avcodec/h263dec: Remove redundant code to set cur_pic_ptr

It is done later in ff_mpv_frame_start() (and nobody uses
current_picture_ptr between setting it in ff_mpv_frame_start()).

(The reason the vsynth*-h263-obmc ref files change is because
the call to ff_find_unused_picture() now happens after the older
pictures have been unreferenced in ff_mpv_frame_start(),
so that their slots in the picture array can be immediately
reused; the obmc code is somehow buggy and changes its output
depending on the earlier contents of the motion_val buffer.)

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

libavcodec/h263dec.c

@@ -543,13 +543,6 @@ retry:
             return ret;
     }
 
-    if (!s->current_picture_ptr || s->current_picture_ptr->f->data[0]) {
-        int i = ff_find_unused_picture(s->avctx, s->picture, 0);
-        if (i < 0)
-            return i;
-        s->current_picture_ptr = &s->picture[i];
-    }
-
     avctx->has_b_frames = !s->low_delay;
 
     if (CONFIG_MPEG4_DECODER && avctx->codec_id == AV_CODEC_ID_MPEG4) {

tests/ref/vsynth/vsynth1-h263-obmc

@@ -1,4 +1,4 @@
 7dec64380f375e5118b66f3baaaa1e24 *tests/data/fate/vsynth1-h263-obmc.avi
 657320 tests/data/fate/vsynth1-h263-obmc.avi
-844f7ee27fa122e199fe20987b41a15c *tests/data/fate/vsynth1-h263-obmc.out.rawvideo
-stddev:    8.16 PSNR: 29.89 MAXDIFF:  113 bytes:  7603200/  7603200
+2a69f6b37378aa34418dfd04ec98c1c8 *tests/data/fate/vsynth1-h263-obmc.out.rawvideo
+stddev:    8.38 PSNR: 29.66 MAXDIFF:  116 bytes:  7603200/  7603200

tests/ref/vsynth/vsynth2-h263-obmc

@@ -1,4 +1,4 @@
 2d8a58b295e03f94e6a41468b2d3909e *tests/data/fate/vsynth2-h263-obmc.avi
 208522 tests/data/fate/vsynth2-h263-obmc.avi
-4a939ef99fc759293f2e609bfcacd2a4 *tests/data/fate/vsynth2-h263-obmc.out.rawvideo
-stddev:    6.10 PSNR: 32.41 MAXDIFF:   90 bytes:  7603200/  7603200
+3500b4227c1e6309ca5213414599266f *tests/data/fate/vsynth2-h263-obmc.out.rawvideo
+stddev:    6.19 PSNR: 32.29 MAXDIFF:  111 bytes:  7603200/  7603200

tests/ref/vsynth/vsynth_lena-h263-obmc

@@ -1,4 +1,4 @@
 3c6946f808412ac320be9e0c36051ea2 *tests/data/fate/vsynth_lena-h263-obmc.avi
 154730 tests/data/fate/vsynth_lena-h263-obmc.avi
-588d992d9d8096da8bdc5027268da914 *tests/data/fate/vsynth_lena-h263-obmc.out.rawvideo
-stddev:    5.39 PSNR: 33.49 MAXDIFF:   82 bytes:  7603200/  7603200
+737af7fb166e2260ba049ae6bc30673d *tests/data/fate/vsynth_lena-h263-obmc.out.rawvideo
+stddev:    5.42 PSNR: 33.44 MAXDIFF:   77 bytes:  7603200/  7603200