Implement BPM support

Based on #62896, only implements the BPM support part.

* Implements BPM support in the AudioStreamOGG/MP3 importers.
* Can select BPM/Bar Size and total beats in a song file, as well as edit looping points.
* Looping is now BPM aware
* Added a special importer UI for configuring this.
* Added a special preview showing the audio waveform as well as the playback position in the resource picker.
* Renamed `AudioStream::instance` to `instantiate` for correctness.

1 files changed, 23 insertions, 2 deletions

diff --git a/modules/minimp3/audio_stream_mp3.h b/modules/minimp3/audio_stream_mp3.h
index c1a60ddccb..428ac1240e 100644
--- a/modules/minimp3/audio_stream_mp3.h
+++ b/modules/minimp3/audio_stream_mp3.h
@@ -41,6 +41,12 @@ class AudioStreamMP3;
 class AudioStreamPlaybackMP3 : public AudioStreamPlaybackResampled {
 	GDCLASS(AudioStreamPlaybackMP3, AudioStreamPlaybackResampled);
 
+	enum {
+		FADE_SIZE = 256
+	};
+	AudioFrame loop_fade[FADE_SIZE];
+	int loop_fade_remaining = FADE_SIZE;
+
 	mp3dec_ex_t *mp3d = nullptr;
 	uint32_t frames_mixed = 0;
 	bool active = false;
@@ -64,6 +70,8 @@ public:
 	virtual float get_playback_position() const override;
 	virtual void seek(float p_time) override;
 
+	virtual void tag_used_streams() override;
+
 	AudioStreamPlaybackMP3() {}
 	~AudioStreamPlaybackMP3();
 };
@@ -85,17 +93,30 @@ class AudioStreamMP3 : public AudioStream {
 	float loop_offset = 0.0;
 	void clear_data();
 
+	double bpm = 0;
+	int beat_count = 0;
+	int bar_beats = 4;
+
 protected:
 	static void _bind_methods();
 
 public:
 	void set_loop(bool p_enable);
-	bool has_loop() const;
+	virtual bool has_loop() const override;
 
 	void set_loop_offset(float p_seconds);
 	float get_loop_offset() const;
 
-	virtual Ref<AudioStreamPlayback> instance_playback() override;
+	void set_bpm(double p_bpm);
+	virtual double get_bpm() const override;
+
+	void set_beat_count(int p_beat_count);
+	virtual int get_beat_count() const override;
+
+	void set_bar_beats(int p_bar_beats);
+	virtual int get_bar_beats() const override;
+
+	virtual Ref<AudioStreamPlayback> instantiate_playback() override;
 	virtual String get_stream_name() const override;
 
 	void set_data(const Vector<uint8_t> &p_data);