mad-user February 2001

mad-user@lists.mars.org

12 participants
12 discussions

MAD 0.12.5b
by Magnus Holmgren 04 Mar '01

04 Mar '01

Hi, It seems that the 0.12.5b version of the MAD WinAmp plugin is a bit unstable. Since installing it, I've had WinAmp (2.72) crash several times on me (generally trying to read memory it isn't allowed to read). I think this happens at the end of a file. Once or twice it has even crashed Windows 2000 on me (as luck would have it, once it happened when I'd just started burning a CD)... Have anyone else had problems with this version? -- Magnus Holmgren

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MAD w/ 4.1 speakers
by RSWAVE2000＠aol.com 25 Feb '01

25 Feb '01

Is MAD made only for 2 speakers and it also for 4.1 speakers. MAD sounds good on my front speakers but not my rear speakers. I only hear sound from my front speakers sitting down but if I go up to my rear speakers it is sound coming out. ???

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Re: Clipping - Some naive (?) questions
by D D 15 Feb '01

15 Feb '01

Dear all, Thank you for your lengthy responses, things seem to be much clearer in my head now. By reading the replies and ff123's article I think realise three points: a) Clipping is an inherent feature of the mp3 decoding-encoding process as related to the necessary time domain (integers) <--> frequency domain (floating point) transformations. b) Clipping during the reproduction of digital audio is also inevitable, due to sampling effects, because of players (domestic or computers) trying to restore the waveform parts contained within the samples. c) If I understood well, these two effects are interrelated. (a) implies that any wav file close to 100% risks of being clipped, and (b) implies that the extent of clipping depends on the type of music program encoded. (b) also for me implies that whenever there is high frequency content present in the wav (e.g. cymbals), the decoding process has few samples to process and moreover the respective analog waveform has acute peaks, so repeated short-term clippings are inevitable. On the other hand, low frequencies (violins, voice) have smooth peaks so when when clipping occurs, we have a long-term clipping i.e. a flattening of the waveform. I am convinced that both of these phenomena, detected by the peak detector of Mad, are quite audible - perhaps the low-frequency cases are a bit easier to detect because of higher ear and brain sensitivity to them. I wonder whether modern recording engineers are fully aware of these effects. The "Remastered" stickers on all those new generation CD's make me think ...

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Conditional setting in MAD plugin
by Helmut Hübers 14 Feb '01

14 Feb '01

How does this conditional stuff for the tag work? I would like MAD to show me the trackname if an ID3 tag is not present, not only this "? - ?". Can someone give me an example? In the MAD plugin configuration there is mentioned a conditional option %?x<IF|ELSE>, but I don't understand how it should be used. Thanks, HelH

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flaws in 12.2 fixed ?
by Samuel Tan 14 Feb '01

14 Feb '01

Hear there's a problem with the dithering in 12.2b from decoder test page. http://privatewww.essex.ac.uk/~djmrob/mp3decoders/decoders_winampmad.html Just wondering, has it been fixed yet ? And what about the clipping of the end of files ? _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

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end of files
by ff123 14 Feb '01

14 Feb '01

I don't know if it's a general problem or not, but I notice that MAD produces glitches in the output at the end of files. For instance, take a short .wav file and cut off the end with a sound editor so that there's still music playing at the end (not silence). Encode to mp3 and play with MAD. Then try the same thing with the decoder in Winamp 2.7x. I tried this test with MAD versions .12.3, .12.4, and .12.5. Maybe there's something about my PC or soundcard, I don't know. Also, I haven't checked recently, but at the time I was doing a MAD listening test on Usenet, I noticed that the MAD decoder (version .12.2) cut off about 30 milliseconds at the end compared with the Fraunhofer decoder in Winamp 2.666. Maybe the two problems are related. ff123

