| <!DOCTYPE html> |
| |
| <!-- |
| Tests that AudioBufferSourceNode can playback at different rates properly. |
| Render 72 notes over a 6 octave range. |
| --> |
| |
| <html> |
| <head> |
| <script type="text/javascript" src="resources/audio-testing.js"></script> |
| <script type="text/javascript" src="resources/buffer-loader.js"></script> |
| |
| </head> |
| <body> |
| |
| <script> |
| |
| window.onload = init; |
| |
| var sampleRate = 44100.0; |
| var numberOfNotes = 72; // play over a 6 octave range |
| var noteDuration = 0.050; |
| var noteSpacing = noteDuration + 0.005; // leave 5ms of silence between each "note" |
| var lengthInSeconds = numberOfNotes * noteSpacing; |
| |
| var context = 0; |
| var sinWaveBuffer = 0; |
| |
| function createOneCycleSinWaveBuffer(frequency, sampleRate) { |
| var duration = 1 / frequency; |
| var sampleFrameLength = duration * sampleRate; |
| |
| var audioBuffer = context.createBuffer(2, sampleFrameLength, sampleRate); |
| |
| var n = audioBuffer.length; |
| var channelL = audioBuffer.getChannelData(0); |
| var channelR = audioBuffer.getChannelData(1); |
| |
| for (var i = 0; i < n; ++i) { |
| channelL[i] = Math.sin(frequency * 2.0*Math.PI * i / sampleRate); |
| channelR[i] = channelL[i]; |
| } |
| |
| return audioBuffer; |
| } |
| |
| function playNote(time, duration, playbackRate) { |
| var source = context.createBufferSource(); |
| source.buffer = sinWaveBuffer; |
| source.playbackRate.value = playbackRate; |
| |
| var gainNode = context.createGain(); |
| source.connect(gainNode); |
| gainNode.connect(context.destination); |
| |
| // Loop and play for the given duration. |
| source.loop = true; |
| source.start(time); |
| source.stop(time + duration); |
| |
| // Apply quick fade-in and fade-out to avoid clicks. |
| gainNode.gain.value = 0; |
| gainNode.gain.setValueAtTime(0, time); |
| gainNode.gain.linearRampToValueAtTime(1, time + 0.005); |
| gainNode.gain.setValueAtTime(1, time + duration - 0.005); |
| gainNode.gain.linearRampToValueAtTime(0, time + duration); |
| } |
| |
| function init() { |
| if (!window.testRunner) |
| return; |
| |
| // Create offline audio context. |
| context = new webkitOfflineAudioContext(2, sampleRate * lengthInSeconds, sampleRate); |
| |
| // Create a single cycle of a sine wave. |
| // We'll loop this to play notes of a given duration, at a given playback rate. |
| sinWaveBuffer = createOneCycleSinWaveBuffer(440.0, sampleRate); |
| |
| // Play 48 notes over a 4 octave range. |
| for (var i = 0; i < numberOfNotes; ++i) { |
| var time = i * noteSpacing; |
| |
| var semitone = i - numberOfNotes/2; // start three octaves down |
| |
| // Convert from semitone to rate. |
| var playbackRate = Math.pow(2, semitone / 12); |
| |
| playNote(time, noteDuration, playbackRate); |
| } |
| |
| context.oncomplete = finishAudioTest; |
| context.startRendering(); |
| |
| testRunner.waitUntilDone(); |
| } |
| |
| </script> |
| |
| </body> |
| </html> |
