Orc and conversion from I420 to BGRA/RGBA

[Peter Maersk-Moller]

Hi.

Noticing that conversion from I420 to BGRA and RGBA still uses different
amount of CPU with conversion to BGRA being the fastest (lowest CPU load).

Looking into gst-plugins-base-1.8.1/gst-libs/gst/video/video-converter.c I
have identified the Orc enabled function video_orc_convert_I420_BGRA() used
for converting to BGRA, but I can't seem to find the similar function for
RGBA. What function is used for conversion to RGBA?

Is there a quality difference in color quality between converting I420 to
BGRA respectively RGBA ? I seem to remember mentioned the "fast path
conversion" for I420 to some variant of RGB/BGR. Is fast path conversion
the video_orc_convert_I420_BGRA() ?

In case there is a color quality difference between fast path conversion
and non fast path conversion (slow/normal path conversion?), is it the
possibly to quantify this difference either specifically or loosly (like a
little degradation, a lot, about 10% or these color ranges gets wrong etc) ?

Looking into the Orc code for video_orc_convert_I420_BGRA(), I see this can
be modified to convert to RGBA with just copying the
video_orc_convert_I420_BGRA() function and then make it save in another
order for the color components. Wouldn't that be a low hanging fruit for
GStreamer since the conversion, as it is now, can be done in almost half
the time for BGRA compared to RGBA .... or is there a quality aspect I
don't now about, making the current conversion to RGBA preferred?

best regards
Peter Maersk-Moller
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