This will allow to make the TIFF decoder's init function thread-safe.
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
The only thing that stands in the way of adding the
FF_CODEC_CAP_INIT_THREADSAFE flag to the SMV JPEG decoder is its usage
of ff_codec_open2_recursive(): This function requires its caller to hold
the lock for the mutex that guards initialization of AVCodecContexts
whose codecs have a non-threadsafe init function and only callers whose
codec does not have the FF_CODEC_CAP_INIT_THREADSAFE flag set hold said
lock (the others don't need to care about said lock). But one can set
the flag if one switches to avcodec_open2() at the same time.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
The only thing that stands in the way of adding the
FF_CODEC_CAP_INIT_THREADSAFE flag to the Cintel RAW decoder is its usage
of ff_codec_open2_recursive(): This function requires its caller to hold
the lock for the mutex that guards initialization of AVCodecContexts
whose codecs have a non-threadsafe init function and only callers whose
codec does not have the FF_CODEC_CAP_INIT_THREADSAFE flag set hold said
lock (the others don't need to care about said lock). But one can set
the flag if one switches to avcodec_open2() at the same time.
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Normally no two codecs with FF_CODEC_CAP_INIT_THREADSAFE unset
can be initialized at the same time: a mutex in avcodec_open2()
ensures this. This implies that one cannot simply open a codec
with a non-threadsafe init-function from the init function of
a codec whose own init function is not threadsafe either as the child
codec couldn't acquire the lock.
ff_codec_open2_recursive() exists to get around this limitation:
If the init function of the child codec to be initialized is not
thread-safe, the mutex is unlocked, the child is initialized and
the mutex is locked again. This of course has as a prerequisite that
the parent AVCodecContext actually holds the lock, i.e. that the
parent codec's init function is not thread-safe. If it is, then one
can (and has to) just use avcodec_open2() directly (if the child's
init function is not thread-safe, then avcodec_open2() will have to
acquire the mutex itself (and potentially wait for it), so that it is
perfectly fine for an otherwise thread-safe init function to open
a codec with a potentially non-thread-safe init function via
avcodec_open2()).
Yet several of the users of ff_codec_open2_recursive() have the
FF_CODEC_CAP_INIT_THREADSAFE flag set; this only worked because
all the child codecs' init functions were thread-safe themselves
so that ff_codec_open2_recursive() didn't touch the mutex at all.
But of course the real solution to this is to directly use
avcodec_open2().
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This affected all decoders that used ff_mjpeg_decode_init() as init
function; and it also affected decoders that open jpeg decoders via
ff_codec_open2_recursive() as well as MxPEG.
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
ff_slice_thread_init() uses a static variable to hold a function
pointer, although the value of said pointer needn't be saved between
different runs of this function at all.
The reason for this being so is probably that said pointer points to
a static function (if used); but storage class specifiers like "static"
are not part of the type of an object and so including it in the pointer
declaration is wrong (anyway, "static" means different things in both
contexts: for the function declaration it affects linkage, for the
variable storage duration).
Using a static variable here can lead to races, e.g. when initializing
VP9 (for which said function pointer was added) and H.264 with slice
threading. The latter has the FF_CODEC_CAP_INIT_THREADSAFE flag set and
is therefore unaffected by the lock guarding initializations of
decoders.
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Using MPEG-2 intra VLC tables is spec-incompliant for MPEG-1 and given
that an MPEG-1 bitstream can't signal whether MPEG-2 intra VLC tables
have been used the output is broken. Therefore this option is removed
immediately without any deprecation period.
Reviewed-by: James Almer <jamrial@gmail.com>
Reviewed-by: Marton Balint <cus@passwd.hu>
Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Andreas Rheinhardt
Paul B Mahol
Marton Balint
James Almer