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kleisauke / wasm-vips

libvips for the browser and Node.js, compiled to WebAssembly with Emscripten.
https://kleisauke.github.io/wasm-vips/
MIT License
518 stars 26 forks source link

Accurate progress tracking #78

Closed miloxeon closed 1 month ago

miloxeon commented 1 month ago

Hi again!

In this playground demo, progress tracked using onProgress goes to 100% very quickly, but the lag after that takes way longer, making the tracking near useless. How do I track progress accurately?

kleisauke commented 1 month ago

AVIF compression is relatively slow and more memory-intensive compared with most other formats. The performance can also vary depending on the input image, see for example: https://github.com/libvips/libvips/issues/2983

Additionally, libvips only emits the "eval" signal (on which the image.onProgress callback depends) once per work unit during image computation. Since AVIF does not support streaming/chunk-wise encoding, libvips must assemble the entire image in memory before passing it to the AVIF encoder. Consequently, there's no progress feedback during this final compression stage, as libvips considers the computation complete once it reaches this point.

Note that you can control the CPU effort spent on improving AVIF output by passing the effort argument: https://github.com/kleisauke/wasm-vips/blob/4702f7df3feeed3efcc07e904de2557a330fce18/lib/vips.d.ts#L7178-L7181

It defaults to 4; lowering it to 0 will significantly speed up encoding (but will result in larger file sizes).

miloxeon commented 1 month ago

wow, it indeed speeds things up. Didn't know about the AVIF situation. Thanks!