patch-1.3.58 linux/drivers/sound/experimental.txt

• Lines: 166
• Date: Thu Jan 1 02:00:00 1970
• Orig file: v1.3.57/linux/drivers/sound/experimental.txt
• Orig date: Tue Jul 11 10:02:52 1995

diff -u --recursive --new-file v1.3.57/linux/drivers/sound/experimental.txt linux/drivers/sound/experimental.txt
@@ -1,165 +0,0 @@
-This version contains some features which is may NOT be enabled by default. 
-I'm trying to release an official/reliable version soon so that the
-Linux version of Doom (and other games) becomes possible. For that reason
-I have disabled some features which are not reliable enough to be
-released for wide public. If you are interested to try them, please
-read this file carefully.
-
-1) ECHO PSS (Personal Sound System support)
-
-This version contains support for soundcards based on the AD20msp614
-chipset made by Analog Devices. This chipset consist of the
-AD1848 codec, ADSP-21xx DSP chip and a ESC614 ASIC and is used in some
-soundcards made by Orchid, Cardinal, Echo Speech Corporation, Western
-Digital and Wearnes Technology. The PSS support is by Marc M. Hoffman
-(marc.hoffman@analog.com). I received this stuff about a week ago and
-have not been able to test it yet.
-If you are interested, remove the B(OPT_PSS) from the DISABLED_OPTIONS
-(see above).
-You have also to enable the MSS support since I have not integrated
-the AD1848 driver with the PSS one yet.
-
-2) /dev/music (/dev/sequencer2)
-
-This version has a new device file called /dev/music. I have not
-implemented all parts of it but it's there. It's only interesting if
-you are writing a sequencer program yourself. Enable by creating
-the device file /dev/music. Use the script at the end of linux/Readme
-
-3) /dev/midi##
-
-These are tty like raw devices for MIDI ports. Since there is a minor
-incompatibility between different versions of Linux, I have disabled
-this feature by default. You just need to create the device files yourself.
-
-4) Support for hardware based u-Law/A-Law and ADPCM formats.
-
-The AD1848 (and compatibles) are able to do compression and
-decompression by hardware. This version has experimental support
-for some of them. Currently they are implemented just in the
-AD1848 driver. The GUS MAX (and the 16 bit daughtercard) support
-also 16->4 bit ADPCM (the IMA one) but it don't work yet.
-The argument ioctl(SNDCTL_DSP_SAMPLESIZE) can have some new values
-in addition to the 8 and 16 supported earlier. Look at soundcard.h
-for more info.
-(In case somebody dares to ask: The ASP chip of SB16 is not supported
-so the hardware compression/decompression doesn't work with it. Also
-the ADPCM format is different than the standard (IMA) one (I guess).
-This feature is enabled by default.
-
-5) Real time fix to /dev/dsp and /dev/audio drivers
-
-The following feature should help game writers. This stuff is enabled
-by default.
----------------- cut here ---------------------
-There is a new ioctl called SNDCTL_DSP_SETFRAGMENT. It accepts a
-int parameter which has format 0x00nn00ss where the nn is max number of 
-buffer fragments (between 0x02 and 0xff) and the ss gives indirectly the 
-size of a buffer fragment (fragment_size = (1 << ss)). Valid sizes are 
-between (ss=0x07 -> 128 bytes and ss=0x11 (17 dec) -> 128k).
-
-This ioctl must be used ONCE between open() and first call to 
-read()/write() or ioctl(SNDCTL_DSP_GETBLKSIZE). 
-
-You need just to force the fragment size to a value which is sufficiently 
-short (gives the 1/20th of sec with the speed/#channels/#bits you are using).
-
-Using a small number of fragments offers (I guess) a significant advantage.
-For example with 2 fragments the driver works as the following (at least 
-I hope so). Assuming that the process writes exactly 'fragment_size' of 
-bytes each time (this is really important).
-
-	1) When the process writes the first fragment, it will be copied to
-	the DMA buffer area and the playback begins. The write() returns
-	immediately and the process is free to continue.
-
-
-	2a) If the fragment gets played before the application writes a new
-	one, the device will be stoppen and restarted which causes a click.
-	When the process calls write next time, it will be processes as 
-	in step 1.
-
-	2b) If the process calls write before the buffer underflows, the
-	data will be queued and the process is free to continue. (There
-	is now one full and one partially played fragment in the kernel
-	buffers. This gives average delay of 1.5*fragment_time (for 
-	example 1/20th sec) before the last byte in the buffer gets played.
-
-
-	3a) If the device gets both fragments played before the next write
-	(underflow), there will be a click. The write will be processed as
-	in step 1.
-
-	3b) If the 1st fragment gets played before next write (the process
-	calls write during playback of the second fragment), it will be
-	processed as step 2b.
-
-	3c) If the process writes 3rd fragment when there is already 2
-	fragments in the queue (1 playing and 1 waiting), the process
-	will block until the 1st fragment gets played. It will then be
-	woken up and it continues as in step 2b. This means that
-	the process blocks for at most the time required to play a
-	buffer fragment.
-
-This method syncronizes the process and the audio device together 
-automaticly. The process will block at most the 'fragment_time'. Usually 
-less, depending on how much it needs time to do other things. The maximum
-delay between writing a byte and the time when it finally plays is
-at most 3 times the 'fragment_time'. 
-
-The delay depends on how much time the program needs to do it's 
-computations for the next sample (updating screen etc). If it's about
-80% of the 'fragment_time' the game will run almost without delays. If it 
-uses more time, there is a risk that the audio buffer gets empty.
-	
-The application code should be something like the following:
-
-int frag = 0x00020008;	/* 2 fragments of 2^8=256 bytes */
-int frag_size;
-
-int fd=open("/dev/dsp");
-ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &frag);
-ioctl(NDCTL_DSP_SPEED); /* And #channels & #bits if required */
-
-/*
- * Query the actual fragment sice since the driver may refuse
- * the requested one (unlikely but possible?)
- */
-
-ioctl(fd, SNDCTL_DSP_GETBLKSIZE, &frag_size);
-
-while(True)
-{
-	do_computations();
-	write(fd, buf, frag_size);	/* Always the same size!!!!!!! */
-}
-
-I have tested this with a modified version of str.c. The algorithm works 
-as long as the playing program gets enough time to run. Hitting ENTER on 
-another virtual console causes a pause/click (with 2 frags of 64 bytes).
-
-NOTE! It's important to know that this call may be called just once and
-it must be done immediately after open(). The fragment size will remain
-in effect until the device is closed.
-------------------- cut here ---------------------
-
-6)	Detection and initialization code for Ensoniq Soundscape
-
-This version is able to initialize SoundScape (almost). However
-PCM recording and playback don't work. Also MIDI playback sounds wierd
-since the driver is not able to set volume controls properly.
-The soundscape support is disabled. You need to enable it by editing
-beginning of configure.c. Also read comments in sndscape/README.
-
-7)	select() support for /dev/audio and /dev/dsp. (/dev/midi## and
-	/dev/sequencer had it already in v2.90).
-
-There is now select() support in the audio/dsp driver (for Linux only).
-However I have not tried this feature yet. 
-There are also some new ioctl() calls (please look at soundcard.h).
-
-8)	MIDI recording in /dev/music (/dev/sequencer2)
-
-MIDI recording was earlier implemented only with full MPU-401 devices.
-This version has it also for dumb MIDI ports. However I have not tested it
-yet.