Hi everybody,
I'm wondering how to correctly build a shared library using alsa
pcm. Setting the hardware parameters in a function which is part of a
shared library produces an error, snd_pcm_hw_params gives "invalid
argument". The example below with three primitive files (main file,
header and function code) illustrates the problem. With a static
library, everything works fine.
My system: gcc 3.4.6 on Gentoo with alsa 1.0.11.
Does anybody have an idea about the cause of this problem or how to
solve it?
Many thanks,
Gerald
***
main.c:
#include "object.h"
int main()
{
object () ;
return 0;
}
object.h:
void object();
object.c:
#include <alsa/asoundlib.h>
#include "object.h"
void object ()
{
snd_pcm_t* pcm;
snd_pcm_hw_params_t* hwparams;
int rc;
unsigned int rate = 44100;
unsigned int channels = 2;
int dir = 0;
if ( snd_pcm_open(&pcm, "default", SND_PCM_STREAM_PLAYBACK, 0) < 0 )
printf("Cannot open pcm.\n");
snd_pcm_hw_params_alloca(&hwparams);
snd_pcm_hw_params_any(pcm, hwparams);
snd_pcm_hw_params_set_access(pcm, hwparams,
SND_PCM_ACCESS_RW_INTERLEAVED);
snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE);
snd_pcm_hw_params_set_channels (pcm, hwparams, channels);
snd_pcm_hw_params_set_rate_near(pcm, hwparams, &rate, &dir);
rc = snd_pcm_hw_params(pcm, hwparams) ;
if ( rc < 0 )
printf("Error setting hw params: %s.\n", snd_strerror(rc));
}
Compilation:
gcc -c -fPIC object.c
gcc -shared -fPIC -o libTest.so object.o
gcc -o main main.c -L. -lTest -lasound
Output:
Error setting hw params: Invalid argument.
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