mad-dev August 2007

mad-dev@lists.mars.org

4 participants
6 discussions

Calculation error
by Tim Dylla 07 Sep '07

07 Sep '07

Hi List, I did some testing on my own implementation of mp3, and used MAD as reference. Therefore I generated a sine-sweep from 0Hz to 22kHz ( as far as this is possible ;) ) at 0dBFS, and 48kHz Samplerate. Then I encoded it with Lame for a single Channel MPEG-1 Layer III Bitstream, 48kHz Samplerate, 320kbps Bitrate. (I don't know the exact Lame-version and optionstring anymore, but I didn't use anything weird) As expected, the resulting bitstream can be decoded without any obvious error with my Decoder and also with the dist10 decoder. MAD in contrast introduces a perceivable error right on the first half wave of the sine sweep. I think, it's an overflow in the requantization or the IMDCT (when I remember right, the huffman decoder produces very high output at this moment). I used MAD 0.15.2b in conjunction with MADFrontend on a 32bit-Windoze-machine. The option string was -b24 -d I'm not a friend of posting large files on a mailing list without any agreement with the moderator, so if someone is interested in the bitstream and the resulting raw file, pleas feel free to send me a message. With regards, Tim Dylla

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libMad Vs ffmpeg
by Chulwoong Jeon 24 Aug '07

24 Aug '07

I am porting MP3 at ARM9 platform. If I use only fixed-point(Integer), I wonder which one is faster between MAD mp3 decoding and ffmpeg mp3 decoding. CW

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Re: [mad-dev] Calculation error
by Tim Dylla 24 Aug '07

24 Aug '07

Andre schrieb: > Tim Dylla <tim.dylla(a)gmx.net> wrote: >> MAD in contrast introduces a perceivable error right on the first >> half wave of the sine sweep. I think, it's an overflow in the >> requantization or the IMDCT (when I remember right, the huffman >> decoder produces very high output at this moment). > > Just a hunch, but if you are able to build MAD from source, maybe you > could try the follow patch posted to the list a few years back... > perhaps it helps ?? > > diff -ruN mad-0.14.2b_orig/libmad/layer3.c > mad-0.14.2b/libmad/layer3.c > --- mad-0.14.2b_orig/libmad/layer3.c Thu Nov 8 15:28:02 2001 > +++ mad-0.14.2b/libmad/layer3.c Tue Mar 25 15:21:12 2003 > @@ -910,7 +910,7 @@ > fprintf(stderr, "requantize overflow (%f * 2^%d)\n", > mad_f_todouble(requantized), exp); > # endif > - requantized = MAD_F_MAX; > + requantized = MAD_F_MAX / 2; > } > else > requantized <<= exp; Nope, same Result. I'm sorry, I'm still sticking with my diploma, so I don't have the time for extensive tests right now. Maybe someone can confirm the problem and have a look at? Feel free to contact me for the Bitstream in Question and the correct decoder output. Best, Tim Dylla > > > Andre > -- > >

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[Offtopic] Stories about Process Change
by Christopher Oezbek 23 Aug '07

23 Aug '07

Hi MAD-Hackers, Hi Rob, I am researching what happens if a developer attempts to change the way a project works (in contrast to changing the software being developed) and have picked MAD as a small OSS project in long-term existence that seems to use a closed development strategy. I would be very interested in hearing if there was ever the need to modify the development process and if yes how successful have those changes been. I put up a survey of 13 questions (should take between 10 and 20 minutes) at http://survey.mi.fu-berlin.de/public/survey.php?name=changeEpisodeSurvey but you can also email me directly if you prefer. Thank you very much, Christopher Oezbek P.S.: If you are thinking about making such a change or are currently on it, feel free to drop me a note so I can share what I have learned so far. P.P.S.: Results will be made available at http://www.inf.fu-berlin.de/w/SE/SurveyChange over the next month, where you can also find further information. -- Christopher Oezbek Freie Universität Berlin http://www.inf.fu-berlin.de/~oezbek/

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problem with the seeking over
by cab 17 Aug '07

17 Aug '07

Hi, Ok, I managed to seek in a frame Thanks for your help Cab

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Re: [mad-dev] mad-dev Digest, seeking problem with libmad
by cab 16 Aug '07

16 Aug '07

Hi, You said I had to map the current file at a seek point but I just can't do itn there's a problem with the function mmap itself here's my source: (from minimad) int main(int argc, char *argv[]) { struct stat stat; void *fdm; if (argc != 1) return 1; int fd; FILE*fichier=fopen("essai.mp3","r+"); fd=fileno(fichier); lseek(fd,10,SEEK_SET); if (fstat(fd, &stat) == -1 || stat.st_size == 0) return 2; fdm = mmap(0,stat.st_size/2-1 , PROT_READ, MAP_SHARED, fd,stat.st_size/2); if (fdm == MAP_FAILED) return 3; decode(fdm, stat.st_size/2-1); if (munmap(fdm, stat.st_size/2-1) == -1) return 4; return 0; } I've got an error return 22 I know it's because the offset is not set to 0 thanks for your help

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mad-dev August 2007