From: Christian Schoenebeck <qemu_oss@crudebyte.com>
To: qemu-devel@nongnu.org
Cc: "Volker Rümelin" <vr_qemu@t-online.de>,
"Thomas Huth" <huth@tuxfamily.org>,
"Gerd Hoffmann" <kraxel@redhat.com>
Subject: Re: [PATCH 00/15] reduce audio playback latency
Date: Mon, 10 Jan 2022 14:11:23 +0100 [thread overview]
Message-ID: <3415099.zrPmtJVVhH@silver> (raw)
In-Reply-To: <988cdc99-ed34-00cb-bef1-e73b94672a28@t-online.de>
On Sonntag, 9. Januar 2022 18:06:44 CET Volker Rümelin wrote:
> > On Donnerstag, 6. Januar 2022 10:21:47 CET Volker Rümelin wrote:
> >> This patch series reduces the playback latency for audio backends,
> >> in some cases significantly. For PulseAudio, the audio buffer is
> >> also moved from the QEMU side to the PulseAudio server side. This
> >> improves the drop-out safety for PulseAudio.
> >>
> >> I actually measured the latency reduction with the PulseAudio
> >> backend. For the test I used my Linux host configured to play
> >> audio with PulseAudio. The guest was a Linux guest, also
> >> configured to use PulseAudio.
> >
> > I haven't reviewed all the patches yet, but from what I read so far, does
> > that mean the additional 3rd buffer is solely for PulseAudio, so for JACK
> > and other backends these changes would overall be a degradation, wouldn't
> > they?
> No, nothing changes for JACK and it's an improvement for all the other
> backends where I added a buffer_get_free function. The important changes
> are in [PATCH 10/15] audio: restore mixing-engine playback buffer size.
> That patch tries to keep the mixing-engine buffer empty at the end of
> audio_run_out().
>
> I couldn't reduce the playback latency for JACK, because the JACK audio
> buffers are already very small and any further reduction introduces
> playback glitches on my system.
And that's actually my concern. A split 2 buffers -> 3 buffers while
(approximately) retaining overall latency increases the chance of dropouts.
> For PulseAudio there is no additional buffer. I only increased the size
> of the server side buffer from 15ms to 46,4ms and added a
> buffer_get_free function. Before this patch series a few ten ms after
> playback started the mixing-engine buffer was full which added 2 *
> 46,4ms to the playback latency. With these patches the mixing-engine
> buffer is empty. This looks like the buffer in use was moved from the
> mixing-engine to the PulseAudio server side.
next prev parent reply other threads:[~2022-01-10 13:23 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-06 9:21 [PATCH 00/15] reduce audio playback latency Volker Rümelin
2022-01-06 9:23 ` [PATCH 01/15] audio: replace open-coded buffer arithmetic Volker Rümelin
2022-01-06 10:18 ` Thomas Huth
2022-01-07 12:10 ` Volker Rümelin
2022-01-06 9:23 ` [PATCH 02/15] audio: move function audio_pcm_hw_clip_out() Volker Rümelin
2022-01-07 13:30 ` Philippe Mathieu-Daudé
2022-01-06 9:23 ` [PATCH 03/15] audio: add function audio_pcm_hw_conv_in() Volker Rümelin
2022-01-06 9:23 ` [PATCH 04/15] audio: inline function audio_pcm_sw_get_rpos_in() Volker Rümelin
2022-01-06 9:23 ` [PATCH 05/15] paaudio: increase default latency to 46ms Volker Rümelin
2022-01-06 9:23 ` [PATCH 06/15] jackaudio: use more jack audio buffers Volker Rümelin
2022-01-06 9:23 ` [PATCH 07/15] audio: copy playback stream in sequential order Volker Rümelin
2022-01-06 9:23 ` [PATCH 08/15] audio: add pcm_ops function table for capture backend Volker Rümelin
2022-01-06 9:23 ` [PATCH 09/15] audio: revert tests for pcm_ops table Volker Rümelin
2022-01-13 9:43 ` Gerd Hoffmann
2022-01-06 9:23 ` [PATCH 10/15] audio: restore mixing-engine playback buffer size Volker Rümelin
2022-01-06 9:23 ` [PATCH 11/15] paaudio: reduce effective " Volker Rümelin
2022-01-06 9:23 ` [PATCH 12/15] dsoundaudio: " Volker Rümelin
2022-01-06 9:23 ` [PATCH 13/15] ossaudio: " Volker Rümelin
2022-01-07 13:42 ` Philippe Mathieu-Daudé
2022-01-06 9:23 ` [PATCH 14/15] paaudio: fix samples vs. frames mix-up Volker Rümelin
2022-01-06 9:23 ` [PATCH 15/15] sdlaudio: " Volker Rümelin
2022-01-06 9:48 ` [PATCH 00/15] reduce audio playback latency Volker Rümelin
2022-01-09 14:17 ` Christian Schoenebeck
2022-01-09 17:06 ` Volker Rümelin
2022-01-10 13:11 ` Christian Schoenebeck [this message]
2022-01-10 21:50 ` Volker Rümelin
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