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Weekly notes 3 — Intense amen choppage
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Mozilla

This week as well I didn’t write too much code, but did some investigation nonetheless. Monday was a bank holiday, that was pretty cool.

Gecko

I landed a few things that are not interesting, and then got pinged by Steven Yi on the amazing Web Audio API slack, that said that Firefox doesn’t decode AAC properly. It doesn’t trim the encoder delay (often 1024 or 2112 sample-frames), and also doesn’t trim the padding (whatever number of frame is needed to align the last packet to 1024 frames), so I’m fixing that. I fixed the same bug, but for mp3 not too long ago, although I still need to do a follow-up because I found a couple files where my approach falls apart (in a weird edge case where you have the padding spanning two packets — that makes no sense to me).

I’m really rusty when it comes to the playback code of Firefox, but it’s getting better.

I had been using the venerable Mp4 Explorer tool, but I just got pointed to https://gpac.github.io/mp4box.js/test/filereader.html, which is essentially the same, but on the Web, so I can run it on my Linux box. That said, Mp4 Explorer runs very well using Wine and the Windows-version of the .Net runtime (an .msi installer), when you install it in the Wine environment.

Specifications

That’s where most of the time in the week went, mostly reviewing the image decoder proposal for Web Codecs, and a bunch of other PRs on audio/video. We are continuing to chat with people that are the target users for this API, and finding new stuff.

Nothing on the Web Audio API, as expected. We’re working on V2 issues though.

Personal

I did a comparison study on all the different ways to resample and chop a classic break (of course I started with the amen) in Ableton Live. There is quite a few ways to do it, but only a small numbers of those technique allow getting it to sound like it would on, say, an Akai S950. I have a MUM M8 in my modular system, that is based on the S950 filter, so I should be able to get pretty convincing result at the end, with a workflow a bit more modern than working on one of those hardware samplers.

I then proceeded to do a ridiculous demo tune where lots of clichés of UK hardcore/happy hardcore are represented:

Oi oi.

© 2022 — Paul Adenot