Add note on Zstd compression levels about memory usage#120639
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Calinou
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Jun 26, 2026
| </member> | ||
| <member name="compression/formats/zstd/compression_level" type="int" setter="" getter="" default="3"> | ||
| The default compression level for Zstandard. Affects compressed scenes and resources. Higher levels result in smaller files at the cost of compression speed. Decompression speed is mostly unaffected by the compression level. | ||
| [b]Note:[/b] Levels above [code]19[/code] require significantly more memory during compression and decompression. |
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Is there a ballpark estimate of "significantly"? Is it something like 2x on average, or more like 5x?
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This source claims level 19 has a window size of 8MB. That size increases to 32MB, 64MB and 128MB in levels 20, 21 and 22, respectively.
Which means level 20 will allocate 4x more memory than level 19. Level 22 allocates 16x.
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Zstandard levels above 19 use more memory, as stated in the
zstdcommand-line tool's--ultraflag, which unlocks their usage. Source.Delta Encoding already has a note about levels above 19, so I think it's fair the project settings have it too.