![]() Below, we'll modify our onAudioLoaded() method to use an append window and a timestamp offset to remove this silence.In our previous post, where we discuss the basics of the HTML audio element, we mentioned that each individual web browser presents its own version of an audio player and that it will look different in every browser. Luckily, this is easily done with MediaSource. To achieve gapless playback, we need to remove these sections of silence. The sections of silence at the beginning and end of each file are what cause the glitches between segments in the previous demo. The amount of padding varies by encoder and content, but we know the exact values based on metadata included within each file. If we peek ahead at the sintel_1.mp3 track we'll see another 576 samples of padding exists at the front. In addition to the padding at the end, each file also had padding added to the beginning. ![]() In this case LAME added exactly 576 padding samples to the end of the file. Almost every encoder introduces some type of padding. What's with all that those zero (silent) samples!? They're actually due to compression artifacts introduced during encoding. Each pixel on the red line is a floating point sample in the range of. Below, is a graph of the last 3000 samples averaged across both channels from the sintel_0.mp3 track. We'll come back to the code in a moment, but let's now look more closely at the file we've just appended, specifically at the end of it. In the example above, we're creating an audio/mpeg one, which is able to parse and decode our MP3 segments there are several other types available. Once the MediaSource object is connected, it will perform some initialization and eventually fire a sourceopen event at which point we can create a SourceBuffer. addEventListener ( 'sourceopen', function ( ) ) Īudio. Below, we're assigning an Object URL, representing our MediaSource instance, to the source attribute of an audio element just like you would set a standard URL. Media Source Extensions, as the name implies, are just extensions to the existing media elements. # Basic Setupįirst, let's backtrack and cover the basic setup of a MediaSource instance. Where each file has been encoded separately without regard for the audio segments before or after it. For the purposes of this demo, we'll focus on the type of files a normal user might have lying around. There are a variety of ways to create gapless content. On Chrome 38+ this will playback seamlessly! The green lines in the next demo indicate where the files have been joined and the gaps removed. ![]() With a little more work, using the exact same MP3 files in the above demo, we can use MSE to remove those annoying gaps. Yuck! That's not a great experience we can do better. The red lines indicate gaps introduced during the creation (encoding) of each MP3 you'll hear glitches at these points. Below is the first thirty seconds of the excellent Sintelchopped into five separate MP3 files and reassembled using MSE. We'll get into the details of why below, but for now let's start with a demonstration. Unfortunately, due to the way modern audio codecs like MP3 and AAC work, this seamless aural experience is often lost today. Artists create these gapless playback experiences both as an artistic choice as well as an artifact of vinyl records and CDs where audio was written as one continuous stream. You've likely listened to a music album where songs flowed seamlessly across tracks you may even be listening to one right now. While originally developed to facilitate Dynamic Adaptive Streaming over HTTP (DASH) based video players, below we'll see how they can be used for audio specifically for gapless playback. ![]() Media Source Extensions (MSE) provide extended buffering and playback control for the HTML5 and elements.
0 Comments
Leave a Reply. |