On 2016-06-08 21:54, Mark Thompson wrote:
On 08/06/16 13:59, Carl Eugen Hoyos wrote:
Mark Thompson <sw <at> jkqxz.net> writes:
Uses the global -hwaccel_lax_profile_check option (may be
misnamed for this purpose, but it has the right spirit).
Iirc, all old x264 files have a very high profile set (5.0?).
Is there a usecase for the default not being to accept any
profile?
(You mean level rather than profile there, right?)
The point here is that the driver has declared its capabilities, and
the given
stream is not within those capabilities so the hwaccel should not be
used
because it will not work (the software decoder should be used instead,
which
will supports a wider set of streams). However, in reality we have
known cases
where the driver is broken and incorrectly reports this information,
and can in
fact decode some streams which it has stated it is unable to.
Now, obviously fixing the driver to correctly report capabilities would
be the
way to actually fix the problem, but we don't control that. This
option allows
the user to ignore the declared capabilities of the driver and attempt
decode
anyway - it may then fail, but the user did explicitly request it so if
it
doesn't work then it is their problem. Setting it by default would
result in
some streams which previously worked now unexpectedly failing, which
would be
worse than the current situation.
I hope that was clearer.
Is there a specific example you're thinking of? As with Carl, the only
thing I'm
aware of is the handling of h.264 levels. The nvidia driver doesn't
declare support
for anything higher than 4.1, although the hardware will successfully
decode files
that are not 4.1 conformant, and in fact, there is an inherent
contradiction as
the driver does declare support for 4K resolutions, which requires level
4.2/4.3
for practical bitrates and framerates.
In this specific case, I think level enforcement is unhelpful and it's
common to
see media players setting the flag to ignore level enforcement. So I'd
probably
be in favour of reversing the default on level enforcement.
Do you have real world examples that are genuinely out-of-spec for the
hardware,
and would have been correctly excluded by the level check?
--phil
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