On 08.07.19 15:51, Sergei Steshenko wrote:
On 07/07/2019 21:47, tony.chabot@xxxxxxxxxxxx wrote:
I have searched
Setup: Desktop machine (Centos 7, PulseAudio 10.0), and a Raspberry
Pi 2B (Raspbian (Debian) Buster PulseAudio 12.2) with DAC and speaker.
If I play a video point-to-point over TCP the synch is fine, but over
RTP (with latency_msec=1 on RPi) there is signifcant audio latency -
enough to be irritating.
If I add a second, identical RPi (although with Raspbian Stretch and
PulseAudio 12.2), the RTP sound is synchronous on each machine (but
not with the video).
This is on a small private wired LAN (Netgear GS724T V3), 1G to
desktop, 100M to RPI.
I have set tsched=0 in order to eradicate pops and sprogs.
What can I do to reduce RTP latency?
I eventually want to connect a guitar, and would need realtime
loop-through, so no suggestions about increasing audio latency to
obtain lip-synch, please.
Tony
"I eventually want to connect a guitar" - I was doing some estimates,
and if I were you, I would bypass not only pulseuadio, but also ALSA
I.e. I would create a dedicated audio program that bypasses the kernel
and interacts with device directly. I would also starve the OS WRT
scheduling. I.e. I would allocate, say, 99% of time to the dedicated
program. I would also tune kernel ticks to be in sync with sample rate.
--Sergei.
What do you think is the actual latency you can live with? And is RTP a
requirement?
If ~ 10ms is sufficient and you can you also use a tunnel sink, you
could try this merge
request:
https://gitlab.freedesktop.org/pulseaudio/pulseaudio/merge_requests/53
It allows to reduce the latency of the tunnel sink by using a command
line parameter.
I was able to get down to around 7ms (real latency, measured with an
oscilloscope).
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