mad-dev

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682 discussions

How to unroll the imdct??
by forks.tw 30 Nov '03

30 Nov '03

The IMDCT function in MAD seems not easy to understand. Rob Leslie says that it is custom unrolled and factorized implementation. But I still don't know how ... Would you please tell me about the IMDCT algorithm in MAD or any reference documents? Thank you very much!! -- forks forks.tw(a)yahoo.com.tw --------------------------------- Do you Yahoo!? Free Pop-Up Blocker - Get it now

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error recovery?
by Gerd Knorr 28 Nov '03

28 Nov '03

Hi, Any hints how to recover from decoding errors, i.e. how to continue after mad_frame_decode() returned MAD_ERROR_LOSTSYNC? Just call mad_stream_buffer() with the next data block and then mad_frame_decode() again seems not to work. In the mad.h header file is a function called "mad_stream_sync", should I call that one? Before calling mad_stream_buffer() or thereafter? Gerd -- You have a new virus in /var/mail/kraxel

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RE: [mad-dev] A question for mmap()
by hank.jan＠billionton.com.tw 27 Nov '03

27 Nov '03

Hi, The explanation is very clear. Thanks a lot. Regards, Hank -----Original Message----- From: Jesse McGrew [mailto:jmcgrew@hansprestige.com] Sent: Thursday, November 27, 2003 3:12 PM To: mad-dev(a)lists.mars.org Subject: Re: [mad-dev] A question for mmap() On Thu, 27 Nov 2003 14:57:11 +0800, <hank.jan(a)billionton.com.tw> wrote: > I have a question about mmap(), hope someone can clarify for me. > As I know, mmap() maps the whole file into memory, so OS can access the > source file directly from memory. > However there should be a restriction to memory size on the embedded > system. > > In my test, I compile madplay with mmap supported, and then play a mp3 > file > of 43MB, and it plays well. > But my question is I only get 32MB SDRAM on my development board. > It seems that the memory size is not large enough to store all the data. > How does mmap() work? mmap() maps pages of memory to correspond to the file, but it doesn't actually load the file into memory. The file is loaded on demand. When you access one of the mapped pages, the OS loads the correct part of the file into memory. The effect is similar to virtual memory, where pages are swapped to and from the disk when they're needed. Thus, if you're using a 32 bit CPU, you may be able to map up to 4 GB with mmap(), even if you only have 32 MB of RAM. Adding more RAM will allow you to keep more of the file in memory at once, so random access will be faster, but it doesn't affect the size of the file you can map.

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A question for mmap()
by hank.jan＠billionton.com.tw 27 Nov '03

27 Nov '03

Hi, I have a question about mmap(), hope someone can clarify for me. As I know, mmap() maps the whole file into memory, so OS can access the source file directly from memory. However there should be a restriction to memory size on the embedded system. In my test, I compile madplay with mmap supported, and then play a mp3 file of 43MB, and it plays well. But my question is I only get 32MB SDRAM on my development board. It seems that the memory size is not large enough to store all the data. How does mmap() work? Besides, I want to implement the fast forward/rewind function. But it is a little slow to rewind, because it needs to search the location from the first frame, if mmap() isn't enabled. (Maybe there are other better methods, but I don't know...) If mmap() works, then it should be faster than without mmap(), shouldn't it? Sorry for any unclear expression. Thanks for help. Regards, Hank

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Re: [mad-user] Build problem with cygwin/mingw
by Jedediah Smith 17 Nov '03

17 Nov '03

This doesn't work.. error looks like this: /usr/bin/install -c .libs/libmad.lai c:\source\vc\mixer\libmad/lib/libmad.la /usr/bin/install: cannot create regular file `c:sourcevcmixerlibmad/lib/libmad.la': No such file or directory Those windows paths just aren't making it through everything without getting mangled. How exactly would I install manually? Just copy libmad.a? On Fri, 14 Nov 2003 14:22:02 -0800, Rob Leslie <rob(a)mars.org> wrote: > [Note Reply-To.] > > On Nov 14, 2003, at 12:52 PM, Jedediah Smith wrote: >> Following steps were followed: >> >> ./configure --host=mingw32 --prefix==/cygdrive/c/source/vc/mixer/libmad >> >> Configure step goes fine. The prefix is the dir I want to install to >> e.g. c:\source\vc\mixer\libmad which already exists. > [...] >> ranlib /cygdrive/c/source/vc/mixer/libmad/lib/libmad.a >> c:\mingw\bin\ranlib.exe: >> /cygdrive/c/source/vc/mixer/libmad/lib/libmad.a: No such file or >> directory > [...] >> It looks like ranlib is being passed the cygwin version of the path but >> it doesn't recognize it as it's part of mingw and only allows normal >> Windows paths. What shall I do about this? > > I think both Cygwin and Mingw understand Windows paths, so try: > > ./configure --host=mingw32 --prefix='C:\\source\\vc\\mixer\\libmad' > > If not you can just install the library by hand; libmad doesn't hardcode > any paths from the configured prefix, so it's safe to omit. >

