time_stretch: Simplify audio stretcher

src/audio_core/time_stretch.h

@@ -4,57 +4,39 @@
 
 #pragma once
 
+#include <array>
 #include <cstddef>
 #include <memory>
-#include <vector>
 #include "common/common_types.h"
 
+namespace soundtouch {
+class SoundTouch;
+}
+
 namespace AudioCore {
 
-class TimeStretcher final {
+class TimeStretcher {
 public:
     TimeStretcher();
     ~TimeStretcher();
 
-    /**
-     * Set sample rate for the samples that Process returns.
-     * @param sample_rate The sample rate.
-     */
     void SetOutputSampleRate(unsigned int sample_rate);
 
-    /**
-     * Add samples to be processed.
-     * @param sample_buffer Buffer of samples in interleaved stereo PCM16 format.
-     * @param num_samples Number of samples.
-     */
-    void AddSamples(const s16* sample_buffer, std::size_t num_samples);
+    /// @param in       Input sample buffer
+    /// @param num_in   Number of input frames in `in`
+    /// @param out      Output sample buffer
+    /// @param num_out  Desired number of output frames in `out`
+    /// @returns Actual number of frames written to `out`
+    std::size_t Process(const s16* in, std::size_t num_in, s16* out, std::size_t num_out);
+
+    void Clear();
 
-    /// Flush audio remaining in internal buffers.
     void Flush();
 
-    /// Resets internal state and clears buffers.
-    void Reset();
-
-    /**
-     * Does audio stretching and produces the time-stretched samples.
-     * Timer calculations use sample_delay to determine how much of a margin we have.
-     * @param sample_delay How many samples are buffered downstream of this module and haven't been
-     * played yet.
-     * @return Samples to play in interleaved stereo PCM16 format.
-     */
-    std::vector<s16> Process(std::size_t sample_delay);
-
 private:
-    struct Impl;
-    std::unique_ptr<Impl> impl;
-
-    /// INTERNAL: ratio = wallclock time / emulated time
-    double CalculateCurrentRatio();
-    /// INTERNAL: If we have too many or too few samples downstream, nudge ratio in the appropriate
-    /// direction.
-    double CorrectForUnderAndOverflow(double ratio, std::size_t sample_delay) const;
-    /// INTERNAL: Gets the time-stretched samples from SoundTouch.
-    std::vector<s16> GetSamples();
+    unsigned int sample_rate;
+    std::unique_ptr<soundtouch::SoundTouch> sound_touch;
+    double stretch_ratio = 1.0;
 };
 
 } // namespace AudioCore