The major mmdevapi and winmm audio bugs

[Joerg-Cyril.Hoehle at t-systems.com]

Hi,

Bugzilla admins, please set the 1.4 milestone on all bugs mentioned here.

I'm not yet looking at dsound issues since I first want a correct
foundation upon which to build to upper layers.

o #28039 IAudioClock_GetPosition must ignore underruns (MacOS) 
Here I've no idea how to solve this.  My initial query remained unanswered:
http://lists.apple.com/archives/coreaudio-api//2011/Sep/msg00024.html
Ken?  Andrew's yesterday patch (using GetCurrentPadding) is an interim
work-around.  GetPosition (speaker) is unrelated to padding which is
solely about buffering.

o #28093 GetCurrentPadding must slowly decrease (MacOS) 
may cause an app to play audio using a single buffer, causing
underruns and audio drop outs.

o #28056 Problems with sound under FreeBSD
which became "blocking calls with OSS"
recently addressed by Andrew.

o snd_pcm_drop causes incorrect GetPosition after mmdevapi Stop
which I believe to be the cause of:
#27901 winmm tests timing out waiting for hevent after waveOutRestart 
May get solved by Andrew's work in:
#28517 Pikachu Volleyball stops playing sound effects 

Every snd_pcm_drop and reset must be inspected with care w.r.t. its
effect on GetPosition.  Wine must ensure that after playing ends,
GetPosition == sum of written samples for both mmdevapi and winmm.

o #27937 winmm kept busy playing silence after play finishes 
IIRC because winmm writes silence.  Once mmdevapi handles underruns
correctly, my patch "winmm: Never write silence, mmdevapi must handle
underruns." will become applicable:
http://www.winehq.org/pipermail/wine-patches/2011-September/107108.html

Playing silence causes:
#28027 μ-law rendering with pauses and repetitions (MacOS)
as well as presumably:
#28413 Sound play in games and programs causes brief "pauses"
at the time dsound used winmm prior to 1.3.29.

o #28047 IAudioClock_GetPosition must not depend on buffering (ALSA/Pulse)
ALSA must derive GetPosition from snd_pcm_delay, not snd_pcm_avail_update


There are other issues not associated with a bug entry.  I'm off for
vacation, but here's a snippet from my TODO list:
- OSS GetPosition from DSP_GETODELAY
- ALSA+OSS: ReleaseBuffer: check method ordering and max size
- GetStreamLatency = Xms + SHAREDMODE:period
  Stream latency is a static property of the audio graph's components.
- wineoss GetStreamLatency must be constant, and SNDCTL_DSP_GETODELAY
  is only usable once running
- Check WHDR_BEGIN/ENDLOOP code and write tests
- WINMM_GetPosition is simply written_frames, not even minus padding
  (as the old alsa driver did), later use mmdevapi:GetPosition.
- winmm PushData without IAC_Reset or last_clock_pos=0 in case of underrun
- Investigate OSS4 underrun behaviour
- Align wineOSS on newest ALSA code improvements
- Submit CoreAudio memory leak fix to #28023; Write error handling patch
- Check ALSA laptop suspend w.r.t. GetPosition
- Add run-time consistency checks in renderer and
  abort audio stream (GetData) upon trouble instead of hanging.

and finally:

- Test compatibility with native DSound and file bug if unusable.
There are several reports in bugzilla mentioning that this work-around
ceased to work since 1.3.25.  Loss of interoperability is not acceptable.

Regards,
	Jörg Höhle