snd_pcm_access_name((snd_pcm_access_t)val)); } printf("\nPCM formats:\n"); for (val =0; val<= SND_PCM_FORMAT_LAST; val++) { if (snd_pcm_format_name((snd_pcm_format_t)val)!= NULL) { printf(" %s (%s)\n", snd_pcm_format_name((snd_pcm_format_t)val), snd_pcm_forma...
frame size = sizeof(one sample) * nChannels alsa中配置的缓存(buffer)和周期(size)大小在runtime中是以帧(frames) 形式存储的。 period_bytes = frames_to_bytes(runtime, runtime->period_size); bytes_to_frames() The period and buffer sizes are not dependent on the sample format because they a...
snd_pcm_hw_params_set_channels( pcm_handle, hw_params, 2); //设置为立体声 snd_pcm_hw_params_get_period_size( hw_params, &period_size); //获取周期长度 bit_per_sample = snd_pcm_hw_format_physical_width( hw_params.format ); //获取样本长度 chunk_byte = period_size * bit_per_sampl...
snd_pcm_hw_params_get_period_size(params, &frames, &dir); size = frames * 4; /* 2 bytes/sample, 2 channels */ printf("size = %d\n",size); buffer = (char *) malloc(size); /* We want to loop for 5 seconds */ snd_pcm_hw_params_get_period_time(params, &val, &dir); lo...
snd_pcm_hw_params_set_rate_near(*handle, params, &val,0); //8把设置好的参数设置到pcm设备 snd_pcm_hw_params(*handle,params); //9.分配一个周期空间 //获取一个周期的帧数 snd_pcm_hw_params_get_period_size(params, frame, 0);
PCM操作句柄,这是一个成员不公开的结构: /** PCM handle */typedefstruct_snd_pcmsnd_pcm_t; PCM硬件参数,这是一个成员不公开的结构: typedefstruct_snd_pcm_hw_paramssnd_pcm_hw_params_t; PCM的流类型,主要指播放和录音两种: /** PCM stream (direction) */typedefenum_snd_pcm_stream{/** Playback...
snd_pcm_hw_params_set_rate_near( pcm_handle, hw_params, 44100, 0); //设置采样率为44.1KHz snd_pcm_hw_params_set_channels( pcm_handle, hw_params, 2); //设置为立体声 snd_pcm_hw_params_get_period_size( hw_params, &period_size); //获取周期长度 bit_per_sample = snd_pcm_hw_format...
Int32Audio_alsaSetparams(Alsa_Env*pEnv,int verbose){Int32 err=0;Uint32 rate,n;snd_pcm_t*handle;snd_output_t*log;snd_pcm_hw_params_t*params;snd_pcm_sw_params_t*swparams;snd_pcm_uframes_t buffer_size;snd_pcm_uframes_t start_threshold,stop_threshold;unsigned int buffer_time,period_ti...
4.2.1. pcm operations 操作函数的实现是本模块的主体,见snd_pcm_ops结构体描述: structsnd_pcm_ops{int(*open)(structsnd_pcm_substream*substream);int(*close)(structsnd_pcm_substream*substream);int(*ioctl)(structsnd_pcm_substream*substream,unsignedintcmd,void*arg);int(*hw_params)(structsnd_...
1.static void set_params(void) 2.{ 3.snd_pcm_hw_params_t *params; 4.snd_pcm_sw_params_t *swparams; 5.snd_pcm_uframes_t buffer_size; 6.int err; 7.size_t n; 8.snd_pcm_uframes_t xfer_align; 9.unsigned int rate; 10.snd_pcm_uframes_t start_threshold, stop_threshold;//设...