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u-law
Neuron
post Dec 16 2012, 01:50
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How come u-law was not used with high sample rates in the old days of computing? A quick search here says u-law is not good for sampling above 16 khz because of high frequency distortion, but when I encoded a 320 kbps mp3 44.1 khz into an 8-bit u-law 44.1 khz format it actually sounded quite ok especially compared to 8-bit linear PCM and even 4-bit ADPCM. So how come it was not used in games and multimedia at good sample rates before mp3 came? I understand that it distorts the sound slightly however this distortion is much less hearable on my samples created with audacity than in the same sample encoded to either linear 8-bit PCM or 4-bit ADPCM. And that encoded music was a 1980s OMD track with high dynamic range, not a modern day overcopressed/clipped sample. I am kind of interested in old formats and computing, so that's why I'm asking. I would insert short sound samples, but I don't know how to add them on this forum.

EDIT - I uploaded some sample files here http://www.hydrogenaudio.org/forums/index....showtopic=98358 .

This post has been edited by Neuron: Dec 16 2012, 02:09
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Kujibo
post Dec 18 2012, 04:33
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As a game audio developer that lived through 8-bit -> ADPCM -> MP3 here's my take.

The simple answer is ADPCM = 4:1, u-law = 2:1. Sound designers are quite happy to be able to put twice as much audio in the game - this is a really big deal for them, there sure wasn't much memory around back then to use. It's still a huge deal today, you'll find it very rare to find 16-bit or FLAC samples in a game - it would be a waste of memory even if it does sound better. Programmers and producers like the sound of better compression too, better technical numbers just sound nicer right?

Back then nobody was performing super critical listening tests like you see on here either. A guy like me would put ADPCM in the audio engine, sound artists would hear the result and be happy with it. We wouldn't have even bothered trying u-law as it's only going to give half as much compression.

It's only when you start to critically listen to the audio and put all sorts of killer samples through it that you realize ADPCM creates some pretty bad noise in some cases. But for almost all audio in the game, it was good enough. It's kind of similar to what happens when you dissect MP3. It's often not until you start looking for problems do you notice them. The average person will never notice or care.

As well, u-law did get the rare bit of use too in video games way back then, granted not anywhere even close to what ADPCM did.
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