On 2020-08-19 10:53, Paul B Mahol wrote:
On 8/19/20, Jim DeLaHunt <list+ffmpeg-u...@jdlh.com> wrote:
On 2020-08-19 07:34, Paul B Mahol wrote:
You are deeply confused about our filters.
Any filter can change pixel formats to one that they accepts thus gbrp
is picked instead of packed rgb, this is already documented
implicitly.
Wow, "documented implicitly". This is such a classic FFmpeg project
statement. The role of documentation is to explain, explicitly, at a
suitable level of detail. What does "documented implicitly" even mean?
I think this thread points out is that FFmpeg documentation is
inadequate. It is hard to prove a negative, but I suspect that the term
"pixel format" is not actually defined in the FFmpeg documentation. I
suspect that the statement, "Any filter can change pixel formats" is not
stated either. Certainly the maskedmerge filter documentation[1] doesn't
mention pixel formats at all, much less say what pixel formats the
filter sets for its output.
…And yet "You are deeply confused about our filters". In other words, the
documentation has failed to explain to you what FFmpeg does, the project
has failed to write or welcome improved documentation, you do not
understand how FFmpeg works — and somehow this is your fault.
http://ffmpeg.org/ffmpeg-filters.html#toc-Filtergraph-syntax-1
mention it explicitly:
Libavfilter will automatically insert scale filters where format
conversion is required. It is possible to specify swscale flags for
those automatically inserted scalers by prepending sws_flags=flags; to
the filtergraph description.
This continues to be a great example of the FFmpeg project's approach to
documentation.
1. A sentence about a library adding functional processing steps ("scale
filters") in buried in a section entitled "syntax", amid paragraphs
about syntax.
2. the "scale filters" name alludes to changing pixel counts, and the
linked-to filter documentation[2] talks about "(resize) the input video"
and about "the input image format" (without defining that term); it does
not have a parameter for pixel formats or document the pixel formats it
uses or sets or changes.
3. this reference to "scale filters" is supposed to be responsive to a
thread about pixel formats.
4. no acknowledgement that the documentation might actually be less than
perfect. Is it so hard to concede, "you have a point, the docs could be
better here"?
[1] http://ffmpeg.org/ffmpeg-all.html#maskedmerge
[2] http://ffmpeg.org/ffmpeg-filters.html#scale
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