On Wed, 25 Feb 2004, Arno van Amersfoort wrote: > I'm currently trying to setup a multitrack recording system with several > soundcards. Now I've to get 2 identical soundcards (SoundBlaster PCI64 > with ensonique1361 chipset) to work. How can I accomplish this? Somehow
Highly dangerous. The clocks on the two can be out. which means that the two digital streams will gradually get out of sync. For example my sound card and my CD player are out by two samples per second at 44100. This means that by 22000 sec, the two streams would be out by 1 sec. Now that would not be too bad, but two sound cards can easily be out by more than that. ONe way to check is to feed the output of one to the input of the other, sending say a 11025 Hz sine wave out. Then either do a fourier transform or count the bumps to see what the other received that signal as. (I was writing a program to automatically do that but did not finish it). If the cards are really close, then the timing mismatch might never be noticed, but if in the course of the song ( say 5 min) the timing were out by 1/100 of a sec ( so an error of 1/30000) it might well be audible. Certainly if they were out by 1/10 sec it would be. also sounds would get frequency shifted by the same amount. Now 1/22000 is about 0.1 cent of frequency shift, is almost certainly inaudible. But 100 times that would be audible. Ie, you want two sound cards driven by the same clock (do not know that exists or is possible) or one card with a multitude of inputs. Altenatively you could calibrate the timing difference and use speed shifting to try to compensate. That however requires interpolation and results in high frequency noise. If you record at 96000 that noise could be shifted out of the range of hearing with a high enough order interpolation routine from my very brief experiments. (5th order interpolation). It is probably adviseable to just get a multiple input soundcard so all imputs are driven from the same clock. > I have to (probably) load the ens1371 alsa module 1x and tell linux that > there are 2 soundcards using (thus creating to alsahw-devices). I think > this should be done in /etc/modules.conf but I'm unable (even after > thoroughly searching the web etc.) to make it work. > > Any help is highly appreciated... > > > > ------------------------------------------------------- > SF.Net is sponsored by: Speed Start Your Linux Apps Now. > Build and deploy apps & Web services for Linux with > a free DVD software kit from IBM. Click Now! > http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click > _______________________________________________ > Alsa-user mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/alsa-user > -- William G. Unruh | Canadian Institute for| Tel: +1(604)822-3273 Physics&Astronomy | Advanced Research | Fax: +1(604)822-5324 UBC, Vancouver,BC | Program in Cosmology | [EMAIL PROTECTED] Canada V6T 1Z1 | and Gravity | www.theory.physics.ubc.ca/ ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id=1356&alloc_id=3438&op=click _______________________________________________ Alsa-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-user
