A lot of audio sync issues can arise from MP3 VBR being used instead of CBR. Unfortunately, many encoding programs default to VBR, so the vast majority of MP3 AVIs out there have VBR audio.
The AVI container does not properly support VBR MP3 audio. (Look at Avery Lee's website) The problems caused by VBR are not so easy to identify as such, but the result is that some standalone players can drift in and out of sync. You can also have strange problems when transcoding to another format.
You will notice that aXXo's releases are *never* VBR audio. For good reason.
Rather than get lost in the process outlined above, all you have to do is load the movie into VirtualDub-MP3 which you should be able to find with a bit of googling. Choose "Save WAV" from the file menu. This will demux the audio without doing any processing on it. It's a bit misleading as it doesn't really make a "WAV", it just demuxes it and saves it as whatever it is, mp2, mp3, ac3, whatever. So if it is an MP3 track, then give it *.mp3 extension. File Information from the File menu will give you info about audio and video codecs used if you're not sure. If you don't have all the codecs, I can recommend the K-Lite Codec Pack. (Google for that, too)
Doing file Properties on your demuxed audio track should show you the bitrate; if it's some odd number then it's likely VBR. If it's 80,96,112,128,160,192... you know, multiples of 16, then it's probably CBR. Load the track into Mp3Trim Pro (What? you don't have this vitally essential tool? Well,
get it!) and it will tell you exactly what you've got. While you've got it there, press the "Auto" button, which will normalize the level. (You might be surprised to find that the vast majority of movies are 10-20 db down in audio level. That's a lot. A common cause of this is that somewhere along the line an AC3 decoder ignored the dialnorm parameter, used to set the dialog level relative to the surround channels. If this is ignored, the level will probably end up much too low.) Click on "Save" and it will rewrite the headers to normalize the volume. I would recommend you funnel your whole mp3 collection through this indispensable tool so that all your songs play at the same volume. It has a batch feature which makes it really easy.
If your audio track is identified as VBR, then you can fire up DBPowerAmp and quickly convert it to CBR. (What? You haven't got DBPowerAmp? Well, go to the
Illustrate website and get it. It's free.) The DMCr9 conversion utility handles WAV and MP3; there are plugins available for most other audio formats. If you need to deal with AC3, then you need the AC3Filter and the DirectShow plugin. There are instructions on how to configure it. Avoid using the Blade mp3 encoder; Lame gives much better result. If the original track was reported as being, say, 132kb/s, then tell DBPowerAmp to convert it to 128 CBR. In other words, use the next lowest of the standard CBR settings. Joint Stereo may give a better compression and will sound just as good as full stereo.
Now here's something that aXXo (and I) realized a long time ago. If you want your movie to fit on 1 CD, then there has to be some compromises. The most important thing is the picture quality. Having to look through compression artifacts ruins the viewing experience. In order to give the picture component sufficient bitrate, you might have to steal some from the audio. I see the audio purists throwing up their hands in horror. Nothing less than 320kb/s will do. That is not the case. 128, 112, 96 or even 80kb/s can be quite acceptable. If you examine aXXo rips, you will see that sometimes the audio is as low as 80. What? But it should sound like crap. Well, it doesn't. It is surprising how low you can go and still keep the audio quality acceptably good. However, the lower the audio bitrate the more important it is for it to be CBR to avoid sync issues.
Off the soapbox and back to the audio track:
You can then load your converted and normalized audio into VirtualDub MP3. (Pick "MP3 Audio" from the Audio menu) You can play a portion of the movie on the timeline to determine whether it's in sync or not. If not, you can use the Interleaving function to add or subtract a delay (in milliseconds) to correct it. (You get pretty good at guessing the number of milliseconds after a few tries) Then, after making sure both audio and video are set to "Direct Stream Copy", save AVI to a new name and you're finished. In this mode V-Dub only remuxes, doesn't do any other processing, so this is very quick.
-freddy
