andy/tinyUSB
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

changes proposal to audio feedback computation

Browse Source
This commit is contained in:
hathach
2022-05-13 22:54:47 +07:00
parent 11f0ffd9a8
commit c5ba1ea8c1
5 changed files with 136 additions and 231 deletions
Download Patch File Download Diff File Expand all files Collapse all files

102
src/class/audio/audio_device.h
View File

@@ -191,41 +191,6 @@
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_FORMAT_CORRECTION 0 // 0 or 1
#endif
// Possible options for determination of feedback value
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER 1 // Feedback value must be determined by the user itself and set by use of tud_audio_n_fb_set(). The feedback value may be determined e.g. from some fill status of some FIFO buffer. Advantage: No ISR interrupt is enabled, hence the CPU need not to handle an ISR every 1ms or 125us and thus less CPU load, disadvantage: typically a larger FIFO is needed to compensate for jitter (e.g. 8 frames), i.e. a larger delay is introduced.
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER 2 // Feedback value is calculated within the audio driver by use of SOF interrupt. The driver needs information about the master clock f_m from which the audio sample frequency f_s is derived, f_s itself, and the cycle count of f_m at time of the SOF interrupt (e.g. by use of a hardware counter) - see tud_audio_set_fb_params(). Advantage: Reduced jitter in the feedback value computation, hence, the receive FIFO can be smaller (e.g. 2 frames) and thus a smaller delay is possible, disadvantage: higher CPU load due to SOF ISR handling every frame i.e. 1ms or 125us. This option is a great starting point to try the SOF ISR option but depending on your hardware setup (performance of the CPU) it might not work. If so, figure out why and use the next option. (The most critical point is the reading of the cycle counter value of f_m. It is read from within the SOF ISR - see: audiod_sof() -, hence, the ISR must has a high priority such that no software dependent "random" delay i.e. jitter is introduced).
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_USER 3 // Feedback value is determined by the user by use of SOF interrupt. The user may use tud_audio_sof_isr_cb() which is called every SOF (of course only invoked when an alternate interface other than zero was set). The number of frames used to determine the feedback value for the currently active alternate setting can be get by tud_audio_get_fb_n_frames(). The feedback value must be set by use of tud_audio_n_fb_set().
// Determine feedback value within SOF ISR within audio driver - if disabled the user has to call tud_audio_n_fb_set() with a suitable feedback value on its own. If done within audio driver SOF ISR, tud_audio_n_fb_set() is disabled for user
#ifndef CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER
#endif
#ifdef CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION
#if (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION != CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER && CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION != CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER && CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION != CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_USER)
#error Unknown CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION. Possible choices are: CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER, CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER, or CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_USER!
#endif
#endif
// Feeback calculation mode
#if CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_POWER_OF_TWO_SHIFT 1
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FLOAT 2
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FIXED_POINT 3
#ifndef CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE
#error You must tell the driver the feedback determination mode! Possible choices are: CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_POWER_OF_TWO_SHIFT, CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FLOAT, or CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FIXED_POINT!
#endif
#ifdef CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE
#if (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE != CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_POWER_OF_TWO_SHIFT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE != CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FLOAT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE != CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FIXED_POINT)
#error Unknown CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE. Possible choices are: CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_POWER_OF_TWO_SHIFT, CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FLOAT, or CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_MODE_FIXED_POINT!
