Re: [hatari-devel] STe DMA sound

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On 13/04/2018 at 11:10, Vincent Rivière a wrote:
*BUT* that didn't fix the issue!
I can still hear the bogus-treeble which makes my ears bleeding.
Those annoying frequencies are definitely above the low-pass filter.

By thinking twice, I may have been fooled by 2 different bugs:

1) The bogus peak on stairs, visible on Audacity waveforms, including with simple sine wave testcase. Definitely wrong, might come from wrong upsampling combined to LMC1992 bass/treeble, as Christian suspects.

2) The 7 KHz artifact in Lethal Xcess music, visible on Audacity spectrogram.
This is the most annoying issue for the ears, like ultrasounds inserted in the music at some places. Listening carefully to the music and digidrums at lower rate, I'm finally not sure at all that it comes from the DMA sound. That might explain things. That bogus sound may be simply generated by the YM-2149, due to bogus input or emulation.

There is no clue that 1) and 2) are related.

Strange coincidence:
I have reported the "restore memory snapshot" issue in other thread.
When I press AltGr+l, it freezes (bug), but most of the time I hear that continuous 7 KHz high pitched sound.

But strangely, there is no such 7 KHz issue in Lethal Xcess *ST* mode (even if display fails due to another Hatari bug).
Maybe the ST digidrums resets some YM registers, avoiding the STe 7 KHz bug...

Really, we must be sure to avoid confusing between different issues when investigating.

Vincent Rivière

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