linux获取音频及播放代码实例
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代码功能:采集441帧然后播放出来
详细功能参考代码:
1 #include <stdio.h> 2 #include <stdlib.h> 3 #include <alsa/asoundlib.h> 4 5 6 int main(void){ 7 /*Name of the PCM device ,like "default"*/ 8 char *dev_name; 9 int rate = 44100;/*Sample rate*/ 10 int exact_rate;/*Sample rate returned by*/ 11 int dir;/*(1)exact_rate == rate --> dir=0,(2)exact_rate < rate --> dir=-1,(3)exact_rate > rate*/ 12 int periods = 3;/*Number of periods*/ 13 int err; 14 int size; 15 int pcmreturn; 16 // snd_pcm_uframes_t periodsize = 8192; 17 snd_pcm_uframes_t periodsize = 441; 18 snd_pcm_t *play_handle; 19 snd_pcm_t *capture_handle; 20 snd_pcm_stream_t play_stream = SND_PCM_STREAM_PLAYBACK; 21 snd_pcm_stream_t capture_stream = SND_PCM_STREAM_CAPTURE; 22 /*This structure contains information about */ 23 /*the hardware and can be used to specify the */ 24 /*configuration to be used for the PCM stream*/ 25 snd_pcm_hw_params_t *hwparams; 26 snd_pcm_hw_params_t *c_hwparams; 27 /*Init dev_name, Of course, later you will make this configure*/ 28 dev_name = strdup("default"); 29 /*Allocate the snd_pcm_hw_params_t structure on the stack*/ 30 snd_pcm_hw_params_alloca(&hwparams); 31 snd_pcm_hw_params_alloca(&c_hwparams); 32 /* Open PCM. The last parameter of this function is the mode. */ 33 /* If this is set to 0, the standard mode is used. Possible */ 34 /* other values are SND_PCM_NONBLOCK and SND_PCM_ASYNC. */ 35 /* If SND_PCM_NONBLOCK is used, read / write access to the */ 36 /* PCM device will return immediately. If SND_PCM_ASYNC is */ 37 /* specified, SIGIO will be emitted whenever a period has */ 38 /* been completely processed by the soundcard. */ 39 if (snd_pcm_open(&play_handle, dev_name, play_stream, 0) < 0) { 40 fprintf(stderr, "Error opening PCM device %s\n", dev_name); 41 return(-1); 42 } 43 if (snd_pcm_open(&capture_handle, dev_name, capture_stream, 0) < 0) { 44 fprintf(stderr, "Error opening PCM device %s\n", dev_name); 45 return(-1); 46 } 47 /* Init hwparams with full configuration space */ 48 if (snd_pcm_hw_params_any(play_handle, hwparams) < 0) { 49 fprintf(stderr, "Can not configure this PCM device.\n"); 50 return(-1); 51 } 52 if (snd_pcm_hw_params_any(capture_handle, c_hwparams) < 0) { 53 fprintf(stderr, "Can not configure this PCM device.\n"); 54 return(-1); 55 } 56 /* Set access type. This can be either */ 57 /* SND_PCM_ACCESS_RW_INTERLEAVED or */ 58 /* SND_PCM_ACCESS_RW_NONINTERLEAVED. */ 59 /* There are also access types for MMAPed */ 60 /* access, but this is beyond the scope */ 61 /* of this introduction. */ 62 if (snd_pcm_hw_params_set_access(play_handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED) < 0) { 63 fprintf(stderr, "Error setting access.\n"); 64 return(-1); 65 } 66 if (snd_pcm_hw_params_set_access(capture_handle, c_hwparams, SND_PCM_ACCESS_RW_INTERLEAVED) < 0) { 67 fprintf(stderr, "Error setting access.\n"); 68 return(-1); 69 } 70 /* Set sample format */ 71 if (snd_pcm_hw_params_set_format(play_handle, hwparams, SND_PCM_FORMAT_S16_LE) < 0) { 72 fprintf(stderr, "Error setting format.\n"); 73 return(-1); 74 } 75 if (snd_pcm_hw_params_set_format(capture_handle, c_hwparams, SND_PCM_FORMAT_S16_LE) < 0) { 76 fprintf(stderr, "Error setting format.\n"); 77 return(-1); 78 } 79 exact_rate = rate; 80 if (snd_pcm_hw_params_set_rate_near(play_handle, hwparams, &exact_rate, 0) < 0) { 81 fprintf(stderr, "Error setting rate.\n"); 82 return(-1); 83 } 84 if (rate != exact_rate) { 85 fprintf(stderr, "The rate %d Hz is not supported by your hardware.\ 86 ==> Using %d Hz instead.\n", rate, exact_rate); 87 } 88 exact_rate = rate; 89 if (snd_pcm_hw_params_set_rate_near(capture_handle, c_hwparams, &exact_rate, 0) < 0) { 90 fprintf(stderr, "Error setting rate.