Or more generally, watch the histogram of samples On 10 January 2011 11:09, Roman Haefeli <[email protected]> wrote: > On Sun, 2011-01-09 at 20:26 -0500, Mathieu Bouchard wrote: >> On Mon, 10 Jan 2011, ~E. wrote: >> >> > I'm searching how i can detect the change in the compression of an audio >> > signal. The purpose is to detect (and quantified) the compression >> > changes between the music and the ads in a radioshow. Have any ideas ? >> >> If you don't have the original uncompressed recordings, I don't see how >> you could be doing that. You'd have to guess how complex sounds are >> supposed to fade out normally, to find out how much the fade out has been >> messed with. >> >> And then, in the compressor, you have both a measurement of input volume >> and a formula for turning that input volume into a gain to be applied, and >> both of those parts are subject to a lot of variation and tweaking. > > Assuming that the more compression is applied, the more the RMS > amplitude [1] approaches the Peak amplitude [2] of an audio signal, you > could measure the two and probably get a raw grasp how much compression > was applied. This is simply an idea for which I don't have any reference > that it is really working. > > I could imagine that recordings of certain sets of natural instruments > show always a similar relation between peak and RMS amplitude for that > set. However, usually there is already some compression applied when > releasing the recording which makes it hard to distinct compression > applied in the radio station from the compression shipped with the > recording. I also could imagine, that it's much harder to find > applicable rules for synthesized sounds. > > Roman > > > [1] http://en.wikipedia.org/wiki/Amplitude#Root_mean_square_amplitude > [2] http://en.wikipedia.org/wiki/Amplitude#Peak_amplitude > > > > > _______________________________________________ > [email protected] mailing list > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list >
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