[x265] Unclear VUI options

[dave]

First, I have to say that I am new to development of h265 and never 
worked with h264 so this is all new to me.

On 02/20/2014 11:31 PM, Mario *LigH* Rohkrämer wrote:
> The possibly unintended indentation of this line (due to a later 
> inserted [no-], I believe) made me wonder what the desired format of 
> this parameter is:
>
> --[no-]range — Specify black level and range of luma and chroma 
> signals. Default of disabled
>
> I use to know terms like "TV range" (Luma: 16-235; Chroma: 16-240) and 
> "PC range" (both 0-255). This parameter looks as if to be used like a 
> boolean value, which is not really plausible to me.
My description is based on the h265 spec description of 
video_full_range_flag which as the name suggests, is a boolean value.  
There is nothing in the spec about TV or PC but if that is more accurate 
of what range represents then I have no problems changing it.  x264 also 
provides an auto option that lets x264 decide the range based on the 
video to be encoded, which is what I thought when I first read the 
description of video_full_range_flag in the spec.  Not until I saw the 
range cli option in x264 did I add it to x265.

Since the VUI, according to the h265 spec, is optional and is supposed 
to help decoders I didn't think anything about it affected encoding but 
x264 seems to be using range quite a bit though I haven't had time to 
explore it in depth.  Right now, in x265 range is taken from the command 
line and inserted into the VUI and nothing else.

Based on my limited knowledge of range, this looks like something that 
should be set by the input video.  x264 even generates an error message 
if the cli option conflicts with the input video so why bother?
>
>
> Furthermore, a few additions from your "German Grammar Nazi":
>
> Some parameter descriptions use "Default", others "Default of". And 
> "Usability" has no "e".
>