[FFmpeg-devel] [PATCH] af_hdcd.c: only hdcd_update_info() when something changes, add error detection

[Burt P.]

Only call hdcd_update_info() when the control code changes
instead of every frame, so the counters are more meaningful.

Also, adds some basic error detection. After scanning through
about 30 HDCD-encoded CD's I've found errors where a code
is signaled, but then fails to match one of the patterns, so
it is ignored. Often, it is very close to a code, differing
by only one bit. I don't know enough to say whether it is
using some unknown feature of HDCD that this filter doesn't
know about, or if there was just an error in the encoding.
I've added some comments so that it should be easier for
others to examine.

An example with many errors is Līve - Secret Samadhi, if
anyone wants to look into it.

Patch is attached.
Any comments would be appreciated.
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