Re: DMIX and capture stream

[Takashi Iwai <tiwai@suse.de>]

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At Mon, 05 Jan 2004 12:41:12 -0500,
Paul Davis wrote:
> 
> >I have application A that needs to open payback and capture streams 
> >because it's a two-way communications program.  Application B is a game 
> >that uses playback only.  I want to use these both at the same time.
> 
> but i don't think you can do this with OSS. why should ALSA's OSS
> emulation make it possible? the OSS API doesn't support this. if they
> used the ALSA API, it would work without (much) work on your part.

ok, finally i got his question - well, i didn't read carefully it
before, since i still have 5,000 unread mails...

anyway, it's possible if you use aoss wrapper and specify dmix/dsnoop
as the device.  you're right for the kernel emulation.  no way.
but still we need a fix for aoss wrapper.  the only necessary change
is to allow aoss open different pcm per playback and capture stream.

for example, the below is a minute quick hack (untested) for that.
you can specify pcm.dsp0p and pcm.dsp0c for playback and capture
directions, respectively.


Takashi

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Index: alsa-oss/alsa-oss.c
===================================================================
RCS file: /suse/tiwai/cvs/alsa/alsa-oss/alsa-oss.c,v
retrieving revision 1.24
diff -u -r1.24 alsa-oss.c
--- alsa-oss/alsa-oss.c	1 Dec 2003 13:25:58 -0000	1.24
+++ alsa-oss/alsa-oss.c	5 Jan 2004 18:08:18 -0000
@@ -394,6 +394,7 @@
 	int fd = -1;
 	int result;
 	char name[64];
+	static char *suffix[2] = { "p", "c" };
 
 	switch (device) {
 	case OSS_DEVICE_DSP:
@@ -447,11 +448,16 @@
 	dsp->oss_format = format;
 	result = -EINVAL;
 	for (k = 0; k < 2; ++k) {
+		char tmpname[64];
 		if (!(streams & (1 << k)))
 			continue;
-		result = snd_pcm_open(&dsp->streams[k].pcm, name, k, pcm_mode);
-		if (result < 0)
-			break;
+		snprintf(tmpname, sizeof(tmpname), "%s%s", name, suffix[k]);
+		result = snd_pcm_open(&dsp->streams[k].pcm, tmpname, k, pcm_mode);
+		if (result < 0) {
+			result = snd_pcm_open(&dsp->streams[k].pcm, name, k, pcm_mode);
+			if (result < 0)
+				break;
+		}
 	}
 	if (result < 0) {
 		result = 0;