Readme for OS2ENC/OS2DEC v.0.1: OS2ENC/OS2DEC is a freeware Mpeg audio Encoder/Decoder for OS/2. It was compiled with Gcc, so it requires that you have the emx 0.9c runtimes installed on your system. As it's only an encoder/decoder, you don't need to have any multimedia hardware installed. (you'll need it if you want to sample some songs and test it by yourself, obviously) This version is a raw port of the public source code available at ftp://ftp.tnt.uni-hannover.de/pub/MPEG/audio/mpeg2/software/technical_report/dist08.tar.gz So don't expect ANY performance. Anyway, it's the first layer-3 encoder available for OS/2 at this present time and it's not crippled (in the general meaning of the term). In fact, it's crippled by its own limitations, especially by its speed ! Installation: ------------ Just unzip the file in an empty directory, say x:\mp3\os2enc\, make sure you have the amx 0.9c runtimes installed on your computer, make sure you are in an OS/2 session (no, it won't work under Dos or the nasty windoze). Last thing to do is to set an environment variable for the translation tables. Either type SET MPEGTABLES=x:\mp3\os2enc at the prompt for this particular session, or put it in your CONFIG.SYS (and don't forget to reboot for changes to take effect) Features: -------- The encoder/decoder is fully MPEG-1 and MPEG-2 compatible, for the three available layers (Layer-1, layer-2 and ... layer-3). As MPEG-2 introduces multichannel notions, it's only been tested for being compatible with MPEG-1, and it's probably the only thing you'll need, as MPEG-1 is used for 44Khz, stereo, 16b compression, that means CD-quality. MPEG-2 is used for lower sampling frequencies (ie: 22.05 Khz or below) The import format for the sound files is PCM, which means a raw sound file, with signed integer and 16bits. This version doesn't handle WAV files yet. The output format of the decoder is either raw (PCM) or AIFF. Hint: if you don't know how to make a PCM file, just take a WAV file and cut the first 44 byter of it, it should work. The decoder decodes almost any MPEG-1 and -2 compliant files. The encoder lets you chose between the 3 available layers, the output bitrate, and some other options: 1. First, you'll enter the input filename of your sound file 2. Then, the output filename, default is .mpg 3. Then, you'll need to enter its sample frequency in KHZ: correct values are 44100 (default) or 22050, 11025 not available yet If you chose 44100 KHz, the encoding algorithm will be MPEG-1 If you chose 22050 KHz, it will be MPEG-2 4. Then the layer you would like to use: Layer-2 is designed for an output bitrate of 128 Kbps/channel Layer-3 is designed for an output bitrate of 64 Kbps/channel So, depending on the type of compression you need, use layer-2 or layer-3 Layer-2 gives a lossless compression of 6:1 for a 256 Kbps bitrate for a stereo signal. Layer-3 gives a lossless compression of 10 to 12:1 for a 128 to 112 Kbps for a stereo signal. This means, if you use layer-3 at 112 Kbps on CD-quality sound, you'll get a 1 Mb/mn of audio sound with the same quality as a Wav file, which sucks 10 Mb/mn of music... Ain't it cool ... ! :) 5. Next is the mode you want: Available are (s) for stereo (default) (j) for joint-stereo (fake stereo from both channels) (d) dual channel (i) single channel (use this one if the input is a mono signal) For some reasons, joint-stereo doesn't work yet, so forget it ... 6. Then chose the psychoacoustic model (uh ? ..): Don't worry, here's the hint, use '2' for layer-3 and '1' for layer-2 (caution: '1' is the default, think about it when you use layer-3) 7. Then enter the bitrate for the output file (this value is the global output bitrate, for both channels). Common values are 384 - 320 - 256 - 192 - 128 - 112 - 96 - 64 - 56 - 32 You can try layer-2 at 256 for high quality, 192 with a little loss For layer-3, preferred values are 128 or 112 Kbps for lossless quality. 8. Then, you'll be prompt for the de-emphasis ... use one . 9. Then you'll be prompted for some adding stuff, the private bit, error protection, copyright ,etc... chose what you want. 10. And yet, go for it... you'll get a summary of the options you chose, and you'll 'see' the coding. Remember, encoding takes a looooooong time, don't blame me for it right now, okay ... :) Now, even if you don't have a descent player, or if your computer is not a Pentium and though can't play a mp2 or mp3 file in real-time, if you want to keep some wav files and save some hard-disk space, use this program as a compressor... It achieves far better than Rar or Zip, believe me. You can also use these options at the command-line prompt, just type 'encode -h' to get help. To-do list: ---------- - test every option (esp. the MPEG-2 algorithm) - fix the joint_stereo option and 11025 Khz - add input/output file formats (Wav,AIFF,etc) - change the defaults dialogs according to the layer choices - change the verbose output to a descent one - optimize the code (yeah, that's the main stuff) History: ------- February, 1 1997: version 0.01 First beta version Acknowledgments: --------------- This program is provided 'as is', which means I won't be responsible for any thing that turns wrong (as Murphy said, 'if something can go wrong, it will')... Obviously, it won't wipe out your hard-drive (on the contrary, if your hard drive is full of wav files, it will clean it up safely). Be careful when you uncompress mp3 files, remember layer-3 compresses up to 12:1 so if you have a 5 MB mp3 file, you'll get a 60 MB WAV file (AIF in fact). That's all folks... enjoy it, feel free to distribute it to your OS/2 friends, and look for the next releases of this software. --