Reduce calls to Init() in sound drivers

[ann0see]

Description

Findings from the last ASIO4ALL bug fix showed that the Init() function might be called 4 times in the ASIO backend. This feels inefficient. I remember that iOS even refused to start due to having too many audio initialization calls.
We might need to rethink the sound design - not now but for after the review freeze.

[mcfnord]

🤖 AI: The four is in CClient::Init(), not the ASIO backend: three frame-size capability probes (client.cpp:1129-1131) and one real call (:1146). iOS already skips the three.

Settings load multiplies it: of the thirteen Init() call sites in client.cpp, nine are settings setters. On a Focusrite USB ASIO device an instrumented client made 9 CClient::Init() calls before the window appeared -- so 36 CSound::Init(), spending 11 952 ms inside ASIOCreateBuffers, all of it before anything is on screen. The charge lands on a buffer-size change, and the three probes ask for three different sizes.

The TODO directly above the fourth call already says 9 inits at launch <- slow. Same nine.

Separate from launch: connecting to a stock server doubles connect-time re-init too, 4 to 8 CSound::Init calls, regardless of the client's own audio-quality setting. CClient::OnRawAudioSupported() stops/inits/starts the device with no eAudioQuality check, and the server sends that message to every client on connect (opened by #3653). Measured on Linux/JACK, stock binary, gdb breakpoints, --noraw as control: 44 CSound::Init (36 launch + 8 connect) vs. 40 (36 + 4) -- corroborating the 36/9 launch count above on a second platform. At 328-391 ms per call on the Focusrite trace, the extra 4 is ~1.3-1.6 s of avoidable re-init per connect.

[ann0see]

Thanks for the clarification. It's worth investigating it even more then...

[dingodoppelt]

Thanks for the clarification. It's worth investigating it even more then...

The connection process is all over the place and should be redesigned to negotiate a proper handshake. The freely available 4 bytes (#3896) could be helpful.

[dingodoppelt]

We could save another call to Init() (and the reliance on the version and os message) by deprecating packets without a sequence number. Just a thought.

[pljones]

We could save another call to Init() (and the reliance on the version and os message) by deprecating packets without a sequence number. Just a thought.

Now, if we had stats from the Directories as to how many IPs generated those, we'd be in a better position to judge.

I don't remember which version brought them in.