video: support setting libswscale chroma position

configure

@@ -2647,6 +2647,17 @@ fi
 echores "$_avcodec_has_text_flag_api"
 
 
+echocheck "libavcodec avcodec_enum_to_chroma_pos API"
+_avcodec_has_chroma_pos_api=no
+statement_check libavcodec/avcodec.h 'int x, y; avcodec_enum_to_chroma_pos(&x, &y, AVCHROMA_LOC_UNSPECIFIED)' && _avcodec_has_chroma_pos_api=yes
+if test "$_avcodec_has_chroma_pos_api" = yes ; then
+  def_avcodec_has_chroma_pos_api='#define HAVE_AVCODEC_CHROMA_POS_API 1'
+else
+  def_avcodec_has_chroma_pos_api='#define HAVE_AVCODEC_CHROMA_POS_API 0'
+fi
+echores "$_avcodec_has_chroma_pos_api"
+
+
 echocheck "libavutil QP API"
 _avutil_has_qp_api=no
 statement_check libavutil/frame.h 'av_frame_get_qp_table(NULL, NULL, NULL)' && _avutil_has_qp_api=yes
@@ -3169,6 +3180,7 @@ $def_zlib
 $def_avutil_has_refcounting
 $def_avutil_has_qp_api
 $def_avcodec_has_text_flag_api
+$def_avcodec_has_chroma_pos_api
 $def_libpostproc
 $def_libavdevice
 $def_libavfilter

video/csputils.c

@@ -116,6 +116,15 @@ enum mp_chroma_location avchroma_location_to_mp(int avloc)
     }
 }
 
+int mp_chroma_location_to_av(enum mp_chroma_location mploc)
+{
+    switch (mploc) {
+    case MP_CHROMA_LEFT:                return AVCHROMA_LOC_LEFT;
+    case MP_CHROMA_CENTER:              return AVCHROMA_LOC_CENTER;
+    default:                            return AVCHROMA_LOC_UNSPECIFIED;
+    }
+}
+
 // Return location of chroma samples relative to luma samples. 0/0 means
 // centered. Other possible values are -1 (top/left) and +1 (right/bottom).
 void mp_get_chroma_location(enum mp_chroma_location loc, int *x, int *y)

video/csputils.h

@@ -144,6 +144,7 @@ int mp_csp_levels_to_avcol_range(enum mp_csp_levels range);
 enum mp_csp mp_csp_guess_colorspace(int width, int height);
 
 enum mp_chroma_location avchroma_location_to_mp(int avloc);
+int mp_chroma_location_to_av(enum mp_chroma_location mploc);
 
 void mp_get_chroma_location(enum mp_chroma_location loc, int *x, int *y);
 

video/mp_image.c

@@ -411,7 +411,8 @@ bool mp_image_params_equals(const struct mp_image_params *p1,
            p1->w == p2->w && p1->h == p2->h &&
            p1->d_w == p2->d_w && p1->d_h == p2->d_h &&
            p1->colorspace == p2->colorspace &&
-           p1->colorlevels == p2->colorlevels;
+           p1->colorlevels == p2->colorlevels &&
+           p1->chroma_location == p2->chroma_location;
 }
 
 void mp_image_params_from_image(struct mp_image_params *params,
@@ -426,6 +427,7 @@ void mp_image_params_from_image(struct mp_image_params *params,
         .d_h = image->display_h,
         .colorspace = image->colorspace,
         .colorlevels = image->levels,
+        .chroma_location = image->chroma_location,
     };
 }
 

video/out/vo_x11.c

@@ -387,6 +387,7 @@ static bool resize(struct vo *vo)
         .d_w = p->dst_w,
         .d_h = p->dst_h,
     };
+    mp_image_params_guess_csp(&p->sws->dst);
 
     if (mp_sws_reinit(p->sws) < 0)
         return false;

video/sws_utils.c

@@ -19,6 +19,7 @@
 #include <assert.h>
 
 #include <libswscale/swscale.h>
+#include <libavcodec/avcodec.h>
 #include <libavutil/opt.h>
 
 #include "sws_utils.h"
@@ -227,6 +228,20 @@ int mp_sws_reinit(struct mp_sws_context *ctx)
     av_opt_set_double(ctx->sws, "param0", ctx->params[0], 0);
     av_opt_set_double(ctx->sws, "param1", ctx->params[1], 0);
 
+#if HAVE_AVCODEC_CHROMA_POS_API
+    int cr_src = mp_chroma_location_to_av(src->chroma_location);
+    int cr_dst = mp_chroma_location_to_av(dst->chroma_location);
+    int cr_xpos, cr_ypos;
+    if (avcodec_enum_to_chroma_pos(&cr_xpos, &cr_ypos, cr_src) >= 0) {
+        av_opt_set_int(ctx->sws, "src_h_chr_pos", cr_xpos, 0);
+        av_opt_set_int(ctx->sws, "src_v_chr_pos", cr_ypos, 0);
+    }
+    if (avcodec_enum_to_chroma_pos(&cr_xpos, &cr_ypos, cr_dst) >= 0) {
+        av_opt_set_int(ctx->sws, "dst_h_chr_pos", cr_xpos, 0);
+        av_opt_set_int(ctx->sws, "dst_v_chr_pos", cr_ypos, 0);
+    }
+#endif
+
     // This can fail even with normal operation, e.g. if a conversion path
     // simply does not support these settings.
     sws_setColorspaceDetails(ctx->sws, sws_getCoefficients(s_csp), s_range,