mad-dev October 2002

mad-dev@lists.mars.org

8 participants
15 discussions

Mac OS9 / CodeWarrior
by pmisteli 10 Oct '02

10 Oct '02

Hello, I have yet to find a MacOs9 player that uses mad. I found the latest Audacity but it sounds funny on my OS9 iMac. So I made my own MacOS9/Mad/iMAc player. It occurred to me that other people might be interested so I packaged libmad as a stand-alone CodeWarrior project, but have no idea how to release it, if anyone is indeed interested. The following describes what is currently packaged in a 240kb file libmadmac9.sit : /*************************************************************************** ** * README libmadmac9 * * libmad for Mac OS9 compiled with CodeWarrior * * Copyright (C) 2002 pmisteli * * This program is free software. you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation@ either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY, without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program@ if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * **************************************************************************** */ /* This is a CodeWarrior 5 project to generate libmadmac9.lib, a library for linking libmad with Mac OS9 apps built with CodeWarrior. It includes the libmad directory from the SourgeForge mad-0.14.2b release. Only two files from the SourgeForge release were slightly modified : - huffman.h - layer3.c The originals of these two files are included as huffmanORIG.h layer3ORIG.c. File libmadmac9Prefix.h specifies the FPM_64BIT build for libmad. This is just my way of building libmad with the compiler I have so that it works on my MacOS 9.1 iMac, and has not been tested with other compilers/machines. 8 October 02 - better late than never pmisteli(a)terpalum.umd.edu */

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Updating tags in memory
by Mark Malson 08 Oct '02

08 Oct '02

I wrote this function (in Objective-C) to update the contents of a tag for writing out later. Am I on the right track? Do I need to update both the UTF8 and the latin strings? bool libid3tag_SetString (struct id3_tag const *tag, char const *id, NSString *newStr) { bool retVal = NO; struct id3_frame const *frame; id3_latin1_t *latin1; id3_utf8_t *utf8; /* text information */ union id3_field const *field; unsigned int nstrings, j; extern id3_ucs4_t *id3_utf8_deserialize(id3_byte_t const **ptr, id3_length_t length); if ((frame = id3_tag_findframe(tag, id, 0)) == nil) return NO; field = &frame->fields[1]; nstrings = id3_field_getnstrings(field); for (j = 0; j < nstrings; ++j) { id3_byte_t *ptr; id3_ucs4_t *ucs4; switch (field->type) { case ID3_FIELD_TYPE_STRINGLIST: ptr = [ newStr UTF8String ]; ucs4 = id3_utf8_deserialize (&ptr, [ newStr length ]); id3_field_setstrings (field, 1, &ucs4); free (ucs4); break; case ID3_FIELD_TYPE_LATIN1LIST: ptr = [ newStr cString ]; ucs4 = id3_latin1_deserialize (&ptr, [ newStr length ]); id3_field_setstrings (field, 1, &ucs4); free (ucs4); break; } } return YES; }

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tag options
by Mark Malson 08 Oct '02

08 Oct '02

In writing out tags to a file I had trouble reading them back in using iTunes. I'm not EXACTLY sure why, but when I compared the id3v2.4 tags that iTunes generates vs. libid3tag, I found that libid3tag defaults to always using an extended tag header and writing out a CRC for each tag?? I'm not exactly sure what I'm talking about because I can't get to id3.org to get the latest spec, but that's another story. To fix it, I had to comment out everything in the "tag->options = " line in id3_tag_new, i.e., zeroing out the compression and CRC options. This prevented the extended header from being generated and it prevented the longer header from being generated on each tag. However, I know I'm disabling something that could be useful. Does anyone have any insight into this? I'd rather not flat out disable a feature in this lib.

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Question about ID3v2.4 tags vs. older tags
by Mark Malson 08 Oct '02

08 Oct '02

All right, now for the questions. When libid3tag reads in a TYER tag (and other date/time tags) it coalesces them (at least when writing a v2.4 tag) into a TDRC tag. It appears that iTunes does not read the TDRC tag and prefers TYER, even in v2.4 tags. The comments in libid3tag say that TYER et al. are obsolete, but I'd like to go ahead and write them out anyway. Has anyone encountered this problem and maybe coded a workaround? My initial try was unsuccessful. Also, I would _love_ to read the id3v2.4 spec, (especially regarding TDRC vs. TYER) but www.id3.org has been down for quite some time. Is it gone? Does anyone have the spec that they could email me? Thanks, - Mark Malson

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To parse ID3v2.4
by rahul_dsp 01 Oct '02

01 Oct '02

Hi All, I am new to the list ,I am working on ID3 tags decoding. I want to parse ID3v2.4 tag but facing lots of problems as basic idea of ID3v2.4 is not very much clear. Regarding SEEK Frame can anyone highlight how it works. What I know is that it gives the minimum offset of the next tag from the end of the current tag. This minimum offset is in synchsafe integers of four bytes does that mean that every 8th bit of the byte will be zero as was the case for size of tag and total bits will be 28 instead of 32. Please clear this out. Also I need sample tag of ID3v2.4 and ID3v2.2 or it would be great if someone provide me the link where it is available. regards, Rahul --------------------------------------------- http://mail.indiainfo.com India's first ISO certified portal Check world time at http://time.indiainfo.com

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mad-dev October 2002