Pyramids

To draw an hour of a 384-channel recording you can’t read every sample per frame. A min/max pyramid stores, for each block of samples, the minimum and the maximum, at several block sizes.

A plain average would hide a spike. A min/max pair keeps every peak visible at any zoom.

To draw a view, dsp-kitchen uses the coarsest level with at most one bucket per pixel column, with column edges aligned to the buckets. Every sample falls into exactly one column, so no peak is lost. When you zoom in past the finest level, it reads the raw samples.

Where a pyramid lives

Recording size	Pyramid	Finest bucket
Under 64 MiB	In memory, for this session	256 samples
64 MiB or more	A file, reused between runs	64 samples

The file sits in a cache/ folder next to the recording, at about 1/16 of the recording’s size as float32. So the folder must be writable the first time.

Pyramids are filled page by page, nearest to where you are looking first, so you can start working while the rest is still being built.

Servers use the same pyramids: a remote view asks the server for the envelope, not the samples.