[FFmpeg-devel] [PATCH] swresample: SWR_CH_MAX as config, default 64 (PR #20412)

[Renjianguang-mi via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20412 opened by Renjianguang-mi
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20412
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20412.patch

For memory-constrained products, reduce the memory overhead of swresample.
Optimizing swresample SwrContext memory:
    double matrix[SWR_CH_MAX][SWR_CH_MAX]
    float matrix_flt[SWR_CH_MAX][SWR_CH_MAX]
    int32_t matrix32[SWR_CH_MAX][SWR_CH_MAX]
    uint8_t matrix_ch[SWR_CH_MAX][SWR_CH_MAX+1]
eg:
 SWR_CH_MAX = 64
 matrix Total memory: 68KB

 SWR_CH_MAX = 8
 matrix Total memory: 1.07KB

Signed-off-by: renjianguang <renjianguang@xiaomi.com>


>From 4cb2102d9e7ff12506ec33e40a1eb88477f53c3f Mon Sep 17 00:00:00 2001
From: renjianguang <renjianguang@xiaomi.com>
Date: Wed, 3 Sep 2025 17:28:36 +0800
Subject: [PATCH] swresample: SWR_CH_MAX as config, default 64

For memory-constrained products, reduce the memory overhead of swresample.
Optimizing swresample SwrContext memory:
    double matrix[SWR_CH_MAX][SWR_CH_MAX]
    float matrix_flt[SWR_CH_MAX][SWR_CH_MAX]
    int32_t matrix32[SWR_CH_MAX][SWR_CH_MAX]
    uint8_t matrix_ch[SWR_CH_MAX][SWR_CH_MAX+1]
eg:
 SWR_CH_MAX = 64
 matrix Total memory: 68KB

 SWR_CH_MAX = 8
 matrix Total memory: 1.07KB

Signed-off-by: renjianguang <renjianguang@xiaomi.com>
---
 configure                           | 5 +++++
 libswresample/swresample_internal.h | 2 --
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 7ec4c3975b..b93d5dd5fb 100755
--- a/configure
+++ b/configure
@@ -445,6 +445,7 @@ Advanced options (experts only):
                             crashes and arbitrary code execution, it may be faster, but
                             should only be used with trusted input)
   --sws-max-filter-size=N  the max filter size swscale uses [$sws_max_filter_size_default]
+  --swr-ch-max=N           the max channel number swresamle uses [$swr_ch_max_default]
 
 Optimization options (experts only):
   --disable-asm            disable all assembly optimizations
@@ -2755,6 +2756,7 @@ CMDLINE_SET="
     stdcxx
     strip
     sws_max_filter_size
+    swr_ch_max
     sysinclude
     sysroot
     target_exec
@@ -4242,6 +4244,8 @@ enable valgrind_backtrace
 
 sws_max_filter_size_default=256
 set_default sws_max_filter_size
+swr_ch_max_default=64
+set_default swr_ch_max
 
 # internal components are enabled by default
 enable $EXTRALIBS_LIST
@@ -8413,6 +8417,7 @@ cat > $TMPH <<EOF
 #define BUILDSUF "$build_suffix"
 #define SLIBSUF "$SLIBSUF"
 #define SWS_MAX_FILTER_SIZE $sws_max_filter_size
+#define SWR_CH_MAX $swr_ch_max
 EOF
 
 test -n "$assert_level" &&
diff --git a/libswresample/swresample_internal.h b/libswresample/swresample_internal.h
index 21c9e33fa1..81eae2eb63 100644
--- a/libswresample/swresample_internal.h
+++ b/libswresample/swresample_internal.h
@@ -25,8 +25,6 @@
 #include "libavutil/channel_layout.h"
 #include "config.h"
 
-#define SWR_CH_MAX 64
-
 #define SQRT3_2      1.22474487139158904909  /* sqrt(3/2) */
 
 #define NS_TAPS 20
-- 
2.49.1

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