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From: | Kővágó Zoltán |
Subject: | Re: [Qemu-devel] [PATCH] pulseaudio: reduce 24s recording latency |
Date: | Sat, 12 Sep 2015 16:35:56 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 |
2015-09-12 13:23 keltezéssel, Volker Rümelin írta:
Hi, Am 12.09.2015 um 01:22 schrieb Marc-André Lureau:Current code doesn't provide pulseaudio buffer attributes for recording. Without buffer attributes pulseaudio uses a default buffer of 4MB. 4MB is approximately 24s 16bit stereo audio data at 44.1kHz.Why isn't the buffer processed as soon as some data is available?On start up qemu opens a connection to pulseaudio in function qpa_init_in and pulseaudio immediately starts recording to the 4MB ringbuffer. The qemu guest, Windows 8.1 in my case, doesn't consume that data if there is no process listening on the audio interface. Now if the guest starts recording, it will see audio data which was recorded 24s ago.
Weird, pulseaudio shouldn't delay the input more than 2 seconds in the default config. Maybe PA_STREAM_EARLY_REQUESTS help. See my patch at [1]. Alternatively we should maybe call pa_stream_flush when enabling the input to tell pulseaudio to drop previously recorded samples.
[1]: https://lists.gnu.org/archive/html/qemu-devel/2015-08/msg02455.html Zoltan
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