[pulseaudio-discuss] Why does PA need to rewrite and rewind when I change the volume while playing audio?

[Arun Raghavan]

On Mon, 26 Jul 2021, at 11:18 PM, Chengyi Zhao wrote:
> Hi guys,
> 
> I found the following logic when I change the volume while playing 
> audio.I guess there is some audio expertise here, would you please tell 
> me the principle, thanks a lot!
> 
> In the file sink-input.c(./src/pulsecore/sink-input.c), why does pa need 
> to invoke the function pa_sink_input_request_rewind to rewrite and 
> rewind the data?

Because you might have a large buffer, and you want volume updates to be audible immediately. More details here:

https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Rewinding/

-- Arun