我正试图在一个类中包围alsa。 问题是当我尝试使用时:
snd_pcm_hw_params_get_period_size(this->__params, &period_size, NULL);
或
snd_pcm_hw_params_get_period_time(this->__params, &time_period, NULL);
在void alsa_control::record_to_file(std::string filename, int duration_in_us);
在cpp中它在期间发送0并且似乎在期间未被修改
.h
#ifndef ALSA_RECORDING_H
#define ALSA_RECORDING_H
#include <iostream>
#include <alsa/asoundlib.h>
#include <wav_functions.h>
#define STEREO 2
#define MONO 1
using std::cout;
using std::endl;
class alsa_control {
public:
void record_to_file(std::string filename, int duration_in_us);
alsa_control(unsigned int rate, unsigned long frames, int bits, unsigned int stereo_mode);
~alsa_control();
private:
unsigned int __rate;
unsigned int __stereo_mode;
int __bits;
snd_pcm_uframes_t __frames;
snd_pcm_hw_params_t *__params;
snd_pcm_t *__handle;
void open_pcm_device();
void set_parameters_ALSA();
alsa_control()=delete;
alsa_control(const alsa_control&)=delete;
};
#endif /* ALSA_RECORDING_H */
和.cpp
#include <alsa_control.h>
alsa_control::alsa_control(unsigned int rate, unsigned long frames, int bits, unsigned int stereo_mode)
: __rate(rate),
__stereo_mode(stereo_mode),
__bits(bits),
__frames(frames) {
this->open_pcm_device();
snd_pcm_hw_params_alloca(&this->__params);
this->set_parameters_ALSA();
}
alsa_control::~alsa_control() {
snd_pcm_drain(this->__handle);
snd_pcm_close(this->__handle);
}
void alsa_control::open_pcm_device() {
int rc = snd_pcm_open(&this->__handle, "default", SND_PCM_STREAM_CAPTURE, 0);
if (rc < 0) {
cout << "ERROR : unable to open pcm device: " << snd_strerror(rc) << endl;
exit(1);
}
}
void alsa_control::set_parameters_ALSA() {
snd_pcm_hw_params_any(this->__handle, this->__params); // def values
snd_pcm_hw_params_set_access(this->__handle, this->__params, SND_PCM_ACCESS_RW_NONINTERLEAVED); //non interleaved
snd_pcm_hw_params_set_format(this->__handle, this->__params, SND_PCM_FORMAT_S16_LE); //16bits little-endian
snd_pcm_hw_params_set_channels(this->__handle, this->__params, this->__stereo_mode); // stereo ou mono
snd_pcm_hw_params_set_rate_near(this->__handle, this->__params, &this->__rate, NULL); // sample rate (freq echantillonage)
auto ret = snd_pcm_hw_params_set_period_size_near(this->__handle, this->__params, &this->__frames, NULL); //frames pour une période
int rc = snd_pcm_hw_params(this->__handle, this->__params);
if (rc < 0) {
cout << "ERROR - unable to set hw parameters: " << snd_strerror(rc) << endl;
exit(1);
}
}
void alsa_control::record_to_file(std::string filename, int duration_in_us) {
std::ofstream f;
int rc;
int nb_ech = 0;
snd_pcm_uframes_t period_size;
unsigned int time_period;
filename += ".wav";
f.open(filename, std::ios::binary);
write_header_wav(f, this->__rate, (short) this->__bits, (short) this->__stereo_mode, 10000); //10000 is a constant because we don't know the size of the recording
snd_pcm_hw_params_get_period_size(this->__params, &period_size, NULL);
period_size = 2048;
snd_pcm_uframes_t size = period_size * 2; /* 2 bytes/sample, 1 channels */
char *buffer = (char *) malloc(size);
snd_pcm_hw_params_get_period_time(this->__params, &time_period, NULL);
time_period = 128000;
long loops = duration_in_us / time_period;
while (loops-- > 0) {
