video: remove slice based filtering and video output

Slices allowed filtering or drawing video in horizontal bands or
blocks. This allowed working on the video in smaller units. In theory,
this could bring a performance win by lowering cache pressure, as you
didn't have to keep the whole video frame in cache while filtering,
only the slice.

In practice, the slice code path was barely used for the following
reasons:
- Multithreaded decoding with ffmpeg didn't use slices. The ffmpeg
  slice callback was disabled, because it can be called from another
  thread, and the mplayer video chain is not thread-safe.
- There was nothing that would turn "full" images into appropriate
  slices, so slices were rarely used.
- Most filters didn't actually support slices.

On the other hand, supporting slices lead to code duplication and more
complex code in general. I made some experiments and didn't find any
actual measurable performance improvements when using slices. Even
ffmpeg removed slices based filtering from libavfilter in favor of
simpler code.

The most broken thing about the slices code path is that slices can't
be queued, like it is done for images in vo.c.

1 files changed, 0 insertions, 4 deletions

diff --git a/video/mp_image.h b/video/mp_image.h
index d2c7d38f50..69e9c87c19 100644
--- a/video/mp_image.h
+++ b/video/mp_image.h
@@ -73,10 +73,6 @@
 
 #define MP_IMGFLAGMASK_COLORS 0xF00
 
-// codec uses drawing/rendering callbacks (draw_slice()-like thing, DR method 2)
-// [the codec will set this flag if it supports callbacks, and the vo _may_
-//  clear it in get_image() if draw_slice() not implemented]
-#define MP_IMGFLAG_DRAW_CALLBACK 0x1000
 // set if it's in video buffer/memory: [set by vo/vf's get_image() !!!]
 #define MP_IMGFLAG_DIRECT 0x2000
 // set if buffer is allocated (used in destination images):