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| author | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | 2020-10-08 21:45:21 +0200 |
|---|---|---|
| committer | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | 2020-10-10 04:26:38 +0200 |
| commit | fe9bc1cc45e2bebba1efa7b9a20b0d66679bf2d5 (patch) | |
| tree | fe07756b61693916f5f8cda67d0ef74074ef4438 | |
| parent | a11cc04786c298a8e4df3da12d8e275eaaf6b333 (diff) | |
| download | ffmpeg-fe9bc1cc45e2bebba1efa7b9a20b0d66679bf2d5.tar.gz | |
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 <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
| -rw-r--r-- | libavcodec/mpeg12dec.c | 10 |
1 files changed, 4 insertions, 6 deletions
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) { |