4 ms·

>What's the benefit to shipping any empty KBs with every song purchased or streamed? For (quicker) in-place metadata updates? You just said it. You can do so w

>What's the benefit to shipping any empty KBs with every song purchased or streamed? For (quicker) in-place metadata updates? You just said it. You can do so with the purchased music in iTunes. Not sure about the streaming services, but the article isn't about it at all (nor did it talk about if they actually have these 500 KB padding to begin with).

CharlesW 5y ago
> For (quicker) in-place metadata updates? I just tested this, and it takes about ~140ms for ffmpeg to faststart/remux one song-length .m4a file (M1 Air, internal storage).
- giantrobot 5y ago
  Here's my slightly educated guess (I worked at Apple and for a time iTunes adjacent) the empty space is for file watermarking on edge servers. All iTunes (Apple Music) content is served via CDN. By leaving some empty space in the file the edge server can just write the owner's account ID fingerprint without having to remux the whole file. Apple can just send a virgin copy of a song to the edge servers and they can do the customization inline with serving it. That will be computationally cheaper than remuxing it and require no extra storage since the file is tweaked in flight. Leaving a lot of space provides enough room for some worst case size of watermark data without producing invalid files. But that's only my guess. I haven't looked at any files in question.
  - iggldiggl 5y ago
    Good point about the watermarking, although 500 kB still seems rather generous for that: As far as I'm aware, the "watermark" only encompasses a few IDs plus name and e-mail of your Apple ID (compare https://github.com/avibrazil/un-istore https://github.com/avibrazil/un-istore).
- thrdbndndn 5y ago
  You may feel it's very small delay, but if you batch edit your songs often (which I do) it's actually pretty noticeable. Try to select 10 tracks and update the album name and feel the difference. Most of time wasted on remuxing the file comes from re-writing the whole thing on your hard disk, which is more noticable if you save your songs on HDD. Is it really that bad? No. But it's nice to have some padding. Same goes to MP3s and especially FLACs (which is even more noticeable because file size is much larger). Some of the digital distributors for hi-res (hi resolution) music do use "flatten" files, and it's quite annoying to edit them.

CharlesW 5y ago

> For (quicker) in-place metadata updates? I just tested this, and it takes about ~140ms for ffmpeg to faststart/remux one song-length .m4a file (M1 Air, internal storage).

giantrobot 5y ago
Here's my slightly educated guess (I worked at Apple and for a time iTunes adjacent) the empty space is for file watermarking on edge servers. All iTunes (Apple Music) content is served via CDN. By leaving some empty space in the file the edge server can just write the owner's account ID fingerprint without having to remux the whole file. Apple can just send a virgin copy of a song to the edge servers and they can do the customization inline with serving it. That will be computationally cheaper than remuxing it and require no extra storage since the file is tweaked in flight. Leaving a lot of space provides enough room for some worst case size of watermark data without producing invalid files. But that's only my guess. I haven't looked at any files in question.
- iggldiggl 5y ago
  Good point about the watermarking, although 500 kB still seems rather generous for that: As far as I'm aware, the "watermark" only encompasses a few IDs plus name and e-mail of your Apple ID (compare https://github.com/avibrazil/un-istore https://github.com/avibrazil/un-istore).
thrdbndndn 5y ago
You may feel it's very small delay, but if you batch edit your songs often (which I do) it's actually pretty noticeable. Try to select 10 tracks and update the album name and feel the difference. Most of time wasted on remuxing the file comes from re-writing the whole thing on your hard disk, which is more noticable if you save your songs on HDD. Is it really that bad? No. But it's nice to have some padding. Same goes to MP3s and especially FLACs (which is even more noticeable because file size is much larger). Some of the digital distributors for hi-res (hi resolution) music do use "flatten" files, and it's quite annoying to edit them.