On Fri, 27 Apr 2007, Takashi Iwai wrote: > At Fri, 27 Apr 2007 13:27:00 +0100, > Gordon Miller wrote: > > > > Hi > > > > All my snd_pcm_readi calls return too few frames. Also when I switch to > > stereo, the sound is muted. I cannot change this by adjusting period & > > buffer sizes. dsnoop is enabled by default. The documentation for > > snd_pcm_readi says that the only way that the frame count can be short > > is because of a signal or xrun. Well this clearly isn't the case. > > Actually, the documentation is wrong, IMO. The typical behavior of > read syscall is that it returns a value actually read by that call. > It doesn't guarantee whether the requested size is filled, and can be > shorter than requested. As snd_pcm_readi() emulates the read syscall, > it should behave in that way. I don't think so completely. For blocking mode (!O_NONBLOCK), all possible data should be read. Only signal or an error should break this. The read logic for dsnoop is in snd_pcm_read_areas() in pcm/pcm.c (alsa-lib). > The blocking mode means that the function waits until the threshold > (watermark) condition is fulfilled. I don't think so. The snd_pcm_read_areas() does only xfer_align alignment for wrong user input. If less frames are returned, then it is an error IMO. Jaroslav ----- Jaroslav Kysela <perex@xxxxxxx> Linux Kernel Sound Maintainer ALSA Project, SUSE Labs _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
