[Qemu-devel] Re: [PATCH] alsaaudio: increase default buffer sizes

[Jan Kiszka]

malc wrote:
> On Sun, 4 May 2008, Jan Kiszka wrote:
> 
>> Jan Kiszka wrote:
>>> malc wrote:
>>>> On Sun, 4 May 2008, Jan Kiszka wrote:
>>>>
> 
> [..snip..]
> 
>>>
>>> Yeah, great, that was the key! Find below the version that works for me
>>> (on 64 bit 8) ). It even obsoletes my buffer size patch. Please merge!
>>
>> Declaring the buffer size tweak obsolete was too quick. I still need
>> more under certain guest load, but now I'm already fine with
>> DEFAULT_BUFFER_SIZE=4096. Or all in one:
> 
> I wonder if everyone will be happy with quadrupled latency, apart from

Hmm, I wonder about the scenario where this latency may actually hurt.
QEMU is not /that/ fast anyway. ;)

> you and this other user on some (kvm was it) mailing list there are no
> huge outcries of dissatisfaction, then again i'm not sure how many people
> use ALSA+QEMU or QEMUs+AUDIO in general.

I don't think many users are actually running QEMU (or KVM) against
ALSA. You have to
 - manually enable it during configure
 - pass QEMU_AUDIO_DRV=alsa (OSS remains default even if ALSA is on - I
   ran into this trap first.)
 - possibly have to fix up your configuration with FIXED_FREQ and
   BUFFER_SIZE (as reported by >1 kvm users) until

As OSS does not give us shared sound device access and, in the end, is a
deprecated API under Linux, my goal is to overcome remaining issues of
the ALSA support and then make /this/ the default one (under Linux).

Jan

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