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Old 30 May 2002, 11:59 PM   #1
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Default Divx w/ AC3 question?

Ok I am fairly new to the MPEG-4 thing so I have a few easy questions and looking for input.

Here's how I made the DivX Video:

I used DVD2AVI and VFAPI to make a dummy .avi and frameserve the ripped .vob files off the DVD. Then I opened the fake .avi in VirtualDub and compressed it using a 2-pass method with DivX 5.x pro codec and a resize filter. Used a bitrate of 1680kbps calculated to fill 2 CDs with the AC3 file. Video turned out good and looks good. I tried XVid codec but find the DivX 5.x gives better quality.

The reason I used VirtualDub for the video is I tried FlaskMpeg but I aborted after starting a compress and now it crashes after every first pass. Flask and XMpeg just crash too often. Is there any problems using my method with the fake AVI and VirtualDub to make the DivX video? Are there any better methods I could try?

Audio:

I extracted the AC3 audio using VSTRIP. I extracted the .ac3 file from the .vob files then merged them using the copy command in DOS. So far so good both work. I can view the video and listen to the .ac3 streams in windows media player no problem.

Now time to merge the 2 together and I'm praying I don't run into sync problems...thinking it's oging to take me a week to get it right. So I open the AC3 version of VirtualDub, open the video file, open the .ac3 files which then gives me a box with the audio properties. Says 2-channel? So I proceed to merge the 2 keeping the interleave at the default settings to test it out. 3 minutes later it's done. I play the completed file with video no audio. Why does the seperate .ac3 file play but the merged files have no audio. So I try playing it with my Hollywood Plus and the audio works and it displays AC3 and of course no video cause the Hollywood Plus doesn't support MPEG4. Then I get the Nimo Codec pack and install only the AC3 codec and the completed file works like a charm no sync problems.


Questions:

How come the seperate .ac3 I got using VSPLIT plays but when I merge it with the video using VirtualDub it won't play without an .ac3 codec installed?

How come VirtualDub says the .ac3 audio track is 2-channel?

Will the Dolby Digital 5.1 AC3 audio actually work? I don't have a dolby digital system but am making an AC3 DivX so I'll have it in the future. Also so I can bring it to my sister's house and play it on her Dolby Digital system. Any way to ensure that it will work?

Why do people use MP3 to make their DIVX when AC3 rocks the shit out of MP3? My 1hr40min movie has an .ac3 file of only 140MB, and with a 2 CD rip the video looks great.

Any tips on how to improve my process? Perhaps a suggestion to use XVid or Nandub SBC instead of DivX 5.x.

Sorry for the long post but this is my first DivX ever and I'm nervous as hell. I have many little easy questions.
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Old 31 May 2002, 03:45 AM   #2
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Wow huge posting...

If you have several seperate questions feel free to post them in seperate threads. Answering postings like this is really really cumbersome.

Quote:
Originally posted by Gondo

The reason I used VirtualDub for the video is I tried FlaskMpeg but I aborted after starting a compress and now it crashes after every first pass. Flask and XMpeg just crash too often. Is there any problems using my method with the fake AVI and VirtualDub to make the DivX video? Are there any better methods I could try?
VFAPI is a useable solution. But you might want to try using GordianKnot0.26 it's the perfect tool for DVD->divx5.02 transcoding.

Quote:
Originally posted by Gondo

How come the seperate .ac3 I got using VSPLIT plays but when I merge it with the video using VirtualDub it won't play without an .ac3 codec installed?
Which player did you use for ac3 playback ?, my guess is that the player you used has an inbuild ac3 decoder, but to decode an ac3 stream in a avi file, wmp needs a registred ac3 decoder.

Quote:
Originally posted by Gondo

How come VirtualDub says the .ac3 audio track is 2-channel?
Probably because it is only a stereo ac3 stream, 1h40m at 140MB equals 192kbps which is not nearly enough for a 5 channel stream.

Quote:
Originally posted by Gondo

Will the Dolby Digital 5.1 AC3 audio actually work? I don't have a dolby digital system but am making an AC3 DivX so I'll have it in the future. Also so I can bring it to my sister's house and play it on her Dolby Digital system. Any way to ensure that it will work?
The only way to make sure something works, is to try it.

Quote:
Originally posted by Gondo

Why do people use MP3 to make their DIVX when AC3 rocks the shit out of MP3? My 1hr40min movie has an .ac3 file of only 140MB, and with a 2 CD rip the video looks great.
Well 192kbs is rather low for an ac3 stream. AC3 streams can be upto 448kbs, puting that on a 2 CD rip would,in my opinion, be a waste of space that could otherwise be used for better video quality. And for a 1CD rip ac3 is ofcause out of the question.

Quote:
Originally posted by Gondo

Any tips on how to improve my process? Perhaps a suggestion to use XVid or Nandub SBC instead of DivX 5.x.
As I said you should defintly try using GordianKnot.

Quote:
Originally posted by Gondo

Sorry for the long post but this is my first DivX ever and I'm nervous as hell. I have many little easy questions.
No need to be nervous, I don't bite .
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Last edited by khp; 31 May 2002 at 03:49 AM
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Old 31 May 2002, 06:29 AM   #3
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Quote:
Why do people use MP3 to make their DIVX when AC3 rocks the shit out of MP3
this pretty much sounds like crap to me!

you cant judge what other peoples mp3 might sound like and still you think an ac3 is better?

unless you HAVENT got a dolby digital system, an mp3 - if its well done - sounds much better on any pc with normal sound-systems (like e.g. cambridge soundworks), because you dont have to turn up your loudness for dialogues or almost switch off sound in case of action/explosion etc.

if you havent got an idea of what a good mp3 in dolby surround miight sound like, i'll be glad to provide you with a sample!
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Old 31 May 2002, 09:07 AM   #4
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Thanks for the info. I saw lots about this Gordian Knot. I'll check it out.

As far as the AC3 goes, I agree that on computer speakers MP3 sounds amazing and just as good as a 2-channel dolby. But if you have a Dolby System why not take advantage it? Dolby 5.1 is better than 2-channel MP3 any day.

And the AC3 stream I had is 2-channel. I guess if I had a new DVD with a 5-channel ac3 stream I'd rethink about using MP3.

Hey is this possible? Encode the DivX file 2-CD rip using MP3. And use a 3rd CD for a a 5-channel AC3 stream you can overlay if desired in BS player.
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Old 31 May 2002, 09:15 AM   #5
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bsplayer might be able to handle this. but you could also go for a 2-3 cd rip with a primary and secondary audio stream you choose from!

thus, an ac3 + mp3 could be possible.

i'd personally not consider any such method, though, and rather stick to a bilingual avi file.

anyway, i didnt intend starting some flame-war on ac3 vs mp3 here but rather take a stand for mp3, as it might sound very good if done with a little more than average-flask-knowhow.

Last edited by UncasMS; 31 May 2002 at 04:14 PM
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Old 31 May 2002, 10:42 AM   #6
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How about the new MP3PRO format? That might be able to save you 50MB or so better used for video bitrate. Would be useful for Single CD encodes.
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