From fe9bc1cc45e2bebba1efa7b9a20b0d66679bf2d5 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Thu, 8 Oct 2020 21:45:21 +0200 Subject: avcodec/mpeg12dec: Optimize reading mpeg2 intra escape codes Said escape code is only six bits long, so that one has at least 25 - 6 bits in the bitstream reader's cache after reading it; therefore the whole following 18 bits (containing the actual code) are already in the bitstream reader's cache, making it unnecessary to reload the cache. Reviewed-by: Michael Niedermayer Signed-off-by: Andreas Rheinhardt --- libavcodec/mpeg12dec.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) (limited to 'libavcodec') diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c index 2494226aa3..1cccfd1742 100644 --- a/libavcodec/mpeg12dec.c +++ b/libavcodec/mpeg12dec.c @@ -526,10 +526,9 @@ static inline int mpeg2_decode_block_intra(MpegEncContext *s, } else { /* escape */ run = SHOW_UBITS(re, &s->gb, 6) + 1; - LAST_SKIP_BITS(re, &s->gb, 6); - UPDATE_CACHE(re, &s->gb); + SKIP_BITS(re, &s->gb, 6); level = SHOW_SBITS(re, &s->gb, 12); - SKIP_BITS(re, &s->gb, 12); + LAST_SKIP_BITS(re, &s->gb, 12); i += run; if (i > MAX_INDEX) break; @@ -610,10 +609,9 @@ static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, } else { /* escape */ run = SHOW_UBITS(re, &s->gb, 6) + 1; - LAST_SKIP_BITS(re, &s->gb, 6); - UPDATE_CACHE(re, &s->gb); + SKIP_BITS(re, &s->gb, 6); level = SHOW_SBITS(re, &s->gb, 12); - SKIP_BITS(re, &s->gb, 12); + LAST_SKIP_BITS(re, &s->gb, 12); i += run; j = scantable[i]; if (level < 0) { -- cgit v1.2.3