care whether it's divx or wmv that i use as long as it works properly..

btw here's some steps to take to encode to divx:

http://geocities.com/efuest/Encode_D...e_PocketPC.htm

it's pretty much the same as pocketmatrix's tutorial.

I guess i'll try going lower than 150kbps and see if there's a point where i get no sync issues.. since it plays fine in media player on my pc there's no way it's a vdub issues...

thewisteron · 05-27-03, 09:25 AM

Any news on this?

red-i · 05-27-03, 09:29 AM

no new news from me.. i cannot get reliable playback at 320x240 fullscreen still :(

LFNNS · 05-27-03, 12:25 PM

Redi-I,

Try a smaller aspect ratio. Instead of 320x240 try half that and don't rotate it. (160x120). Start with the basics and then work your way up to a custom encode. Start with a fresh boot of the PC and only open the programs you need. Try encoding at 100kbps. These settings should be in the safe zone. The quality will suck but you need a starting point to build upon.

LFNNS

geezer · 05-27-03, 05:50 PM

red-i: Have you looked at this page at Nicky's? It cleared up a few of my questions. The page is outdated and there may be newer programs that can be used, but the basic A/V sync issues are well explained.

As for your wma/wmv experience - can you run the file through Vdub - filter and rotate - save to .avi - then encode to .wmv? I've no experience with encoding to Windows Media Player. (yet)

Tch0rT · 05-27-03, 05:58 PM

I believe I have figured out the problem with the Audio Sync issues. I believe it has to do with the audio conversion between sample rates, and down mixing stereo to mono. As an example whenever I downsample 44khz to 22khz or change stereo to mono my audio goes out of sync but if I do not convert the audio it plays back just fine. I also noticed if you try to downsample the compression VD won't let you encode the file, example : Audio 44khz, 16 bit, stereo and you try to compress it to Mp3 22Khz Mono it gives an error message. Anyway I've noticed that as long as I don't convert the audio to something different the Audio video sync is just fine, yet another example : Audio 44khz, 16 bit, stereo, you have to compress the audio to fit with 44khz and stereo but any bit rate seems to work (though it sucks you can't get 32Kbps 44khz stereo, I end up with 128Kbps as the lowest I can encode with 44khz stereo).

Anyway I hope this might help someone if not I can try to explain better. Btw I do not own an Axim I have a Toshiba E335, I just come to this site cuz you guys have the best info for all Pocket PC's that I can find on the net.

Ryan

red-i · 05-27-03, 09:21 PM

Tch0rT, when you get the sync issue.. does it start out playing fine and then start getting out of sync.. or is it out of sync right off the bat?

geezer, yeah acutally I've tried what you suggested.. however for some reason wmv still rotated it yet again so the image was upside down (and a bit stretched since it was playing at 240x320).. however there weren't any sync issues. Forgot to mention that previously

thankx for the suggestions guys, i'm gonna try some more experimenting and post back what I find.