Can't play a loop without gaps...

[massimag]

I need to control the volumes of various audio loops being played, and am trying to do this with webaudio. The web application must work on both Android and IOS:
The files have been edited on a DAW in order to be perfect loops. However, during webaudio playback there is always a gap between the end and the beginning. The gap appears variable and device dependent. If multiple files are played, the gaps often interrupt the whole mix (so even the files that are far from their ends).
At the moment I got the best behavior using AudioBuffer (see minimal code below). Using ogg instead of mp3 the situation improves (although not entirely). However webaudio does not seem to play ogg files on iOS. :-(
I can't find a solution. Is there a webaudio code example that plays loops without any glitches on both Android and iOS?

<script>

var source;
var audioBuffer;
var audioCtx
createAudio = async() =>{
audioCtx = new AudioContext();
source = audioCtx.createBufferSource();
const arrayBuffer = await fetch(
"test.mp3",
).then((res) => res.arrayBuffer());
audioBuffer = await audioCtx.decodeAudioData(arrayBuffer);
}

function startAudio(){
source.buffer = audioBuffer;
source.loop = true;
source.connect(audioCtx.destination);
source.start();
}

</script> TEST

[tgrajewski]

MP3 files are not generally gapless, they contain some padding samples (there are some workarounds). The AAC files might work better and if possible try Opus, which is truly gapless.

[padenot]

Those are browser bugs, please report the bugs to the browser vendors. mp3 files can be gapless, aac files can also be gapless, what matters is how the browser uses the codec implementation, and more importantly, if it skips the encoder delay and the padding appropriately.

[padenot]

The bug is in the browser (or the decoding side, in general).

I've filed w3c/webcodecs#626 for Web Codecs, it can work in some cases, but there is no general solution to make it work with all codecs.

[padenot]

We're certainly not in control of the codec implementation, some codecs are patented and some implementations have to use the OS library.

More over, the encoder delay can vary, it can depend on the implementation. ffmpeg AAC encoder has usually 1024 frames of encoder delay, while Apple encoder has usually 2112 frames of encoder delay.

We need to have Web Codecs output the exact number each time for this reason, we're adding this to Web Codecs.

[massimag]

Thanks for all replies.

In the end my solution was to use very long samples, and do a fade at the beginning and at the end. Obviously the fade is perceived, but not often, and the final experience was acceptable for the user.

Please note this: webaudio does not seem to play ogg files on iOS (or, at least, I had no success).

[padenot]

This is expected, iOS (and by extension Safari and other browsers on iOS) don't support Vorbis, which is the codec most often included in OGG containers.