duma
10th August 2011, 17:53
Hi guys,
I have two problems:
Problem number 1: I am using pcm.c to build a gui to generate sine waves using user input. I have integrated the code into Qt Creator and I compiled and ran the code with no errors.
However, every time I click the pushButton (which is supposed to output the sine wave), my program terminates. I have tracked the problem code. In my pushButton function, I have called a function called write_loop which calls generate_sine(). This is causing the problem. I have debugged the code in generate_sine() and I found out that the line which causes it to terminate is this one:
if ((areas[chn].first % 8) != 0) {
printf("areas[%i].first == %i, aborting...", chn , areas[chn].first);
exit(EXIT_FAILURE);
}
I found out that the problem is that it is refusing to use this specific code:
areas[chn].first. Also, I did a check to see areas[chn].first is divisible by 8 and it is for all the values of chn. THis program seems only to have the problem of calling areas[chn].first. I have found the problem, but now I don't know how to fix it. Any help would be greatly appreciated.
The code I have under my pushButton function(on_pushButton_clicked) and generate_sine.cpp is shown below.
generate_sine.cpp:
void generate_sine(snd_pcm_channel_area_t *areas,
snd_pcm_uframes_t offset,
int count, double *_phase)
{
static double max_phase = 2. * M_PI;
double phase = *_phase;
double step = max_phase*freq/(double)rate;
unsigned char *samples[channels];
int steps[channels];
unsigned int chn;
int format_bits = snd_pcm_format_width(format);
unsigned int maxval = (1 << (format_bits - 1)) - 1;
int bps = format_bits / 8; /* bytes per sample */
int phys_bps = snd_pcm_format_physical_width(format) / 8;
int big_endian = snd_pcm_format_big_endian(format) == 1;
int to_unsigned = snd_pcm_format_unsigned(format) == 1;
int is_float = (format == SND_PCM_FORMAT_FLOAT_LE ||
format == SND_PCM_FORMAT_FLOAT_BE);
float amplitude_scale = amplitude/8.56;
// verify and prepare the contents of areas
for (chn = 0; chn < channels; chn++) {
if (areas[chn].first!=0) {
printf("areas[%i].first == %i, aborting...", chn , areas[chn].first);
exit(EXIT_FAILURE);
}
samples[chn] = (((unsigned char *)areas[chn].addr) + (areas[chn].first / 8));
if (areas[chn].step !=0) {
printf("areas[%i].step == %i, aborting... ", chn, areas[chn].step);
exit(EXIT_FAILURE);
}
steps[chn] = areas[chn].step / 8;
samples[chn] += offset * steps[chn];
}
//fill the channel areas
while (count-- > 0) {
union {
float f;
int i;
} fval;
int res, i;
if (is_float) {
fval.f = amplitude_scale * sin(phase) * maxval;
res = fval.i;
} else
res = amplitude_scale * sin(phase) * maxval;
if (to_unsigned)
res ^= 1U << (format_bits - 1);
for (chn = 0; chn < channels; chn++) {
/* Generate data in native endian format */
if (big_endian) {
for (i = 0; i < bps; i++)
*(samples[chn] + phys_bps - 1 - i) = (res >> i * 8) & 0xff;
} else {
for (i = 0; i < bps; i++)
*(samples[chn] + i) = (res >> i * 8) & 0xff;
}
samples[chn] += steps[chn];
}
phase += step;
if (phase >= max_phase)
phase -= max_phase;
}
*_phase = phase;
}
on_pushButton_clicked():
void wave::on_pushButton_clicked()
{
struct transfer_method {
const char *name;
snd_pcm_access_t access;
int (*transfer_loop)(snd_pcm_t *handle,
signed short *samples,
snd_pcm_channel_area_t *areas);
};
static struct transfer_method transfer_methods[] = {
{ "write", SND_PCM_ACCESS_RW_INTERLEAVED, write_loop },
{ NULL, SND_PCM_ACCESS_RW_INTERLEAVED, NULL }
};
snd_pcm_t *handle;
int err;
snd_pcm_hw_params_t *hwparams;
snd_pcm_sw_params_t *swparams;
int method = 0;
