mad-user December 2000

mad-user@lists.mars.org

12 participants
35 discussions

Re: [mad-user] clipping
by David Shin 16 Dec '00

16 Dec '00

"Roberts, Wes" wrote: > > Wow, I always wondered why I saw the winamp graphics equalizer show the > dancing waveform as level and at the top of the range of loudness. > > But these songs always sounded the best. > > Before I read your email I even wanted to know how to make my own songs like > that. > > Should I still do it, (not to point of clipping). It's hard to do it right in software. You can use tools like Cool Edit Pro, which sounds the best, but that's tedious. Most people just use what's available in their ripping software to merely normalize tracks, which isn't really the same as compression. A lot of these kind of encodes sound very boomy and distorted. I think the normalize function in AudioGrabber is flawed in some way as a matter of fact. Read the specifics of that somewhere, but the main problem is that it's using a crude and fast algorithm to merely get the job done and nothing more. But I take Anthony's view on this matter: "To me material that has been dynamically compressed too much sounds boring. The ear gets used to it, same as it gets used to too much treble boost and you yawn after a few minutes." I like to minimize the flaws in badly mastered discs, but for discs that are made well--meaning no dynamic compression or clipping--I like to keep it untouched (except for encoding into a 256kbps or VBR MP3 file of course).

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Re: [mad-user] re: .12.3b pre3
by Rob Leslie 15 Dec '00

15 Dec '00

"Anthony Airon Oetzmann" <airon(a)gmx.net> wrote: > David, you wrote: >> I have a question though, how does the gradual attenuation work? How >> about something that clips yet isn't continuous, like a cymbal crash? >> And are all those graduations for the setting necessary? I think >> instead of this, a self-adjusting attenuation would be even better. It >> should work at an aggressive level however, and step back or >> un-attenuate as soon as the clipping stops. What I'm thinking is >> something like the concept of variable bitrate MP3 encoding. When the >> decoder sees the first instance of a clipped sample, it automatically >> attenuates the full level, but after so many samples of no clipping, it >> steps back to no attenuation. And so on. What I fear is that a large >> spike could occur in the beginning or middle of a file, setting a high >> attenuation level, and then muffling the rest of the song which might >> not clip at all. > > What you're describing is a Limiter. It would indeed be neat to have this > function. > > Of course this should be a lookahead limiter. The Ultramaximizer L1 by Waves > looks ahead by up to 68 samples on a Protools TDM system(that's its > processing latency anyway). I don't think having a second latency i our case > would be all that bad. Problem is, who can write a Limiter like that ? > Perhaps one the authors of a free VST plugin would include his Limiter code > in here. For short peaks this would be the right thing. Are there any papers or web sites that discuss the pros/cons of limiters? I have always had the impression limiters are undesirable because of the continuous fluctuation of the output signal level. The way attenuation is currently implemented in the MAD plug-in, doing any kind of look-ahead is unfortunately promblematic. This could be changed, but the primary benefit of the current method is that attenuation changes are less audible than they would be otherwise. -rob

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Re: [mad-user] clipping
by Gabriel Bouvigne 15 Dec '00

15 Dec '00

There is something I don't understand. Clipping is sound above the maximum > >allowed sound. As the sound of a CD is stored on a CD, and the maximum > >amplitude sound that can be stored on a CD is obviously the maximum allowed > >intensity on a CD, how can there be clipping on a CD, ie the sound of the CD > >exceding the sound that can be stored on this CD. > >That seems strange to me. > > I'll repeat what I sent to Peter. > > You're thinking lossless compression here, 'cause you won't get a signal > different from the original with lossless compression such as Monkeyaudio. No, I'm speaking of the original CD, without any compression. Some users are telling that there is some clipping on the CD itself. I personnaly think that it's impossible, but wanted to know if I was missing something about it. Regards, -- Gabriel Bouvigne - France bouvigne(a)mp3-tech.org mobile phone: gsm(a)mp3-tech.org icq: 12138873 MP3' Tech: www.mp3-tech.org personal page: gabriel.mp3-tech.org

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Winamp plug-in pre-release 0.12.3b-pre3
by Rob Leslie 15 Dec '00

15 Dec '00

The third installment in the pre-release series... http://www.mars.org/home/rob/proj/mpeg/mad-plugin/in_mad-0.12.3b-pre3.zip This version adds configurability to the automatic attenuation, and also fixes the problem with the joint stereo pie graph. I decided it might be better to control the sensitivity of the auto attenuation rather than use a simple hard limit. The default is somewhat less aggressive than it was before (which would correspond to the "Most" setting.) The idea is to control how gradually the attenuation is increased. If only a few isolated samples clip, a less sensitive setting will attenuate less than a more sensitive setting would. Continuous clipping will continuously increase the attenuation until the signal no longer clips; the sensitivity controls how fast this occurs. Let me know what you think. Cheers, -rob

