Re: [hatari-devel] Regression in Falcon sound

[Anders Eriksson <evldhs@xxxxxxxxxxxxxx>]

On Tuesday, 2 April 2024 at 22:24, Nicolas Pomarède <npomarede@xxxxxxxxxxxx> wrote:

> Le 31/03/2024 à 14:16, Anders Eriksson a écrit :
> 
> > Hello,
> > 
> > after all of Nicolas recent Falcon fixes, I'm sorry to report some regressions and some old standing bugs.
> > 
> > 1. DUMP v1.71 (DSPMOD) module player + Hyperbased module (or any other module)
> > 
> > - Old bug: When starting a second time, there's old sample data played for a frame or two, VGA+RGB (also present in 2.4.1)
> > - Old bug: Each time starting the modplayer the left/right channels can be swapped around, VGA+RGB (also present in 2.4.1)
> > - Regression: Big stuttering in VGA mode after some time (like skipping forward or backwards, the moment when it happen differs each test run (OK in 2.4.1)
> > - Regression: Same as above in RGB mode, but much more subtle and more often (OK in 2.4.1)
> > 
> > DUMP: https://demozoo.org/productions/95633/
> > Hyperbased: https://demozoo.org/music/2233/
> > 
> > 2. MP2 Audio (direct from RAM playback to avoid any drive streaming issues)
> > 
> > Same problems as with DSPMOD, except I haven't verified the left/right channel mixup.
> > 
> > Test package: http://ae.dhs.nu/tmp/hatari250mp2test.zip
> > (music from New Beats "That time of the year" demo). Set machine to 14 MB so it can fit the file in RAM.
> > 
> > Hatari version:
> > https://api.cirrus-ci.com/v1/artifact/github/hatari/hatari/macos12/hatari/hatari-snapshot.zip
> > INFO : Hatari v2.5.0-devel (Mar 29 2024), compiled on: Mar 29 2024, 01:39:05
> > 
> > Host system: macOS 13.6.5, ARM64 (M1)
> > 
> > Double checked against a real Falcon (RGB+VGA) and none of these problems appear there.
> 
> 
> Hi
> 
> thanks for the download link and the detailed description.
> 
> I confirm I get the same result as you did, there's some kind of
> randomness that makes it a little more difficult to reproduce exactly on
> every run.
> 
> For now, I don't know why there's this regression but as it involves DSP
> it's not sure that it's related to the very recent changes I made to DMA
> audio.
> 
> I will try to get some time to bisect, but even so this could imply
> quite some changes, as Falcon audio still uses some "float" types to mix
> at different frequencies and this can give too much rounding errors that
> accumulate over time and can cause drift or "jump" in the sound buffer.
> The plan is to replace this with integer math that "self adjusts" over
> time to keep rounding unnoticable (as done for YM2149 and STE/TT audio)
> 
> It's quite possible it will be fixed after Hatari 2.5 is released, else
> I'm afraid this would postpone the release for too long :(


Hi,

after some further tests, it looks like the stuttering only happens "live".
I tried to video record the problem (using Hataris built-in recording), and to my surprise there was no stuttering in the recorded video. I used the MP2 example for testing.

So Hatari seems to be rendering the sound correct but somewhere in the audio output it goes a bit bananas.


--
Anders Eriksson
ae@xxxxxx