signed short *samples;
unsigned int chn;
snd_pcm_channel_area_t *areas;
snd_pcm_hw_params_alloca(&hwparams);
snd_pcm_sw_params_alloca(&swparams);
err = snd_output_stdio_attach(&output, stdout, 0);
if (err < 0) {
printf("Output failed: %s" , snd_strerror(err));
}
if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
printf("Playback open error: %s", snd_strerror(err));
}
if ((err = set_hwparams(handle, hwparams, transfer_methods[method].access)) < 0) {
printf("Setting of hwparams failed: %s", snd_strerror(err));
exit(EXIT_FAILURE);
}
if ((err = set_swparams(handle, swparams)) < 0) {
printf("Setting of swparams failed: %s", snd_strerror(err));
exit(EXIT_FAILURE);
}
if (verbose > 0)
snd_pcm_dump(handle, output);
samples = new signed short [period_size * channels * snd_pcm_format_physical_width(format)];
if (samples == NULL) {
printf("Not enough memory");
exit(EXIT_FAILURE);
}
areas = new snd_pcm_channel_area_t [channels];
if (areas == NULL) {
printf("Not enough memory");
exit(EXIT_FAILURE);
}
for (chn = 0; chn < channels; chn++) {
areas[chn].addr = samples;
areas[chn].first = chn * snd_pcm_format_physical_width(format);
areas[chn].step = channels * snd_pcm_format_physical_width(format);
}
err = transfer_methods[method].transfer_loop(handle, samples, areas);
delete [] areas;
delete []samples;
snd_pcm_close(handle);
}
Problem number 2:
When I set my while loop in the write_loop function to 'true', i.e while(isTrue), (when bool isTrue = true; is defined at the top), my program immediately terminates. And to make sure that it isn't the generate_sine() function that isn't doing it(as described above, I commented the generate_sine() function out, and it still just terminates. However, If I don't set any value for bool isTrue (i.e. just define bool isTrue; at the top, the program doesn't terminate.
Here is my write_loop function:
int write_loop(snd_pcm_t *device_handle,
signed short *samples,
snd_pcm_channel_area_t *areas)
{
double phase = 0;
signed short *ptr;
int err, cptr;
generate_sine(areas, 0, period_size, &phase);
while (isTrue) {
ptr = samples;
cptr = period_size;
while (cptr > 0) {
err = snd_pcm_writei(device_handle, ptr, cptr);
if (err == -EAGAIN)
continue;
if (err < 0) {
if (xrun_recovery(device_handle, err) < 0) {
printf("Write error: %s ", snd_strerror(err));
exit(EXIT_FAILURE);
}
break; // skip one period
}
ptr += err * channels;
cptr -= err;
}
}
}
I have two problems:
Problem number 1: I am using pcm.c to build a gui to generate sine waves using user input. I have integrated the code into Qt Creator and I compiled and ran the code with no errors.
However, every time I click the pushButton (which is supposed to output the sine wave), my program terminates. I have tracked the problem code. In my pushButton function, I have called a function called write_loop which calls generate_sine(). This is causing the problem. I have debugged the code in generate_sine() and I found out that the line which causes it to terminate is this one:
if ((areas[chn].first % 8) != 0) {
printf("areas[%i].first == %i, aborting...", chn , areas[chn].first);
exit(EXIT_FAILURE);
}
I found out that the problem is that it is refusing to use this specific code:
areas[chn].first. Also, I did a check to see areas[chn].first is divisible by 8 and it is for all the values of chn. THis program seems only to have the problem of calling areas[chn].first. I have found the problem, but now I don't know how to fix it. Any help would be greatly appreciated.
The code I have under my pushButton function(on_pushButton_clicked) and generate_sine.cpp is shown below.
