This is version 0.96 of my buffered audio play/record program for Linux. Note that this is BETA software and may not work for you. Please mail me with any bugs/feature enhancements etc.
If you receive a BINARY version of this software and it doesn't work, I advise you to get the source and rebuild it. Certain interfaces to the kernel sound driver have evolved over the life of the Linux kernel and a program compiled for one version may not work correctly with another kernel version. Recompiling fixes this problem.
- Features
- Handles the following file types: Raw sound files (no header) Micro$oft WAV files Creative Labs Voc files (including the 16bit stereo variants and with support for loops).
When recording there is currently a limit of 16MB files when recording in WAV format. There are a couple of limitations with the VOC recording; in particular only the v1.20 format files are produced, which won't work on older player programs.
Details
The program uses two processes and a large block of shared memory to
allow asynchronous reading and writing of the file and the device. It
also runs at the highest possible priority. Using this method it is
possible to record at full speed (44.1kHz 16 bit stero, or about
176Kb/s) without overruns on 486DX/33 using 8bit DMA with a slow IDE
disk in multiuser mode until the disk gets very close to full (ie the
head is seeking all over the disk to find free blocks and can't keep
up).
Building
Basically, type make.
Note that there are two commented options on the CFLAGS command line
Adding -DDEBUG just causes lots of debuggin messages to be printed to
the screen. Adding -DUSEBUFFLOCK compiles in some code that causes the
shared memory to be locked down in memory. Although this seems to be a
good idea, on older Linux versions it caused lockups (I think a deadlock
in the kernel) and I haven't tested it for about a year, so use at own
risk.
Other things to tweak: the size of the share buffer is 256K by default, or just under 1.5 seconds of CD audio. Change BIGBUFFSIZE at the top of shmbuf.c to change this. It should always be a multiple of abuf_size, which is set on line 42 of sndfunc.c. This is set to 64K, which works well.
Installing
bplay/brec should be installed suid root. This is so that the program
can renice itself to a higer priority. As far as I am aware there are no
security holes in this program (it only uses the root privs when it has
to and then immediately drops them again). Check the code and see what
you think if you are worried. Make a link (symbolic or hard, doesn't
matter) from brec top bplay.
Install the man pages somewhere sensible. You will have to edit the brec manpage if you don't install it in ...../man1/brec.1
TODO
Tidy up and generalize the code.
Improve the Makefile and add an installation target.
Improve the documentation.
Add support for the realtime scheduling extensions in the new Linux
kernels.
Fix the recording limits on WAV and VOC files.
Add support for other formats (IRCAM floating point etc).
Merge in the SunOS/Ariel version.
Provide a Tk front end.
David Monro
davidm@cs.usyd.edu.au