[FFmpeg-user] FFmpeg & hashing algorithm speed

Carl Eugen Hoyos ceffmpeg at gmail.com
Thu Nov 7 01:09:12 EET 2019

Am Mi., 6. Nov. 2019 um 23:40 Uhr schrieb Peter B. <pb at das-werkstatt.com>:

> Hashing for fixity and transfer-checking seems to be quite a bottleneck
> for archiving big video/film files for archiving.
> Therefore I was considering if using "simpler" algorithms (like CRC
> instead of SHA256) could speed up the process.

> I was surprised that e.g. MD5 vs CRC in Python as well as PHP
> seemed to be equally "fast".

But this is not related to FFmpeg, no?

> So I was wondering:
> Does FFmpeg have/do any speed optimization for hashing functionality
> (framemd5, hash muxer, etc) in its code?

Some of Giorgio's commits were meant to increase hash function
There is an email with a script to compare the implementation's speeds,
I don't know when it was sent to the development mailing list though.

> I've noticed, for example that "-f hash" for MD5 uses only half, SHA256
> just a quarter of my CPU.

Command line and complete, uncut console output missing.

Carl Eugen

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