FWIW the SCREAMER_BUFFER_SIZE issue and a few others were fixed in the last rebase
which can be found at https://github.com/mcayland/qemu/tree/screamer-v9.1.0. The
implementation is mostly working well for qemu-system-ppc -M mac99.
The main bits missing are underflow/overflow management of the DBDMA stream, and also
to figure out why MacOS 9 is liable to hang on startup with screamer.
What I seem to remember, this is the state of the screamer:
For all Mac OS 9.x the screamer starts behaving badly when memory is set to more than 1023 Mb (the Mac OS switch-off point for virtual memory).
#9.0.4
mac99: sound fine (known issue: needs adb wake-up wiggle before screen resolution switch, etc.)
pmu: boots, no mouse, so no test (known issue: mouse is by default the second usb device which will not work)
#9.1
mac99: sound fine (known issue: needs adb wake-up wiggle before screen resolution switch, etc.)
pmu: sound fine
#9.2.2
mac99: sound fine.
pmu: sound fine.
For OSX guests: the sound stream starts echoing (duplicated?) as soon as the sound prefs are opened.
#10.0.img
mac99: crackling sound, see repeating command 4000, invalid key 0 message.
pmu: boots, no mouse, so no test (known issue: mouse is by default the second usb device which will not work)
#10.1
mac99: crackling sound, sound CP slow to react on clicks. Left/right channels are not separated correctly.
pmu: boots, no mouse, so no test (known issue: mouse is by default the second usb device which will not work)
#10.2
mac99: sound fine. (but left/right channels are reversed)
pmu: the clock runs about 3x slower than normal. no sound!
#10.3.img
mac99: sound fine, maybe with very small crackle.
pmu: sound fine, maybe with very small crackle.
#10.4
mac99: sound fine.
pmu: sound fine.
#10.5
mac99: will not run without pmu
pmu: sound fine.