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Unofficial VirtualDub Support Forums > Codec Discussion > Ac-3 Acm Encoding Problem

Posted by: rincewind Feb 10 2008, 11:33 PM

XP Pro SP2 Virtualdub 1.7.6
Installed ac-3 acm 1.4.
Rebooted
Loaded avi file which virtualdub reports as being 48000Hz; 5.1; AC-3 ACM Codec 448kbps. Audio plays just fine but a bit quiet.

Tried to recompress the audio (Having fiddled with the volume)
* Audio->Full Processing
* Audio->compression->AC-3ACM codec; 128kBits's,48000Hz,5.1 channels
* File->Save

Virtualdub reports
"Error initializing audio stream compression
The audio codec cannot compress the source audio to the desired format
Check that the sampling rate and number of channels in the source is compatible with the selected compressed audio format"

Well I dont see how it can be less compatible!!! (I did try 448kbps as well and got the same message)

So what am I doing wrong?
All help gratefully appreciated.

Posted by: fccHandler Feb 13 2008, 11:23 AM

I don't know whether VirtualDub supports recompressing six channel audio. Using the "Audio / Conversion" menu to change it to stereo should work.

Posted by: DarrellS Feb 13 2008, 05:48 PM

I used Virtualdub 1.8.0 to convert a WMV-HD file to XviD/AC3 and used the AC-3 ACM Codec to compress the audio to 48000Hz 192 kb/s 6 channel sound.

Virtualdub would not decode the 5.1 WMA so I had to convert it to 5.1 Wave with dbpoweramp and insert into VDub and recode.

Posted by: phaeron Feb 14 2008, 05:01 AM

QUOTE

I don't know whether VirtualDub supports recompressing six channel audio. Using the "Audio / Conversion" menu to change it to stereo should work.

Other way around -- VirtualDub has supported 5.1 pass-through since 1.6.13, and it can also translate between the WAVEFORMATEX and WAVEFORMATEXTENSIBLE versions. It can't, however, do downmix from 6-ch to 2-ch.

Posted by: rincewind Feb 14 2008, 07:01 AM

Sorry - bit of a newbie and am defeated by the jargon.

1. I often use VirtualDub to take 5.1 audio input and output 2 ch stereo - is this 'downmix from 6-ch to 2-ch'?

2. Back to the original question: Can VirtualDub (or I suppose VirtualDubMod) take a 6 channel sound track, decode it, process it (e.g. increase the volume) present it to the AC-3 ACM codec and put the re-encoded audio into the output avi file?
If Yes - how do I do it?
If No - what should I use to do this?

TFAI

PS phaeron: Virtualdub - brilliant. Dunno what I'd do without it. Thanks.

Posted by: fccHandler Feb 16 2008, 06:22 AM

QUOTE (rincewind @ Feb 14 2008, 03:01 AM)

1. I often use VirtualDub to take 5.1 audio input and output 2 ch stereo - is this 'downmix from 6-ch to 2-ch'?

Yes, this works because AC3ACM does the downmixing.

QUOTE

2. Back to the original question: Can VirtualDub (or I suppose VirtualDubMod) take a 6 channel sound track, decode it, process it (e.g. increase the volume) present it to the AC-3 ACM codec and put the re-encoded audio into the output avi file?

I've done some testing, and I haven't gotten that to work either. I tested VirtualDub-MPEG2 1.6.19 and VirtualDub 1.7.7 with the MPEG2 plugin. The file I tested is here:

http://fcchandler.home.comcast.net/THX.vob

I don't know yet whether the problem is VirtualDub or the AC3ACM codec, but you're absolutely right that it doesn't work.

Posted by: pintcat Feb 16 2008, 04:05 PM

Interesting issue! I think the problem is related to the AC3 decoder, because if you convert the audio to 5.1 LPCM and import this as "Audio from file...", VDub will be able to encode it to 5.1 AC3. On the other hand, if you try to convert the imported AC3 to any other codec which provides 5.1 encoding, you'll always get the same error message.

@rincewind: Don't you think 128 kbit is a little low for 6 channel sound? Just tried it with fcchandler's THX video and it sounds terrible!

Posted by: DarrellS Feb 17 2008, 06:25 AM

If I remember correctly, I always had trouble with AC3 audio from VOB files in VirtualdubMod or Virtualdub-MPEG2 and had to save as Wave, reinsert and recode to MP3.

With fcchandler's AC3 input plugin, you might be able to direct stream copy the audio as a Wave file and change the extension to AC3 and reload back into Virtualdub and do what you want.

Also, you can use AC3 filter to raise the volume of the audio in the player. You don't need to recode the audio. From my understanding, this is a software player problem, not an AC3 problem. The AC3 audio should play fine on a hardware player.

If file size is the issue then MP3 is probably a better option. You can use VirtualdubMod Aud-X to get 5.1 surround MP3 or convert the AC3 to 5.1 surround with the Fraunhofer converter and use Virtualdub 1.8.0 to insert the 5.1 MP3 and direct stream copy (not sure if this option will decode correctly in your player).

Posted by: rincewind Feb 25 2008, 06:00 PM

QUOTE (pintcat @ Feb 16 2008, 10:05 AM)

Thanks to all for your replies. nice to know it was not me being stupid (for once!) I'll try one of the more roundabout approaches.

Pintcat: well I guess 128kb might be a little slow but as I could never make it work, I never got to find out !! :-)

Posted by: n:CorE Nov 16 2008, 05:38 AM

Guys, even i am facing the same problem....So this means that i cannot make a DVDRip with untouched audio in VirtualDub MPEG2 1.6.19 ?....The source audio is 48kHz 5.1 448 Kbps @ AC-3... I want this same to be stable for my DVDRip....?? Is it possible....?

The source file is a *.vob file and not AVI ....

Posted by: phaeron Nov 16 2008, 07:11 PM

No discussion about DVD ripping, please....

Posted by: realdark86 May 27 2010, 09:11 AM

Maybe you should try aud-x codec. It enables to compress 5.1 audio.