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Davaris

Compressing Wav Files

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Davaris    118
Hi Guys, I''ve just hooked up a compressor library to my resource file manager and it works fine. It uses gzip. The same thing that winzip uses. The only problem is it only compresses wav files by 30%. I know it is possible to do much better than this as Interplays acm format reduces wav files by 75%. Only problem is the technology is *supposedly* a secret. There is a program floating around called acm2wav.exe which converts acm files to wavs but so far I haven''t been able to find the source code. If anyone has it and is willing to share it please mail me. Dave

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quote:
Original post by Davaris

Hi Guys,
I''ve just hooked up a compressor library to my
resource file manager and it works fine. It uses gzip.
The same thing that winzip uses. The only problem is
it only compresses wav files by 30%. I know it is
possible to do much better than this as Interplays acm
format reduces wav files by 75%. Only problem is the technology
is *supposedly* a secret.

There is a program floating around called acm2wav.exe which converts acm files to wavs but so far
I haven''t been able to find the source code. If anyone has it
and is willing to share it please mail me.

Dave



MP3 is the way to go. You can achieve great compression ratios.
www.wotsit.org

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felisandria    739
Okay, well.

The reason your zip library isn''t compressing as well as you think it should is because you''re compressing something totally different than what the acm format is compressing. You''re compressing the bytes you get in ADPCM (standard .wav is ADPCM which stands for Advance Pulse Code Modulation, basically it''s a digital sampling of the literal waveform with a little brains thrown in so it''s not raw PCM). What MP3 and pretty much every other sound format (acm included I''m sure) is compressing is an interpretation of the sound data, not the bytes. The converter regurgitates its interpretation of the original sampled waveform from the ADPCM, then takes that waveform and performs ACM compression on it.

I would guess with a compression rate that high that ACM would have to be a lossy format. Note: Lossy != sounds terrible. MP3 is a lossy format. Really lossy, if you look at it.

Is there a compelling reason you really really want to use ACM format, or would MP3 be okay? There''s a lot more info on MP3, compression is just as good if not better, and it''s really not that bad of a format to use (I''ve written an OKI24 to MP3 converter, not too bad.)

-fel

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Davaris    118
>Is there a compelling reason you really really want to use ACM >format, or would MP3 be okay?

Fallouts .acm music files are 4 meg on average and when you
decompress them they become 20 meg .wav. I just want to learn how they did it. The sound quality is great so I don''t think its lossy or MP3.

Fallout 1 & 2 use this format for
all their music and sfx. I''m sure you''ll agree if you''ve
ever played the games that the sound quality is excellent.

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Muzzafarath    146
I've got two words for all of you recommending MP3: Ogg Vorbis. Who wants a proprietary format anyway? It is licensed under the GNU LGPL (Lesser General Public License) btw.

Edited by - Muzzafarath on November 1, 2000 3:32:03 AM

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Shannon Barber    1681
Just crank up the bit rate on the mp3 and you''ll get an excellent quality at a compression ratio of 1:4. I think you could do 300kbps and get that.

Typical compression rates are 1:9 using 128kbps or about 1:8 using 192kbps. 192kbps sounds the same to me for all my CD''s. Pink Floyd & Rush sound kinda crappy at 128kbps, but with Green Day or Bush you can''t tell any difference

You can''t use a propietary compression algorithm and not pay for it, at least not legally

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Muzzafarath    146
quote:
Original post by Magmai Kai Holmlor

You can't use a propietary compression algorithm and not pay for it, at least not legally


Heh, but what would you rather use: a non-propietary algorithm that's totally free and compresses better than the other algo or a propietary algorithm that doesn't compress as good as the other algo (and then breaking the law by not paying for it)? Tough choice

Edited by - Muzzafarath on November 2, 2000 5:00:09 AM

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