On 12/06/2020 12:59, Timo Rothenpieler wrote:
On 12.06.2020 00:31, Gavin Smith wrote:
On 11/06/2020 22:03, Timo Rothenpieler wrote:
On 11.06.2020 22:27, Gavin Smith wrote:
This is to address trac ticket #8724. The filter did not preserve
alpha transparency. Items that were transparent in the input would
appear black on the output or pixels that were semi-tranparent
would appear opaque.
What is the performance impact for inputs without an alpha channel?
Firstly, I'm new to this world of filters. Now my patch only applies
to chromakey and not chromahold. On that note, is it not the case
that the chromakey mandates that all its inputs surfaces contain
alpha (as per query_formats function)? Would any AVPixelFormat that
does not match query_formats get converted to a format containing
alpha transparency?
But it still adds new code, and given it's in the very hot path of the
filter, it can easily add a performance penalty.
Sure. I understand. I'll see what numbers I can get. Having a quick
cursory look over the code, I wonder if my code actually might be
slightly more performant because it checks the case if a0 != 0. However,
this jmp/cmp may negatively impact performance.
Generally looks fine to me, but might need hidden behind an option,
as to not break existing setups that rely on this filter
discarding/ignoring the input alpha channel.
Yes. No problem. "preserve_transparency" and default to the
equivalent of 'false'?
That seems a bit clunky. Maybe something like "use_alpha"?
Sure.
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