mad-dev

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682 discussions

Re: [mad-dev] DirectShow filter based on MAD
by armin.gerritsen＠philips.com 25 Apr '02

25 Apr '02

>Also I think there is this big question wether a GPL DShow filter is >considered as a program or as a library. Program .... It is "reasonably considered independent and separate work" :-) There is no way a COM writer can know or predict how and when its component is going to be used. It is 100% dynamic during runtime. In the COM philosophy it should also be considered independent to be flexible and re-usable. That is the whole idea of COM. For those who are not convinced: look at CORBA. I've been working on CORBVA for a few years before I started working on COM. You have GPL and non-GPL implementations. They operate however together and servers created by GPL cannot see the difference between a client created with a GPL implementation and a client created with a non-GPL version. Since COM is nothing more than a localised version of DCOM and the latter is sometimes called the Microsoft version of CORBA, the resemblance should be clear. Still not convinced! :-) See the GPL OpenDivX filter. > In the second case that means >you should be able to use it from other projects than GPL (or GPL >compatible). For example Windows Media Player is not allowed. But AFAIK >you can't deny this access to different programs while the Filter is >installed on the computer... I think in the GPL world a definition should be made once and for all about things like COM, CORBA, etc. Or actually, one should clear out that these things do indeed qualify as a program an not as a library. Now this topic keeps poping up again and again for no reason. But to keep back to the subject. I think I'm just going to wait for Rob's reply. And in case he - to my surprise - isn't interested I'm going to put up a SourceForge page or so. Regards, Armin

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Re: [mad-user] rendering using libid3tag
by Rob Leslie 23 Apr '02

23 Apr '02

[This thread belongs on mad-dev; note Reply-To. Dominic, I'm not sure whether you're subscribed there...] On Wednesday, April 10, 2002, at 10:26 PM, Dominic Mazzoni wrote: > I'd like to also switch over to using libid3tag. We had > been using id3lib, but it's buggy and has trouble compiling > on a lot of systems. > > Our needs are minimal. We're not trying to be the ultimate > ID3 editor; we just want to be able to read and write > the most common tags for convenience. > > I didn't see any documentation on libid3tag...did I miss > something? The sample code only uses a small subset > of its features. I documented some of the interface here: http://www.mars.org/mailman/public/mad-dev/2002-January/000439.html Although this doesn't cover rendering tags, it may answer some questions about the data structures. > Anyway, I was able to figure out how to use libid3tag > to import tags from a file. But I'm stuck trying to > render them using id3_tag_render. > > 1. First of all, the only way I was able to figure out to > add new frames was to muck around in the data structures. > Is this correct? It might be nice if there were more > API functions to make it easier... > > For example, id3lib has a "simple API" which provides > functions that let you add and/or query the most common > tags (Title, Artist, etc.), without mucking in the > data structure at all. You shouldn't need to muck with the data structures. The general approach to adding a frame is: frame = id3_frame_new("XXXX"); id3_tag_attachframe(tag, frame); By indicating the frame ID ("XXXX" above), libid3tag knows automatically which fields to create in the frame. For text frames, there are two fields, a text encoding and a string list. If you're using Unicode, you should be sure to set the text encoding accordingly: id3_field_settextencoding(&frame->fields[0], ID3_FIELD_TEXTENCODING_UTF_16); To manipulate the string list field, you can either make an array of id3_ucs4_t pointers and call id3_field_setstrings(), or you can call id3_field_addstring() once for each string. In either case, the strings you pass are copied, so it is your responsibility to dispose of them. > 2. What's the proper way to convert an ASCII string to > an id3_ucs4_t string? (I used a for loop, casting > chars to longs...is that OK?) Instead of your own loop, you can call id3_latin1_decode(). > 3. When I try to enable the ID3_TAG_OPTION_ID3V1, > the rendering fails. Is it supported? Yes, it is supported. Probably it failed for you because mucking around in the data structures corrupted them... > 4. Finally, I do get some bytes back from id3_tag_render > without the ID3V1 option, but when I prepend them to > the beginning of my MP3 file, programs don't recognize > them. In fact even libid3tag doesn't even load any > tags from the resulting file. Is there something else > I need to do to the id3_tag_render output? Nope; again I think the problem stems from corrupt data structures. > I'm including some of my source code below. Thanks for > any help anyone can offer. Your ::ExportID3() looks good; try the following MakeID3Frame() instead: struct id3_frame *MakeID3Frame(const char *name, const char *data) { struct id3_frame *frame; id3_latin1_t *latin1; id3_ucs4_t *ucs4; frame = id3_frame_new(name); latin1 = data; ucs4 = malloc((id3_latin1_length(latin1) + 1) * sizeof(*ucs4)); if (ucs4) { id3_latin1_decode(latin1, ucs4); id3_field_setstrings(&frame->fields[1], 1, &ucs4); free(ucs4); } return frame; } -- Rob Leslie rob(a)mars.org

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libid3tag DLLs for Win32
by Robert Kaye 18 Apr '02

