Logic is loosely on equivalent decisions in libplacebo. The basic idea is to try
and be a bit conservative by treating AVCOL_*_UNSPECIFIED as a no-op, unless the
other primaries set are non-standard / wide-gamut or HDR. This helps avoid
unintended or unexpected colorspace conversions, while forcing it in cases where
we are almost certain it is needed. The major departure from libplacebo semantics
is that we no default to a 1000:1 contrast ration for SDR displays, instead modelling
them as idealized devices with an infinite contrast ratio.
In either case, setting SWS_STRICT overrides this behavior in favor of always
requiring explicit colorspace metadata.
Only add the condensed values that we actually care about. Group them into
a new struct to make it easier to discard or replace this metadata.
Define a special comparison function that does not choke on undefined/unknown
metadata.
Replacing the old sws_isSupported* API with a more consistent family
of functions that follows the same signature and naming convention,
including a placeholder for testing the color space parameters that
we don't currently implement conversions for.
These functions also perform some extra basic sanity checking.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
Groups together all relevant color metadata from an AVFrame. While we could
use AVFrame directly, keeping it a separate struct has three advantages:
1. Functions accepting an SwsFormat will definitely not care about the
data pointers.
2. It clearly separates sanitized and raw metadata, since the function to
construct an SwsFormat from an AVFrame will also sanitize.
3. It's slightly more lightweight to pass around.
Move these into a new header file "utils.h" to avoid crowding
swscale_internal.h even more, and also to solve a circular dependency issue
down the line.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
