Aspect ratio and ac3 sound woes......

[sterankin]

Hi there, first off. If I have an avi/divx that appears to be in
widescreen format, what setting do I choose in TMPEng?
Do I choose 1:1VGA or 16:9 ?

Also, I am having real trouble extracting the ac3 audio from the avi.
I used virtualdub to save the wav using direct stream processing, but how do I change the file extension to .ac3?

The file wont open in headac3he "could not find data chunk", I tried using ac3fix, but it won't open, it opens in a dos window and then disappears
again (I'm using windows 2k)

Can anyone give me a simple way to get the ac3 audio to wav?
Thanks.

[ralfbeckers]

Hello,

I haver never used the divx format but AVIs from various sources so what I'm gonna tell you refers to AVI, only. Needless to say you have to take this info for what it is: a subjective opinion. Make your own experiments. That said AVI is always 1:1 i.e. the pixel is exactly square (as opposed to just rectangular). Oixels on a DVD are not, neither are pixels in (S)VCDs. Remeber that the aspect ratio is eventually determined by the display device you use. The number of pixels per picture width is known but doesn't determin the aspect ratio. The same goes for the number of (active) pixels per picture height which can be anywhere from 576 to 480 pixels for SDTV (standard definition television).
ASSUMING that you use displays in the traditional 4:3 shape for authoring and watching your material ans ASSUMING that you want to preserve the original aspect ratio of the material in repect to the film maker's intention you want to maintain the letterboxed format you now have with your AVI file. This means that you leave it to 1:1 in the source and to 4:3 for the encoding. This will give you a file that maintains the original aspect ratio as well as the correct geometry of objects when played on a display with the 4:3 shape.

Now for sound. It is my understanding that AVI CAN contain sound but need not. If yours does, great. For all that I care AVIs contain uncompressed PCM and there is no need to splice the audio from the AVI just to have TMPG mux them again. If the AVI conatins sound in a format that TMPG understands then the sound file source is selected automatically. I believe that it is permissible for AVIs to contain compressed audio in various formats. To hear those sounds you need the appropriate codec installed on your system. I wouldn't be surprised if TMPG did not understand any arbitrary compression scheme. If that is the case with your file you might want to extract an uncompressed PCM wave file from it first and feed that the TMPG later.

Good luck!
Ralf

[bugster]

Widescreen or not? Well, it depends mainly on your final display device. If you are converting to mpeg for use on a DVD player, select 16:9 or 4:3 depending on your TV. Also, under advanced I would select Video arrange method as Full Screen - keep aspect ratio but just bear in mind that if your TV set is 4:3, then an aspect ratio of 16:9 and this video arrange method will result in a wide black bars top and bottom. Maybe experiment to see which looks best to you.

AC3, to change the filename extension, make sure that 'hide extensions for known file types' is Not checked in the explorer folder options. Then you can change the extension.
Ac3fix is a dos app and needs to be run from the command line. To do this 1st I would copy ac3fix.exe to your windows/system folder. This way it will be in the search path and you can run it from anywhere. Then open a dos window and change dir to where your movie is stored. Then simply type ac3fix movie.ac3 movie_fixed.ac3, <CR>. It will then run. Headac3he should then be able to open the fixed file and convert it to wav.

[sterankin]

Thanks for those raplies, very helpful, I have sorted the audio problems,
and the file extensions too.

But I am still confused about the aspect ratio, I have a 4:3 tv, but I want to preserve the aspect ratio of the original, which is widescreen (the avi appears to be in widescreen )

So what settings do I select?

[banjazzer]

bugster's advice is incorrect - if he was talking about the *Advanced* settings in TMPG. Source aspect ratio is always 1:1(VGA) for DivX. Video arrange method should be Full screen(keep aspect ratio), and it will do exactly what it says on the tin. 8)

[bugster]

bugster's advice is incorrect - if he was talking about the *Advanced* settings in TMPG. Source aspect ratio is always 1:1(VGA) for DivX. Video arrange method should be Full screen(keep aspect ratio), and it will do exactly what it says on the tin. 8)

Maybe a misunderstanding or I wasn't clear enough. When I said 4:3 or 16:9 I was referring to Aspect ratio setting on the video menu,

I think we mean the same thing just expressed differently.

W.R.T to aspect ratio on the video menu, I believe this sets the DAR value in the mpeg which may or may not be used by the player. Correct me if I am wrong but my understanding is that for VCD only 4:3 is valid but for SVCD and DVD 16:9 is valid also, tho not all SVCD players handle 16:9 correctly, is this right?

[banjazzer]

I think we mean the same thing just expressed differently

Very possibly.

Correct me if I am wrong but my understanding is that for VCD only 4:3 is valid but for SVCD and DVD 16:9 is valid also, tho not all SVCD players handle 16:9 correctly, is this right?

I'm not sure from direct experience. I believe there can be compatibility problems if you choose (Video setting) 16:9. What I do know is that I have a widescreen TV and always leave the video setting as (default) 4:3. So all my encodes work perfectly on a standard TV, and on my widescreen I use the zoom setting, which also works perfectly. Basically, I have not had any reason to set the video setting to anything other than the default (4:3).