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Author: midaszhou

Makefile

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+CC = /home/midas/openwrt_widora/staging_dir/toolchain-mipsel_24kec+dsp_gcc-4.8-linaro_uClibc-0.9.33.2/bin/mipsel-openwrt-linux-gcc
+
+APP = autorecord4
+
+INCLUDES += -I/.
+INCLUDES += -I/home/midas/openwrt_widora/build_dir/target-mipsel_24kec+dsp_uClibc-0.9.33.2/alsa-lib-1.0.28/include 
+LDFLAGS  += -L.
+LDFLAGS  += -L/home/midas/openwrt_widora/build_dir/target-mipsel_24kec+dsp_uClibc-0.9.33.2/alsa-lib-1.0.28/ipkg-install/usr/lib
+LIBS	 += -lasound -lm  -lshine
+
+$(APP): $(APP).c
+	$(CC) $(INCLUDES) $(LDFLAGS) $(LIBS) -o $(APP) $(APP).c
+
+PHONY:all
+all: $(APP)
+
+clean:
+	rm -rf $(APP)
+	

README

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+NOTE:
+1. Widora C test programs for ALSA, automatic record and playback, with options of a simple noise filter. 
+   The recorded sound wav can be saved as wav and mp3.
+   See more notes and descriptions in respective source files.
+
+2. The Makefile only gives an example for 'autorecord4' compilation, you can modify it easily for other applications.
+   Modify INCLUDE and LIB directories according to your own setup.
+

