Am 30.04.2015 um 10:41 schrieb dave(a)661.org:
I've been playing around with libsndfile, libvorbisfile, libmodplug, and
libao to provide background music and sound effects for a game engine. I
have a solid handle on making one noise at a time, but I don't understand
mixing. At first I thought I would have to write my own mixer and handle
the channels, sample rate, and sample size issues myself. I really don't
want to have to do that. Then I noticed in the libao documentation that
nothing says that I cannot spawn two threads, each of which calls
ao_open_live() and ao_play() on different sound files. Indeed, the docs
for ao_initialize() seem to suggest this can be done with the statement
that it be called in the main thread.
I tried this and it works so erratically that I'm not sure libao was
written with this in mind. I get these results in order of likelihood:
1) "Segmentation fault"
2) "*** glibc detected *** ./threadtest7: malloc(): memory corruption
(fast): 0x0000000001bc5390 *** Bus error"
3) "*** glibc detected *** ./threadtest7: double free or corruption (out):
0x00000000018ba2e0 ***"
4) A bit of the first file, then the second file.
5) Only the second file.
6) Both files messily mixed with a zipping noise. (very rare)
Is libao in fact intentionally capable of doing this? If not, what are my
options for mixing music and sound effects? I really don't want to use
SDL_mixer for a variety of reasons, chiefly because my program is
terminal-only. Virtual beer if you can guess what the program is.
Hi
It seems libao is able to do this. Attached is the example code from the
libao side, roughly hacked in a second thread to play to signals
simultaneous. Works stable here.
This has trouble opening the second device:
ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave
Error opening device2.
I'm using Debian Wheezy amd64 without Pulseaudio. Maybe Debian's default
setup for ALSA is wrong? There are no /etc/asound.conf or ~/.asoundrc
files.
--
David Griffith
dave(a)661.org
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