avisynth: more intelligent RGB flipping

avs_is_color_space provides a generic way of checking whether the
video is RGB, and has been available through AVSC_API since 2.6.
This means that GetProcAddress doesn't have to run on every frame.

Signed-off-by: Stephen Hutchinson <qyot27@gmail.com>

libavformat/avisynth.c

@@ -57,6 +57,7 @@ typedef struct AviSynthLibrary {
     AVSC_DECLARE_FUNC(avs_get_version);
     AVSC_DECLARE_FUNC(avs_get_video_info);
     AVSC_DECLARE_FUNC(avs_invoke);
+    AVSC_DECLARE_FUNC(avs_is_color_space);
     AVSC_DECLARE_FUNC(avs_release_clip);
     AVSC_DECLARE_FUNC(avs_release_value);
     AVSC_DECLARE_FUNC(avs_release_video_frame);
@@ -133,6 +134,7 @@ static av_cold int avisynth_load_library(void)
     LOAD_AVS_FUNC(avs_get_version, 0);
     LOAD_AVS_FUNC(avs_get_video_info, 0);
     LOAD_AVS_FUNC(avs_invoke, 0);
+    LOAD_AVS_FUNC(avs_is_color_space, 1);
     LOAD_AVS_FUNC(avs_release_clip, 0);
     LOAD_AVS_FUNC(avs_release_value, 0);
     LOAD_AVS_FUNC(avs_release_video_frame, 0);
@@ -628,7 +630,6 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     const unsigned char *src_p;
     int n, i, plane, rowsize, planeheight, pitch, bits, ret;
     const char *error;
-    int avsplus av_unused;
 
     if (avs->curr_frame >= avs->vi->num_frames)
         return AVERROR_EOF;
@@ -638,19 +639,6 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
     if (discard)
         return 0;
 
-#ifdef _WIN32
-    /* Detect whether we're using AviSynth 2.6 or AviSynth+ by
-     * looking for whether avs_is_planar_rgb exists. */
-    if (GetProcAddress(avs_library.library, "avs_is_planar_rgb") == NULL)
-        avsplus = 0;
-    else
-        avsplus = 1;
-#else
-    /* AviSynth+ is now the only variant of AviSynth we support
-     * on Linux and macOS. */
-    avsplus = 1;
-#endif
-
     bits = avs_library.avs_bits_per_pixel(avs->vi);
 
     /* Without the cast to int64_t, calculation overflows at about 9k x 9k
@@ -687,14 +675,9 @@ static int avisynth_read_packet_video(AVFormatContext *s, AVPacket *pkt,
         planeheight = avs_library.avs_get_height_p(frame, plane);
 
         /* Flip RGB video. */
-        if (avs_is_rgb24(avs->vi) || avs_is_rgb(avs->vi)) {
-            src_p = src_p + (planeheight - 1) * pitch;
-            pitch = -pitch;
-        }
-
-        /* Flip Planar RGB video */
-        if (avsplus && (avs_library.avs_is_planar_rgb(avs->vi) ||
-                        avs_library.avs_is_planar_rgba(avs->vi))) {
+        if (avs_library.avs_is_color_space(avs->vi, AVS_CS_BGR)   ||
+            avs_library.avs_is_color_space(avs->vi, AVS_CS_BGR48) ||
+            avs_library.avs_is_color_space(avs->vi, AVS_CS_BGR64)) {
             src_p = src_p + (planeheight - 1) * pitch;
             pitch = -pitch;
         }