Unnecessary check for mmap/trigger in audiolib.c

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Hi, developers!

Today, I decided to try setting up some tools for a project of mine. It w=
ould involve three lavplays in parallel, and require use of the padsp wra=
pper for the sound, as I don't have OSS on this computer, and only one ha=
rdware channel, anyway.

I was rewarded with a curious message: "Soundcard cant do mmap or trigger=
"

Fair enough, the PA OSS emulation can't do mmap, but that's what lavplay'=
s -U flag is for. Still no cake when using that, though; still the messag=
e about no mmap support (which I already knew, and tried to avoid...).

It turned out that audiolib.c, as far as I can tell, doesn't honor the mm=
ap_io, nor the use_read_write flag, and look for mmap/trigger support eve=
n when it shouldn't. My proposed patch takes care of that, skipping the c=
heck when read/write is requested instead of mmap.

This let me play the audio through padsp, but lavplay will often hang
with the message "Buffer overflow writing audio". I haven't yet tried
to improve that situation, but I have observed the hang occur in either o=
ne of the
audio_errno =3D AUDIO_ERR_BOVFL lines.

Regards,
/Sam

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diff -urN mjpegtools-2.0.0/lavtools/audiolib.c mjpegtools-2.0.0-sam/lavtools/audiolib.c
--- mjpegtools-2.0.0/lavtools/audiolib.c	2006-08-25 06:01:47.000000000 +0200
+++ mjpegtools-2.0.0-sam/lavtools/audiolib.c	2011-05-29 02:21:19.000000000 +0200
@@ -756,11 +756,13 @@
  * Check that the device has capability to do mmap and trigger
  */
 
-   ret = ioctl(fd, SNDCTL_DSP_GETCAPS, &caps);
-   if(ret<0) system_error("getting audio device capabilities",fd,1);
+   if(mmap_io) {
+      ret = ioctl(fd, SNDCTL_DSP_GETCAPS, &caps);
+      if(ret<0) system_error("getting audio device capabilities",fd,1);
 
-   if (!(caps & DSP_CAP_TRIGGER) || !(caps & DSP_CAP_MMAP))
-      system_error("Soundcard cant do mmap or trigger",fd,0);
+      if (!(caps & DSP_CAP_TRIGGER) || !(caps & DSP_CAP_MMAP))
+         system_error("Soundcard cant do mmap or trigger",fd,0);
+   }
 
 /*
  * Get the size of the input/output buffer and do the mmap

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