18 Apr '02

Hi! First off, a big thanks to Rob for the cool decoder and the new Id3 lib implementation. I am going to dump the original and crappy Id3lib implementation from all of my projects as soon as I can. Hence the reason for my e-mail -- is there an MSVC++ build project available for building an id3tag.dll? I've got a Borland C++ Builder project that I'm trying to convert away from the classic ID3lib, and C++ Builder does not like working with .lib files generated with MSVC++. I've even tried creating my own DLL, but they don't seem to work correctly - - none of the text fields ever load any strings. Where I would expect a string, I get an int32 field. :-( I suspect that I missed some compilation settings somewhere... This also holds true for the madlib -- it would be nice to have a DLL of that as well -- I'll probably dump the Xing decoder from FreeAmp and use the Madlib instead. BTW: Check out http://www.musicbrainz.org to see what I am working on... -- --ruaok Freezerburn! All else is only icing. -- Soul Coughing Robert Kaye -- rob(a)eorbit.net -- http://www.mayhem-chaos.net

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mp3 information library
by Neil Hodge 17 Apr '02

17 Apr '02

All: I was wondering if anyone on the list knows of a good mp3 information (bitrate, sampling rate, total frames, etc) library, written in C, or a nice clean program that is conducive to being hacked up. Thanks. -- Neil Hodge nhodge(a)attbi.com

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api
by Henning, Brian 16 Apr '02

16 Apr '02

Hello- I have compiled the mad library on my windows 2000 machine using mingw. I have the libraries and headers now. Can someone guide me to some documentation for the mad api? Is it online? I didn't find it on the website but, maybe I just missed it. I would like to write a simple program that reads in mp3 frames and prints to the screen some info in the headers. Is there any example programs in the documentation? I would like to see a simple example of some code to read a frame/header and print it to the screen. thanks for any help!!! brian

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frame decoding question
by Haig C Didizian 11 Apr '02

11 Apr '02

Hello - I hope this question doesn't fall outside this list's domain, but I figure there's probably a ton of mp3 know-how in this group... :) Anyway, I was looking at the mp3 headers from a file, and my calculation of the frame length appears to be wrong, but I can't figure out why. The first frame of the file looks like this: ff f3 68 64 which tells me that this is a 48kbps MPEG2 Layer-3 file at 16000Hz in joint-stereo, which is true based on what madplay says. I'd like to calculate the frame size based on this info, and using this equation for Layer-III files from http://www.dv.co.yu/mpgscript/mpeghdr.htm - FrameLengthInBytes = 144 * BitRate / SampleRate + Padding I calculate that the frame size is 432 bytes. When I scan through the file given this information, I find a total of 1924 frames. When madplay scans through the file, though, it finds twice as many, 3848 frames. So it seems that my frame length is 2x too big. Why does this equation hold for my 128kbps version of the same file, but not for this version (or am I missing something obvious)? On that note, does anyone have any suggestions for an mp3 frame-related resource? The one I mentioned above seems decent, but if there are any better ones, I'd love to know... Thanks for any help, Haig

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Static and dynamic linking
by Gareth 11 Apr '02

11 Apr '02

Hi, Once I had compiled minimad for ARM using the Lart cross compiler I used the 'file' command to see some stats on the resulting executable. It tells me that the file is an ELF arm executable, dynamicly linked (uses shared libraries) and a few other things. Now shared libraried are linked at runtime, right? So when I take the minimad executable and dowload it onto the arm evaluator board the shared libraries will be left behind and it will not work. Is this reasoning correct or am i missing something? If I am correct how do I go about telling the compiler to do static linking? Thanks Gareth

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Recalculate CRC checksum
by Dirk Nehring 31 Mar '02

31 Mar '02

Hi, I'm writing a program to correct bad MP3 files (by dropping bad frames, dropping IDv2 tags on demand, etc.) by using libmad. One point is that I want to add an CRC-16 checksum to the header. Can I use the libmad low level interface for this (i.e. set protection bit, and call mad_frame_decode(), get crc-checksum from header->crc_target)? Any ideas? Dirk

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configure scripts and cross-compiling
by Tripp Lilley 29 Mar '02

29 Mar '02

In many places, the configure scripts do tests like this: case "$host" in ... Should those be changed to: case "$target" in ... ? I find, in trying to cross-compile for arm-linux from i686-linux (for the Rio Receiver), that the configure doesn't "do the right thing", which is what leads to the fix-make script in Jeff Mock's patch here: http://www.mock.com/receiver/demo/ I'd rather get the configure scripts "corrected" (if I am, in fact, right about the host vs. target bit) in the sources :) While I'm at it :) what would it take to get Jeff's Rio Receiver audio device patches applied? Thanks!

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Re: [mad-dev] MAD Licence and Static link
by armin.gerritsen＠philips.com 28 Mar '02

28 Mar '02

>You forgot the most important one: to qualify for this exemption, you >must "distribute [the non-GPL linking parts] as separate works." OK, but that is also no problem for me. The non-GPL part will be distributed only through and by the company and the generic part that uses MAD will be on some public non-company related server available to the whole world. Thanks for claring this up. I think I'm going to wrap the MAD in a GPL DirectShow COM component which will use an as generic possible setup (which for those who know DirectShow know, means basicly using standard MEDIATYPE definitions). That way there is no doubt about it that it is indeed independant and seperate from any other program ever using it. (So something similar to what they did with LAME.) Regards, Armin

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