The branch, master has been updated
via ce9d1814449d6ff6323dd1030fb4c8d1093c6744 (commit)
from dad06a445f9aa3c19c01d9d4f0e98e00fefcd05b (commit)
- Log -----------------------------------------------------------------
commit ce9d1814449d6ff6323dd1030fb4c8d1093c6744
Author: Andreas Rheinhardt <[email protected]>
AuthorDate: Wed Oct 8 03:12:19 2025 +0200
Commit: Andreas Rheinhardt <[email protected]>
CommitDate: Sat Oct 11 08:20:42 2025 +0200
avcodec/mjpegdec: Remove unnecessary reloads
Hint: The parts of this patch in decode_block_progressive()
and decode_block_refinement() rely on the fact that GET_VLC
returns -1 on error, so that it enters the codepaths for
actually coded block coefficients.
Reviewed-by: Ramiro Polla <[email protected]>
Signed-off-by: Andreas Rheinhardt <[email protected]>
diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index 69bc003490..5fd77073da 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -854,9 +854,9 @@ static int decode_block(MJpegDecodeContext *s, int16_t
*block, int component,
i += ((unsigned)code) >> 4;
code &= 0xf;
if (code) {
- if (code > MIN_CACHE_BITS - 16)
- UPDATE_CACHE(re, &s->gb);
-
+ // GET_VLC updates the cache if parsing reaches the second stage.
+ // So we have at least MIN_CACHE_BITS - 9 > 15 bits left here
+ // and don't need to refill the cache.
{
int cache = GET_CACHE(re, &s->gb);
int sign = (~cache) >> 31;
@@ -918,8 +918,6 @@ static int decode_block_progressive(MJpegDecodeContext *s,
int16_t *block,
code &= 0xF;
if (code) {
i += run;
- if (code > MIN_CACHE_BITS - 16)
- UPDATE_CACHE(re, &s->gb);
{
int cache = GET_CACHE(re, &s->gb);
@@ -950,7 +948,8 @@ static int decode_block_progressive(MJpegDecodeContext *s,
int16_t *block,
} else {
val = (1 << run);
if (run) {
- UPDATE_CACHE(re, &s->gb);
+ // Given that GET_VLC reloads internally, we always
+ // have at least 16 bits in the cache here.
val += NEG_USR32(GET_CACHE(re, &s->gb), run);
LAST_SKIP_BITS(re, &s->gb, run);
}
@@ -1012,7 +1011,6 @@ static int decode_block_refinement(MJpegDecodeContext *s,
int16_t *block,
if (code & 0xF) {
run = ((unsigned) code) >> 4;
- UPDATE_CACHE(re, &s->gb);
val = SHOW_UBITS(re, &s->gb, 1);
LAST_SKIP_BITS(re, &s->gb, 1);
ZERO_RUN;
@@ -1033,7 +1031,8 @@ static int decode_block_refinement(MJpegDecodeContext *s,
int16_t *block,
val = run;
run = (1 << run);
if (val) {
- UPDATE_CACHE(re, &s->gb);
+ // Given that GET_VLC reloads internally, we always
+ // have at least 16 bits in the cache here.
run += SHOW_UBITS(re, &s->gb, val);
LAST_SKIP_BITS(re, &s->gb, val);
}
-----------------------------------------------------------------------
Summary of changes:
libavcodec/mjpegdec.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
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