[FFmpeg-user] Alexa input dpx

Reto Kromer amia-l at reto.ch
Thu May 21 07:01:25 CEST 2015

Dave Rice wrote:

>AFAIK ffmpeg only supports linear sampling in dpx. I think
>support for logarithmic dpx would be very helpful. For now
>there's various workarounds with
>filters such as haldclut, see:

I agree with Dave, and I second the request. However:

AFAIK there are three flavours of "logarithmic" DPX:

  - "log neg encoding" ("Cineon printing density encoding")
  - "power-law encoding" (also called "gamma encoding» or
    "DIT-linear encoding")
  - "quasi-log encoding" ("log RGB encoding")

The most useful approach is in my opinion and for today's
use the quasi-log. Still AFAIK there are many proprietary
variants (e.g. ARRI log, Panalog, Sony-log, REDLOG) that are
badly documented - or not documented at all.

Hope this is correct - and helps! Reto

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