[FFmpeg-devel] [PATCH] swscale: Fix ff_sws_pixel_type_to_uint (PR #20968)

["Martin Storsjö via ffmpeg-devel" <ffmpeg-devel@ffmpeg.org>]

PR #20968 opened by Martin Storsjö (mstorsjo)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20968
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20968.patch

This function uses ff_sws_pixel_type_size to switch on the
size of the provided type. However, ff_sws_pixel_type_size returns
a size in bytes (from sizeof()), not a size in bits. Therefore,
this would previously never return the right thing but always
hit the av_unreachable() below.

This fixes compilation with MSVC 2026 18.0, which previously
hit an internal compiler error [1].

[1] https://developercommunity.visualstudio.com/t/Internal-Compiler-Error-targeting-ARM64-/10962922


From 5c5530b528f2a336c68c674850271b362f591f13 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin@martin.st>
Date: Wed, 19 Nov 2025 10:43:26 +0200
Subject: [PATCH] swscale: Fix ff_sws_pixel_type_to_uint

This function uses ff_sws_pixel_type_size to switch on the
size of the provided type. However, ff_sws_pixel_type_size returns
a size in bytes (from sizeof()), not a size in bits. Therefore,
this would previously never return the right thing but always
hit the av_unreachable() below.

This fixes compilation with MSVC 2026 18.0, which previously
hit an internal compiler error [1].

[1] https://developercommunity.visualstudio.com/t/Internal-Compiler-Error-targeting-ARM64-/10962922
---
 libswscale/ops.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libswscale/ops.c b/libswscale/ops.c
index 21aeb16931..2d22c4a5fa 100644
--- a/libswscale/ops.c
+++ b/libswscale/ops.c
@@ -99,9 +99,9 @@ SwsPixelType ff_sws_pixel_type_to_uint(SwsPixelType type)
         return type;
 
     switch (ff_sws_pixel_type_size(type)) {
-    case 8:  return SWS_PIXEL_U8;
-    case 16: return SWS_PIXEL_U16;
-    case 32: return SWS_PIXEL_U32;
+    case 1: return SWS_PIXEL_U8;
+    case 2: return SWS_PIXEL_U16;
+    case 4: return SWS_PIXEL_U32;
     }
 
     av_unreachable("Invalid pixel type!");
-- 
2.49.1

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