mp_image: add support for AVAlphaMode

video/mp_image.c

@@ -1102,9 +1102,17 @@ struct mp_image *mp_image_from_av_frame(struct AVFrame *src)
         dst->params.stereo3d = p->stereo3d;
         // Might be incorrect if colorspace changes.
         dst->params.light = p->light;
+#if LIBAVUTIL_VERSION_INT < AV_VERSION_INT(60, 11, 100) || PL_API_VER < 356
         dst->params.repr.alpha = p->repr.alpha;
+#endif
     }
 
+#if LIBAVUTIL_VERSION_INT >= AV_VERSION_INT(60, 11, 100) && PL_API_VER >= 356
+    // mp_image_setfmt sets to PL_ALPHA_INDEPENDENT, if format has alpha.
+    if (dst->params.repr.alpha == PL_ALPHA_INDEPENDENT)
+        dst->params.repr.alpha = pl_alpha_from_av(src->alpha_mode);
+#endif
+
     sd = av_frame_get_side_data(src, AV_FRAME_DATA_DISPLAYMATRIX);
     if (sd) {
         int32_t *matrix = (int32_t *) sd->data;