from_lavc_pf_priority: fine-grain selection

If there is no direct conversion from a AV PF compatible with internal
format, penalize a bit.

This may be mostly unneeded but just in case. It can be safely reverted,
anyways.

Author: MartinPulec

src/libavcodec/from_lavc_vid_conv.c

@@ -3175,10 +3175,19 @@ from_lavc_pf_priority(struct pixfmt_desc internal, codec_t ugc)
         if (internal.depth == 0) { // unspecified internal format
                 return VDEC_PRIO_LOW;
         }
-        /// @todo what about returning lower prio if
-        /// !pixdesc_equals(av_pixfmt_get_desc(av_to_uv_conversion.av_codec),
-        /// internal)
-        return VDEC_PRIO_NORMAL;
+        for (unsigned i = 0; i < ARR_COUNT(av_to_uv_conversions); i++) {
+                if (av_to_uv_conversions[i].uv_codec != ugc) {
+                        continue;
+                }
+                if (pixdesc_equals(
+                        av_pixfmt_get_desc(av_to_uv_conversions[i].av_codec),
+                        internal)) {
+                        // conv from AV PF with same props as internal
+                        return VDEC_PRIO_NORMAL;
+                }
+        }
+        // the conversion may be not direct but over intermediate UG codec_t
+        return VDEC_PRIO_NOT_PREFERRED;
 }
 
 #pragma GCC diagnostic pop

src/video_decompress.h

@@ -6,7 +6,7 @@
  * @brief API for video decompress drivers
  */
 /*
- * Copyright (c) 2011-2019 CESNET, z. s. p. o.
+ * Copyright (c) 2011-2025 CESNET
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -141,11 +141,8 @@ enum vdec_priority {
         VDEC_PRIO_NORMAL = 500, ///< decoder can decode the given properties but
                                 ///< is not dedicated (lavd)
         VDEC_PRIO_NOT_PREFERRED =
-            800, ///< decoder can decode given properties but the decode
-                 ///< is suboptimal (like color space conversion)
-                 ///< @todo consider removing this - as this is after
-                 ///<       probe, the CS conv will be needed for all
-                 ///<       decoders (so it will not differentiate)
+            800, ///< decoder can perhaps decode given properties but the decode
+                 ///< may be is suboptimal (not efficient PF conversion or so)
         VDEC_PRIO_LOW = 900, ///< the decoder is unsure if it can decode the
                              ///< stream (eg. unknown properties)
 };