[FFmpeg-user] Yes or No? About the processing pipeline.

[Mark Filipak]

On 19/06/2025 15.34, Reindl Harald wrote:
> Am 19.06.25 um 21:33 schrieb Mark Filipak:
>> If the input is 8-bit ybr420-smpte170m, then the head end of the processing pipeline is also 8-bit 
>> ybr420-smpte170m. Yes or No?
> what else should it be moron?

I'm not asking what it should be. I'm asking what it is. It could be whatever the decoder outputs or 
whatever FFmpeg makes it to be. I'm trying to determine that. It's not documented, I know nothing 
definitive about the decoder, and FFmpeg plainly does some things to the stream before applying any 
directives. So, I ask.

You see, my basic assumption is that codesmiths work hard to make processes uniform and as simple 
and straightforward as possible. So, my assumption is that FFmpeg after FFmpeg reports the input's 
characteristics, it converts the decoded pictures (or fields) into some sort of generalized 
processing form such as raw yuv444p16le for example. Such considerations come up all the time, such 
as whether or not HDR10 and HDR12 should be internally processed as HDR16.

(Now, to be clear, I know that the decoders in players retain pixel scope and colorspace. I don't 
know that about FFmpeg.)

When FFmpeg reports "Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'c:\FATAL ATTRACTION [1987].mp4'", for 
example, it can't be reporting the decoder's output. It must be the file's contents. So the question 
comes up: What is the decoder's output, and what, if anything, does FFmpeg do to the decoder's 
output prior to loading the head end of the processing pipeline?

I know that seems silly to you, but it's a valid question. It's a simple 'Yes' or 'No' question, or 
at least that's what I thought.

If the input is 8-bit ybr420-smpte170m, then the head end of the processing pipeline is also 8-bit 
ybr420-smpte170m. Yes or No?

(Yes, I know there's no such thing as ybr, but there's no such thing as yuv either, at least, not in 
the digital realm. There's Y'CbCr, but "ybr" comes a lot closer to "Y'CbCr" than does "yuv", that's 
for sure.)

Regards,
Mark.