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Ensures no input data is dropped when changing output rates.
I think this 'completely' deals with the problem. At least until someone wants dynamic output buffer sizes or something like that. We'll see.
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@ -109,6 +109,12 @@ template <typename T> class LowpassSpeaker: public Speaker {
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}
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private:
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enum class Conversion {
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ResampleSmaller,
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Copy,
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ResampleLarger
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} conversion_ = Conversion::Copy;
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/*!
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Advances by the number of cycles specified, obtaining data from the sample source supplied
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at construction, filtering it and passing it on to the speaker's delegate if there is one.
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@ -131,69 +137,41 @@ template <typename T> class LowpassSpeaker: public Speaker {
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delegate_->speaker_did_change_input_clock(this);
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}
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// If input and output rates exactly match, and no additional cut-off has been specified,
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// just accumulate results and pass on.
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if( filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second &&
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filter_parameters.high_frequency_cutoff < 0.0) {
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while(cycles_remaining) {
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const auto cycles_to_read = std::min(output_buffer_.size() - output_buffer_pointer_, cycles_remaining);
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switch(conversion_) {
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case Conversion::Copy:
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while(cycles_remaining) {
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const auto cycles_to_read = std::min(output_buffer_.size() - output_buffer_pointer_, cycles_remaining);
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sample_source_.get_samples(cycles_to_read, &output_buffer_[output_buffer_pointer_]);
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output_buffer_pointer_ += cycles_to_read;
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sample_source_.get_samples(cycles_to_read, &output_buffer_[output_buffer_pointer_]);
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output_buffer_pointer_ += cycles_to_read;
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// announce to delegate if full
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if(output_buffer_pointer_ == output_buffer_.size()) {
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output_buffer_pointer_ = 0;
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did_complete_samples(this, output_buffer_);
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}
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cycles_remaining -= cycles_to_read;
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}
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return;
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}
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// If the output rate is less than the input rate, or an additional cut-off has been specified, use the filter.
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if( filter_parameters.input_cycles_per_second > filter_parameters.output_cycles_per_second ||
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(filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second && filter_parameters.high_frequency_cutoff >= 0.0)) {
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while(cycles_remaining) {
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const auto cycles_to_read = std::min(cycles_remaining, input_buffer_.size() - input_buffer_depth_);
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sample_source_.get_samples(cycles_to_read, &input_buffer_[input_buffer_depth_]);
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cycles_remaining -= cycles_to_read;
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input_buffer_depth_ += cycles_to_read;
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if(input_buffer_depth_ == input_buffer_.size()) {
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output_buffer_[output_buffer_pointer_] = filter_->apply(input_buffer_.data());
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output_buffer_pointer_++;
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// Announce to delegate if full.
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// announce to delegate if full
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if(output_buffer_pointer_ == output_buffer_.size()) {
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output_buffer_pointer_ = 0;
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did_complete_samples(this, output_buffer_);
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}
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// If the next loop around is going to reuse some of the samples just collected, use a memmove to
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// preserve them in the correct locations (TODO: use a longer buffer to fix that) and don't skip
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// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
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const auto steps = stepper_->step();
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if(steps < input_buffer_.size()) {
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auto *const input_buffer = input_buffer_.data();
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std::memmove( input_buffer,
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&input_buffer[steps],
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sizeof(int16_t) * (input_buffer_.size() - steps));
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input_buffer_depth_ -= steps;
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} else {
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if(steps > input_buffer_.size())
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sample_source_.skip_samples(steps - input_buffer_.size());
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input_buffer_depth_ = 0;
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cycles_remaining -= cycles_to_read;
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}
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break;
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case Conversion::ResampleSmaller:
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while(cycles_remaining) {
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const auto cycles_to_read = std::min(cycles_remaining, input_buffer_.size() - input_buffer_depth_);
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sample_source_.get_samples(cycles_to_read, &input_buffer_[input_buffer_depth_]);
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cycles_remaining -= cycles_to_read;
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input_buffer_depth_ += cycles_to_read;
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if(input_buffer_depth_ == input_buffer_.size()) {
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resample_input_buffer();
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}
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}
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}
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break;
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return;
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case Conversion::ResampleLarger:
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// TODO: input rate is less than output rate.
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break;
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}
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// TODO: input rate is less than output rate
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}
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T &sample_source_;
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@ -239,8 +217,68 @@ template <typename T> class LowpassSpeaker: public Speaker {
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high_pass_frequency,
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SignalProcessing::FIRFilter::DefaultAttenuation);
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input_buffer_.resize(std::size_t(number_of_taps));
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input_buffer_depth_ = 0;
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// Pick the new conversion function.
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if( filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second &&
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filter_parameters.high_frequency_cutoff < 0.0) {
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// If input and output rates exactly match, and no additional cut-off has been specified,
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// just accumulate results and pass on.
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conversion_ = Conversion::Copy;
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} else if( filter_parameters.input_cycles_per_second > filter_parameters.output_cycles_per_second ||
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(filter_parameters.input_cycles_per_second == filter_parameters.output_cycles_per_second && filter_parameters.high_frequency_cutoff >= 0.0)) {
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// If the output rate is less than the input rate, or an additional cut-off has been specified, use the filter.
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conversion_ = Conversion::ResampleSmaller;
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} else {
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conversion_ = Conversion::ResampleLarger;
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}
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// Do something sensible with any dangling input, if necessary.
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switch(conversion_) {
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// Neither direct copying nor resampling larger currently use any temporary input.
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// Although in the latter case that's just because it's unimplemented. But, regardless,
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// that means nothing to do.
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default: break;
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case Conversion::ResampleSmaller:
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// Reize the input buffer only if absolutely necessary; if sizing downward
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// such that a sample would otherwise be lost then output it now. Keep anything
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// currently in the input buffer that hasn't yet been processed.
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if(input_buffer_.size() != size_t(number_of_taps)) {
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if(input_buffer_depth_ >= size_t(number_of_taps)) {
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resample_input_buffer();
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input_buffer_depth_ %= size_t(number_of_taps);
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}
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input_buffer_.resize(size_t(number_of_taps));
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}
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break;
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}
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}
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inline void resample_input_buffer() {
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output_buffer_[output_buffer_pointer_] = filter_->apply(input_buffer_.data());
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output_buffer_pointer_++;
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// Announce to delegate if full.
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if(output_buffer_pointer_ == output_buffer_.size()) {
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output_buffer_pointer_ = 0;
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did_complete_samples(this, output_buffer_);
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}
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// If the next loop around is going to reuse some of the samples just collected, use a memmove to
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// preserve them in the correct locations (TODO: use a longer buffer to fix that?) and don't skip
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// anything. Otherwise skip as required to get to the next sample batch and don't expect to reuse.
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const auto steps = stepper_->step();
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if(steps < input_buffer_.size()) {
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auto *const input_buffer = input_buffer_.data();
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std::memmove( input_buffer,
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&input_buffer[steps],
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sizeof(int16_t) * (input_buffer_.size() - steps));
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input_buffer_depth_ -= steps;
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} else {
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if(steps > input_buffer_.size())
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sample_source_.skip_samples(steps - input_buffer_.size());
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input_buffer_depth_ = 0;
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}
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}
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};
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