[FFmpeg-devel] [PATCH 1/8] swscale: fix sws_setColorspaceDetails after sws_init_context

[Niklas Haas]

From: Niklas Haas <git at haasn.dev>

More commonly, this fixes the case of sws_setColorspaceDetails after
sws_getContext, since the latter implies sws_init_context.

The problem here is that sws_init_context sets up the range conversion
and fast path tables based on the values of srcRange/dstRange at init
time. This may result in locking in a "wrong" path (either using
unscaled fast path when range conversion later required, or using
scaled slow path when range conversion becomes no longer required).

There are two way outs:

1. Always initialize range conversion and unscaled converters, even if
   they will be unused, and extend the runtime check.
2. Re-do initialization if the values change after
   sws_setColorspaceDetails.

I opted for approach 1 because it was simpler and easier to reason
about.
---
 libswscale/swscale.c | 2 +-
 libswscale/utils.c   | 5 +----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 90e5b299ab..46ba68fe6a 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -1016,7 +1016,7 @@ static int scale_internal(SwsContext *c,
     reset_ptr(src2, c->srcFormat);
     reset_ptr((void*)dst2, c->dstFormat);
 
-    if (c->convert_unscaled) {
+    if (c->convert_unscaled && !c->lumConvertRange && !c->chrConvertRange) {
         int offset  = srcSliceY_internal;
         int slice_h = srcSliceH;
 
diff --git a/libswscale/utils.c b/libswscale/utils.c
index e1ad685972..455955e907 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -1728,9 +1728,7 @@ static av_cold int sws_init_single_context(SwsContext *c, SwsFilter *srcFilter,
     }
 
     /* unscaled special cases */
-    if (unscaled && !usesHFilter && !usesVFilter &&
-        (c->srcRange == c->dstRange || isAnyRGB(dstFormat) ||
-         isFloat(srcFormat) || isFloat(dstFormat))){
+    if (unscaled && !usesHFilter && !usesVFilter) {
         ff_get_unscaled_swscale(c);
 
         if (c->convert_unscaled) {
@@ -1738,7 +1736,6 @@ static av_cold int sws_init_single_context(SwsContext *c, SwsFilter *srcFilter,
                 av_log(c, AV_LOG_INFO,
                        "using unscaled %s -> %s special converter\n",
                        av_get_pix_fmt_name(srcFormat), av_get_pix_fmt_name(dstFormat));
-            return 0;
         }
     }
 
-- 
2.42.0