unsigned int channels; /* channels */ snd_pcm_uframes_t period_size; /* period size */ unsigned int periods; /* periods */ snd_pcm_uframes_t buffer_size; /* buffer size */ snd_pcm_uframes_t min_align; /* Min alignment for the format */ size_t byte_align; unsigned int frame...
int snd_pcm_new(struct snd_card *card, const char *id, int device, int playback_count, int capture_count, struct snd_pcm **rpcm) { return _snd_pcm_new(card, id, device, playback_count, capture_count, false, rpcm); } EXPORT_SYMBOL(snd_pcm_new); 1. 2. 3. 4. 5. 6. 7....
sample_bits;27unsignedintinfo;28unsignedintrate_num;29unsignedintrate_den;30unsignedintno_period_wakeup:1;3132/*-- SW params --*/33inttstamp_mode;/*mmap timestamp is updated*/34unsignedintperiod_step;35snd_pcm_uframes_t start_threshold;36snd_pcm_uframes_t stop_threshold;37snd_pcm_uframes_...
*pcm); int pcm_wait(struct pcm *pcm, int timeout); int pcm_set_avail_min(struct pcm *pcm, int avail_min); 对于pcm设备的操作只需要注意所操作的设备是否存在,以及设备的能力问题不要设置设备所不能及的能力设备就可以正常工作了,其实就是需要注意channels、rate、format、period_size和period_count。
{ struct pcm_config config; struct pcm *pcm; int ret; // 配置PCM参数 config.channels = 2; // 立体声 config.rate = 44100; // 采样率44.1kHz config.period_size = 1024; // 每个周期的样本数 config.period_count = 4; // 周期数 config.format = PCM_FORMAT_S16_LE; // 16位小端格式 ...
= 1; config.rate = 16000; config.period_size = 80; config.period_count = 4; ...
之后需要定义snd_pcm_t结构体指针pcm,定义缓冲区大小buf_bytes,缓冲区指针void指针buf,文件描述符fd,snd_pcm_uframes_t结构体period_size定义周期大小为1024帧,最后定义periods指定周期数为4。 编写snd_pcm_init函数,先定义snd_pcm_hw_params_t结构体指针hwparams,然后通过snd_pcm_open打开PCM设备,通过snd_pcm_hw...
SNDRV_PCM_HW_PARAM_PERIOD_SIZE:Approx frames between interrupts; SNDRV_PCM_HW_PARAM_PERIOD_BYTES:Approx bytes between interrupts; SNDRV_PCM_HW_PARAM_PERIODS:Approx interrupts per buffer; SNDRV_PCM_HW_PARAM_BUFFER_TIME:Approx duration of buffer in us; ...
dma_params)return 0;/** For mysterious reasons (and despite what the manual says)* playback samples are lost if the DMA count is not a multiple* of the DMA burst size. Let's add a rule to enforce that.*/ret = snd_pcm_hw_constraint_step(runtime, 0,SNDRV_PCM_HW_PARAM_PERIOD_...
...period_bytes =pcm_format_to_bits 用来计算一个帧有多少bits,实际应用的时候经常用到 下面有个老外的讲的音频帧,很多解释都是从这里翻译来的,大家自行体味一下https...五、CODEC介绍 (1)专用术语 ASLA - Advanced SoundLinuxArchitecture OSS - 以前的Linux音频体系结构,被ASLA取代并兼容 Codec -...可...