generate_sine.cpp:
void generate_sine(snd_pcm_channel_area_t *areas,
snd_pcm_uframes_t offset,
int count, double *_phase)
{
static double max_phase = 2. * M_PI;
double phase = *_phase;
double step = max_phase*freq/(double)rate;
unsigned char *samples[channels];
int steps[channels];
unsigned int chn;
int format_bits = snd_pcm_format_width(format);
unsigned int maxval = (1 << (format_bits - 1)) - 1;
int bps = format_bits / 8; /* bytes per sample */
int phys_bps = snd_pcm_format_physical_width(format) / 8;
int big_endian = snd_pcm_format_big_endian(format) == 1;
int to_unsigned = snd_pcm_format_unsigned(format) == 1;
int is_float = (format == SND_PCM_FORMAT_FLOAT_LE ||
format == SND_PCM_FORMAT_FLOAT_BE);
float amplitude_scale = amplitude/8.56;
// verify and prepare the contents of areas
for (chn = 0; chn < channels; chn++) {
if (areas[chn].first!=0) {
printf("areas[%i].first == %i, aborting...", chn , areas[chn].first);
exit(EXIT_FAILURE);
}
samples[chn] = (((unsigned char *)areas[chn].addr) + (areas[chn].first / 8));
if (areas[chn].step !=0) {
printf("areas[%i].step == %i, aborting... ", chn, areas[chn].step);
exit(EXIT_FAILURE);
}
steps[chn] = areas[chn].step / 8;
samples[chn] += offset * steps[chn];
}
//fill the channel areas
while (count-- > 0) {
union {
float f;
int i;
} fval;
int res, i;
if (is_float) {
fval.f = amplitude_scale * sin(phase) * maxval;
res = fval.i;
} else
res = amplitude_scale * sin(phase) * maxval;
if (to_unsigned)
res ^= 1U << (format_bits - 1);
for (chn = 0; chn < channels; chn++) {
/* Generate data in native endian format */
if (big_endian) {
for (i = 0; i < bps; i++)
*(samples[chn] + phys_bps - 1 - i) = (res >> i * 8) & 0xff;
} else {
for (i = 0; i < bps; i++)
*(samples[chn] + i) = (res >> i * 8) & 0xff;
}
samples[chn] += steps[chn];
}
phase += step;
if (phase >= max_phase)
phase -= max_phase;
}
*_phase = phase;
}
on_pushButton_clicked():
void wave::on_pushButton_clicked()
{
struct transfer_method {
const char *name;
snd_pcm_access_t access;
int (*transfer_loop)(snd_pcm_t *handle,
signed short *samples,
snd_pcm_channel_area_t *areas);
};
static struct transfer_method transfer_methods[] = {
{ "write", SND_PCM_ACCESS_RW_INTERLEAVED, write_loop },
{ NULL, SND_PCM_ACCESS_RW_INTERLEAVED, NULL }
};
snd_pcm_t *handle;
int err;
snd_pcm_hw_params_t *hwparams;
snd_pcm_sw_params_t *swparams;
int method = 0;
signed short *samples;
unsigned int chn;
snd_pcm_channel_area_t *areas;
snd_pcm_hw_params_alloca(&hwparams);
snd_pcm_sw_params_alloca(&swparams);
err = snd_output_stdio_attach(&output, stdout, 0);
if (err < 0) {
printf("Output failed: %s" , snd_strerror(err));
}
if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
printf("Playback open error: %s", snd_strerror(err));
}
if ((err = set_hwparams(handle, hwparams, transfer_methods[method].access)) < 0) {
printf("Setting of hwparams failed: %s", snd_strerror(err));
exit(EXIT_FAILURE);
}
if ((err = set_swparams(handle, swparams)) < 0) {
printf("Setting of swparams failed: %s", snd_strerror(err));
exit(EXIT_FAILURE);
}
if (verbose > 0)
snd_pcm_dump(handle, output);
samples = new signed short [period_size * channels * snd_pcm_format_physical_width(format)];
if (samples == NULL) {
printf("Not enough memory");
exit(EXIT_FAILURE);
}
areas = new snd_pcm_channel_area_t [channels];
if (areas == NULL) {
printf("Not enough memory");
exit(EXIT_FAILURE);
}
for (chn = 0; chn < channels; chn++) {
areas[chn].addr = samples;
areas[chn].first = chn * snd_pcm_format_physical_width(format);
areas[chn].step = channels * snd_pcm_format_physical_width(format);
}
err = transfer_methods[method].transfer_loop(handle, samples, areas);
delete [] areas;
delete []samples;
snd_pcm_close(handle);
}
Problem number 2:
When I set my while loop in the write_loop function to 'true', i.e while(isTrue), (when bool isTrue = true; is defined at the top), my program immediately terminates. And to make sure that it isn't the generate_sine() function that isn't doing it(as described above, I commented the generate_sine() function out, and it still just terminates. However, If I don't set any value for bool isTrue (i.e. just define bool isTrue; at the top, the program doesn't terminate.
Here is my write_loop function:
int write_loop(snd_pcm_t *device_handle,
signed short *samples,
snd_pcm_channel_area_t *areas)
{
double phase = 0;
signed short *ptr;
int err, cptr;
generate_sine(areas, 0, period_size, &phase);
while (isTrue) {
ptr = samples;
cptr = period_size;
while (cptr > 0) {
err = snd_pcm_writei(device_handle, ptr, cptr);
if (err == -EAGAIN)
continue;
if (err < 0) {
if (xrun_recovery(device_handle, err) < 0) {
printf("Write error: %s ", snd_strerror(err));
exit(EXIT_FAILURE);
}
break; // skip one period
}
ptr += err * channels;
cptr -= err;
}
}
}