1 0

Clipping - Some naive (?) questions
by D D 14 Feb '01

14 Feb '01

Greetings to all, I'm a new user to MAD and it's immediately become my standard for mp3 listening and decoding. The first thing that shook me when using Mad, was something that I never had encountered before, the mp3 clipping indicator. Low-bit distortion is one thing, but high-bit problems is surely a worse one, if not the worst! And when I witnessed Mad reports clipping even with files produced by the best encoders like Lame, this rang a red alert for me: are we constantly exposed to clipping distortion when using winamp's decoder or other decoding apps? Research in the web showed that there are people who claim that clipping is a well-known artifact of lossy mp3 compression. For me this is still a mystery, since I had the misconception (or is it true ?) that a well-established or even commercial encoder cannot possibly produce an mp3 that exceeds the 100% level. I am not familiar with the binary pcm structure of wav files, but I know it uses 16-bit numbers, so clipping is by the definition either the presence of a 17th bit (impossible) or the miscoding of a music level of 99% as 100% (which means that everything above 99% is clipped cause it's represented as a constant 100%). On the other hand, I understand that an encoded mp3 level of 99% is possible to be interpreted by a decoder as a level of 100%, which would mean that clipping is indeed possible to occur, but *only* when the file is badly decoded. For me two possibilities exist: a) The offending mp3 does not contain clipped samples but Mad misreports them (rather improbable, I do trust Mad's author programming skills) b) The offending mp3 does contain clipped samples which were produced by bad encoding (therefore Mad is correct) c) The offending mp3 does not contain clipped samples, but a decoder (either because of bad programming or because of the nature of mp3 lossy compression) *could* misinterpret them, so a decoder should take corrective action (i.e. attenuation like Mad does). I cannot easily find a way to produce convincing evidence as to which of the above is the case. At first sight one could propose: "just take an mp3 and decode it with a standard decoder and see if it contains clipped samples". However this is not good enough for me, for the following reason: If i use 10 standard decoders I'll get 10 wavs which will almost certainly differ. The next step would be to *visually* inspect the wavs for clipping, cause I do not think that any wav editor is capable of detecting and reporting (and possibly take action like Mad's attenuation) levels above 100% when opening a wav or importing an mp3 (am I wrong here?). In conclusion, to rephrase my (naive ?) questions: how is it in principle possible that Mad detects clipping, how does Mad do it and where exaclty is Mad detecting it: a) is clipping stored inside the mp3 file content? b) is it an artifact of decoding programs ? In addition, can you suggest another reliable means of verifying that an mp3 contain or not clipped content ? Excuse me for the lenghty post, but I think the issue I bring forward is an important one. For one, I would hate the idea of being forced to first normalise all my wav's to a safe e.g. 95% before encoding it, to just prevent the eventual clipping upon decoding.... Moreover if my worries are justified, we should definitely propose "response to mp3 clipping" as a very important criterium for the evaluation of mp3 decoders (and encoders ?) in that famous www page that does "objective" mp3 software comparisons. Best regards, Mits

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MAD 0.12.5b available
by Rob Leslie 13 Feb '01

13 Feb '01

Hot on the heels of 0.12.4b, MAD 0.12.5b is now available with even more performance improvements. This version incorporates the long-awaited Huffman decoding optimization that performs requantization in the same step. Many thanks to Andre McCurdy for his help that led to this release. There are still a few more improvements to be made, but this probably represents the bulk of what can be optimized for significant gains. The source code release: ftp://ftp.mars.org/pub/mpeg/ The MAD plug-in for Winamp: http://www.mars.org/home/rob/proj/mpeg/mad-plugin/ The MAD home page: http://www.mars.org/home/rob/proj/mpeg/ Cheers, -- Rob Leslie rob(a)mars.org

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ID3v2 support?
by Vlad Indiukov 12 Feb '01

12 Feb '01

What about this stuff for winamp plugin?

2 1

resample problem..
by J.Saravanan 12 Feb '01

12 Feb '01

Hi All, I've compiled madplay for my arm target ( Its a CLPS7500 evaluation board). When I try to run the application I get the following error message... output: sample frequency 44100 Hz not availlable;closest 41666 Hz output: cannot resample 44100 Hz to 41666 Hz And the program quits. Can sombody tell me how to fix this problem. Thanks, _Saran_

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mad-user February 2001