Creating the Best Visually Lossless JPGs and WEBPs

[The Enigma]

In ffmpeg, if I use -vf format=rgb24, will I always get the correct colors for any image format, including jpg and webp? What should I set -qscale:v (-q:v) to so I can get the best quality, 2 or 1? Will adding -qmin 1 and -qmax 1 also improve the quality?

[vongooB9]

No, as you can see in the documentation of mjpeg and libwebp, which are the default encoders used by ffmpeg for jpg and webp, neither supports the rgb24 pixel format.

ffmpeg -help encoder=mjpeg

Encoder mjpeg [MJPEG (Motion JPEG)]:
    General capabilities: threads
    Threading capabilities: frame and slice
    Supported pixel formats: yuvj420p yuvj422p yuvj444p yuv420p yuv422p yuv444p
...

ffmpeg -help encoder=libwebp

Encoder libwebp [libwebp WebP image]:
    General capabilities: dr1
    Threading capabilities: none
    Supported pixel formats: bgra yuv420p yuva420p
...

"-qscale:v (-q:v)" works with mjpeg but not for libwebp.

libwebp encoder AVOptions:
  -lossless          <int>        E..V....... Use lossless mode (from 0 to 1) (default 0)
  -preset            <int>        E..V....... Configuration preset (from -1 to 5) (default none)
     none            -1           E..V....... do not use a preset
     default         0            E..V....... default preset
     picture         1            E..V....... digital picture, like portrait, inner shot
     photo           2            E..V....... outdoor photograph, with natural lighting
     drawing         3            E..V....... hand or line drawing, with high-contrast details
     icon            4            E..V....... small-sized colorful images
     text            5            E..V....... text-like
  -cr_threshold      <int>        E..V....... Conditional replenishment threshold (from 0 to INT_MAX) (default 0)
  -cr_size           <int>        E..V....... Conditional replenishment block size (from 0 to 256) (default 16)
  -quality           <float>      E..V....... Quality (from 0 to 100) (default 75)

To configure the quality of libwebp use the parameter "-quality 0-100" or "-lossless".

[_Al_]

That bgra format for libwebp is perhaps 8bit rgb, like rgb24 is, not planar as rgb24 is, but I guess that does not matter. I read, most likely here (poisondeathray inputs) that it could be done losslessly. It was discussed here, try to google "videohelp forum rgb lossless webp"

[DB83]

Do these topics/posts remind anyone of a recently banned 'Troll' who kept starting topics about 'lossless' pic formats despite already having all the answers presented to him.

[Cornucopia]

Yup, pretty sure it's the same character.


Scott