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One of the things that's been driving me nuts while working on RP-8 has been how unstable the PCM audio output has felt. I can check (via logs or asserts) that, at 60fps, stat(108) is always above 256 and stat(1) never exceeds 0.9, and I'll still get occasional crackles or small time skips in the output. If I record the audio out with extcmd('audio_rec') these issues generally appear there as well - most often as small intervals of 0 samples. The one or two dropout cases I've been able to inspect in Audacity made it look like the dropout was in the low 10s of milliseconds range. I have not yet been able to track down a skip on the Audacity waveform display.

I've been trying to chase down the bugs in my code, but today I instead tried RP-8 - specifically the current BBS version, #rp8-2 - on two machines that aren't my normal development machine. It was rock solid. Flawless. (Or, well, nearly flawless, just heard a dropout on the Intel Mac after leaving it running for 15 minutes, but the ARM Mac shows problems much earlier and more frequently than that.) My main development machine is an ARM Mac, and the two other machines I tried today were a Windows box and an Intel Mac. The only conclusion I can draw right now is that there's something wonky about Pico-8's PCM audio out on ARM Macs that causes it to skip and/or drop frames.

These issues will happen even what feels like it should be easy for the machine to handle - no other CPU-intensive apps running, Pico-8 is the foreground app, etc. I have not heard these problems with Pico-8's builtin music and SFX. I'm also seeing parallel issues on the web: I thought Pico-8's PCM output was super crackly on all Mac browsers, but RP-8 runs fine in Chrome on the Intel Mac I'm trying out right now.

If there's more information I can give, I'm happy to try to help debug this!

edit: Realized I was behind on OS patches - moved up to 12.3.1 and I'm still definitely getting skips forward, though mystery dropouts seem perhaps rarer? Browser audio has not improved. Not sure how much here is under Pico-8's control, but it's certainly experiencing more audio issues with Pico-8 than with anything else I use.

edit 2: managed to get a skip captured with extcmd - hard to determine exactly how much got sliced out, but it was a small fraction of a kick drum hit.

P#110383 2022-04-18 04:00 ( Edited 2022-04-19 03:10)


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