From f8e284be69d6eae480c6d7291763b840959b7bf1 Mon Sep 17 00:00:00 2001
From: rcombs <rcombs@rcombs.me>
Date: Thu, 23 Dec 2021 03:49:27 -0600
Subject: [PATCH] swscale: introduce isSwappedChroma

---
 libswscale/swscale_internal.h    | 19 +++++++++++++++++++
 libswscale/tests/pixdesc_query.c |  1 +
 tests/ref/fate/sws-pixdesc-query |  5 +++++
 3 files changed, 25 insertions(+)

diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h
index b4acaceebd..3a78d95ba6 100644
--- a/libswscale/swscale_internal.h
+++ b/libswscale/swscale_internal.h
@@ -911,6 +911,25 @@ static av_always_inline int isDataInHighBits(enum AVPixelFormat pix_fmt)
     return 1;
 }
 
+/*
+ * Identity formats where the chroma planes are swapped (CrCb order).
+ */
+static av_always_inline int isSwappedChroma(enum AVPixelFormat pix_fmt)
+{
+    const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
+    av_assert0(desc);
+    if (!isYUV(pix_fmt))
+        return 0;
+    if ((desc->flags & AV_PIX_FMT_FLAG_ALPHA) && desc->nb_components < 4)
+        return 0;
+    if (desc->nb_components < 3)
+        return 0;
+    if (!isPlanarYUV(pix_fmt) || isSemiPlanarYUV(pix_fmt))
+        return desc->comp[1].offset > desc->comp[2].offset;
+    else
+        return desc->comp[1].plane > desc->comp[2].plane;
+}
+
 extern const uint64_t ff_dither4[2];
 extern const uint64_t ff_dither8[2];
 
diff --git a/libswscale/tests/pixdesc_query.c b/libswscale/tests/pixdesc_query.c
index dce2e50577..eb793877a0 100644
--- a/libswscale/tests/pixdesc_query.c
+++ b/libswscale/tests/pixdesc_query.c
@@ -46,6 +46,7 @@ static const struct {
     {"PlanarRGB",   isPlanarRGB},
     {"usePal",      usePal},
     {"DataInHighBits", isDataInHighBits},
+    {"SwappedChroma", isSwappedChroma},
 };
 
 static int cmp_str(const void *a, const void *b)
diff --git a/tests/ref/fate/sws-pixdesc-query b/tests/ref/fate/sws-pixdesc-query
index a17284784f..76104bc5a6 100644
--- a/tests/ref/fate/sws-pixdesc-query
+++ b/tests/ref/fate/sws-pixdesc-query
@@ -964,3 +964,8 @@ DataInHighBits:
   y210be
   y210le
 
+SwappedChroma:
+  nv21
+  nv42
+  yvyu422
+