ZSNES and osspd

[QuattroPro]

I know that sound and Linux is a contentious topic on this forum. That being said, there is another effort that is attempting to make the situation more manageable.

Kernel 2.6.31 brings CUSE, character device emulation in userspace. Tejun Heo used this to implement osspd, a daemon which emulates /dev/dsp, adsp, and mixer and redirects their sound output to...whatever. Currently, the only redirection implemented sends this input to pulseaudio. However, this means that OSS mixing on Linux happens without intervention (having to run aoss or padsp). Contrary to Tejun's webpage, osspd 1.3 does implement mmap. (here: http://thread.gmane.org/gmane.comp.file-systems.fuse.devel/6843/focus=7723

This makes OSS, at least for linux users using pulseaudio, a viable way to play sound.

Using Fedora 11, I had to install 2.6.31, an updated version of FUSE (currently 2.8.1), and the osspd daemon (found here: http://www.kernel.org/pub/linux/kernel/people/tj/ossp/). The kernel has to be compiled with

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CONFIG_PREEMPT=y
CONFIG_SND_HRTIMER=m
CONFIG_SCHED_HRTICK=y
CONFIG_HZ_1000=y
CONFIG_HZ=1000

and ALSA's oss emulation disabled

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# CONFIG_SOUND_OSS_CORE is not set
# CONFIG_SND_MIXER_OSS is not set
# CONFIG_SND_PCM_OSS is not set
# CONFIG_SND_SEQUENCER_OSS is not set

Once modules cuse and snd_hrtimer are loaded, osspd is run (chmod a+rw /dev/dsp etc.), and you have permission to write to the dev entires, applications using OSS work with no intervention.

I have a Realtek ALC888 codec, and when using this setup + zsnes -ad oss, the latency is way better than using -ad alsa. Granted this is with the unofficial "Link Swing Test", but from my viewpoint, he doesn't swing faster than the speed of sound.

Since it is relatively new, there are bugs. Some OSS applications play at a much faster rate than normal (festalon, in my experience).

I believe that osspd is set to be adopted in Mandriva 2010 and Ubuntu 10.04.

[Nach]

This doesn't really help us in any way. But thanks for the information.