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how must I align buffers passed to mad_stream_buffer?
by Jedediah Smith 17 Nov '03

17 Nov '03

My decoder uses an arbitrary buffer length and passes data blocks of this size, read from the MP3 file, to mad_stream_buffer. However, MAD throws a "lost synchronization" error immediately after returning from the input callback which feeds the data to mad_stream_buffer. The resulting decoded audio has artifacts at the equivelant locations. Clearly mad expects the MP3 data to be aligned, perhaps on frame boundaries, but I can't find any mention of this in the source comments.

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III_decode function question
by Grigory Abuladze 07 Nov '03

07 Nov '03

Hi! I am working with mad-0.15.0 Could someone explain to me this? why in III_decode() - layer3.c the IMDCT processing is split for subBand 0-1 & rest - up to 31? It is look like subBand 0 & 1 is not tested to "nonzero" Is it reason for this split? Thank for Your answers. -- Best regards, Grigory mailto:Ryhor@tut.by

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AM_MAINTAINER_MODE
by Dominic Mazzoni 27 Oct '03

27 Oct '03

For convenience, I have specific versions of libmad and libid3tag checked into the Audacity CVS tree, so that developers can get a known working version of all dependencies easily. However, we've been running into the well-known problem where CVS timestamps interact with "make" poorly; running "make" triggers all of the autotools even though configure.ac and Makefile.am haven't been touched, and this causes the build process to fail when users have incompatible versions of the autotools. It looks like AM_MAINTAINER_MODE may be a solution to this problem. It turns off the rules that call autotools by default, unless specifically enabled as an options to configure. I tried adding AM_MAINTAINER_MODE to configure.ac in libid3tag, but I can't seem to get it to generate a working configure script. After editing configure.ac, if I run aclocal and then autoconf, I get: configure.ac:66: error: possibly undefined macro: AC_PROG_LIBTOOL Running libtoolize doesn't help. If I run automake, I get: Makefile.am:27: Libtool library used but `LIBTOOL' is undefined Can anyone help straighten me out? Note that AM_MAINTAINER_MODE doesn't seem to be the problem; I'm not able to run automake even in a clean download of libid3tag-0.15.0b. Thanks, Dominic P.S. Versions I have installed: autoconf 2.57 automake 1.7.7 libtoolize 1.4.2

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III_requantize question
by Grigory Abuladze 20 Oct '03

20 Oct '03

Hi! I am working with mad-0.15.0 I hope someone may give me answer on this questions: 1. The result of this function III_exponents() in layer3.c file is signed int exponents[39] array. My question - in which format is result presented? 2. Xr = is^(4/3) * 2^(exp) (sign not discussed) What value exp can be and what step? -88.5 <= exp <= 11.5, 0 <= is[i] <= 8207 are this equation true? From III_requantize() it is look like step is 2^(1/4) - where can I take this information? Thank for Your answers. -- Best regards, Grigory mailto:Ryhor@tut.by

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[patch] libdid3tag - getting text encoding value
by Alastair Tse 20 Oct '03

20 Oct '03

Hi, I'm not sure where patches should be sent, so please re-direct me if this is not the best place. I've been writing a small program to help me convert ID3 tags from Big5 encoding to UTF-8 and libid3tag has made it _really_ easy. The API is so much cleaner than id3lib :) Anyway, I came across a bug which prevented me from fetching the text encoding value using id3_field_getint() from a field of type ID3_FIELD_TYPE_TEXTENCODING. Here is a simple one-liner to fix this behaviour. I hope it can be included in the next version. On another note, is there anyone who has python bindings for libid3tag? If not, I'd probably spend a little time writing some. Cheers, -- Alastair 'liquidx' Tse >> Gentoo Developer >> http://www.liquidx.net/ | http://dev.gentoo.org/~liquidx/ >> GPG Key : http://dev.gentoo.org/~liquidx/liquidx_gentoo_org.asc >> FingerPrint : 579A 9B0E 43E8 0E40 EE93 BB1C 38CE 1C7B 3907 14F6

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