silence_trimmer.h

Go to the documentation of this file.

#ifndef AUDIOGRAPHER_SILENCE_TRIMMER_H
#define AUDIOGRAPHER_SILENCE_TRIMMER_H
 
#include <cassert>
 
#include "audiographer/visibility.h"
#include "audiographer/debug_utils.h"
#include "audiographer/flag_debuggable.h"
#include "audiographer/sink.h"
#include "audiographer/exception.h"
#include "audiographer/utils/listed_source.h"
 
#include <cmath>
#include <cstring>
 
namespace AudioGrapher {
 
template<typename T> struct SilenceTester;
 
// this needs to be implemented for every datatype T
// currently Ardour always uses Sample aka float
template <>
struct SilenceTester<float> {
        public:
        SilenceTester (const float dB) {
                threshold = dB > -318.8f ? pow (10.0f, dB * 0.05f) : 0.0f;
        }
        bool is_silent (const float d) {
                return fabsf (d) <= threshold;
        }
        private:
        float threshold;
};
 
 
template<typename T = DefaultSampleType>
class /*LIBAUDIOGRAPHER_API*/ SilenceTrimmer
  : public ListedSource<T>
  , public Sink<T>
  , public FlagDebuggable<>
  , public Throwing<>
{
  public:
 
        SilenceTrimmer(samplecnt_t silence_buffer_size_ = 1024, float thresh_dB = -INFINITY)
          : silence_buffer_size (0)
          , silence_buffer (0)
          , tester (thresh_dB)
        {
                reset (silence_buffer_size_);
                add_supported_flag (ProcessContext<T>::EndOfInput);
        }
 
        ~SilenceTrimmer()
        {
                delete [] silence_buffer;
        }
 
        void reset (samplecnt_t silence_buffer_size_ = 1024)
        {
                if (throw_level (ThrowObject) && silence_buffer_size_ == 0) {
                        throw Exception (*this,
                          "Silence trimmer constructor and reset() must be called with a non-zero parameter!");
                }
 
                if (silence_buffer_size != silence_buffer_size_) {
                        silence_buffer_size = silence_buffer_size_;
                        delete [] silence_buffer;
                        silence_buffer = new T[silence_buffer_size];
                        TypeUtils<T>::zero_fill (silence_buffer, silence_buffer_size);
                }
 
                processed_data = false;
                processing_finished = false;
                trim_beginning = false;
                trim_end = false;
                silence_samples = 0;
                max_output_frames = 0;
                add_to_beginning = 0;
                add_to_end = 0;
        }
 
        void add_silence_to_beginning (samplecnt_t samples_per_channel)
        {
                if (throw_level (ThrowObject) && processed_data) {
                        throw Exception(*this, "Tried to add silence to beginning after processing started");
                }
                add_to_beginning = samples_per_channel;
        }
 
        void add_silence_to_end (samplecnt_t samples_per_channel)
        {
                if (throw_level (ThrowObject) && processed_data) {
                        throw Exception(*this, "Tried to add silence to end after processing started");
                }
                add_to_end = samples_per_channel;
        }
 
        void set_trim_beginning (bool yn)
        {
                if (throw_level (ThrowObject) && processed_data) {
                        throw Exception(*this, "Tried to set beginning trim after processing started");
                }
                trim_beginning = yn;
        }
 
        void set_trim_end (bool yn)
        {
                if (throw_level (ThrowObject) && processed_data) {
                        throw Exception(*this, "Tried to set end trim after processing started");
                }
                trim_end = yn;
        }
 
        void process (ProcessContext<T> const & c)
        {
                if (debug_level (DebugVerbose)) {
                        debug_stream () << DebugUtils::demangled_name (*this) <<
                                "::process()" << std::endl;
                }
 
                check_flags (*this, c);
 
                if (throw_level (ThrowStrict) && processing_finished) {
                        throw Exception(*this, "process() after reaching end of input");
                }
 
                // delay end of input propagation until output/processing is complete
                processing_finished = c.has_flag (ProcessContext<T>::EndOfInput);
                c.remove_flag (ProcessContext<T>::EndOfInput);
 
                /* TODO this needs a general overhaul.
                 *
                 * - decouple "required silence duration" from buffer-size.
                 * - add hold-times for in/out
                 * - optional high pass filter (for DC offset)
                 * -> allocate a buffer "hold time" worth of samples.
                 * check if all samples in buffer are above/below threshold,
                 *
                 * https://github.com/x42/silan/blob/master/src/main.c#L130
                 * may lend itself for some inspiration.
                 */
 
                samplecnt_t output_start_index = 0;
                samplecnt_t output_sample_count = c.samples();
 
                if (!processed_data) {
                        if (trim_beginning) {
                                samplecnt_t first_non_silent_sample_index = 0;
                                if (find_first_non_silent_sample (c, first_non_silent_sample_index)) {
                                        // output from start of non-silent data until end of buffer
                                        // output_sample_count may also be altered in trim end
                                        output_start_index = first_non_silent_sample_index;
                                        output_sample_count = c.samples() - first_non_silent_sample_index;
                                        processed_data = true;
                                } else {
                                        // keep entering this block until non-silence is found to trim
                                        processed_data = false;
                                }
                        } else {
                                processed_data = true;
                        }
 
