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Ensures no input data is dropped when changing output rates.

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I think this 'completely' deals with the problem. At least until someone wants dynamic output buffer sizes or something like that. We'll see.
This commit is contained in:
Thomas Harte 2020-02-09 19:14:25 -05:00
parent b04daca98e
commit 6bda4034c6
1 changed files with 92 additions and 54 deletions
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118
Outputs/Speaker/Implementation/LowpassSpeaker.hpp
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@ -109,6 +109,12 @@ template <typename T> class LowpassSpeaker: public Speaker {
} }
private: private:
enum class Conversion {
ResampleSmaller,
Copy,
ResampleLarger
} conversion_ = Conversion::Copy;
/*! /*!
Advances by the number of cycles specified, obtaining data from the sample source supplied Advances by the number of cycles specified, obtaining data from the sample source supplied
at construction, filtering it and passing it on to the speaker's delegate if there is one. at construction, filtering it and passing it on to the speaker's delegate if there is one.
@ -131,10 +137,8 @@ template <typename T> class LowpassSpeaker: public Speaker {
delegate_->speaker_did_change_input_clock(this); delegate_->speaker_did_change_input_clock(this);
} }
// If input and output rates exactly match, and no additional cut-off has been specified, switch(conversion_) {
// just accumulate results and pass on. case Conversion::Copy:
if( filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second &&
filter_parameters.high_frequency_cutoff < 0.0) {
while(cycles_remaining) { while(cycles_remaining) {
const auto cycles_to_read = std::min(output_buffer_.size() - output_buffer_pointer_, cycles_remaining); const auto cycles_to_read = std::min(output_buffer_.size() - output_buffer_pointer_, cycles_remaining);
@ -149,13 +153,9 @@ template <typename T> class LowpassSpeaker: public Speaker {
cycles_remaining -= cycles_to_read; cycles_remaining -= cycles_to_read;
} }
break;
return; case Conversion::ResampleSmaller:
}
// If the output rate is less than the input rate, or an additional cut-off has been specified, use the filter.
if( filter_parameters.input_cycles_per_second > filter_parameters.output_cycles_per_second ||
(filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second && filter_parameters.high_frequency_cutoff >= 0.0)) {
while(cycles_remaining) { while(cycles_remaining) {
const auto cycles_to_read = std::min(cycles_remaining, input_buffer_.size() - input_buffer_depth_); const auto cycles_to_read = std::min(cycles_remaining, input_buffer_.size() - input_buffer_depth_);
sample_source_.get_samples(cycles_to_read, &input_buffer_[input_buffer_depth_]); sample_source_.get_samples(cycles_to_read, &input_buffer_[input_buffer_depth_]);
@ -163,37 +163,15 @@ template <typename T> class LowpassSpeaker: public Speaker {
input_buffer_depth_ += cycles_to_read; input_buffer_depth_ += cycles_to_read;
if(input_buffer_depth_ == input_buffer_.size()) { if(input_buffer_depth_ == input_buffer_.size()) {
output_buffer_[output_buffer_pointer_] = filter_->apply(input_buffer_.data()); resample_input_buffer();
output_buffer_pointer_++; }
}
break;
// Announce to delegate if full. case Conversion::ResampleLarger:
if(output_buffer_pointer_ == output_buffer_.size()) { // TODO: input rate is less than output rate.
output_buffer_pointer_ = 0; break;
did_complete_samples(this, output_buffer_);
} }
// If the next loop around is going to reuse some of the samples just collected, use a memmove to
// preserve them in the correct locations (TODO: use a longer buffer to fix that) and don't skip
// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
const auto steps = stepper_->step();
if(steps < input_buffer_.size()) {
auto *const input_buffer = input_buffer_.data();
std::memmove( input_buffer,
&input_buffer[steps],
sizeof(int16_t) * (input_buffer_.size() - steps));
input_buffer_depth_ -= steps;
} else {
if(steps > input_buffer_.size())
sample_source_.skip_samples(steps - input_buffer_.size());
input_buffer_depth_ = 0;
}
}
}
return;
}
// TODO: input rate is less than output rate
} }
T &sample_source_; T &sample_source_;
@ -239,9 +217,69 @@ template <typename T> class LowpassSpeaker: public Speaker {
high_pass_frequency, high_pass_frequency,
SignalProcessing::FIRFilter::DefaultAttenuation); SignalProcessing::FIRFilter::DefaultAttenuation);
input_buffer_.resize(std::size_t(number_of_taps));
// Pick the new conversion function.
if( filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second &&
filter_parameters.high_frequency_cutoff < 0.0) {
// If input and output rates exactly match, and no additional cut-off has been specified,
// just accumulate results and pass on.
conversion_ = Conversion::Copy;
} else if( filter_parameters.input_cycles_per_second > filter_parameters.output_cycles_per_second ||
(filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second && filter_parameters.high_frequency_cutoff >= 0.0)) {
// If the output rate is less than the input rate, or an additional cut-off has been specified, use the filter.
conversion_ = Conversion::ResampleSmaller;
} else {
conversion_ = Conversion::ResampleLarger;
}
// Do something sensible with any dangling input, if necessary.
switch(conversion_) {
// Neither direct copying nor resampling larger currently use any temporary input.
// Although in the latter case that's just because it's unimplemented. But, regardless,
// that means nothing to do.
default: break;
case Conversion::ResampleSmaller:
// Reize the input buffer only if absolutely necessary; if sizing downward
// such that a sample would otherwise be lost then output it now. Keep anything
// currently in the input buffer that hasn't yet been processed.
if(input_buffer_.size() != size_t(number_of_taps)) {
if(input_buffer_depth_ >= size_t(number_of_taps)) {
resample_input_buffer();
input_buffer_depth_ %= size_t(number_of_taps);
}
input_buffer_.resize(size_t(number_of_taps));
}
break;
}
}
inline void resample_input_buffer() {
output_buffer_[output_buffer_pointer_] = filter_->apply(input_buffer_.data());
output_buffer_pointer_++;
// Announce to delegate if full.
if(output_buffer_pointer_ == output_buffer_.size()) {
output_buffer_pointer_ = 0;
did_complete_samples(this, output_buffer_);
}
// If the next loop around is going to reuse some of the samples just collected, use a memmove to
// preserve them in the correct locations (TODO: use a longer buffer to fix that?) and don't skip
// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
const auto steps = stepper_->step();
if(steps < input_buffer_.size()) {
auto *const input_buffer = input_buffer_.data();
std::memmove( input_buffer,
&input_buffer[steps],
sizeof(int16_t) * (input_buffer_.size() - steps));
input_buffer_depth_ -= steps;
} else {
if(steps > input_buffer_.size())
sample_source_.skip_samples(steps - input_buffer_.size());
input_buffer_depth_ = 0; input_buffer_depth_ = 0;
} }
}
}; };
} }