Tch0rT

Quote:

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?

It starts off fine and about half way through it goes out of sync.

Ryan

geezer

Ryan,

You are correct. From the PMVP help file:

*******
AUDIO
There are a few tricks to be cognizant of when encoding the audio portion of your clip.

- Your PDA's ability to handle specific sampling rates. (ie older IPAQ's don't support 48 Khz sampling but rather 44.1 Khz or 22.05 Khz or 11 Khz)

- Converting between some sampling rates such as 48 to 44 Khz can cause synchronization problems. On the desktop one can and should leave the audio at 48 Khz if that is what it was originally, but on some PDA's you have no choice. Use Besweet or HeadAche to do this properly.

- Converting between video frame rates causes synchronization problems. (ie 29.97 to 24 fps)

- an mp3 cbr audio encode has fewer synchronization issues than vbr or nbr.

- Stereo ( joint or otherwise) takes twice the PDA processing power than mono.

- Your desktop needs either the MPEG3 codec or the LAME codec installed.

- joint stereo uses less bits that 2 channel stereo but uses about the same processing power on the PDA

- OGG compresses more than mp3, has better quality at lower bit rates (ie 64 kbps) but also uses more PDA processing power than mp3.

- synchronize your video and audio using software such as Multiquence which permits you to see the video and audio in separate tracks. You can zoom the video to see individual frames and thereby make precise alignments. You can shift the start of the audio to sync with the appropriate frame.

You can then use Goldwave to stretch the audio to make it match the video's length without changing the pitch of the audio. Or you can use the freeware programs that try to emulate this procedure without the visuals to guide you.


red-i : Good luck and hope you find some good tips for the rest of us.

Jeff

__________________
Learn as you go - share what you know

red-i

well looks like i've got some serious experimenting to do :)

What sucks is that my goal was just to encode news at full screen in the morning so i cna watch on the way to work. Having to demux/mux audio and video is too time consuming to do just for that.. however I guess I don't really need full screen for something like the news.. wma in a smaller window will suffice.

but .. i'm gona try out some simpsons encodes and see if i can get a sync'd fullscreeen playback.. thanx for the info geezer ;)

Talyn

Ok the stereo/bitrate settings seems to solve the audio sync issue, at least for the most part.

I took a 41.3mb, 5:01 minute .avi resized to 320x240 with DivX 3.03 encoding at 250 kbps (higher than I'd previously been using) and this time, rather than converting to 8 bit mono at 22050Hz with the MPEG Layer 3 codec, I chose the LAME MP3 codec set to 44100Hz at 128 kbps stereo.

The resulting file was a bit larger than most, at 13.5mb. Though to be fair, I then re-encoded another version of it, this time using the old mono audio settings, and it turned out to be 10.1mb so overall not that big a difference.

As far as I could tell, the stereo version stayed in sync the whole time, while the mono was immediately out of sync by approximately 1 second, as usual.

Considering this, plus the fact that all movies play in sync on the desktop, I'm thinking it's simply a matter of DivX being CPU-intensive while low bitrate mono MP3 is not. So find a combination where both the video and audio take the same CPU resources, and things should equal out.

I'll continue experimenting with other settings as I find the time and motivation... :)

red-i

how do i use the lame mp3 codec with vdub? i got the lame dll and put it in system32 but it doesn't show up in the list avialable to vdub and also doesnt show up in audio codecs in device manager under sound hardware. i've put the dll in system folder alsobut no go.. i've rebooted of course, doesn't make a diff

Talyn

Just drop lame_enc.dll into the VirtualDub folder and you'll be set.

After encoding several more videos, I think I will stand by my higher bitrate+stereo statement. So far, every single one I've encoded this way has stayed in sync. If the original video was already 8bit and/or mono, I even went as far as encoding an uncompressed video & audio version, set to 44100Hz stereo first, then loading up the new (huge) file and then using the DivX & MP3 codecs on it. It's a little extra effort, but it's worked like a charm so far.

lsout

is there any other encoder apart from divx ?

red-i

for us, we're pretty much restricted to divx, mpg1, and wmv. I've read that ON2 is gonna release their latest codec for public use ? (i think it's VP6).. it's supposed to require less cpu power than divx to decode so that would be great for us ppc users.

thanx for the tip on the lame dll.. i should have thought of dropping it in the vdub folder

red-i

hmmm.. i put lame_enc.dll in the vdub folder but i still don't see it listed in audio compression list.. i see mp3 but i don't think it's the lame codec.. should it specifically say lame? wtf???

Talyn

Yes, you should now have 3 entries:

Lame MP3
MPEG Layer 3
MP3 (this is a decoder only, don't use it for anything)

One thing about Lame, it's not as cooperative as MPEG Layer 3, meaning it only wants to do higher bitrate stereo. Every time I've tried to force it to do something else, VDub stopped with an audio compression error.

red-i

hmm am i missing something then? i've got lame_enc.dll in the vdub folder (main folder not in a subfolder of vdub's folder).. but it't not showing up :( i'm using vdub 1.4 btw.

Talyn

Honestly, if you have MPEG Layer 3, just use that, I doubt Lame is going to make much difference...

Ok here's my latest findings:

I took the Delgo QuickTime trailer, and converted it to a 38.9mb DivX file for the desktop. (I cranked up the bitrate really high for the desktop version, that's why it's so huge.)

Then ran it through VDub again for 2 PPC versions.

v1) 250kbps DivX and 128kbps stereo MP3, left at the original 24 fps. On the Axim, the audio did get out of sync, but less than a second. I'm guessing that even at those bitrates and framerate, the video is still taking too much CPU and the audio decodes faster. File size: 7.82mb.

v2) Same settings, but decimated the framerate by 2. Surprisingly, even though 12 fps sounds low, the playback on the Axim was just fine, and it stayed in sync perfectly. File size: 7.73mb.

-----------------------

I also noticed that VirtualDub is up to v1.5.4 now... I just upgraded mine.

-----------------------

On the issue of VirtualDub getting livelocked at 99% on Job 2: this is hardly a definitive solution, but I have noticed that it tends to only happen when I'm only processing audio on Job 2. If I process audio on both jobs, VirtualDub seems to complete just fine...so far.

red-i

well.. success using LAME :)

one thing that I finally figured out is that you can't simply drag n' drop the lame_enc.dll into the vdub folder. you have to download lame_acm.inf and lame_somthing.acm and install via right clicking on the inf file.

anyhow I took an mpeg, encoded at 100kbit video (every other frame of course), with 44khz 128kbit stereo audio and it played back flawlessly. I did a 3 min encode of a scene from shaft, as well as a 24min simpsons episode (no commercials) and watched both. It played back perfectly :) I'm gonna try higher bitrates and different combinations of audio settings to try to get the best possible video with no syncing issues. woohoo finally fullscreen divx :)

one question, how do I check how many frames have been dropped in pocket mvp? this way i can keep doing trial runs to see when i start getting dropped frames.

Talyn

Yeah I went back and checked the full LAME installer and noticed that there was indeed the .inf you have to use. Sorry 'bout that.

In PocketMVP look in Settings->Configure... and you will find an option to 'Show dropped frame.' That will display a dialog with the dropped frames at the end of each video. (It also displays it again when you open a new video if a video was already loaded...that's slightly annoying but, oh well.)

red-i

Thanks Talyn, with my current settings I get zero dropped frames.
I'm thinkin of starting a new thread for people to post their current settings, as well as a note if they've gotten any dropped frames.. that way we can see what kind of quality people are getting without loosing any frames.