[FFmpeg-user] Illustration review, Streams and GOP Frame Reordering [was: a couple of things to look at]

Jim DeLaHunt list+ffmpeg-user at jdlh.com
Mon Mar 4 03:02:18 EET 2024

On 2024-03-03 16:11, Mark Filipak wrote:
> On 03/03/2024 18.33, Jim DeLaHunt wrote:
>> Regarding the Streams illustration 
>> <https://markfilipak.github.io/Video-Object-Notation/Streams.html>:
>> The macroblock to slice to picdata transition is clear. Showing 45 
>> macroblocks in a horizontal slice works.  Good work.
>> ... It is hard to count out 45 from single-digit numbers. 00..44 
>> would be much clearer.
> I agree, and I would have "0..44" if I could. If I used 2-digit 
> numbers, I'd have to almost double the table width. The issue is that 
> FireFox doesn't support 'font-size' style, so making the font smaller 
> to fit can't be done.
Hence, elide some of the table, and use ellipses.
>> The complete list of 0..29 slices is visually overwhelming, and not 
>> necessary.  I think you could keep slices 0..2, elide slices 3..27 
>> with a vertical ellipsis, and keep slices 28..29.  That would get the 
>> slice structure across.
> I'm going for visual impact, too. Do you find what I have confusing?
Confusing, yes, and overwhelming, and not necessary.
>> The slice structure lacks a comment with size, of the sort you 
>> included for macroblock and picdata. The full slice structure does 
>> not leave any room for such a comment.
> Well, I felt that with all 30 slices and all 1350 macroblocks 
> explicitly shown, comments were superfluous. They will get looked at 
> one time, then ignored for the rest of time.
The diagram implied, but did not say, that one slice contains the full 
pixel width of the frame. I had to count to 45 macroblocks in a slice 
(difficult, because part of the macroblock index was left out), and 
multiply by 16, to get to 720. A comment could just explicitly state 
this information. That would have been clearer to me.

    —Jim DeLaHunt

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