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Topic: Ask for help, any lossless ACM? (Read 4218 times) previous topic - next topic
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Ask for help, any lossless ACM?

Hello,

Recently I started to do some video editing, but soon I found using WAV file is stupid because it write very large files and slow my PC down. For video I found Huffyuv but can't spot any lossless codec that can be seen in VIRTUALDUB, can anyone suggest any lossless codec?

Thanks in advance.
Hong Kong - International Joke Center (after 1997-06-30)

Ask for help, any lossless ACM?

Reply #1 –
The chance to ever get a  lossless.ACM is close to zero, as lossless means always VBR ( Variable Bitrate ) by definition and the ACM codec API doesnt support VBR codecs.

In the surrounding of the matroska container project we have plans to also release a new codec API that would overcome this problem ( UCI shows the direction, Ogg API could be another solution ), and to integrate that into VirtualdubMod ( http://sf.net/projects/virtualdubmod ).

As we want to be able to at least capture into matroska files fully lossless ( audio and video ) by the end of this year there are plans to integrate either FLAC or Wavpack into VirtualdubMod ( hardcode it ), the GPL license allows doing that, so we wont have to wait for the mentioned new codec API to use lossless audio with matroska ( and maybe even OGM ) files.

Ask for help, any lossless ACM?

Reply #2 –
Quote
The chance to ever get a  lossless.ACM is close to zero, as lossless means always VBR ( Variable Bitrate ) by definition and the ACM codec API doesnt support VBR codecs.

But how OGGACM works as it is also VBR???????/

Ask for help, any lossless ACM?

Reply #3 –
I think Christian is confused...

AFAIK, you can perfectly code a VBR ACM codec. No problems with that.

Problem is, the AVI container format doesn't handle well VBR audio streams. That leads to errors like lost sync, impossibility to search, etc.

If there was a lossless ACM codec, using it to put an audio stream inside AVI would be unwise. But if you use OGM as container, all would be fine.

Ask for help, any lossless ACM?

Reply #4 –
Quote
The chance to ever get a  lossless.ACM is close to zero, as lossless means always VBR ( Variable Bitrate ) by definition and the ACM codec API doesnt support VBR codecs.

In the surrounding of the matroska container project we have plans to also release a new codec API that would overcome this problem ( UCI shows the direction, Ogg API could be another solution ), and to integrate that into VirtualdubMod ( http://sf.net/projects/virtualdubmod ).

As we want to be able to at least capture into matroska files fully lossless ( audio and video ) by the end of this year there are plans to integrate either FLAC or Wavpack into VirtualdubMod ( hardcode it ), the GPL license allows doing that, so we wont have to wait for the mentioned new codec API to use lossless audio with matroska ( and maybe even OGM ) files.

Thanks for your detail explaination.

Looking forward to "matroska" project, hope it bring some light to us.
Hong Kong - International Joke Center (after 1997-06-30)

Ask for help, any lossless ACM?

Reply #5 –
Quote
Problem is, the AVI container format doesn't handle well VBR audio streams. That leads to errors like lost sync, impossibility to search, etc.

If there was a lossless ACM codec, using it to put an audio stream inside AVI would be unwise. But if you use OGM as container, all would be fine.

Sorry for my stupidity ...

I just to replace the stupid WAV with something like FLAC, Monkey's Audio or LA inside the AVI.
Is the format of AVI so suck that it didn't able to put those lossless codec inside?

Can you talk a bit more about OGM? I've seen it but no idea what it is.

Thanks.
Hong Kong - International Joke Center (after 1997-06-30)

Ask for help, any lossless ACM?

Reply #6 –
Quote
I think Christian is confused...

AFAIK, you can perfectly code a VBR ACM codec. No problems with that.

no, it won't work "perfectly" (i.e. "there are problems with this  ), because of the way ACM is designed.

basically, it assumes CBR, declared in the header, but codec still can generate arbitrary-sized output from input (as long as it does not overflow application's buffer). this hack will work for streaming, but seeking and time-estimation for WAV files will be wrong. (look at how Vorbis ACM works with winamp2 Waveform decoder)

Ask for help, any lossless ACM?

Reply #7 –
A good example is Nic's AAC2WAV, adding a WAV header to an ( existing ) AAC track, being VBR by default. It has to scan the file before adding the WAV header to find out the actual average bitrate, as the WAV header will require this. IMHO this is impossible to do with an ACM codec in a spec compliant way.

Of course, you can simply set an estimation of the bitrate in the WAV header if you start with the lossless encoding, but then you are 100% certain to get sync problems when writing the lossless audio track into the AVI. So, yes, AVI is absolutely not prepared to contain lossless audio in a stable and spec compliant way. The only reason that VBR MP3 does work in AVI somehow is a 'bug' in the DirectShow MP3 parser coming with every Windows installation. Nando was abusing this behaviour when making nandub, and it was copied on Linux also .... Cyrius, the author of VirtualdubMod, could tell you more or give a link to one of his explanations on Doom9 i guess.

OGM would work, but i dont think there is anybody to look at this right now.

And May 1st is big release date for matroska  .....