Re: C program for playing sound

> now the problem is that the sound is skipping.

Can you provide a recording of what it sounds like?

In alsa-lib there is an example test/latency.c which just moves samples from one device to another.

When I run it, the sound that comes out of my speakers is what I would call "scratchy".

I submitted a bug report here, which has recordings of what I hear when I run ./latency:

https://github.com/alsa-project/alsa-lib/issues/53

It was closed by someone named Jaroslav Kysela who is the author of ALSA, according to Wikipedia. But I'm not sure if he read the actual bug report.

I don't know where you got the idea to call snd_pcm_prepare in your loop, or why that fixed the problem.

I hope this is helpful.

Frederick

On Tue, Jun 23, 2020 at 04:54:09PM -0300, Sleep wrote:
>Update, forgot snd_pcm_prepare(), now the problem is that the sound is 
>skipping.
>
>#include <stdlib.h>
>#include <stdint.h>
>#include <alsa/asoundlib.h>
>
>#define STEREO 2
>#define BITS 16 / 8
>#define FRAMEBUFFERSIZE 512 // in samples
>#define PERIODS 2
>#define SAMPLERATE 11025
>
>int main(void)
>{
>    snd_pcm_t *handle;
>    uint32_t channels = STEREO;
>    uint32_t sample_size = BITS; // 16 bit
>    uint32_t frame_size = sample_size * channels;
>    snd_pcm_uframes_t frames = FRAMEBUFFERSIZE;
>    snd_pcm_uframes_t frames_per_period = frames / PERIODS;
>    int dir = 0; // No idea what this does.
>    snd_pcm_hw_params_t *params;
>    int16_t framebuffer[FRAMEBUFFERSIZE * STEREO * BITS] = {0};
>    FILE *wav;
>    int size;
>    int status;
>
>    snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0); // 
>SND_PCM_NONBLOCK);
>    snd_pcm_hw_params_alloca(&params);
>    snd_pcm_hw_params_any(handle, params);
>    snd_pcm_hw_params_set_buffer_size(handle, params, frames);
>    snd_pcm_hw_params_set_period_size(handle, params, 
>frames_per_period, dir);
>    snd_pcm_hw_params_set_rate(handle, params, SAMPLERATE, dir);
>    snd_pcm_hw_params_set_access(handle, params, 
>SND_PCM_ACCESS_RW_INTERLEAVED);
>    snd_pcm_hw_params_set_channels(handle, params, STEREO);
>    snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
>    snd_pcm_hw_params(handle, params);
>
>    // Insert samples to framebuffer.
>    wav = fopen("pcm1611s.wav", "r");
>    fseek(wav, 0L, SEEK_END);
>    size = ftell(wav);
>    fseek(wav, 0L, SEEK_SET);
>    size /= sizeof(signed short);
>    while (size > 0)
>    {
>        fread(framebuffer, sizeof(int16_t), FRAMEBUFFERSIZE * STEREO * 
>BITS, wav);
>        status = snd_pcm_writei(handle, framebuffer, frames);
>        if (status == -EPIPE)
>        {
>            snd_pcm_prepare(handle);
>        }
>        size -= FRAMEBUFFERSIZE * STEREO * BITS;
>    }
>    snd_pcm_drain(handle);
>    snd_pcm_close(handle);
>    exit(EXIT_SUCCESS);
>}
>
>
>
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