audio_stream_preview.cpp

/*************************************************************************/
/*  audio_stream_preview.cpp                                             */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
/*                      https://godotengine.org                          */
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/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
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/* The above copyright notice and this permission notice shall be        */
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/*************************************************************************/

#include "audio_stream_preview.h"

/////////////////////

float AudioStreamPreview::get_length() const {
	return length;
}

float AudioStreamPreview::get_max(float p_time, float p_time_next) const {
	if (length == 0) {
		return 0;
	}

	int max = preview.size() / 2;
	int time_from = p_time / length * max;
	int time_to = p_time_next / length * max;
	time_from = CLAMP(time_from, 0, max - 1);
	time_to = CLAMP(time_to, 0, max - 1);

	if (time_to <= time_from) {
		time_to = time_from + 1;
	}

	uint8_t vmax = 0;

	for (int i = time_from; i < time_to; i++) {
		uint8_t v = preview[i * 2 + 1];
		if (i == 0 || v > vmax) {
			vmax = v;
		}
	}

	return (vmax / 255.0) * 2.0 - 1.0;
}

float AudioStreamPreview::get_min(float p_time, float p_time_next) const {
	if (length == 0) {
		return 0;
	}

	int max = preview.size() / 2;
	int time_from = p_time / length * max;
	int time_to = p_time_next / length * max;
	time_from = CLAMP(time_from, 0, max - 1);
	time_to = CLAMP(time_to, 0, max - 1);

	if (time_to <= time_from) {
		time_to = time_from + 1;
	}

	uint8_t vmin = 255;

	for (int i = time_from; i < time_to; i++) {
		uint8_t v = preview[i * 2];
		if (i == 0 || v < vmin) {
			vmin = v;
		}
	}

	return (vmin / 255.0) * 2.0 - 1.0;
}

AudioStreamPreview::AudioStreamPreview() {
	length = 0;
}

////

void AudioStreamPreviewGenerator::_update_emit(ObjectID p_id) {
	emit_signal("preview_updated", p_id);
}

void AudioStreamPreviewGenerator::_preview_thread(void *p_preview) {
	Preview *preview = (Preview *)p_preview;

	float muxbuff_chunk_s = 0.25;

	int mixbuff_chunk_frames = AudioServer::get_singleton()->get_mix_rate() * muxbuff_chunk_s;

	Vector<AudioFrame> mix_chunk;
	mix_chunk.resize(mixbuff_chunk_frames);

	int frames_total = AudioServer::get_singleton()->get_mix_rate() * preview->preview->length;
	int frames_todo = frames_total;

	preview->playback->start();

	while (frames_todo) {
		int ofs_write = uint64_t(frames_total - frames_todo) * uint64_t(preview->preview->preview.size() / 2) / uint64_t(frames_total);
		int to_read = MIN(frames_todo, mixbuff_chunk_frames);
		int to_write = uint64_t(to_read) * uint64_t(preview->preview->preview.size() / 2) / uint64_t(frames_total);
		to_write = MIN(to_write, (preview->preview->preview.size() / 2) - ofs_write);

		preview->playback->mix(mix_chunk.ptrw(), 1.0, to_read);

		for (int i = 0; i < to_write; i++) {
			float max = -1000;
			float min = 1000;
			int from = uint64_t(i) * to_read / to_write;
			int to = (uint64_t(i) + 1) * to_read / to_write;
			to = MIN(to, to_read);
			from = MIN(from, to_read - 1);
			if (to == from) {
				to = from + 1;
			}

			for (int j = from; j < to; j++) {
				max = MAX(max, mix_chunk[j].l);
				max = MAX(max, mix_chunk[j].r);

				min = MIN(min, mix_chunk[j].l);
				min = MIN(min, mix_chunk[j].r);
			}

			uint8_t pfrom = CLAMP((min * 0.5 + 0.5) * 255, 0, 255);
			uint8_t pto = CLAMP((max * 0.5 + 0.5) * 255, 0, 255);

			preview->preview->preview.write[(ofs_write + i) * 2 + 0] = pfrom;
			preview->preview->preview.write[(ofs_write + i) * 2 + 1] = pto;
		}

		frames_todo -= to_read;
		singleton->call_deferred("_update_emit", preview->id);
	}

	preview->playback->stop();

	preview->generating.clear();
}

Ref<AudioStreamPreview> AudioStreamPreviewGenerator::generate_preview(const Ref<AudioStream> &p_stream) {
	ERR_FAIL_COND_V(p_stream.is_null(), Ref<AudioStreamPreview>());

	if (previews.has(p_stream->get_instance_id())) {
		return previews[p_stream->get_instance_id()].preview;
	}

	//no preview exists

	previews[p_stream->get_instance_id()] = Preview();

	Preview *preview = &previews[p_stream->get_instance_id()];
	preview->base_stream = p_stream;
	preview->playback = preview->base_stream->instance_playback();
	preview->generating.set();
	preview->id = p_stream->get_instance_id();

	float len_s = preview->base_stream->get_length();
	if (len_s == 0) {
		len_s = 60 * 5; //five minutes
	}

	int frames = AudioServer::get_singleton()->get_mix_rate() * len_s;

	Vector<uint8_t> maxmin;
	int pw = frames / 20;
	maxmin.resize(pw * 2);
	{
		uint8_t *ptr = maxmin.ptrw();
		for (int i = 0; i < pw * 2; i++) {
			ptr[i] = 127;
		}
	}

	preview->preview.instantiate();
	preview->preview->preview = maxmin;
	preview->preview->length = len_s;

	if (preview->playback.is_valid()) {
		preview->thread = memnew(Thread);
		preview->thread->start(_preview_thread, preview);
	}

	return preview->preview;
}

void AudioStreamPreviewGenerator::_bind_methods() {
	ClassDB::bind_method("_update_emit", &AudioStreamPreviewGenerator::_update_emit);
	ClassDB::bind_method(D_METHOD("generate_preview", "stream"), &AudioStreamPreviewGenerator::generate_preview);

	ADD_SIGNAL(MethodInfo("preview_updated", PropertyInfo(Variant::INT, "obj_id")));
}

AudioStreamPreviewGenerator *AudioStreamPreviewGenerator::singleton = nullptr;

void AudioStreamPreviewGenerator::_notification(int p_what) {
	if (p_what == NOTIFICATION_PROCESS) {
		List<ObjectID> to_erase;
		for (Map<ObjectID, Preview>::Element *E = previews.front(); E; E = E->next()) {
			if (!E->get().generating.is_set()) {
				if (E->get().thread) {
					E->get().thread->wait_to_finish();
					memdelete(E->get().thread);
					E->get().thread = nullptr;
				}
				if (!ObjectDB::get_instance(E->key())) { //no longer in use, get rid of preview
					to_erase.push_back(E->key());
				}
			}
		}

		while (to_erase.front()) {
			previews.erase(to_erase.front()->get());
			to_erase.pop_front();
		}
	}
}

AudioStreamPreviewGenerator::AudioStreamPreviewGenerator() {
	singleton = this;
	set_process(true);
}