Make file for creating an mp3 audio sprite with an info JSON file for Howler.js. Input files maybe audio or video of any format supported by FFMPEG.

Loader.js

loadAudioSpritesObj("/sounds/audiosprite.json", function (sprites) {
  console.log(sprites);
});

function loadAudioSpritesObj(filenane, callback) {
	$.getJSON(filenane, function(json) {
		var sprites = {};
		var lastPositionMS = 0;
		for (var i=0;i<json.length;i+=2) {
			var spriteEndTime = json[i] + lastPositionMS;
			sprites[json[i+1]] = [lastPositionMS, spriteEndTime];
			lastPositionMS = spriteEndTime;
		}
		callback(sprites);
	});
}

Makefile

# Makefile for creating the audio samples
# Requires mp3info, mediainfo, mp3val

SRC = LED_glitch.mov LEDpulse.mov apavilion.mov backfade_drum.mov green_record.mov light_down.mov light_up.mov pulse_ambient_LED.mov radio_bulb.mov silver_record.mov the_light.mp4 waterfall2.mp4
OUTPUT_FILE = audiosprite

createaudio: 
	$(foreach var, $(SRC), ffmpeg -i $(var) -ab 160k -ac 1 -ar 44100 -vn $(var).mp3;)

mergeaudio:
	cat $(foreach var, $(SRC), $(var).mp3 > $(OUTPUT_FILE).mp3);
	mp3val $(OUTPUT_FILE).mp3 -f -nb
	mp3info -d $(OUTPUT_FILE).mp3
	echo "[" > temp_$(OUTPUT_FILE).json
	$(foreach var, $(SRC),  echo '' >> temp_$(OUTPUT_FILE).json; \
							mediainfo --Output="General;%Duration%" $(var).mp3 \
							>> temp_$(OUTPUT_FILE).json; \
							echo ',"' >> temp_$(OUTPUT_FILE).json; \
							echo $(var).mp3 >> temp_$(OUTPUT_FILE).json; \
							echo '",' >> temp_$(OUTPUT_FILE).json;)
	echo '"terminator"]' >> temp_$(OUTPUT_FILE).json
	tr -d ' \t\n\r\f' <temp_$(OUTPUT_FILE).json >$(OUTPUT_FILE).json
	# on Linux the below first '' would be ommitted
	sed -i '' 's/,"terminator"//g' $(OUTPUT_FILE).json
	rm temp_$(OUTPUT_FILE).json

all: createaudio mergeaudio

.PHONY: all