                        // This block won't be called again so add silence to beginning
                        if (processed_data && add_to_beginning) {
                                add_to_beginning *= c.channels ();
                                output_silence_samples (c, add_to_beginning);
                        }
                }
 
                if (processed_data) {
                        if (trim_end) {
                                samplecnt_t first_non_silent_sample_index = 0;
                                if (find_first_non_silent_sample (c, first_non_silent_sample_index)) {
                                        // context buffer contains non-silent data, flush any intermediate silence
                                        output_silence_samples (c, silence_samples);
 
                                        samplecnt_t silent_sample_index = 0;
                                        find_last_silent_sample_reverse (c, silent_sample_index);
 
                                        // Count of samples at end of block that are "silent", may be zero.
                                        samplecnt_t silent_end_samples = c.samples () - silent_sample_index;
                                        samplecnt_t samples_before_silence = c.samples() - silent_end_samples;
 
                                        assert (samples_before_silence + silent_end_samples == c.samples ());
 
                                        // output_start_index may be non-zero if start trim occurred above
                                        output_sample_count = samples_before_silence - output_start_index;
 
                                        // keep track of any silent samples not output
                                        silence_samples = silent_end_samples;
 
                                } else {
                                        // whole context buffer is silent output nothing
                                        silence_samples += c.samples ();
                                        output_sample_count = 0;
                                }
                        }
 
                        // now output data if any
                        ConstProcessContext<T> c_out (c, &c.data()[output_start_index], output_sample_count);
                        ListedSource<T>::output (c_out);
                }
 
                // Finally, if in last process call, add silence to end
                if (processing_finished && processed_data && add_to_end) {
                        add_to_end *= c.channels();
                        output_silence_samples (c, add_to_end);
                }
 
                if (processing_finished) {
                        // reset flag removed previous to processing above
                        c.set_flag (ProcessContext<T>::EndOfInput);
 
                        // Finally mark write complete by writing nothing with EndOfInput set
                        // whether or not any data has been written
                        ConstProcessContext<T> c_out(c, silence_buffer, 0);
                        c_out().set_flag (ProcessContext<T>::EndOfInput);
                        ListedSource<T>::output (c_out);
                }
 
        }
 
        using Sink<T>::process;
 
private:
 
        bool find_first_non_silent_sample (ProcessContext<T> const & c, samplecnt_t & result_sample)
        {
                for (samplecnt_t i = 0; i < c.samples(); ++i) {
                        if (!tester.is_silent (c.data()[i])) {
                                result_sample = i;
                                // Round down to nearest interleaved "frame" beginning
                                result_sample -= result_sample % c.channels();
                                return true;
                        }
                }
                return false;
        }
 
        bool find_last_silent_sample_reverse (ProcessContext<T> const & c, samplecnt_t & result_sample)
        {
                samplecnt_t last_sample_index = c.samples() - 1;
 
                for (samplecnt_t i = last_sample_index; i >= 0; --i) {
                        if (!tester.is_silent (c.data()[i])) {
                                result_sample = i;
                                // Round down to nearest interleaved "frame" beginning
                                result_sample -= result_sample % c.channels();
                                // Round up to return the "last" silent interleaved sample
                                result_sample += c.channels();
                                return true;
                        }
                }
                return false;
        }
 
        void output_silence_samples (ProcessContext<T> const & c, samplecnt_t & total_samples)
        {
                assert (!c.has_flag (ProcessContext<T>::EndOfInput));
 
                while (total_samples > 0) {
                        samplecnt_t samples = std::min (silence_buffer_size, total_samples);
                        if (max_output_frames) {
                                samples = std::min (samples, max_output_frames);
                        }
                        samples -= samples % c.channels();
 
                        total_samples -= samples;
                        ConstProcessContext<T> c_out (c, silence_buffer, samples);
                        ListedSource<T>::output (c_out);
                }
        }
 
        bool       processed_data;
        bool       processing_finished;
 
        bool       trim_beginning;
        bool       trim_end;
 
        samplecnt_t silence_samples;
        samplecnt_t max_output_frames;
 
        samplecnt_t add_to_beginning;
        samplecnt_t add_to_end;
 
        samplecnt_t silence_buffer_size;
        T *        silence_buffer;
 
        SilenceTester<T> tester;
};
 
} // namespace
 
#endif // AUDIOGRAPHER_SILENCE_TRIMMER_H