I wrote a VOX or Voice Actuated Relay recording program about 4 years ago and have been adding to it. It occurred to me that I may be able to get 2 VOX's for the price of one by opening /dev/dsp in stereo mode instead of the straight /dev/dsp mode I have been using. This should give me a 16-bit value each time with half of it being the left channel audio sample and the other half being the right channel. To cut to the chase, I can't seem to open /dev/dsp in this manner. I found some 90's era documentation about oss-sound and Linux audio. Of course, there is mention of /dev/dspw (my salvation!). As with many older and direct methods, it no longer exists. At least modern Debian systems running the 2.6.5 kernel with ALSA don't have it so there must be another way to do it. Another 90's document has a snippet of code using ioctl and it compiles, but I will show you what happens. Here is what blows up. The source has the following includes: #include <stdio.h> #include <signal.h> #include <ctype.h> #include <sys/types.h> #include <sys/soundcard.h> #include <sys/ioctl.h> #include <time.h> #include <unistd.h> This next variable is defined inside main int format = 0; The audio device file descriptor is defined as FILE *audio_fd; The part of the code that fails is taken right from the example. /*Set 8-K stereo mode.*/ format = AFMT_S16_LE; /*On my system, that sets format to 16.*/ if (ioctl(audio_fd, SNDCTL_DSP_SETFMT, &format)==-1) { /* Fatal error */ perror("SNDCTL_DSP_SETFMT"); exit(1); } The failure appears to have nothing to do with sound capabilities. Here is what gdb shows when stepping through the program. /dev/dsp successfully opens first for reading so that is no problem. The very next thing I do is to try to use the ioctl to set the number of channels. That is the code you see above. Here is what happens when we get there: Breakpoint 2, main (argc=2, argv=0xbffff684) at vx2ch.c:118 118 if (ioctl(audio_fd, SNDCTL_DSP_SETFMT, &format)==-1) (gdb) step 120 perror("SNDCTL_DSP_SETFMT"); (gdb) SNDCTL_DSP_SETFMT: Bad file descriptor 121 exit(1); The file descriptor being passed to SNDCTL_DSP_SETFMT is audio_fd. If I take all this code out, you have the original program which runs just fine but only uses straight /dev/dsp (8-bit, 8-K mono). I'd stick the whole source in here, but it's 322 lines and all of it works except what I have demonstrated. With alsa installed, what is the best practice for opening some version of /dev/dsp for two 8-K 8-bit streams such that you get a 16-bit stream? Thanks for any suggestions or pointers to newer documentation. Martin McCormick WB5AGZ Stillwater, OK Systems Engineer OSU Information Technology Department Network Operations Group -- To UNSUBSCRIBE, email to debian-user-REQUEST(a)lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmaster(a)lists.debian.org