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Re: [mad-user] decoding to wav
by Rob Leslie 15 Dec '00

15 Dec '00

"Anthony Airon Oetzmann" <airon(a)gmx.net> wrote: >> Once a file stops playing the info dialog no longer updates itself. This is >> so the information stays relevant to the file for which the info was >> opened. >> >> If you close and then re-open the info after starting playback again, >> you'll see things have been reset. > > Shure, but I don't close it :). I write the WAV file twice. Once for getting > attenuation and the second for writing with the gathered attenuation setting. What I meant is, everything is reset even if you don't close the window. It's just that the window stops updating itself once decoding stops, so you don't see that things have actually reset until you open the window again. -rob

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Re: [mad-user] decoding to wav
by Rob Leslie 15 Dec '00

15 Dec '00

"Anthony Airon Oetzmann" <airon(a)gmx.net> wrote: >> Unfortunately, the setting is not remembered even when the file is played >> again immediately. Sorry -- this feature is yet to come. > > Ahaa! But it is if you keep the info window open AND have another way to > activate playback. > > If you have the Winamp main window and the Playlist window open, you can > activate the INFO on one and still START/STOP/FF/REWIND the playback in the > other window. > > This is easy to prove by playing a file that clips. Keep the info window > open and click on your other WInamp window(main or Playlist) and hit 'X' to > play. As you will see the attenuation section will not add any more samples > to the "Clipped Samples". The attenuation stays and you're cool to go :). Actually, no. :-( Once a file stops playing the info dialog no longer updates itself. This is so the information stays relevant to the file for which the info was opened. If you close and then re-open the info after starting playback again, you'll see things have been reset. Sorry, -rob

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Re: [mad-user] decoding to wav
by Rob Leslie 14 Dec '00

14 Dec '00

"Anthony Airon Oetzmann" <airon(a)gmx.net> wrote: > IN any case, for all of you who'd like to write mp3 to a WAV file, have the > file all by itself in the playlist of Winamp, decode it once to get the > perfect noclipping signal, then decode it again with that attenuation > setting. Only having one file in the playlist will ensure that that > attenuation setting is kept, since MAD cannot write that attenuation setting > to a file or registry yet(?). Unfortunately, the setting is not remembered even when the file is played again immediately. Sorry -- this feature is yet to come. -rob

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re: .12.3b pre3
by Anthony Airon Oetzmann 14 Dec '00

14 Dec '00

David, you wrote: >I have a question though, how does the gradual attenuation work? How >about something that clips yet isn't continuous, like a cymbal crash? >And are all those graduations for the setting necessary? I think >instead of this, a self-adjusting attenuation would be even better. It >should work at an aggressive level however, and step back or >un-attenuate as soon as the clipping stops. What I'm thinking is >something like the concept of variable bitrate MP3 encoding. When the >decoder sees the first instance of a clipped sample, it automatically >attenuates the full level, but after so many samples of no clipping, it >steps back to no attenuation. And so on. What I fear is that a large >spike could occur in the beginning or middle of a file, setting a high >attenuation level, and then muffling the rest of the song which might >not clip at all. What you're describing is a Limiter. It would indeed be neat to have this function. Of course this should be a lookahead limiter. The Ultramaximizer L1 by Waves looks ahead by up to 68 samples on a Protools TDM system(that's its processing latency anyway). I don't think having a second latency i our case would be all that bad. Problem is, who can write a Limiter like that ? Perhaps one the authors of a free VST plugin would include his Limiter code in here. For short peaks this would be the right thing. Tony

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decoding to wav
by Anthony Airon Oetzmann 14 Dec '00

14 Dec '00

IN any case, for all of you who'd like to write mp3 to a WAV file, have the file all by itself in the playlist of Winamp, decode it once to get the perfect noclipping signal, then decode it again with that attenuation setting. Only having one file in the playlist will ensure that that attenuation setting is kept, since MAD cannot write that attenuation setting to a file or registry yet(?). That's the way I do it with modules too. One decoding cycle for finding the attenuation setting, another to use that perfect setting. Tony

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Re: [mad-user] Winamp plug-in pre-release 0.12.3b-pre2
by Rob Leslie 13 Dec '00

13 Dec '00

"Gabriel Bouvigne" <bouvigne(a)mp3-tech.org> wrote: > Nice looking stats. > There is a little problem with the file I sent you. Play it and look a the > stats: suddendly there is a 100% use of IS. Actually, I discovered a bug: the joint stereo graph is completely wrong. It'll be fixed in the next release. Cheers, -rob

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mad-user December 2000