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Typical signal to noise ratio of ADPCM
Neuron
post Jan 28 2013, 15:08
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So, I have decided to return to this forum (despite my little conflict with greynol) and I have kind of a weird question. I would like to know what is the rough SNR of a 4-bit ADPCM recording (IMA and Microsoft). For those curious why I am asking this, well, I like ripping music and sound effects from old games, and I would like know the technical side as well.
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Neuron
post Jan 29 2013, 22:42
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I have to admit I don't really know how to do such a thing but I've found something http://www.baudline.com/solutions/codec/index.html .

The curious thing is, why does ADPCM achieve lower SNR than 8-bit PCM according to that website even through ADPCM usually sounds much better? Is it because a sine wave was used? Same for u and A-law, I thought they were supposed to increase SNR (and u-law and A-law files indeed hear much cleaner than linear 8 bit).

This post has been edited by Neuron: Jan 29 2013, 22:44
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Woodinville
post Jan 31 2013, 08:33
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QUOTE (Neuron @ Jan 29 2013, 13:42) *
I have to admit I don't really know how to do such a thing but I've found something http://www.baudline.com/solutions/codec/index.html .

The curious thing is, why does ADPCM achieve lower SNR than 8-bit PCM according to that website even through ADPCM usually sounds much better? Is it because a sine wave was used? Same for u and A-law, I thought they were supposed to increase SNR (and u-law and A-law files indeed hear much cleaner than linear 8 bit).



SNR has little to do with audio quality except at extrema.

ADPCM has a variable step size. The mechanics of step-size adaptation mean that you don't quite get 6dB/bit, you usually lose about .5 to 1 bit's worth of SNR, BUT that is adapted to the energy in the coding residual, so you don't get a noise floor like you get from PCM. PCM has a fixed lower noise floor. ADPCM does, but it's much, much lower, and depends on the adaptation paramters, step size leak value, and central step size value. And most often it's teensy-tiny. Of course, when you put in a large signal you get much much more error, but a lot of it is masked.


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J. D. (jj) Johnston
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Posts in this topic
- Neuron   Typical signal to noise ratio of ADPCM   Jan 28 2013, 15:08
- - saratoga   There are various adpcm flavors. Which are you usi...   Jan 28 2013, 16:56
|- - Neuron   QUOTE (saratoga @ Jan 28 2013, 16:56) The...   Jan 28 2013, 20:16
- - Garf   CompAudio from AFsp can calculate this, IIRC. But ...   Jan 28 2013, 17:51
|- - Woodinville   QUOTE (Garf @ Jan 28 2013, 08:51) CompAud...   Jan 31 2013, 08:30
- - kode54   Cool, game soundtrack ripping for the win. I may b...   Jan 29 2013, 06:07
|- - Neuron   QUOTE (kode54 @ Jan 29 2013, 06:07) Cool,...   Jan 29 2013, 11:54
|- - Neuron   QUOTE (kode54 @ Jan 29 2013, 06:07) Cool,...   Jan 29 2013, 16:47
- - Neuron   Here it is:http://www.hydrogenaudio.org/forums/ind...   Jan 29 2013, 12:46
- - saratoga   If you have the lossless and lossy encoded files y...   Jan 29 2013, 17:37
- - Neuron   I have to admit I don't really know how to do ...   Jan 29 2013, 22:42
|- - Neuron   I've added the song in 44 Khz MS ADPCM to the ...   Jan 29 2013, 23:15
||- - bandpass   QUOTE (Neuron @ Jan 29 2013, 22:15) MS AD...   Jan 30 2013, 08:46
|- - Woodinville   QUOTE (Neuron @ Jan 29 2013, 13:42) I hav...   Jan 31 2013, 08:33
- - extrabigmehdi   Well, I used the normalize function of soundforge ...   Jan 30 2013, 00:08
|- - Neuron   QUOTE (extrabigmehdi @ Jan 30 2013, 00:08...   Jan 30 2013, 11:29
|- - extrabigmehdi   QUOTE (Neuron @ Jan 30 2013, 10:29) Thank...   Jan 30 2013, 13:48
- - Neuron   Thank you, but what does "signal: -19 db...   Jan 30 2013, 14:14
|- - db1989   QUOTE (Neuron @ Jan 30 2013, 13:14) ADPCM...   Jan 30 2013, 15:29
|- - extrabigmehdi   QUOTE (Neuron @ Jan 30 2013, 13:14) Thank...   Jan 30 2013, 15:49
|- - Neuron   QUOTE (extrabigmehdi @ Jan 30 2013, 15:49...   Jan 30 2013, 16:07
|- - Neuron   QUOTE (extrabigmehdi @ Jan 30 2013, 15:49...   Jan 30 2013, 16:13
- - pdq   The "dynamic range" of mp3 is actually q...   Jan 30 2013, 15:24
- - Neuron   I did an Audacity convert to mono + match both vol...   Jan 30 2013, 16:00
|- - extrabigmehdi   QUOTE (Neuron @ Jan 30 2013, 15:00) I got...   Jan 30 2013, 17:03
||- - Neuron   QUOTE (extrabigmehdi @ Jan 30 2013, 17:03...   Jan 30 2013, 21:04
|- - saratoga   QUOTE (Neuron @ Jan 30 2013, 10:00) I did...   Jan 30 2013, 18:20
|- - Neuron   QUOTE (saratoga @ Jan 30 2013, 18:20) So ...   Jan 30 2013, 21:24
|- - saratoga   QUOTE (Neuron @ Jan 30 2013, 15:24) QUOTE...   Jan 31 2013, 01:44
|- - Neuron   QUOTE (saratoga @ Jan 31 2013, 01:44) QUO...   Jan 31 2013, 13:44
- - Neuron   That is true, but it does not explain why the ADPC...   Jan 30 2013, 21:10


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