#endif
#endif
#endif
// Audio interrupt control EP size - disabled if 0
#ifndef CFG_TUD_AUDIO_INT_CTR_EPSIZE_IN
#define CFG_TUD_AUDIO_INT_CTR_EPSIZE_IN 0 // Audio interrupt control - if required - 6 Bytes according to UAC 2 specification (p. 74)
@@ -493,9 +458,14 @@ TU_ATTR_WEAK bool tud_audio_rx_done_post_read_cb(uint8_t rhport, uint16_t n_byte
#endif
#if CFG_TUD_AUDIO_ENABLE_EP_OUT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_EP
TU_ATTR_WEAK bool tud_audio_fb_done_cb(uint8_t rhport);
TU_ATTR_WEAK void tud_audio_fb_done_cb(uint8_t func_id);
#if (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER)
// determined by the user itself and set by use of tud_audio_n_fb_set(). The feedback value may be determined e.g. from some fill status of some FIFO buffer. Advantage: No ISR interrupt is enabled, hence the CPU need not to handle an ISR every 1ms or 125us and thus less CPU load, disadvantage: typically a larger FIFO is needed to compensate for jitter (e.g. 8 frames), i.e. a larger delay is introduced.
// Feedback value is calculated within the audio driver by use of SOF interrupt. The driver needs information about the master clock f_m from which the audio sample frequency f_s is derived, f_s itself, and the cycle count of f_m at time of the SOF interrupt (e.g. by use of a hardware counter) - see tud_audio_set_fb_params(). Advantage: Reduced jitter in the feedback value computation, hence, the receive FIFO can be smaller (e.g. 2 frames) and thus a smaller delay is possible, disadvantage: higher CPU load due to SOF ISR handling every frame i.e. 1ms or 125us. This option is a great starting point to try the SOF ISR option but depending on your hardware setup (performance of the CPU) it might not work. If so, figure out why and use the next option. (The most critical point is the reading of the cycle counter value of f_m. It is read from within the SOF ISR - see: audiod_sof() -, hence, the ISR must has a high priority such that no software dependent "random" delay i.e. jitter is introduced).
// Feedback value is determined by the user by use of SOF interrupt. The user may use tud_audio_sof_isr() which is called every SOF (of course only invoked when an alternate interface other than zero was set). The number of frames used to determine the feedback value for the currently active alternate setting can be get by tud_audio_get_fb_n_frames(). The feedback value must be set by use of tud_audio_n_fb_set().
// This function is used to provide data rate feedback from an asynchronous sink. Feedback value will be sent at FB endpoint interval till it's changed.
//
@@ -508,41 +478,11 @@ TU_ATTR_WEAK bool tud_audio_fb_done_cb(uint8_t rhport);
// Feedback value can be determined from within the SOF ISR of the audio driver. This should reduce jitter. If the feature is used, the user can not set the feedback value.
bool tud_audio_n_fb_set(uint8_t func_id, uint32_t feedback);
static inline bool tud_audio_fb_set(uint32_t feedback);
uint8_t tud_audio_n_get_fb_n_frames(uint8_t func_id);
static inline uint8_t tud_audio_get_fb_n_frames();
#endif // (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER)
#if CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER
// f_m : Main clock frequency in Hz i.e. master clock to which sample clock is locked
// f_s : Current sample rate in Hz
// p_cycle_count : Pointer to main clock cycle counter register where the current count can be read from (e.g. a timer register)
// This function must be called from the user within the tud_audio_set_itf_cb(rhport, p_request) callback function, where p_request needs to be checked as
// uint8_t const itf = tu_u16_low(p_request->wIndex);
// uint8_t const alt = tu_u16_low(p_request->wValue);
// such that tud_audio_set_fb_params() gets called with the parameters corresponding to the defined interface and alternate setting
// Also, start the main clock cycle counter (or reset its value) within tud_audio_set_itf_cb()
bool tud_audio_set_fb_params(uint8_t func_id, uint32_t f_m, uint32_t f_s, uint32_t * p_cycle_count);
#endif // CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER
#if (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_USER)
// This function is used to provide data rate feedback from an asynchronous sink. Feedback value will be sent at FB endpoint interval till it's changed.
//
// The feedback format is specified to be 16.16 for HS and 10.14 for FS devices (see Universal Serial Bus Specification Revision 2.0 5.12.4.2). By default,
// the choice of format is left to the caller and feedback argument is sent as-is. If CFG_TUD_AUDIO_ENABLE_FEEDBACK_FORMAT_CORRECTION is set, then tinyusb
// expects 16.16 format and handles the conversion to 10.14 on FS.
