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Implement power of two, shift, and float calculation

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This commit is contained in:
Reinhard Panhuber
2022-03-19 13:37:54 +01:00
parent ceac9d64c0
commit fdfde8883f
3 changed files with 69 additions and 13 deletions
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68
src/class/audio/audio_device.c
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@@ -308,11 +308,15 @@ typedef struct
uint32_t fb_val; // Feedback value for asynchronous mode (in 16.16 format).
#if CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_WITHIN_SOF_ISR
uint8_t n_frames; // Number of (micro)frames used to estimate feedback value
uint8_t n_frames_current; // Current (micro)frame number
uint32_t n_cycles_old; // Old cycle count
uint32_t feeback_param_factor_N; // Numerator of feedback parameter coefficient
uint32_t feeback_param_factor_D; // Denominator of feedback parameter coefficient
uint8_t n_frames; // Number of (micro)frames used to estimate feedback value
uint8_t n_frames_current; // Current (micro)frame number
uint32_t n_cycles_old; // Old cycle count
union {
uint32_t i;
float f;
} feedback_param_factor_N; // Numerator of feedback parameter coefficient
uint32_t feedback_param_factor_D; // Denominator of feedback parameter coefficient
uint32_t * feedback_param_p_cycle_count; // Pointer to cycle counter
#endif
#endif
@@ -2010,14 +2014,39 @@ bool audiod_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint3
// f_s max is 2^19-1 = 524287 Hz
// n_frames_min is ceil(2^10 * f_s / f_m) for full speed and ceil(2^13 * f_s / f_m) for high speed
// f_m max is 2^29/(1 ms * n_frames) for full speed and 2^29/(125 us * n_frames) for high speed
bool tud_audio_set_feedback_params_fm_fs(uint8_t func_id, uint32_t f_m, uint32_t f_s)
bool tud_audio_set_feedback_params_fm_fs(uint8_t func_id, uint32_t f_m, uint32_t f_s, uint32_t * p_cycle_count, bool use_float)
{
audiod_function_t* audio = &_audiod_fct[func_id];
audio->feedback_param_p_cycle_count = p_cycle_count;
uint8_t n_frame = 1; // TODO: finalize that
audio->n_frames = n_frame;
audio->feeback_param_factor_N = f_s << 13;
audio->feeback_param_factor_D = f_m * n_frame;
// Check if parameters reduce to a power of two shift i.e. is n_f * f_m / f_s a power of two?
if ((f_m % f_s) == 0 && tu_is_power_of_two(n_frame * f_m / f_s))
{
audio->feedback_param_factor_N.i = 0; // zero marks power of two option
audio->feedback_param_factor_D = 16 - tu_log2(n_frame * f_m / f_s);
}
else
{
// Next best option is to use float if a FPU is available - this has to be enabled by the user
if (use_float)
{
audio->feedback_param_factor_N.f = (float)f_s / n_frame / f_m * (1 << 16);
audio->feedback_param_factor_D = 0; // non zero marks float option
}
else
{
// Neither a power of two or floats - use fixed point number
audio->feedback_param_factor_N.i = f_s << 13;
audio->feedback_param_factor_D = f_m * n_frame;
}
}
return true;
}
#endif
@@ -2044,10 +2073,27 @@ void audiod_sof (uint8_t rhport, uint32_t frame_count)
audio->n_frames_current++;
if (audio->n_frames_current == audio->n_frames)
{
uint32_t n_cylces = tud_audio_n_get_fm_n_cycles_cb(rhport, audio->ep_fb);
uint32_t feedback = ((n_cylces - audio->n_cycles_old) << 3) * audio->feeback_param_factor_N / audio->feeback_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
uint32_t n_cylces = *audio->feedback_param_p_cycle_count;
uint32_t feedback;
// TODO: Implement fast computation in case n_frames * f_s / f_m is a power of two
if (audio->feedback_param_factor_N.i == 0)
{
// Power of two shift
feedback = n_cylces << audio->feedback_param_factor_D;
}
else
{
if (audio->feedback_param_factor_D == 0)
{
// Float computation
feedback = (uint32_t)(n_cylces * audio->feedback_param_factor_N.f);
}
else
{
// Fixed point computation
feedback = ((n_cylces - audio->n_cycles_old) << 3) * audio->feedback_param_factor_N.i / audio->feedback_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
}
}
tud_audio_n_fb_set(i, feedback);
audio->n_frames_current = 0;

4
src/class/audio/audio_device.h
View File

@@ -193,7 +193,7 @@
// 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_WITHIN_SOF_ISR
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_WITHIN_SOF_ISR 0 // 0 or 1
#define CFG_TUD_AUDIO_ENABLE_FEEDBACK_DETERMINATION_WITHIN_SOF_ISR 1 // 0 or 1
#endif
// Audio interrupt control EP size - disabled if 0
@@ -487,7 +487,7 @@ TU_ATTR_WEAK uint32_t tud_audio_n_get_fm_n_cycles_cb(uint8_t rhport, uint8_t ep_
// f_m : Main clock frequency in Hz i.e. master clock to which sample clock is locked
// f_s : Current sample rate in Hz
bool tud_audio_set_feedback_params_fm_fs(uint8_t func_id, uint32_t f_m, uint32_t f_s);
bool tud_audio_set_feedback_params_fm_fs(uint8_t func_id, uint32_t f_m, uint32_t f_s, uint32_t * p_cycle_count, bool use_float);
#endif
#endif