[FFmpeg-devel] [PATCH v2 3/8] swscale/options: relax src/dst_h/v_chr_pos value range

From: Niklas Haas <ffmpeg@haasn.xyz>
To: ffmpeg-devel@ffmpeg.org
Cc: Niklas Haas <git@haasn.dev>
Subject: [FFmpeg-devel] [PATCH v2 3/8] swscale/options: relax src/dst_h/v_chr_pos value range
Date: Thu,  4 Jul 2024 16:30:59 +0200
Message-ID: <20240704143104.1821386-3-ffmpeg@haasn.xyz> (raw)
In-Reply-To: <20240704143104.1821386-1-ffmpeg@haasn.xyz>

From: Niklas Haas <git@haasn.dev>

When dealing with 4x subsampling ratios (log2 == 2), such as can arise
with 4:1:1 or 4:1:0, a value range of 512 is not enough to cover the
range of possible scenarios.

For example, bottom-sited chroma in 4:1:0 would require an offset of 768
(three luma rows). Simply double the limit to 1024. I don't see any
place in initFilter() that would experience overflow as a result of this
change, especially since get_local_pos() right-shifts it by the
subsampling ratio again.
---
 libswscale/options.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libswscale/options.c b/libswscale/options.c
index b36f13c872..53c4f0651b 100644
--- a/libswscale/options.c
+++ b/libswscale/options.c
@@ -62,10 +62,10 @@ static const AVOption swscale_options[] = {
     { "param0",          "scaler param 0",                OFFSET(param[0]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX,        VE },
     { "param1",          "scaler param 1",                OFFSET(param[1]),  AV_OPT_TYPE_DOUBLE, { .dbl = SWS_PARAM_DEFAULT  }, INT_MIN, INT_MAX,        VE },
 
-    { "src_v_chr_pos",   "source vertical chroma position in luma grid/256"  ,      OFFSET(src_v_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      512,             VE },
-    { "src_h_chr_pos",   "source horizontal chroma position in luma grid/256",      OFFSET(src_h_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      512,             VE },
-    { "dst_v_chr_pos",   "destination vertical chroma position in luma grid/256"  , OFFSET(dst_v_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      512,             VE },
-    { "dst_h_chr_pos",   "destination horizontal chroma position in luma grid/256", OFFSET(dst_h_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      512,             VE },
+    { "src_v_chr_pos",   "source vertical chroma position in luma grid/256"  ,      OFFSET(src_v_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      1024,             VE },
+    { "src_h_chr_pos",   "source horizontal chroma position in luma grid/256",      OFFSET(src_h_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      1024,             VE },
+    { "dst_v_chr_pos",   "destination vertical chroma position in luma grid/256"  , OFFSET(dst_v_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      1024,             VE },
+    { "dst_h_chr_pos",   "destination horizontal chroma position in luma grid/256", OFFSET(dst_h_chr_pos), AV_OPT_TYPE_INT, { .i64 = -513 }, -513,      1024,             VE },
 
     { "sws_dither",      "set dithering algorithm",       OFFSET(dither),    AV_OPT_TYPE_INT,    { .i64  = SWS_DITHER_AUTO    }, 0,       NB_SWS_DITHER,  VE, .unit = "sws_dither" },
     { "auto",            "leave choice to sws",           0,                 AV_OPT_TYPE_CONST,  { .i64  = SWS_DITHER_AUTO    }, INT_MIN, INT_MAX,        VE, .unit = "sws_dither" },
-- 
2.45.2

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