| This directory contains version 1.2 of a simple 16 bit PCM <-> 4 bit |
| ADPCM coder and decoder. See the source and the manpage for comments |
| on the algorithm. |
| |
| If you have previously used version 1.0: there was a bug in it. This |
| version fixes the bug. (1.1 fixed that, but had another slight bug |
| that caused loss of quality on SGI machines). |
| |
| The routines have been tested on an SGI Indigo running Irix 4 and |
| 5 and on a Sun Sparc SLC running SunOS 4.1.1. There are no real |
| machine dependencies, though, so there should be no problems on other |
| architectures. |
| |
| There is a timing program to test how fast the stuff runs on your |
| machine. Here are some sample numbers: |
| |
| R4000 Indigo: compress: 1.1Msample/sec, decompress: 1.7Msample/sec |
| R3000 Indigo: compress: 410Ksample/sec, decompress: 850Ksample/sec |
| Sun SLC: compress: 250Ksample/sec, decompress: 420Ksample/sec |
| Mac-IIsi compress 21Ksample/sec, decompress: 35Ksample/sec |
| 486/DX2-33 SCO: compress 550Ksample/sec, decompress: 865Ksample/sec |
| 486/33 linux: compress 278Ksample/sec, decompress: 464Ksample/sec |
| 386/33 gcc: compress 117Ksample/sec, decompress: 168Ksample/sec |
| (the Borland and MS compilers are a little slower) |
| |
| Also included are some simple test programs that convert audio files |
| to/from 4bit ADPCM samples. Rawcaudio/rawdaudio convert to/from raw |
| 16bit PCM files; sgicaudio/sgidaudio convert to/from SGI AIFF files |
| and suncaudio/sundaudio convert to/from SUN/NeXT format audio files. |
| The Sun program was donated by Hughes Doug, hughes@sde.mdso.vf.ge.com |
| (it is actually only one program and looks at the program name to |
| decide whether to compress or decompress). Oh yeah, the sun and sgi |
| compressors will probably only compile on those machines. Also, for |
| the sgi compressor you need the Digital Media Developers Option. |
| |
| Note: I have had to make a few changes to the sun audio converter, but |
| unfortunately I have no way of testing the result (since it needs |
| Solaris 1.somethingorother which I don't have). If the program does |
| not work and someone fixes it I would like to get a copy. |
| |
| Finally, there is a uuencoded adpcm sound file of me saying "hello |
| world" (with a cold) that you can use to test that everything works |
| correctly. |
| |
| If you use this package I would like to hear from you. |
| I am especially interested in people who can test interoperability |
| with proven Intel/DVI ADPCM coders. I have tried to get the algorithm |
| correct, but you never know.... |
| |
| Answers to often-asked questions: |
| - No, this is *not* a G.721 coder/decoder. The algorithm used by G.721 |
| is very complicated, requiring oodles of floating-point ops per |
| sample (resulting in very poor performance). I have not done any |
| tests myself but various people have assured my that 721 quality is |
| actually lower than DVI quality. |
| |
| - No, it probably isn't a RIFF ADPCM decoder either. Trying to decode |
| RIFF ADPCM with these routines seems to result in something |
| recognizable but very distorted. |
| |
| - No, it is not a CDROM-XA coder either, as far as I know. I haven't |
| come across a good description of XA yet. |
| |
| - No, testc and testd are not full-blown audio-file converters, only |
| simple test programs. If you write a file-converter (like caudio.c, |
| which compresses Sun audio files) and you're willing to donate it |
| I'd be very happy to include it in the distribution. |
| |
| - No, I know of no standard audio file format that supports idvi |
| adpcm. If you find one, please let me know. |
| |
| - Also, I know next-to-nothing about who IMA are. Their address, though, |
| from their May 1992 proceedings (where I got the algorithm from): |
| IMA Compatability Project Headquarters |
| 9 Randall Court |
| Annapolis MD 21401 |
| USA |
| |
| Phone: (410) 626-1380 |
| Fax: (410) 263-0590 |
| |
| They might be able to send back issues of their proceedings, I don't |
| know. |
| |
| Jack Jansen |
| Centre for Mathematics and Computer Science |
| Kruislaan 413 |
| Amsterdam |
| the Netherlands |
| |
| +31 20 592 4098 |
| Jack.Jansen@cwi.nl |
