You Download

While some kinds of app can survive on their own, media players are useless without media. Some Chronotron users work with their own tunes, but many of you rely on instructional videos or similar material from the Internet, to learn how to play an instrument. This is why Chronotron has a built-in YouTube downloader.

The Chronotron built-in downloader allows you to save just one clip at the time, but that’s OK because downloading videos isn’t the app’s main purpose – there are plenty of apps for that. However, despite being pretty basic, there’s a couple of things you should know to get the most out of it.

The two configuration options that influence download behavior are YouTube download folder, under the Location section of the Settings pane, and Maximum video download resolution, under the Performance section. It’s the latter that deserves a bit more explanation.

YouTube clips come in two flavors: those stored as a single file, and those comprising of one audio file plus multiple video files, one per supported resolution. Without going into the technical details, this is related to the way adaptive streaming is implemented.

When Chronotron downloads a clip of the multiple-file flavor, it must select the correct resolution video stream and download it together with the audio stream. Even though the two streams are downloaded simultaneously, the server usually limits – throttles – the speed at which the streams can be read, so downloading this type of clip is relatively slow. After download, the two streams are merged into the final file that gets saved to your media library. This operation is known as multiplexing, or muxing for short.

It turns out that most HD videos (720p or higher) in YouTube are encoded for adaptive streaming, that is, using the multiple-file flavor, while most SD videos (360p or lower) are encoded as single files. This is why setting the maximum download resolution to 360p in Chronotron increases the download speed dramatically, if you don’t mind your music teacher being a little blurry.

As a final word, it’s worth noting that downloading a clip isn’t a supported YouTube scenario since it harms the advertising business (the clips saved to your hard disk lack any ads). Therefore, there’s no official API for downloading. Downloaders work by simulating what a legitimate player does to find out where the actual clips are stored on Google servers. So, downloader apps fail whenever the YouTube web page structure changes in a way unforeseen by the app developer. In the Chronotron change log you can see it happens every now and then.

Hopefully the download scenario will be supported one day in a way that could still benefit the users, the hosting company and the advertisers – I wouldn’t be against embedding the ads in the clip themselves, for example.

Unless or until that happens, be aware that downloading clips from YouTube will only work for as long as they’re looking somewhere else.

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