On Sun, 12 Mar 2023, Volker Rümelin wrote:
Am 12.03.23 um 14:23 schrieb BALATON Zoltan:
On Sun, 12 Mar 2023, Volker Rümelin wrote:
Am 11.03.23 um 23:54 schrieb BALATON Zoltan:
Hello,
I've noticed before that since commit a806f95904cdb audio plays slower
(like half speed) under AmigaOS on sam460ex with ES1370 but I did not
have any other guests to reproduce it and verify this with so I did not
report that yet. Now that we can also test with pegasos2 and via-ac97 it
does not play slower on that machine neither with ES1370 not via-ac97 but
still can reproduce it with sam460ex.
But on another host it seems to play faster with pegasos2. Here is a
video taken by Rene demonstrating the problem:
https://youtu.be/Rg5buzDqGuk So there seems to be a problem with playback
speed here but I'm not sure if this is related to AmigaOS or something
else.
At least we have some issue with AmigaOS on sam460ex and ES1370 playing
too slow since commit a806f95904cdb on Linux with alsa backend and may
also have an issue with sound being too fast on pegasos2 with coreaudio.
However Rene said that recording it with a screen recorder did not show
the problem, only when playing it normally, that's why the video is taken
with a camera. I can't understand how that's possible but maybe you have
some idea to at least how to test this further to find out more what's
happening here or if you can see anything that can cause playback speed
issues with these machines.
So far I've reproduced obviously slow speed with AmigaOS on sam460ex with
ES1370 on Linux with alsa. The MorphOS and AmigaOS on pegasos2 with
via-ac97 or ES1370 (latter only works with AmigaOS) seems to be OK to me
on my machine but is playing too fast in Rene's video.
Could this be related to some differentce in host's sampling rate or some
other settings somewhere? I have defaults.pcm.dmix.rate 44100 in
/etc/asound.conf while Rene is using whatever macOS does with coreaudio.
Any ideas what to check further?
Hi,
perhaps this issue is similar to the Linux guest driver issue with an AC97
device. The Linux driver tries to measure the AC97 clock frequency. It
starts playback with a certain amount of audio frames and measures the
time needed for playback. Since QEMU is not a cycle exact simulation the
result is always wrong. Before my latency reducing patches the result was
always way off and the Linux driver rejected the measurement and used a
clock frequency of 48000Hz. Now the driver sometimes believes the
measurement is correct and adjusts the clock frequency.
I don't think that's the case with the AmigaOS driver. I don't know for
sure what exactly does that driver do but it is probably similiar to the
AROS driver which is here (the via-ac97 is one level up from that):
https://github.com/aros-development-team/AROS/tree/master/workbench/devs/AHI/Drivers/SB128
and I don's see anything like that in it. AROS doesn't run on pegasos2 yet
so I can't test with that. It should work with sam460ex which I've tried
but the SB128 driver used for ES1370 seems to have endianness problems and
only works on pc machine, not on big-endian PPC machines (a lot of AROS
network drivers have the same problem, these seem to be mostly tested on PC
only). On sam460ex it detects the card but doesn't make sound but works
with on the pc machine.
But the question remains how commit a806f95904cdb could change playback
speed as the problem with sam460ex is bisectable to that commit.
To change the playback speed you have to remove or add audio frames from or
to the audio stream. At the moment I don't see how this patch can change the
playback speed. I also don't see how this patch could change the audio
backend sample frequency. Do you think there is a way to reproduce this issue
on my computer?
The reproducer I know needs AmigaOS license for sam460ex. If you don't
have that maybe it can be also reproduced with Linux guest but I don't
know a good distro that supported sam460ex (current ones probably don't
as PPC32 is quite dead so maybe some older ones). The manufacturer's site:
https://www.acube-systems.biz/index.php?page=hardware&pid=5
links to a site in downloads section with some Linux kernels but these
seem to be outdated and don't know which could work. AROS should have a
similar driver and I thought that could help but it does not make sound
likely due to endianness issues as I've wrote before. So this is probably
doesn't help much as the only easy way I know needs a closed source OS.
This can be fixed with the kernel command-line argument
snd_intel8x0.ac97_clock=48000.
If AmigaOS also tries to measure the audio clock frequency, it may help to
increase the playback latency to make the measurement worse. I would start
with -audiodev coreaudio,id=audio0,out.buffer-count=12. The default buffer
count is 4.
Are these options documented somewhere? I don't even know they exist and
which one to tune for different results so if this knowledge is only
something you have now it would be a great contribution to put it in some
docs for reference. Or if this is already described somewhere maybe it
should be made more prominent as I don't even know where to look for it.
Maybe also some generic intro on how the audio infrastructure in QEMU works
would be helpful too so one can understand what the options tweak.
The QEMU documentation describes most of the options. But there is no
detailed description of the function. I have read the code.
Where are these in the docs? I could not find it even by searching under
qemu/docs.
Regards,
BALATON Zoltan