Re: Some fixes for alsa_stream

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 06/14/2011 04:01 AM, Mauro Carvalho Chehab wrote:
> Hi Devin,
>
> I've made a few fixes for your alsa_stream.c, used on tvtime.
> They are at:
> 	http://git.linuxtv.org/xawtv3.git
>
>
> In particular, those are the more interesting ones:
>
> commit a1bb5ade5c2b09d6d6d624d18025f9e2c4398495
>      alsa_stream: negotiate the frame rate
>
> Without this patch, one of my em28xx devices doesn't work. It uses
> 32 k rate, while the playback minimal rate is 44.1 k.
> I've changed the entire frame rate logic, to be more reliable, and to
> avoid needing to do frame rate conversion, if both capture and playback
> devices support the same rate.
>
> commit 8adb3d7442b22022b9ca897b0b914962adf41270
>      alsa_stream: Reduce CPU usage by putting the thread into blocking mode
>
> This is just an optimization. I can't see why are you using a non-block
> mode, as it works fine blocking.
>
> commit c67f7aeb86c1caceb7ab30439d169356ea5b1e72
>      alsa_stream.c: use mmap mode instead of the normal mode
>
> Instead of using the normal way, this patch implements mmap mode, and change
> it to be the default mode. This should also help to reduce CPU usage.
>

hmm, does this include automatic fallback to read mode if mmap mode is not
available, mmap mode does not work with a number of devices (such as pulseaudio's
alsa plugin).

Regards,

Hans