alsatest.c

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+/*--------------------------------------------------
+ALSA auto. record and play test
+Quote from: http://blog.csdn.net/ljclx1748/article/details/8606831
+
+Usage: ./autorecord
+It will monitor surrounding sound wave and trigger 10s recording if loud voice is sensed,
+then it will playback. The sound will also be saved to a raw file.
+
+1. use alsamixer to adjust Capture and ADC PCM value
+	ADC PCM 0-255 (240)
+	Capture 0-63  (53)
+2. some explanation:
+	sample: usually 8bits or 16bits, one sample data width.
+	channel: 1-Mono. 2-Stereo
+	frame: sizeof(one sample)*channels
+	rate: frames per second
+	period: Max. frame numbers hard ware can be handled each time.
+	chunk: frames receive from/send to hard ware each time.
+	buffer: N*periods
+	interleaved mode:record period data frame by frame, such as  frame1(Left sample,Right sample),frame2(), ......
+	uninterleaved mode: record period data channel by channel, such as period(Left sample,Left ,left...),period(right,right...),period()...
+3. lib: lasound 
+--------------------------------------------------*/
+
+#include <asoundlib.h>
+#include <stdbool.h>
+#define CHECK_AVERG 2500 //--threshold value of wave amplitude
+
+snd_pcm_t *pcm_handle;
+snd_pcm_hw_params_t *params;
+snd_pcm_format_t format_val;
+char *wave_buf; //---pointer to wave buffer
+int wave_buf_len; //---wave buffer length in bytes
+int bit_per_sample;
+snd_pcm_uframes_t frames;
+snd_pcm_uframes_t period_size; //length of period (in frames)
+snd_pcm_uframes_t chunk_size=32;//numbers of frames read/write to hard ware each time
+int chunk_byte; //length of chunk (period)  (in bytes)
+unsigned int chanl_val,rate_val;
+int dir;
+
+
+//------------------- functions declaration ----------------------
+bool device_open( int mode);
+bool device_setparams();
+bool device_capture( int dtime );
+bool device_play();
+bool device_check_voice();
+
+/*========================= MAIN ====================================*/
+int main(int argc,char* argv[]){
+int fd;
+int rc;
+
+while(1)
+{
+
+//--------录音   beware of if...if...if...if...expressions
+system("amixer set Capture 53");
+system("amixer set 'ADC PCM' 240");
+
+if (!device_open(SND_PCM_STREAM_CAPTURE ))return 1;
+	 //printf("---device_open()\n");
+if (!device_setparams(1,8000)) return 2;
+	//printf("---device_setparams()\n");
+if(!device_check_voice()) //--checking voice wave amplitude, and start to record if it exceeds preset threshold value,or it will loop checking ...
+	continue;
+
+printf("start recording...\n");
+if (!device_capture( 10 ))return 3;
+	//printf("-----device_capture()\n");
+snd_pcm_close( pcm_handle ); 
+	printf("record finish!\n");
+
+fd=open("/tmp/record.raw",O_WRONLY|O_CREAT|O_TRUNC);
+rc=write(fd,wave_buf,wave_buf_len);
+printf("write to record.raw  %d bytes\n",rc);
+close(fd); //though kernel will close it automatically
+
+//--------播放
+printf("start playback...\n");
+if (!device_open(SND_PCM_STREAM_PLAYBACK)) return 4;
+//printf("-----PLAY: device_open() finish\n");
+if (!device_setparams(1,8000)) return 5;
+//printf("-----PLAY: device_setarams() finish\n");
+if (!device_play()) return 6;
+printf("finish playback.\n\n\n");
+
+snd_pcm_close( pcm_handle );
+//printf("-----PLAY: snd_pcm_close()  ----\n");
+
+free(wave_buf); //--wave_buf mem. to be allocated in device_capture() and played in device_play();
+
+}//while()
+
+return 0;
+
+}
+
+
+//首先让我们封装一个打开音频设备的函数：
+//snd_pcm_t *pcm_handle;
+
+bool device_open(int mode){
+if(snd_pcm_open (&pcm_handle,"default",mode,0) < 0)
+ {
+	printf("snd_pcm_open() fail!\n");
+	return false; 
+ }
+ 	printf("snd_pcm_open() succeed!\n");
+	return true;
+}
+
+
+bool device_setparams(int nchanl,int rate)
+ {
+unsigned int val;
+int dir;
+int rc;
+snd_pcm_hw_params_t *hw_params;
+
+//------ beware of following if..if...if..if...if...expressions ----------
+if(snd_pcm_hw_params_malloc (&hw_params) < 0)return false; //为参数变量分配空间
+//	printf("---- snd_pcm_hw_params_malloc(&hw_params) ----\n");
+if(snd_pcm_hw_params_malloc (&params) < 0)return false;
+//	printf("----snd_pcm_hw_params_malloc(&params) ----\n");
+if(snd_pcm_hw_params_any (pcm_handle, hw_params) < 0)return false; //参数初始化
+//	printf("----snd_pcm_hw_params_any(pcm_handle,hw_params)----\n");
+if(snd_pcm_hw_params_set_access (pcm_handle, hw_params,SND_PCM_ACCESS_RW_INTERLEAVED) < 0)return false; //设置为交错模式
+//	printf("----snd_pcm_hw_params_set_access()----\n");
+if(snd_pcm_hw_params_set_format( pcm_handle, hw_params, SND_PCM_FORMAT_S16_LE) < 0)return false; //使用用16位样本
+//	printf("----snd_pmc_hw_params_set_format()-----\n");
+val=rate;//8000;
