[FFmpeg-devel] [PATCH] avcodec: make use of av_zero_extend() in a few modules (PR #20628)

[James Almer via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20628 opened by James Almer (jamrial)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20628
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20628.patch


>From 45b30fa2363d77b0741f9d334ef659299bb420b9 Mon Sep 17 00:00:00 2001
From: James Almer <jamrial@gmail.com>
Date: Mon, 29 Sep 2025 22:33:27 -0300
Subject: [PATCH 1/3] avcodec/aom_film_grain: use av_zero_extend()

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/aom_film_grain.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/aom_film_grain.c b/libavcodec/aom_film_grain.c
index bd9647afe9..a5b692562d 100644
--- a/libavcodec/aom_film_grain.c
+++ b/libavcodec/aom_film_grain.c
@@ -39,7 +39,7 @@ static inline int get_random_number(const int bits, unsigned *const state) {
     unsigned bit = ((r >> 0) ^ (r >> 1) ^ (r >> 3) ^ (r >> 12)) & 1;
     *state = (r >> 1) | (bit << 15);
 
-    return (*state >> (16 - bits)) & ((1 << bits) - 1);
+    return av_zero_extend(*state >> (16 - bits), bits);
 }
 
 static inline int round2(const int x, const uint64_t shift) {
-- 
2.49.1


>From 96e0fa186b7c2f9b3b85029c5f87d78e681c3a05 Mon Sep 17 00:00:00 2001
From: James Almer <jamrial@gmail.com>
Date: Mon, 29 Sep 2025 22:33:38 -0300
Subject: [PATCH 2/3] avcodec/apv_entropy: use av_zero_extend()

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/apv_entropy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/apv_entropy.c b/libavcodec/apv_entropy.c
index 1cab88d547..30f31a14ff 100644
--- a/libavcodec/apv_entropy.c
+++ b/libavcodec/apv_entropy.c
@@ -288,7 +288,7 @@ int ff_apv_entropy_decode_block(int16_t *restrict coeff,
             // Extract the low bits.
             low_bit_count = leading_zeroes;
             low_bit_shift = 16 - (1 + 2 * leading_zeroes);
-            low_bits = (bits >> low_bit_shift) & ((1 << low_bit_count) - 1);
+            low_bits = av_zero_extend(bits >> low_bit_shift, low_bit_count);
             // Construct run code.
             run = 2 + ((1 << leading_zeroes) - 1) + low_bits;
             // Skip over the bits just used.
@@ -460,7 +460,7 @@ int ff_apv_entropy_decode_block(int16_t *restrict coeff,
             // Extract the low bits.
             low_bit_count = leading_zeroes + k_run;
             low_bit_shift = 16 - (1 + 2 * leading_zeroes + k_run);
-            low_bits = (bits >> low_bit_shift) & ((1 << low_bit_count) - 1);
+            low_bits = av_zero_extend(bits >> low_bit_shift, low_bit_count);
             // Construct run code.
             run = (2 << k_run) +
                 ((1 << leading_zeroes) - 1) * (1 << k_run) +
-- 
2.49.1


>From 03dd856fe1f74365b1b8d7a098a2884da9162de0 Mon Sep 17 00:00:00 2001
From: James Almer <jamrial@gmail.com>
Date: Mon, 29 Sep 2025 22:33:49 -0300
Subject: [PATCH 3/3] avcodec/atrac9dec: use av_zero_extend()

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/atrac9dec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/atrac9dec.c b/libavcodec/atrac9dec.c
index 0748d671f1..3c18ae8b42 100644
--- a/libavcodec/atrac9dec.c
+++ b/libavcodec/atrac9dec.c
@@ -285,7 +285,7 @@ static inline int read_scalefactors(ATRAC9Context *s, ATRAC9BlockData *b,
         for (int i = 1; i < b->band_ext_q_unit; i++) {
             int val = c->scalefactors[i - 1] + get_vlc2(gb, tab,
                                                         ATRAC9_SF_VLC_BITS, 1);
-            c->scalefactors[i] = val & ((1 << len) - 1);
+            c->scalefactors[i] = av_zero_extend(val, len);
         }
 
         for (int i = 0; i < b->band_ext_q_unit; i++)
@@ -339,7 +339,7 @@ static inline int read_scalefactors(ATRAC9Context *s, ATRAC9BlockData *b,
         for (int i = 1; i < unit_cnt; i++) {
             int val = c->scalefactors[i - 1] + get_vlc2(gb, tab,
                                                         ATRAC9_SF_VLC_BITS, 1);
-            c->scalefactors[i] = val & ((1 << len) - 1);
+            c->scalefactors[i] = av_zero_extend(val, len);
         }
 
         for (int i = 0; i < unit_cnt; i++)
-- 
2.49.1

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