rc = (int) snd_pcm_readi(this->__handle, buffer, period_size);
if (rc == -EPIPE) {
cout << "ERROR - overrun occurred" << endl;
snd_pcm_prepare(this->__handle);
} else if (rc < 0) {
cout << "ERROR - error from read: " << snd_strerror(rc) << endl;
} else if (rc != (int) period_size) {
cout << "ERROR - short read, read " << rc << " frames" << endl;
}
if (!(loops % 10))cout << loops << endl;
f.write(buffer, rc * 2);
nb_ech += rc;
}
f.close();
f.open(filename, std::ios::binary | std::ios::in);
write_header_wav(f, this->__rate, (short) this->__bits, (short) this->__stereo_mode, nb_ech);
f.close();
free(buffer);
}
答案 0 :(得分:1)
我只是想办法让它发挥作用。但我总是想知道为什么功能不能正常工作。
在snd_pcm_hw_params_get_period_size(this->_params, period_size, NULL);
方法内部, snd_pcm_hw_params_get_period_time(this->_params, time_period, NULL);
和set_parameters_ALSA
工作正常。
然后我将它们作为私人成员添加到我的班级中:
snd_pcm_uframes_t _period_size;
和unsigned int _time_period;
并将两个功能更改为:
void alsa_control::set_parameters_ALSA() {
snd_pcm_hw_params_any(this->_handle, this->_params); // def values
snd_pcm_hw_params_set_access(this->_handle, this->_params, SND_PCM_ACCESS_RW_NONINTERLEAVED); //non interleaved
snd_pcm_hw_params_set_format(this->_handle, this->_params, SND_PCM_FORMAT_S16_LE); //16bits little-endian
snd_pcm_hw_params_set_channels(this->_handle, this->_params, this->_stereo_mode); // stereo ou mono
snd_pcm_hw_params_set_rate_near(this->_handle, this->_params, &this->_rate, NULL); // sample rate (freq echantillonage)
snd_pcm_hw_params_set_period_size_near(this->_handle, this->_params, &this->_frames, NULL); //frames pour une période
int rc = snd_pcm_hw_params(this->_handle, this->_params);
if (rc < 0) {
cout << "ERROR - unable to set hw parameters: " << snd_strerror(rc) << endl;
exit(1);
}
snd_pcm_hw_params_get_period_size(this->_params, &this->_period_size, NULL);
snd_pcm_hw_params_get_period_time(this->_params, &this->_time_period, NULL);
}
和
void alsa_control::record_to_file(std::string filename, int duration_in_us) {
std::ofstream f;
int rc;
int nb_ech = 0;
filename += ".wav";
f.open(filename, std::ios::binary);
write_header_wav(f, this->_rate, (short) this->_bits, (short) this->_stereo_mode, 10000); //10000 is an arbitrary constant because we don't know the size of the recording
snd_pcm_uframes_t size = this->_period_size * 2; /* 2 bytes/sample, 1 channels */
char *buffer = (char *) malloc(size);
long loops = duration_in_us / this->_time_period;
while (loops-- > 0) {
rc = (int) snd_pcm_readi(this->_handle, buffer, this->_period_size);
if (rc == -EPIPE) {
cout << "ERROR - overrun occurred" << endl;
snd_pcm_prepare(this->_handle);
} else if (rc < 0) {
cout << "ERROR - error from read: " << snd_strerror(rc) << endl;
} else if (rc != (int) this->_period_size) {
cout << "ERROR - short read, read " << rc << " frames" << endl;
}
f.write(buffer, rc * 2);
nb_ech += rc;
}
f.close();
f.open(filename, std::ios::binary | std::ios::in);
write_header_wav(f, this->_rate, (short) this->_bits, (short) this->_stereo_mode, nb_ech);
f.close();
free(buffer);
}
编辑:
这个问题似乎与司机有关
使用:Advanced Linux Sound Architecture Driver Version k3.16.0-31-generic
不要使用问题版本
使用:Advanced Linux Sound Architecture Driver Version k3.18.8+
效果很好