[PATCH] dsound: Use event based threads

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

Hi,

Maarten Lankhorst queried:
>Bump, anything wrong with this patch?
Here's my 0.0$ ... (standard DSound disclaimer here...)

Using mmdevapi's events in DSound is basically TRT.
Then, the DSound mixer will be synchronized with mmdevapi writes.


>+		/* ALSA is retarded, add a timeout.. */
>+		ret = WaitForSingleObject(dev->sleepev, dev->sleeptime);
How does that comment help the reader of the code?

>+    if (period_ms <= 15)
>+        device->sleeptime = period_ms * 5 / 2;
>+    else
>+        device->sleeptime = period_ms * 3 / 2;
I expect such threshold functions to be continuous or at least monotonic.
A sawtooth is certainly unexpected.  What is its purpose?

What I would understand is a comment in the code saying that as of 2012,
all 3 wine*.drv mmdevapi drivers have a bug that they stop sending events
after IAudioClient_Stop.  Therefore add a short timeout to the wait.

If that's the reason for the timeout, then period_ms * 1.5 is
perfectly fine.  There's no reason for a particular threshold.  Note
that neither 1.5 nor 2.5 give you regular spacing around the time of
transition from playing to stopped.


+    IAudioClient_GetStreamLatency(device->client, &period);
+    period_ms = (period + 9999) / 10000;
If IAC_Stop is the reason for the sleep time out, then it's obvious
that GetStreamLatency has no business here, rather than the device period.


I could understand a use of GetStreamLatency when it comes to computing
a reasonable size of the primary buffer.


+		ret = WaitForSingleObject(dev->sleepev, dev->sleeptime);
+		... if (ret)
WaitFor* return values are defined in terms of WAIT_OBJECT_0, WAIT_TIMEOUT
and WAIT_FAILED etc., not zero or non-zero.


>+  device->sleepev = CreateEventW(0, 0, 0, 0);
>+  device->thread = CreateThread(0, 0, DSOUND_mixthread, device, 0, 0);

I haven't checked the overall style of DSound, but I prefer FALSE and
TRUE be used for things advertised as BOOL.
(I tend to write NULL for null pointer initialisation.
 Note that I easily read "if (foo) ..." for boolean and pointer types;
 I don't expect "if (foo == TRUE) or (foo != NULL) ...")


BTW, I still believe that mixing and resampling would find their best place
in mmdevapi, not DSound.

Regards,
	Jörg Höhle