Typical signal to noise ratio of ADPCM Options

[Neuron]

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.

[extrabigmehdi]

Well, I used the normalize function of soundforge .
It says that the RMS for file "Eric_Brosius___02___Med_Sci_1___44_Khz_lossless.flac" (i.e 44khz, lossless) is -19db
Now for the error , I compute the difference between the previous file and ADCPM version, (i.e Eric_Brosius___02___Med_Sci_1___44_Khz_IMA_ADPCM.wav)
using the channel converter function of soundforge.
The normalize function says that the RMS of error is -38.2 db


So basically you have two number for 44hz version :
signal: -19 db
noise: -38.2 db


but sorry I don't know the final formula to compute the snr, especially if you consider that soundforge give negative values for RMS .

[Neuron]

Well, I used the normalize function of soundforge .
It says that the RMS for file "Eric_Brosius___02___Med_Sci_1___44_Khz_lossless.flac" (i.e 44khz, lossless) is -19db
Now for the error , I compute the difference between the previous file and ADCPM version, (i.e Eric_Brosius___02___Med_Sci_1___44_Khz_IMA_ADPCM.wav)
using the channel converter function of soundforge.
The normalize function says that the RMS of error is -38.2 db


So basically you have two number for 44hz version :
signal: -19 db
noise: -38.2 db


but sorry I don't know the final formula to compute the snr, especially if you consider that soundforge give negative values for RMS .

Thank you very much, but what does the first value mean? RMS of what? The second I understand is of noise but the first...
Can you do to the same comparision for the MS ADPCM file please? And perhaps verify it by doing the same with an 8-bit LPCM file? An 8-bit LPCM file should have a SNR of around 48 dB (42 dB with dithering). If the results will be too different something is off.

This post has been edited by Neuron: Jan 30 2013, 11:32