[FFmpeg-devel] [PATCH] swscale/swscale: don't reject scaling when color parameters are not supported but conversion is not required

[James Almer <jamrial@gmail.com>]

Values in csp, prim, trc, etc, are irrelevant if there's no conversion needed.

Signed-off-by: James Almer <jamrial@gmail.com>
---
./ffmpeg -i https://0x0.st/8Hr_.mp4 -vf "scale=1920:1080" -f null -

Fails without this patch, because swscale lacks conversion for the signaled
color primaries.

 libswscale/swscale.c | 13 +++++--------
 libswscale/utils.h   | 16 +++++++++++-----
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 30fbc590fd..70667ebd1c 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -1442,6 +1442,7 @@ int sws_frame_setup(SwsContext *ctx, const AVFrame *dst, const AVFrame *src)
     for (int field = 0; field < 2; field++) {
         SwsFormat src_fmt = ff_fmt_from_frame(src, field);
         SwsFormat dst_fmt = ff_fmt_from_frame(dst, field);
+        int src_ret, dst_ret;
 
         if ((src->flags ^ dst->flags) & AV_FRAME_FLAG_INTERLACED) {
             err_msg = "Cannot convert interlaced to progressive frames or vice versa.\n";
@@ -1449,14 +1450,10 @@ int sws_frame_setup(SwsContext *ctx, const AVFrame *dst, const AVFrame *src)
             goto fail;
         }
 
-        if (!ff_test_fmt(&src_fmt, 0)) {
-            err_msg = "Unsupported input";
-            ret = AVERROR(ENOTSUP);
-            goto fail;
-        }
-
-        if (!ff_test_fmt(&dst_fmt, 1)) {
-            err_msg = "Unsupported output";
+        src_ret = ff_test_fmt(&src_fmt, 0);
+        dst_ret = ff_test_fmt(&dst_fmt, 1);
+        if ((!src_ret || !dst_ret) && !ff_props_equal(&src_fmt, &dst_fmt)) {
+            err_msg = src_ret ? "Unsupported output" : "Unsupported input";
             ret = AVERROR(ENOTSUP);
             goto fail;
         }
diff --git a/libswscale/utils.h b/libswscale/utils.h
index d76fea1133..8e0cdf26ec 100644
--- a/libswscale/utils.h
+++ b/libswscale/utils.h
@@ -98,12 +98,10 @@ static inline int ff_color_equal(const SwsColor *c1, const SwsColor *c2)
             ff_prim_equal(&c1->gamut, &c2->gamut);
 }
 
-/* Tests only the static components of a colorspace, ignoring per-frame data */
-static inline int ff_fmt_equal(const SwsFormat *fmt1, const SwsFormat *fmt2)
+/* Tests only the static components of a colorspace, ignoring dimensions and per-frame data */
+static inline int ff_props_equal(const SwsFormat *fmt1, const SwsFormat *fmt2)
 {
-    return fmt1->width      == fmt2->width      &&
-           fmt1->height     == fmt2->height     &&
-           fmt1->interlaced == fmt2->interlaced &&
+    return fmt1->interlaced == fmt2->interlaced &&
            fmt1->format     == fmt2->format     &&
            fmt1->range      == fmt2->range      &&
            fmt1->csp        == fmt2->csp        &&
@@ -111,6 +109,14 @@ static inline int ff_fmt_equal(const SwsFormat *fmt1, const SwsFormat *fmt2)
            ff_color_equal(&fmt1->color, &fmt2->color);
 }
 
+/* Tests only the static components of a colorspace, ignoring per-frame data */
+static inline int ff_fmt_equal(const SwsFormat *fmt1, const SwsFormat *fmt2)
+{
+    return fmt1->width      == fmt2->width      &&
+           fmt1->height     == fmt2->height     &&
+           ff_props_equal(fmt1, fmt2);
+}
+
 static inline int ff_fmt_align(enum AVPixelFormat fmt)
 {
     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(fmt);
-- 
2.48.1

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