Re: [LAD] mixing music and sound effects using libao

On Thu, 30 Apr 2015, Hermann Meyer wrote:

> Am 30.04.2015 um 10:41 schrieb dave@email-addr-hidden:
>>
>> 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@email-addr-hidden
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
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