The process of making my paging MIDI player has ground to a halt IMMEDIATELY:

Format 1 MIDIs.

There are 3 MIDI types: Format 0, 1, and 2.

Format 0 is two chunks long. One track chunk and the header chunk. Can be played with literally one chunk_load() call in my player.

Format 2 is (n+1) chunks long, with n being defined in the header chunk (which makes up the +1.) Can be played with one chunk_load() call per chunk in my player.

Format 1... is (n+1) chunks long, same as Format 2, but instead of being played one chunk at a time in sequence, it requires you play all chunks

AT THE SAME FUCKING TIME.

65534 maximum chunks (first track chunk is global tempo events and has no notes), maximum notes per chunk of ((FFFFFFFFh byte max chunk data area length)/3 = 1,431,655,763d)/2 (as Note On and Note Off have to be done for every note for it to be a valid note, and each eats 3 bytes) = 715,827,881 notes (truncated from 715,827,881.5), 715,827,881 * 65534 (max number of tracks with notes) = a grand total of 46,911,064,353,454 absolute maximum notes. At 6 bytes per (valid) note, disregarding track headers and footers, that's 281,466,386,120,724 bytes of memory at absolute minimum, or 255.992 TERABYTES of note data alone.

All potentially having to be played

ALL

AT

ONCE.

This wouldn't be so bad I thought at the start... I wasn't planning on supporting them.

Except...

>= 90% of MIDIs are Format 1.

Yup. The one format seemingly deliberately built not to be paged of the three is BY FAR the most common, even in cases where Format 0 would be a better fit.

Guess this is why no other player pages out MIDIs: the files are most commonly built specifically to disallow it.

Format 1 and 2 differ in the following way: Format 1's chunks all have to hit the piano keys, so to speak, all at once. Format 2's chunks hit one-by-one, even though it can have the same staggering number of notes as Format 1. One is built for short, detailed MIDIs, one for long, sparse ones.

No one seems to be making long ones.

Never ever mount a btrfs sparse file (-o compression-force) to /var/lib/docker.

- 70% space usage 😀
+ 300% random system freeze 😰