[Bug 1873769] Re: SB16 audio playback freezes emulation in Windows 95 guest

[Vladislav K. Valtchev]

Hi Allan, 
I've hit EXACTLY the same problem, while writing a SB16 driver.

Reproducing the bug
----------------------
I've tried to QEMU 4 in several scenarios (GTK UI, text mode with the -curses 
option,
just serial console with -nographic and with virt-manager which uses Spice). It 
works
as expected in all the cases EXCEPT for the GTK UI: in that case, the video 
freezes
while playing the sound, exactly as in the video posted by Marko; even QEMU's 
menu
doesn't respond while the audio is playing (the bug affects the whole QEMU UI).

Regression
---------------------
I've also tried the same test with QEMU 2.11, on another machine with Ubuntu 
18.04 (LTS)
and there the problem simply does *not* exist. QEMU's UI (does QEMU 2.x uses 
GTK?),
works GREAT while playing SB16 audio.

Conclusion
----------------
Is there any chance this bug could be fixed easily, or a fix would necessarily 
require
a (partial) re-design of the way the GTK UI works? In particular, why on QEMU 
2.11 the
problem does not exist?


Thanks in advance,
Vlad

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https://bugs.launchpad.net/bugs/1873769

Title:
  SB16 audio playback freezes emulation in Windows 95 guest

Status in QEMU:
  New

Bug description:
  - QEMU 4.2.93 (v5.0.0-rc3) built from latest git master
  20038cd7a8412feeb49c01f6ede89e36c8995472 using MSYS2 on Windows 10 and
  launched on same Windows 10

  - Launched using "qemu-system-i386.exe -drive format=raw,file=hdd-
  2gb.img -soundhw pcspk,sb16 -m 16 -cpu pentium -vga std -cdrom
  Windows_95.iso -boot c"

  - I have attached video screen capture of the issue

  ---

  I decided to make my first ever QEMU build after encountering the
  dsound issues using the latest 4.2.0 binary from
  https://qemu.weilnetz.de/w64/. In my 5.0.0-rc3 build the sound
  playback is working correctly, however the whole Windows 95 UI freezes
  while sound is playing.

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