Update to bsnes v027r02? release.

Okay, here's the deal with sound.

 wertigon's initial OpenAL driver was incomplete and produced no
audio, and _willow_'s had some Windows-specific bindings.

 So, Nach took those, some OpenAL sample code, and some other
application's OpenAL code and produced a working driver for it. Then
Nach and I refined the driver -- I got rid of the crashing on exit and
frequency changing, and both of us wrote new sample() functions.
Nach's is vastly superior on CPU resources, so we'll probably go with
that one.

               That code can be found here:
http://byuu.cinnamonpirate.com/temp/audio.openal.cpp

               This code wouldn't be possible without the help from
wertigon, _willow_ _and_ Nach, so many thanks to everyone, and I'm
sorry I wasn't able to go directly with anyone's specific OpenAL
driver. Linux compatibility was a big concern here. You'll all be
getting full credit in the source and documentation for bsnes v0.028.

               ---

 Now, as for the driver itself. It should work on Windows now with the
sample() and init() corrections, but maybe not. I don't have the means
at the moment to build a Windows binary with it, but maybe I can in
the future.

 But anyway, I don't intend to compile in OpenAL/Win support by
default with bsnes, but rather leave it as an option for those who
compile it themselves. Why? Because Windows does not come with
alut.dll and OpenAL32.dll. I don't want to require another download to
use bsnes, and I don't want to package an extra 300kb of DLLs with it
either. Plus, it doesn't seem to be working too well for most people
anyway thus far.

 Windows does come with DX9, and basically nobody has problems with
DirectSound. It's great, it has very low latency, and it seems to work
on everyone's sound cards, unlike the OpenAL stuff. So it's really not
needed for Windows.

               ---

 However, on Linux, OpenAL has a lot of good points. Unlike with
Linux/OSS3, OpenAL backends to ALSA which supports software mixing.
Meaning audacious and bsnes can run at the same time. And OpenAL has
much lower latency than libao, as well as the ability to disable speed
throttling when necessary.

               But! The OSS4 driver, with SND_DSP_COOKEDMODE,
absolutely _destroys_ even the OpenAL driver. In fact, it's even twice
as good as the DirectSound driver on Windows! No joke!

               From http://wiki.freebsd.org/RyanBeasley/ioctlref :






> ... this ioctl is meant to give processes direct access to the
> hardware buffer, giving the application the most control possible
> (ex: minimizing latency by avoiding in-kernel processing).




 With this, I get roughly ~15-20ms latency, at the very most, with
bsnes. It skips kernel processing entirely! It's hard to even describe
such a low latency. I've never heard Link's sword sound effect start
so quickly. It's really quite impressive. Remember when kode54 was
talking about ASIO or kmixer or whatever? That super low latency
kernel-level audio setup that bypasses the kernel and goes directly to
the sound card? This is it, but for Linux. It's that good.

 But the problem, of course, is Linux' obsession with ALSA, even
though OSS4 is GPLv2 now (and not to mention portable). ALSA is, of
course, total garbage. Anyone who's programmed for it knows that.

 It's very easy to install OSS4, download a DEB package, double click
it, hit install and reboot. But the problem is, many Linux distros try
their best to kill OSS now. Lots of apps are compiled by Linux distro
vendors to only support ALSA, so it does cause some problems, and you
have to reconfigure many apps to use OSS afterwards, so it's not a
very good solution to make bsnes default to the OSS driver.

 Further, because ALSA is so terrible, it causes the OpenAL driver
(which is really just a wrapper to ALSA here) to suck, and it causes
lots of static in the sound. And ALSA's OSS emulation causes severe
video lag -- bizarre, but it has something to do with the blocking
mechanism in ALSA. Only installing OSS4 fixes this. For both drivers,
in fact.

 So, because of ALSA's pathetically poor emulation of both OSS and
OpenAL, I can't default bsnes to either of these drivers. Therefore, I
have to leave the libao driver as the default, but I really recommend
the installation of OSS4 (if you haven't gotten that hint already) if
you really want the best audio possible, and don't mind losing a
couple of your favorite ALSA-only apps. If installing OSS4 is too much
of a plunge, then I still recommend experimenting with the OpenAL and
OSS (in that order) drivers under ALSA. If they work good, great. If
not, sorry, it isn't a problem with the bsnes drivers. You'll have to
stick with libao and it's terrible latency and forced blocking. Unless
someone else wants to write an ALSA driver. I have no intentions of
programming for yet another single-platform API, myself.

               ---

 With all of that said, I have a new WIP up. I'll send the link to any
Linux users who want to test it, as well. Feel free to ask.

               This WIP is source code _only_ (nothing changed on
Windows), and has both the new OpenAL and OSS drivers. Testing would
be greatly appreciated.

[No archive available]
This commit is contained in:
byuu
2007-12-25 17:54:00 +00:00
parent 161366df9b
commit c32195cbd6
Update to bsnes v027r02? release.

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