[pulseaudio-discuss] RTP Latency - how to reduce.

[Sergei Steshenko]

On 07/07/2019 21:47, tony.chabot at vartaxos.com 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
>
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"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.