| <!DOCTYPE html> |
| <html> |
| <head> |
| <title>Test WebAudio Output Clipping</title> |
| <script> |
| var context = new AudioContext(); |
| var gainNode = context.createGain(); |
| gainNode.connect(context.destination); |
| gainNode.gain.value = 100; |
| |
| var frequency = 1000; |
| var duration = 1; |
| |
| function playNormal() { |
| // Play a square wave of amplitude 1 (roughly) |
| var oscillator = context.createOscillator(); |
| oscillator.frequency.value = frequency; |
| oscillator.type = 'square'; |
| oscillator.connect(context.destination); |
| oscillator.start(); |
| oscillator.stop(context.currentTime + duration); |
| } |
| |
| function playLoud() { |
| // Play a large amplitude sine wave. |
| var oscillator = context.createOscillator(); |
| oscillator.frequency.value = frequency; |
| oscillator.type = 'sine'; |
| oscillator.connect(gainNode); |
| oscillator.start(); |
| oscillator.stop(context.currentTime + duration); |
| } |
| |
| function setText() { |
| // Set the text correctly with the actual sine amplitude. |
| document.getElementById("amplitude").textContent = gainNode.gain.value; |
| } |
| |
| window.onload = setText; |
| </script> |
| </head> |
| <body> |
| <p> |
| This tests that output audio is clamped to 0db maximum. Press each button below in turn. The |
| apparent volume for both should be about equal, even though the second button plays with much |
| higher gain than the first. The resulting waveforms are not equal, however, as the second |
| button audio is clipped to a square wave shape. |
| </p> |
| <p> |
| The first button plays a square wave with nominal amplitude of 1. That actual amplitude is |
| slightly less than this because the square wave is band-limited which causes ringing, so the |
| amplitude is reduced slightly to prevent overflows due to the ringing. |
| </p> |
| <p> |
| The second button plays a very loud sine wave of amplitude <span id="amplitude"></span>. This |
| is clipped to unit amplitude so it is approximately equal to a square wave. There will be |
| some buzzing due to the clipping. |
| </p> |
| <p> |
| <strong>WARNING</strong>: Full amplitude signals may be loud. |
| </p> |
| <button onclick="playNormal()" title="Normal square wave with nominal amplitude of 1"> |
| Normal square wave |
| </button> |
| <button onclick="playLoud()" title="Loud sine wave that will be clipped to a square wave"> |
| Loud sine wave (clipped) |
| </button> |
| </body> |
| </html> |
