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Generalize feedback value min and max

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This commit is contained in:
Reinhard Panhuber 2022-04-16 14:47:42 +02:00
parent 7094ff7125
commit 11f0ffd9a8
1 changed files with 13 additions and 6 deletions
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19
src/class/audio/audio_device.c
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@ -312,6 +312,8 @@ typedef struct
#if CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION == CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_OPTION_SOF_BY_AUDIO_DRIVER
volatile uint32_t fb_val; // Feedback value for asynchronous mode (in 16.16 format).
uint32_t fb_val_min; // Maximum allowed feedback value according to UAC2 FMT-2.0 section 2.3.1.1.
uint32_t fb_val_max; // Maximum allowed feedback value according to UAC2 FMT-2.0 section 2.3.1.1.
uint8_t fb_n_frames; // Number of (micro)frames used to estimate feedback value
volatile uint8_t fb_n_frames_current; // Current (micro)frame number
volatile uint32_t fb_n_cycles_old; // Old cycle count
@ -2094,6 +2096,9 @@ TU_ATTR_WEAK bool tud_audio_set_fb_params(uint8_t func_id, uint32_t f_m, uint32_
audio->fb_param_factor_D = (uint64_t)f_m * audio->fb_n_frames;
#endif
audio->fb_val_min = ((TUSB_SPEED_FULL == tud_speed_get() ? (f_s/1000) : (f_s/8000)) - 1) << 16; // Minimal value in 16.16 format for full speed (1ms per frame) or high speed (125 us per frame)
audio->fb_val_max = ((TUSB_SPEED_FULL == tud_speed_get() ? (f_s/1000) : (f_s/8000)) + 1) << 16; // Maximum value in 16.16 format
return true;
}
@ -2139,16 +2144,18 @@ TU_ATTR_WEAK void audiod_sof (uint8_t rhport, uint32_t frame_count)
feedback = ((n_cylces - audio->fb_n_cycles_old) << 3) * audio->fb_param_factor_N / audio->fb_param_factor_D; // feeback_param_factor_N has scaling factor of 13 bits, n_cycles 3 and feeback_param_factor_D 1, hence 16.16 precision
#endif
// Buffer count checks ?
// For Windows: https://docs.microsoft.com/en-us/windows-hardware/drivers/audio/usb-2-0-audio-drivers
// The size of isochronous packets created by the device must be within the limits specified in FMT-2.0 section 2.3.1.1. This means that the deviation of actual packet size from nominal size must not exceed +/- one audio slot (audio slot = channel count samples).
// Magic checks - where are they from?
if (feedback > 2949166){ // 45.0007 in 16.16 format
feedback = 2949166;
if (feedback > audio->fb_val_max){
feedback = audio->fb_val_max;
}
if ( feedback < 2883630) { // 44.0007 in 16.16 format
feedback = 2883630;
if ( feedback < audio->fb_val_min) {
feedback = audio->fb_val_min;
}
// Buffer count checks ?
tud_audio_n_fb_set(i, feedback);
audio->fb_n_frames_current = 0;
audio->fb_n_cycles_old = n_cylces;