core: add --deinterlace option, restore it with resume functionality

The --deinterlace option does on playback start what the "deinterlace"
property normally does at runtime. You could do this before by using the
--vf option or by messing with the vo_vdpau default options, but this
new option is supposed to be a "foolproof" way.

The main motivation for adding this is so that the deinterlace property
can be restored when using the video resume functionality
(quit_watch_later command).

Implementation-wise, this is a bit messy. The video chain is rebuilt in
mpcodecs_reconfig_vo(), where we don't have access to MPContext, so the
usual mechanism for enabling deinterlacing can't be used. Further,
mpcodecs_reconfig_vo() is called by the video decoder, which doesn't
have access to MPContext either. Moving this call to mplayer.c isn't
currently possible either (see below). So we just do this before frames
are filtered, which potentially means setting the deinterlacing every
frame. Fortunately, setting deinterlacing is stable and idempotent, so
this is hopefully not a problem. We also add a counter that is
incremented on each reconfig to reduce the amount of additional work per
frame to nearly zero.

The reason we can't move mpcodecs_reconfig_vo() to mplayer.c is because
of hardware decoding: we need to check whether the video chain works
before we decide that we can use hardware decoding. Changing it so that
this can be decided in advance without building a filter chain sounds
like a good idea and should be done, but we aren't there yet.

2 files changed, 16 insertions, 1 deletions

diff --git a/DOCS/man/en/input.rst b/DOCS/man/en/input.rst
index ea2ebd2f0b..e40457e099 100644
--- a/DOCS/man/en/input.rst
+++ b/DOCS/man/en/input.rst
@@ -432,7 +432,7 @@ Name                            W Comment
 ``audio``                       x alias for ``aid``
 ``balance``                     x audio channel balance
 ``fullscreen``                  x see ``--fullscreen``
-``deinterlace``                 x deinterlacing, if available (bool)
+``deinterlace``                 x similar to ``--deinterlace``
 ``colormatrix``                 x see ``--colormatrix``
 ``colormatrix-input-range``     x see ``--colormatrix-input-range``
 ``colormatrix-output-range``    x see ``--colormatrix-output-range``
diff --git a/DOCS/man/en/options.rst b/DOCS/man/en/options.rst
index f34268bd6d..8ac563004a 100644
--- a/DOCS/man/en/options.rst
+++ b/DOCS/man/en/options.rst
@@ -569,6 +569,21 @@
     Audio delay in seconds (positive or negative float value). Negative values
     delay the audio, and positive values delay the video.
 
+``--deinterlace=<yes|no|auto>``
+    Enable or disable interlacing (default: auto, which usually means no).
+    Interlaced video shows ugly comb-like artifacts, which are visible on
+    fast movement. Enabling this typically inserts the yadif video filter in
+    order to deinterlace the video, or lets the video output apply deinterlacing
+    if supported.
+
+    This behaves exactly like the ``deinterlace`` input property (usually
+    mapped to ``Shift+D``).
+
+    ``auto`` is a technicality. Strictly speaking, the default for this option
+    is deinterlacing disabled, but the ``auto`` case is needed if ``yadif`` was
+    added to the filter chain manually with ``--vf``. Then the core shouldn't
+    disable deinterlacing just because the ``--deinterlace`` was not set.
+
 ``--demuxer=<[+]name>``
     Force demuxer type. Use a '+' before the name to force it; this will skip
     some checks. Give the demuxer name as printed by ``--demuxer=help``.