+if(snd_pcm_hw_params_set_rate_near( pcm_handle, hw_params,&val,0) < 0)return false; //设置采样率
+//	printf("----snd_pcm_hw_params_set_rate_near() val=%d----\n",val);
+if(snd_pcm_hw_params_set_channels( pcm_handle, hw_params, nchanl) < 0)return false; //设置为立体声or Mono.
+//	printf("----snd_pcm_hw_params_set_channels()-----\n");
+frames=32;
+if(snd_pcm_hw_params_set_period_size_near(pcm_handle,hw_params,&chunk_size,&dir) < 0 )return false;
+//	printf("----snd_pcm_hw_params_set_period_size_near() chunk_size=%d----\n",chunk_size);
+if(snd_pcm_hw_params_get_period_size( hw_params, &period_size,0) < 0)return false; //获取周期长度
+//	printf("----snd_pcm_hw_get_period_size(): %d----\n",(int)period_size);
+if(snd_pcm_hw_params_get_format(hw_params,&format_val) < 0)return false;
+//	printf("----snd_pcm_hw_params_get_format()----\n");
+bit_per_sample = snd_pcm_format_width((snd_pcm_format_t)format_val);
+//printf("---bit_per_sample=%d  snd_pcm_format_width()----\n",bit_per_sample);
+//获取样本长度
+snd_pcm_hw_params_get_channels(hw_params,&chanl_val);
+//printf("----snd_pcm_hw_params_get_channels %d---\n",chanl_val);
+chunk_byte = period_size*bit_per_sample*chanl_val/8;
+//chunk_size = frames;//period_size; //frames
+//计算周期长度（字节数(bytes) = 每周期的桢数 * 样本长度(bit) * 通道数 / 8 ）
+
+rc=snd_pcm_hw_params( pcm_handle, hw_params); //设置参数
+if(rc<0){
+printf("unable to set hw parameters:%s\n",snd_strerror(rc));
+exit(1);
+}
+printf("finish setting sound hw parameters\n");
+params = hw_params; //保存参数，方便以后使用
+snd_pcm_hw_params_free( hw_params); //释放参数变量空间
+//printf("----snd_pcm_hw_params_free()----\n");
+return true;
+
+}
+//这里先使用了Alsa提供的一系列snd_pcm_hw_params_set_函数为参数变量赋值。
+//最后才通过snd_pcm_hw_params将参数传递给设备。
+//需要说明的是正式的开发中需要处理参数设置失败的情况，这里仅做为示例程序而未作考虑。
+//设置好参数后便可以开始录音了。录音过程实际上就是从音频设备中读取数据信息并保存。
+
+
+
+ bool device_capture( int dtime ){
+  snd_pcm_hw_params_get_rate(params,&rate_val,&dir); //params=hw_params
+  wave_buf_len=dtime*rate_val*bit_per_sample*chanl_val/8;
+  //printf(" wave_buf_len=%d \n",wave_buf_len);
+   //计算音频数据长度（秒数 * 采样率 * 桢长度）
+  char *data=wave_buf=(char*)malloc(wave_buf_len);
+  int r = 0;
+  chunk_size=32;
+  chunk_byte=chunk_size*bit_per_sample*chanl_val/8;
+  //printf("chunk_byte=%d\n",chunk_byte);
+  while ( (data-wave_buf) <= (wave_buf_len-chunk_byte) ){ //chunk_size*bit_per_sample*chanl_val)){
+	r = snd_pcm_readi( pcm_handle,data,chunk_size);  //chunk_size*bit_per_sample*read interleaved rames from a PCM
+//--- snd_pcm_sframes_t snd_pcm_readi(snd_pcm_t *pcm,void* buffer, snd_pcm_uframes_t size)
+//--- pcm -PCM handle    buffer-frames containing buffer  size - frames to be read
+	if ( r>0 ) {
+//		printf(" r= %d\n",r);
+//		printf("data=%d  wave_buf=%d\n",data,wave_buf);
+		data += chunk_byte;//--move current buffer position pointer
+	}
+	else
+		return false;
+}
+
+return true;
+
+}
+
+//形参dtime用来确定录音时间，根据录音时间分配数据空间，再调用snd_pcm_readi从音频设备读取音频数据，存放到wave_buf中。
+//同样的原理，我们再添加一个播放函数，向音频设备写入数据：
+
+bool device_play(){
+  char *data = wave_buf;
+  int r = 0;
+  chunk_size=32;
+  chunk_byte=chunk_size*bit_per_sample*chanl_val/8;
+  while ( (data-wave_buf) <= (wave_buf_len-chunk_byte)){
+  r = snd_pcm_writei( pcm_handle, data , chunk_size); //chunk_size = frames
+  if(r == -EAGAIN)continue;
+  if(r < 0){
+	printf("wirte error: %s\n",snd_strerror(r));
+	exit(EXIT_FAILURE);
+   }
+  //printf("----- writei()  r=%d -----\n ",r);
+  if ( r>0 ) data += chunk_byte;
+  else
+  return false;
+  }
+  return true;
+
+}
+
+
+bool device_check_voice(void )
+{
+ int i;
+ int r = 0;
+ int count=0;
+ int total=0;
+ int averg=0;//average of sample values in one chunk.
+ chunk_size=32; //--frames each time
+ chunk_byte=chunk_size*bit_per_sample*chanl_val/8; //---bytes
+ //printf("chunk_byte=%d\n",chunk_byte);
+ int16_t *buf=(int16_t *)malloc(chunk_byte); //32bits
+ //printf("size of int16_t = %d\n",sizeof(int16_t));
+ int16_t *data=buf;
+ //char* tmp;
+
+ printf("listening and checking any voice......\n");
+ while(1)
+  {
+	r = snd_pcm_readi( pcm_handle,(char *)buf,chunk_size);  //chunk_size*bit_per_sample*read interleaved rames from a PCM
+        if(r == -EAGAIN)continue;
+	if ( r>=0 ) {
+		    //printf(" r= %d \n ",r);
+		    data=buf;
+		    averg=0;total=0;
+		    for(i=0;i<r;i++){
+			total+=abs((*data)); // !!!!!!
+			data+=1;
+		       }
+		    //printf("total=%d\n",total);
+		    averg=(total>>5);
+		    //printf("averg=%d\n",averg);
+		    if(averg >= CHECK_AVERG){
+			    printf("loud noise sensed!\n");
+			    free(buf);
+			    return true;
+			}
+
+//		usleep(20000); //
+//		snd_pcm_prepare(pcm_handle);
+		//usleep(10000); //---you cann't sleep here,
+	}//if
+	else
+	{
+	        printf(" r= %d \n ",r);
+		free(buf);
+		return false;
+	}
+   } //while(1)
+
+free(buf);
+return true;
+
+}