[mythtv] FFmpeg Resync

[David Hampton]

On Tue, 2020-06-23 at 14:55 -0400, Peter Bennett wrote:
> I have resynced FFmpeg 4.3 to MythTV (master) and placed the result
> in 
> new branch "devel/ffpeg-resync".
> 
> The changes made to FFmpeg code in the MythTV repository since the
> last 
> sync to 4.2 have been discarded.
> 
> Mark - If your changes are necessary please
> 
> 1. Apply them to the MythTV/FFmpeg repository, master branch.
> 2. Cherry-pick them into the MythTV/FFmpeg repository, release/4.3
> branch.
> 3. Copy the code into the MythTV/mythtv repository, master branch
> 
> Note: The code in MythTV/mythtv repository master branch, FFmpeg 
> directory is a copy of the code in MythTV/FFmpeg repository,
> release/4.3 
> branch. so after making changes in MythTV/FFmpeg repository and 
> cherry-picking into release/4.3 you can just copy the modules over
> into 
> the MythTv/mythtv repository master branch without fear of losing
> any 
> changes.
> 
> Mark and David please note:
> 
> Bear in mind the FFmpeg code needs to be resynced from time to time. 
> Please do not make any cosmetic changes to FFmpeg or changes
> designed 
> only to remove compiler warnings.
> 
> If you need to make FFmpeg changes please follow the above procedure,
> so 
> that the changes are in the MythTV/FFmpeg repository and ready for
> the 
> next resync.
> 
> If you are adding any new functions please consider creating a new 
> source file for them.
> 
> It would be helpful to note with comments that a change has been
> made 
> for MythTV so that when conflicts occur in the resync it makes
> things 
> clearer.
> 
> In future, if there is new code, that you need, in FFmpeg that is
> not 
> yet MythTV, let me know and hopefully we could include it by 
> cherry-picking from the main FFmpeg, rather than copying the code
> and 
> causing a conflict later.
> 
> Here is a list of changes that have been lost in the resync (Only
> the 
> changes in the FFmpeg directory have been lost, if the commit
> includes 
> other changes in MythTV they will still be there):
> 
> git log mythtv/external/FFmpeg/
> * 3e1af48033 2020/06/16 David Hampton : Pass the correct stack-
> alignment 
> flag to the clang compiler.
> * 498502a5eb 2020/06/15 David Hampton : tidy: Quiet a couple of
> warnings 
> in FFmpeg.
> *   cc80f6788b 2020/02/11 David Hampton : Merge branch 'master' into 
> branch 'cleanups'.
> > \
> > * 165fc1ca4c 2020/02/06 Mark Kendall  : V4l2: Update FFmpeg v4l2
> > to 
> latest master
> * | 459fccb5aa 2020/02/11 David Hampton : tidy: Remove 
> __STDC_CONSTANT_MACROS and __STDC_LIMIT_MACROS
> > /
> * 669955c6cb 2020/01/30 Mark Kendall  : FFmpeg: Patch v4l2_buffers
> to 
> pass through interlaced fields
> * 2c6f8618e0 2020/01/22 Mark Kendall  : utils-mythtv: Add a couple
> of 
> missing codecs
> * a0fbaa1736 2019/12/11 David Hampton : FFmpeg: Remove obsolete 
> 'register' keyword.
> * 90f41b3860 2019/12/09 Mark Kendall  : FFmpeg: Squash unused
> parameter 
> warning
> * 253d4df440 2019/11/30 Mark Kendall  : FFmpeg: Update v4l2_m2m code
> to 
> latest FFmpeg master
> * fdc0645aba 2019/11/20 Mark Kendall  : V4L2 Codecs: Fix lockup when 
> seeking
> * 785c821f69 2019/11/14 Mark Kendall  : FFmpeg: Further updates to
> v4l2 
> code
> * 8fdb15fc96 2019/11/13 Mark Kendall  : FFmpeg: Update v4l2 codecs
> code 
> to FFmpeg master
> * bc905cfa79 2019/11/12 Mark Kendall  : configure: Try to fix libdrm 
> again...
> * 78dff9718b 2019/11/12 Mark Kendall  : configure: Cleanup setup for 
> drm, opengl, egl and v4l2
> * 783dc8ba7d 2019/11/10 Mark Kendall  : v4l2: Workaround missing DRM
> define
> * cc7572f9b2 2019/11/09 Mark Kendall  : FFmpeg: Patch FFmpeg for
> V4L2 
> codecs DRM PRIME support
> *   cadc149225 2019/11/06 Mark Kendall  : Merge branch 'master' into 
> devel/2019-render
> > \
> > * b99b0424ca 2019/11/05 Peter Bennett : FFmpeg: Sync to latest 4.2
> > source
> 

Peter,

> David: Note I had to add __STDC_CONSTANT_MACROS to libmythtv.pro to
> get the compile to work.

That flag once meant something, but it hasn't in the last decade or so
because the items that used to be dependent on that flag are now always
present. Requiring that flag to be present changes nothing about the
compilation. Since you reverted 459fccb5aa you added back the check for
a flag which is no longer supplied by MythTV, so you needed to add back
the declaration of the flag.

> David: I see a lot of warnings about "register" being obsolete. I
> hope there is some way of avoiding making a change to FFmpeg code for
> this.

I have a one line workaround that can go in the MythTV sources, but
there are still a large number of "unused parameter" warnings caused by
including get_bits.h that can't be fixed without changing the FFmpeg
sources.  If I change get_bits.h to fix the the unused parameter
warnings, I can fix the storage class specifier warnings at the same
time with the same one line addition (but in get_bits.h).

There's one other patch I'd like to keep that adds two comments (of
three lines each). This will allow me to enable automated nightly
checking for nullptr dereferences in MythTV, without producing a bunch
of warning messages that point at FFmpeg.

I would be happy to commit both these sets of change using the
procedure you outlined above. Its a total of nine lines of comments,
and three lines of other stuff.

David