lavu: fix memory leaks by using a mutex instead of atomics

The buffer pool has to atomically add and remove entries from the linked
list of available buffers. This was done by removing the entire list
with a CAS operation, working on it, and then setting it back again
(using a retry-loop in case another thread was doing the same thing).

This could effectively cause memory leaks: while a thread was working on
the buffer list, other threads would allocate new buffers, increasing
the pool's total size. There was no real leak, but since these extra
buffers were not needed, but not free'd either (except when the buffer
pool was destroyed), this had the same effects as a real leak. For some
reason, growth was exponential, and could easily kill the process due
to OOM in real-world uses.

Fix this by using a mutex to protect the list operations. The fancy
way atomics remove the whole list to work on it is not needed anymore,
which also avoids the situation which was causing the leak.

Signed-off-by: Anton Khirnov <anton@khirnov.net>
vf_interlace: get rid of useless loads

Signed-off-by: Anton Khirnov <anton@khirnov.net>
opusdec: make sure all substreams have the same number of coded samples

Fixes invalid writes with invalid multichannel streams.

CC:libav-stable@libav.org
lavf/ffmdec: add common options to recommended encoder configuration

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>
lavf/ffmenc: store recommended encoder configuration

ffmenc will store recommended encoder configuration if present.
This will allow the user to base on local defaults and
apply only explicitly set options.

If recommended encoder configuration is not present, then
non-default context's options are stored.

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>
ffmpeg_opt: make use of recommended encoder configuration

So far ffmpeg used recommended configuration only for codec priv options.
ffmpeg will use now codec defaults and then apply recommended configuration
for all options. Recommended configuration possibly contains minimal
set of options to filful user configuration.

Signed-off-by: Lukasz Marek <lukasz.m.luki2@gmail.com>
lavu/opt: add consts where possible
Merge commit 'fbd6c97f9ca858140df16dd07200ea0d4bdc1a83'

* commit 'fbd6c97f9ca858140df16dd07200ea0d4bdc1a83':
  lavu: fix memory leaks by using a mutex instead of atomics

Conflicts:
	libavutil/buffer.c

The atomics code is left in place as a fallback for synchronization in the
absence of p/w32 threads. Our ABI did not requires applications to
only use threads (and matching ones) to what libavutil was build with
Our code also was not affected by the leak this change fixes, though
no question the atomics based implementation is not pretty at all.
First and foremost the code must work, being pretty comes after that.

If this causes problems, for example when libavutil is used by multiple
applications each using a different kind of threading system then the
default possibly has to be changed to the uglier atomics.

See: cea3a63ba3d89d8403eef008f7a7c54d645cff70
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '96fda42a8f9bf84beaaf7f5991d17f2a057de86c'

* commit '96fda42a8f9bf84beaaf7f5991d17f2a057de86c':
  vf_interlace: get rid of useless loads

See: ca59b5b6eceb1adbf96b8248128e58bfbb79c9a6
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Merge commit '1973079417e8701b52ba810a72cb6c7c6f7f9a56'

* commit '1973079417e8701b52ba810a72cb6c7c6f7f9a56':
  opusdec: make sure all substreams have the same number of coded samples

Merged-by: Michael Niedermayer <michaelni@gmx.at>
Move extralibs variables using ldl after ldl definition

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/pngdec: split P frames handling to a separate function.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/pngdec: add support for 'over' blend operation for 'none' dispose operation.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/hevc_ps: Check num_long_term_ref_pics_sps

Fixes out of array access
Fixes: signal_sigsegv_35bd0f0_1182_cov_791726764_STRUCT_B_Samsung_4.bit
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>