//
// Note that due to a bug in its USB Audio 2.0 driver, Windows currently requires 16.16 format for _all_ USB 2.0 devices. On Linux and macOS it seems the
// driver can work with either format. So a good compromise is to keep format correction disabled and stick to 16.16 format.
// Feedback value can be determined from within the SOF ISR of the audio driver. This should reduce jitter. If the feature is used, the user can not set the feedback value.
// Determine feedback value - The feedback method is described in 5.12.4.2 of the USB 2.0 spec
// Boiled down, the feedback value Ff = n_samples / (micro)frame.
// Since an accuracy of less than 1 Sample / second is desired, at least n_frames = ceil(2^K * f_s / f_m) frames need to be measured, where K = 10 for full speed and K = 13 for high speed, f_s is the sampling frequency e.g. 48 kHz and f_m is the cpu clock frequency e.g. 100 MHz (or any other master clock whose clock count is available and locked to f_s)
// The update interval in the (4.10.2.1) Feedback Endpoint Descriptor must be less or equal to 2^(K - P), where P = min( ceil(log2(f_m / f_s)), K)
// feedback = n_cycles / n_frames * f_s / f_m in 16.16 format, where n_cycles are the number of main clock cycles within fb_n_frames
bool tud_audio_n_fb_set(uint8_t func_id, uint32_t feedback);
static inline bool tud_audio_fb_set(uint32_t feedback);
@@ -550,9 +490,18 @@ static inline bool tud_audio_fb_set(uint32_t feedback);
uint8_t tud_audio_n_get_fb_n_frames(uint8_t func_id);
static inline uint8_t tud_audio_get_fb_n_frames();
TU_ATTR_WEAK void tud_audio_sof_isr_cb(uint8_t func_id, uint32_t frame);
// Update feedback value with passed cycles since last time this update function is called.
// Typically called within tud_audio_sof_isr(). Required tud_audio_feedback_params_cb() is implemented
// This function will also call tud_audio_feedback_set()
// return feedback value in 16.16 for reference (0 for error)
uint32_t tud_audio_feedback_update(uint8_t func_id, uint32_t cycles);
#endif // (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_USER)
// mclk_freq : Main clock frequency in Hz i.e. master clock to which sample clock is locked
// sample_freq : sample frequency in Hz
// fixed_point : 0 float (default), 1 fixed point (for mcu without FPU)
TU_ATTR_WEAK void tud_audio_feedback_params_cb(uint8_t func_id, uint8_t alt_itf, uint32_t* sample_freq, uint32_t* mclk_freq, uint8_t* fixed_point);
TU_ATTR_WEAK void tud_audio_sof_isr(uint8_t func_id, uint32_t frame);
#endif // CFG_TUD_AUDIO_ENABLE_EP_OUT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_EP
@@ -695,7 +644,8 @@ static inline uint16_t tud_audio_int_ctr_write(uint8_t const* buffer, uint16_t l
}
#endif
#if CFG_TUD_AUDIO_ENABLE_EP_OUT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_EP && ((CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_NO_SOF_BY_USER) || (CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_USER))
#if CFG_TUD_AUDIO_ENABLE_EP_OUT && CFG_TUD_AUDIO_ENABLE_FEEDBACK_EP
static inline bool tud_audio_fb_set(uint32_t feedback)
{
return tud_audio_n_fb_set(0, feedback);
@@ -716,7 +666,7 @@ void audiod_reset (uint8_t rhport);
uint16_t audiod_open (uint8_t rhport, tusb_desc_interface_t const * itf_desc, uint16_t max_len);
bool audiod_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_request_t const * request);
bool audiod_xfer_cb (uint8_t rhport, uint8_t edpt_addr, xfer_result_t result, uint32_t xferred_bytes);
void audiod_sof (uint8_t rhport, uint32_t frame_count);
void audiod_sof_isr (uint8_t rhport, uint32_t frame_count);
#ifdef __cplusplus
}