> > Actually, I think I found the problem. I was using the maximum number > > of playback and captures channels reported by the device. For > > "plughw", this number is apparently 10000, rather than the actual > > number the hardware supports! I guess what I have to do is open the > > "hw" device first to get the actual number of channels, then open > > "plughw" with that number of channels. > > This is something of a FAQ, it seems to come up every month or so (at > least it has since i asked it a few months ago ;-) -- the answer is that > plughw can do lots of conversion for you, and downmixing (not sure if > that's the proper term) 10000 channels into 1 or 2 is certainly > plausible, i suppose.
It is going to keep happening more frequently as more people write for the alsa api. Eventually it might sink in that there is a problem with the api that needs to be solved. > So that probably sounds pretty silly to you, and it did to me too, but > the essence of the answer is that you have no business knowing how many > channels the hardware supports. Like it or not, that's the way it is. Even after all this time it still sounds silly to me (sorry). I think I should be able to know how many channels the hardware supports if I want to - when it is possible, of course. It is no bussiness of the driver to withhold information from the programmer, the information in question is there, I suppose. We either need: a) an api for querying the devices that make up a plug pcm. If it is not possible to map things neatly to devices the api should say, "sorry, can't do that" - but in 99% of the cases it would be able to point to a hardware device and say: "that's what's behind the plug pcm". b) a way to add plug conversions one by one to a hw pcm (or remove conversions from a plug pcm - in this case removing channel mixing - if such a thing exists as an entity - would reveal the real number of channels we have to play with). > The flexibility of alsa devices, given the asoundrc, is so large that > concepts like 'how many channels does this device support' can be > meaningless sometimes. Sure, this may not be practical in some cases, but in 99% of the configurations the concept of "number of channels" is perfectly well defined and should be something I can get from the api. "b" is most probably the easiest to do. Jaroslav hinted a long time ago (I seem to remember) that the foundation for that is already there. Obviously the man-hours needed to write the code are not so easy to come by :-) -- Fernando _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
