Android 4.4 Kitkat 音频实现及简要分析
在 Android 4.4 上实现录放音
背景
要求
HAL
Android 的配置
调试
disable tstamp for wm8904. Change-Id: Ia22aa6ed39ede6214657487344d0488be93e5544 diff --git a/pcm.c b/pcm.c index 4501777..94cf6ee 100644 --- a/pcm.c +++ b/pcm.c @@ -691,7 +691,7 @@ struct pcm *pcm_open(unsigned int card, unsigned int device, memset(&sparams, 0, sizeof(sparams)); - sparams.tstamp_mode = SNDRV_PCM_TSTAMP_ENABLE; + sparams.tstamp_mode = SNDRV_PCM_TSTAMP_NONE; sparams.period_step = 1; if (!config->start_threshold) {
具体哪些参数不对,或者不合适,就需要 Android 驱动工程师根据硬件设计和芯片手册,逐个查证,配置到一个音频系统工作的最佳状态。那么用户体验才能最好。
Android 音频系统分析
audio HAL
tinyalsa 与 audioroute
static inline int audio_hw_device_open(const struct hw_module_t* module, struct audio_hw_device** device) { return module->methods->open(module, AUDIO_HARDWARE_INTERFACE, (struct hw_device_t**)device); } static inline int audio_hw_device_close(struct audio_hw_device* device) { return device->common.close(&device->common); }
需要实现 in 和 out 的 数据流
/* Open and close a stream */ struct pcm *pcm_open(unsigned int card, unsigned int device, unsigned int flags, struct pcm_config *config); int pcm_close(struct pcm *pcm); int pcm_is_ready(struct pcm *pcm); /* Obtain the parameters for a PCM */ struct pcm_params *pcm_params_get(unsigned int card, unsigned int device, unsigned int flags); void pcm_params_free(struct pcm_params *pcm_params); unsigned int pcm_params_get_min(struct pcm_params *pcm_params, enum pcm_param param); unsigned int pcm_params_get_max(struct pcm_params *pcm_params, enum pcm_param param); /* Set and get config */ int pcm_get_config(struct pcm *pcm, struct pcm_config *config); int pcm_set_config(struct pcm *pcm, struct pcm_config *config); /* Returns a human readable reason for the last error */ const char *pcm_get_error(struct pcm *pcm); /* Returns the sample size in bits for a PCM format. * As with ALSA formats, this is the storage size for the format, whereas the * format represents the number of significant bits. For example, * PCM_FORMAT_S24_LE uses 32 bits of storage. */ unsigned int pcm_format_to_bits(enum pcm_format format); /* Returns the buffer size (int frames) that should be used for pcm_write. */ unsigned int pcm_get_buffer_size(struct pcm *pcm); unsigned int pcm_frames_to_bytes(struct pcm *pcm, unsigned int frames); unsigned int pcm_bytes_to_frames(struct pcm *pcm, unsigned int bytes); /* Returns the pcm latency in ms */ unsigned int pcm_get_latency(struct pcm *pcm); /* Returns available frames in pcm buffer and corresponding time stamp. * The clock is CLOCK_MONOTONIC if flag PCM_MONOTONIC was specified in pcm_open, * otherwise the clock is CLOCK_REALTIME. * For an input stream, frames available are frames ready for the * application to read. * For an output stream, frames available are the number of empty frames available * for the application to write. */ int pcm_get_htimestamp(struct pcm *pcm, unsigned int *avail, struct timespec *tstamp); /* Write data to the fifo. * Will start playback on the first write or on a write that * occurs after a fifo underrun. */ int pcm_write(struct pcm *pcm, const void *data, unsigned int count); int pcm_read(struct pcm *pcm, void *data, unsigned int count); /* * mmap() support. */ int pcm_mmap_write(struct pcm *pcm, const void *data, unsigned int count); int pcm_mmap_read(struct pcm *pcm, void *data, unsigned int count); int pcm_mmap_begin(struct pcm *pcm, void **areas, unsigned int *offset, unsigned int *frames); int pcm_mmap_commit(struct pcm *pcm, unsigned int offset, unsigned int frames); /* Start and stop a PCM channel that doesn't transfer data */ int pcm_start(struct pcm *pcm); int pcm_stop(struct pcm *pcm); /* Interrupt driven API */ int pcm_wait(struct pcm *pcm, int timeout); /* Change avail_min after the stream has been opened with no need to stop the stream. * Only accepted if opened with PCM_MMAP and PCM_NOIRQ flags */ int pcm_set_avail_min(struct pcm *pcm, int avail_min);
root@sama5d3:/ # tinymix Mixer name: 'wm8904 @ SAMA5D3EK' Number of controls: 41 ctl type num name value 0 INT 1 EQ1 Volume 12 1 INT 1 EQ2 Volume 12 2 INT 1 EQ3 Volume 12 3 INT 1 EQ4 Volume 12 4 INT 1 EQ5 Volume 12 5 INT 2 Digital Capture Volume 96 96 6 ENUM 1 Left Caputure Mode Single-Ended 7 ENUM 1 Right Capture Mode Single-Ended 8 INT 2 Capture Volume 5 5 9 BOOL 2 Capture Switch Off Off 10 BOOL 1 High Pass Filter Switch On 11 ENUM 1 High Pass Filter Mode Hi-fi 12 BOOL 1 ADC 128x OSR Switch On 13 INT 1 Digital Playback Boost Volume 0 14 INT 2 Digital Playback Volume 96 96 15 INT 2 Headphone Volume 45 45 16 BOOL 2 Headphone Switch On On 17 BOOL 2 Headphone ZC Switch On On 18 INT 2 Line Output Volume 57 57 19 BOOL 2 Line Output Switch On On 20 BOOL 2 Line Output ZC Switch On On 21 BOOL 1 EQ Switch Off 22 BOOL 1 DRC Switch Off 23 ENUM 1 DRC Path ADC 24 BOOL 1 DAC OSRx2 Switch Off 25 BOOL 1 DAC Deemphasis Switch Off 26 INT 2 Digital Sidetone Volume 0 0 27 ENUM 1 LINER Mux DAC 28 ENUM 1 LINEL Mux DAC 29 ENUM 1 HPR Mux DAC 30 ENUM 1 HPL Mux DAC 31 ENUM 1 Right Sidetone None 32 ENUM 1 Left Sidetone None 33 ENUM 1 DACR Mux Right 34 ENUM 1 DACL Mux Left 35 ENUM 1 AIFOUTR Mux Right 36 ENUM 1 AIFOUTL Mux Left 37 ENUM 1 Right Capture Inverting Mux IN1R 38 ENUM 1 Right Capture Mux IN2R 39 ENUM 1 Left Capture Inverting Mux IN1L 40 ENUM 1 Left Capture Mux IN2L
audioflinger
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