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avcodec/h261dec: Simplify decoding motion vectors 

Don't use a LUT to negate followed by a conditional ordinary
negation immediately thereafter. Instead fold the two.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2024-06-13 15:45:19 +02:00
parent f793074784
commit 9933dfe103
1 changed files with 1 additions and 7 deletions
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8
libavcodec/h261dec.c
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@ -208,10 +208,6 @@ static int h261_decode_mb_skipped(H261DecContext *h, int mba1, int mba2)
return 0; return 0;
} }
static const int mvmap[17] = {
0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16
};
static int decode_mv_component(GetBitContext *gb, int v) static int decode_mv_component(GetBitContext *gb, int v)
{ {
int mv_diff = get_vlc2(gb, h261_mv_vlc, H261_MV_VLC_BITS, 2); int mv_diff = get_vlc2(gb, h261_mv_vlc, H261_MV_VLC_BITS, 2);
@ -220,9 +216,7 @@ static int decode_mv_component(GetBitContext *gb, int v)
if (mv_diff < 0) if (mv_diff < 0)
return v; return v;
mv_diff = mvmap[mv_diff]; if (mv_diff && get_bits1(gb))
if (mv_diff && !get_bits1(gb))
mv_diff = -mv_diff; mv_diff = -mv_diff;
v += mv_diff; v += mv_diff;