\n"); 91 return(-1); 92 } 93 if (rate != exact_rate) { 94 fprintf(stderr, "The rate %d Hz is not supported by your hardware.\ 95 ==> Using %d Hz instead.\n", rate, exact_rate); 96 } 97 98 /* Set number of channels */ 99 if (snd_pcm_hw_params_set_channels(play_handle, hwparams, 2) < 0) {100 fprintf(stderr, "Error setting channels.\n");101 return(-1);102 }103 if (snd_pcm_hw_params_set_channels(capture_handle, c_hwparams, 2) < 0) {104 fprintf(stderr, "Error setting channels.\n");105 return(-1);106 }107 108 /* Set number of periods. Periods used to be called fragments. */109 if (snd_pcm_hw_params_set_periods(play_handle, hwparams, periods, 0) < 0) {110 fprintf(stderr, "Error setting periods.\n");111 return(-1);112 }113 if (snd_pcm_hw_params_set_periods(capture_handle, c_hwparams, periods, 0) < 0) {114 fprintf(stderr, "Error setting periods.\n");115 return(-1);116 }117 /* Set buffer size (in frames). The resulting latency is given by */118 /* latency = periodsize * periods / (rate * bytes_per_frame) */119 // if(snd_pcm_hw_params_get_buffer_size_max(hwparams,&periodsize) < 0)120 // {121 // fprintf(stderr,"Error get buffer size\n");122 // }123 // printf("periodsize=%lu\n",periodsize);124 125 if (snd_pcm_hw_params_set_buffer_size(play_handle, hwparams, (periodsize * periods)) < 0) {126 fprintf(stderr, "Error setting buffersize.\n");127 return(-1);128 }129 if (snd_pcm_hw_params_set_buffer_size(capture_handle, c_hwparams, (periodsize * periods)) < 0) {130 fprintf(stderr, "Error setting buffersize.\n");131 return(-1);132 }133 /* Apply HW parameter settings to */134 /* PCM device and prepare device */135 if (snd_pcm_hw_params(play_handle, hwparams) < 0) {136 fprintf(stderr, "Error setting HW params.\n");137 return(-1);138 }139 if (snd_pcm_hw_params(capture_handle, c_hwparams) < 0) {140 fprintf(stderr, "Error setting HW params.\n");141 return(-1);142 }143 // snd_pcm_hw_params_free(hwparams);144 // snd_pcm_hw_params_free(c_hwparams);145 if ((err = snd_pcm_prepare (play_handle)) < 0) {146 fprintf (stderr, "cannot prepare audio interface for use (%s)\n",147 snd_strerror (err));148 exit (1);149 }150 if ((err = snd_pcm_prepare (capture_handle)) < 0) {151 fprintf (stderr, "cannot prepare audio interface for use (%s)\n",152 snd_strerror (err));153 exit (1);154 }155 snd_pcm_hw_params_get_period_size(c_hwparams, &periods,0);156 printf("periods=%d\n",periods);157 char *data_buf = (char*)malloc(periods*4);158 if(!data_buf){159 fprintf(stderr, "Cannot malloc buffer for data\n");160 }161 while(1)162 163 {164 pcmreturn = snd_pcm_readi( capture_handle, data_buf, periodsize);165 if( pcmreturn == -EPIPE )166 {167 snd_pcm_prepare( capture_handle );168 fprintf (stderr, "<<<<<<<<<<<<<<<<<<< Buffer Overrun >>>>>>>>>>>>>>>>>\n");169 continue;170 }else if( pcmreturn == -EBADFD ){171 fprintf(stderr, "<<<<<<<<<<<<<<<<<<<< readi error -EBADFD >>>>>>>>>>>>>\n");172 continue;173 }else if( pcmreturn == -ESTRPIPE ){174 fprintf(stderr, "<<<<<<<<<<<<<<<<<<<< readi error -ESTRPIPE >>>>>>>>>>>>>\n");175 }else{176 pcmreturn = snd_pcm_writei(play_handle, data_buf, pcmreturn);177 if( pcmreturn == -EPIPE ){178 fprintf(stderr, "<<<<<<<<<<<< Buffer Underrun >>>>>>>>>>>>>>\n");179 snd_pcm_prepare( play_handle );180 // continue;181 }else if( pcmreturn == -ESTRPIPE ){182 fprintf(stderr, "<<<<<<<<<<<< writei error -ESTRPIPE >>>>>>>>>>>\n");183 }else if( pcmreturn == -EBADFD ){184 fprintf(stderr, "<<<<<<<<<<<< writei error -EABDFD >>>>>>>>>>>>\n");185 }186 }187 printf("pcmreturn = %d\n",pcmreturn);188 189 190 }191 192 193 } 1 0
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