Re: [Qemu-devel] [RFC PATCH] audio/sdlaudio: Allow audio playback with SDL2

[Gerd Hoffmann <kraxel@redhat.com>]

On Mi, 2017-02-01 at 16:30 +0100, Thomas Huth wrote:
> On 01.02.2017 14:25, Gerd Hoffmann wrote:
> > On Di, 2017-01-31 at 09:46 +0100, Thomas Huth wrote:
> >> When compiling with SDL2, the semaphore trick used in sdlaudio.c
> >> does not work - QEMU locks up completely in this case. To avoid
> >> the hang and get at least some audio playback up and running (it's
> >> a little bit crackling, but better than nothing), we can use the
> >> SDL locking functions SDL_LockAudio() and SDL_UnlockAudio() to sync
> >> with the sound playback thread instead.
> > 
> > Does SDL_LockAudio work with sdl1 too?
> > So we can possibly avoid having all those #ifdefs?
> 
> It somehow works, too, but sound quality is - at least for me - much
> worse here than with the semaphore code. Maybe it can be fixed, too, but
> I am really not familiar enough with the QEMU internal audio API to
> figure out how to fix this (e.g. I don't understand why the run_out
> function is called way more often than the callback function, but its
> "live" parameter never reaches the full buffer size).
> So maybe we can start with the #ifdefs for now and remove them once
> somebody figured out how to improve sound quality for SDL1, too? (or
> once we remove support for SDL1 from QEMU completely ... or do we want
> to carry that with us forever?).

Ok, picked as-is for now.  It's better than nothing, and I'm too busy
with other stuff atm to have a closer look myself.

thanks,
  Gerd