| | // | \X/ Flowerpower *proudly* presents | -----+------------------------------------------------------------------------ | | a 14 Bit low level sound driver for CyberSound audio sub system | EMAIL: flowerp@eikon.e-technik.tu-muenchen.de INTRODUCTION ------------ This is a driver to replay a 16 bit Stereo audio stream via the Amiga audio channels in 14 bit quality. It will adapt to different screenmodes, allowing up to 60khz output frequency on AGA machines and about 28khz on ECS machines. For maximum sound quality, the driver can be calibrated using a prefs program. The core routines are written in assembly for maximum speed, but optimizations are always possible. HARDWARE/SOFTWARE REQUIREMENTS ------------------------------ An Amiga with at least Kickstart 2.0 and a MC68020 processor should suffice. The driver takes approximately 150kb of memory, mainly for tables. Chip memory usage is neglectable as this driver uses very small buffers and is heavily interrupt driven. CALIBRATION ----------- Calibration of the driver will decrease the noise level and improve the sound quality. Every Amiga has got a different characteristics in its D/A converters. They are not exactly linear. The calibration program allows you to measure out the step sizes of the D/A converter. So the 14 bit driver can create an optimal conversion table. Calibration will take approximately 20 minutes. If you want to do it very exactly you may invest 2 hours as well ;-) The program will explain itself. Please follow the instructions of the program in order not to damage your HIFI equipment. THEORY OF OPERATION ------------------- 14 bit output is created by mixing a channel at maximum volume with a channel playing at minimum volume. As this is done on the left and on the right side, it takes all 4 audio channels. PROGRAMMER'S DOCUMENTATION -------------------------- This is not yet available, as this driver is not yet finished. The software interface may change at any time. If you are interested in how it works, look into the source code of the CDPlayer program. In the future the cybersound.library will be responsible for creating the audio stream, so direct programming of this driver will be useless. Currently the driver is limited to LITTLE ENDIAN audio streams as created by the Toshiba CDRoms. As this is not the best stream format for realtime mixing on the Amiga, a stream format selection will probably be included. The source code is included for "educational" purposes only. FUTURE ENHANCEMENTS ------------------- * miscellaneous changes in the software interface * further optimizations for special stream formats * program a Toccata and Maestro driver as well PROGRAM HISTORY --------------- Sounddriver 1.1 * The audio hardware was reset even when the driver failed to open. This could disturb other programs, e.g. module players. Fixed. * The audio stream format is now selectable. The application can switch between big and little endian. The CDPlayer uses little endian because the CDRom delivers that data format. A library like cybersound.library would of course use big endian (motorola format). Calibration 1.1 * Fixed some enforcer hits that occured when saving the configuration. You really shouldn't peek into a menu structure that has already been deallocated. ;-) CONTACT ADDRESS --------------- EMAIL: flowerp@eikon.e-technik.tu-muenchen.de FidoNet: 2:2480/465 SnailMail: Christian Buchner Ganghoferstraße 2 82110 Germering Germany Tel.: +49-(0)89/844872