[alsa-devel] problem in set frames and buffer size‏

[Haiping Wang]

hello all,I have write a alsa app from a example from internet.The original code is good running. format 16bitchannel 2rate 44100/*  This example reads from the default PCM device and writes to standard output for 5 seconds of data.  */  /* Use the newer ALSA API */ #define ALSA_PCM_NEW_HW_PARAMS_API  #include <alsa/asoundlib.h>  int main() {   long loops;   int rc;   int size;   snd_pcm_t *handle;   snd_pcm_hw_params_t *params;   unsigned int val;   int dir;   snd_pcm_uframes_t frames;   char *buffer;    /* Open PCM device for recording (capture). */   rc = snd_pcm_open(&handle, "default",                     SND_PCM_STREAM_CAPTURE, 0);   if (rc < 0) {     fprintf(stderr,             "unable to open pcm device: %s\n",             snd_strerror(rc));     exit(1);   }    /* Allocate a hardware parameters object. */   snd_pcm_hw_params_alloca(&params);    /* Fill it in with default values. */   snd_pcm_hw_params_any(handle, params);    /* Set the desired hardware parameters. */    /* Interleaved mode */   snd_pcm_hw_params_set_access(handle, params,                       SND_PCM_ACCESS_RW_INTERLEAVED);    /* Signed 16-bit little-endian format */   snd_pcm_hw_params_set_format(handle, params,                               SND_PCM_FORMAT_S16_LE);    /* Two channels (stereo) */   snd_pcm_hw_params_set_channels(handle, params, 2);    /* 44100 bits/second sampling rate (CD quality) */   val = 44100;   snd_pcm_hw_params_set_rate_near(handle, params,                                   &val, &dir);    /* Set period size to 32 frames. */   frames = 32;   snd_pcm_hw_params_set_period_size_near(handle,                               params, &frames, &dir);    /* Write the parameters to the driver */   rc = snd_pcm_hw_params(handle, params);   if (rc < 0) {     fprintf(stderr,             "unable to set hw parameters: %s\n",             snd_strerror(rc));     exit(1);   }    /* Use a buffer large enough to hold one period */   snd_pcm_hw_params_get_period_size(params,                                       &frames, &dir);   size = frames * 4; /* 2 bytes/sample, 2 channels */   buffer = (char *) malloc(size);    /* We want to loop for 5 seconds */   snd_pcm_hw_params_get_period_time(params,                                          &val, &dir);   loops = 5000000 / val;    while (loops > 0) {     loops--;     rc = snd_pcm_readi(handle, buffer, frames);     if (rc == -EPIPE) {       /* EPIPE means overrun */       fprintf(stderr, "overrun occurred\n");       snd_pcm_prepare(handle);     } else if (rc < 0) {       fprintf(stderr,               "error from read: %s\n",               snd_strerror(rc));     } else if (rc != (int)frames) {       fprintf(stderr, "short read, read %d frames\n", rc);     }     rc = write(1, buffer, size);     if (rc != size)       fprintf(stderr,               "short write: wrote %d bytes\n", rc);   }    snd_pcm_drain(handle);   snd_pcm_close(handle);   free(buffer);    return 0; } now I want to change channel and format to write my own programm.format = 8bit, 24bit and 32bitchannel = 1 or 2how can i change the parameters in  frames and buffer size.for each format 8/16/24/32bit how to set  frames = ?and alsa channel 1/2  how to set buffersize??? I try many times  and failed .I want your help. thanks!! 
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