vo_drm: add support for RGB565

This image format is quite legacy, but uses half as much bandwidth as
the closest XRGB8888, at 16bpp instead of 32bpp, so it is useful to
support on the slowest/oldest display controllers.

DOCS/man/vo.rst

@@ -646,12 +646,13 @@ Available video output drivers are:
         lower resolution (the video when handled by the hwdec will be on the
         drmprime-video plane and at full 4K resolution)
 
-    ``--drm-format=<xrgb8888|xbgr8888|xrgb2101010|xbgr2101010|yuyv>``
+    ``--drm-format=<xrgb8888|xbgr8888|xrgb2101010|xbgr2101010|rgb565|yuyv>``
         Select the DRM format to use (default: xrgb8888). This allows you to
         choose the bit depth and color type of the DRM mode.
 
         xrgb8888 is your usual 24bpp packed RGB format with 8 bits of padding.
         xrgb2101010 is a 30bpp packed RGB format with 2 bits of padding.
+        rgb565 is a 16bpp packed RGB format with reduced colour accuracy.
         yuyv is a 32bpp packed YUV 4:2:2 format. No planar formats are currently
         supported.
 

video/out/drm_common.c

@@ -99,6 +99,7 @@ const struct m_sub_options drm_conf = {
             {"xrgb2101010", DRM_OPTS_FORMAT_XRGB2101010},
             {"xbgr8888",    DRM_OPTS_FORMAT_XBGR8888},
             {"xbgr2101010", DRM_OPTS_FORMAT_XBGR2101010},
+            {"rgb565",      DRM_OPTS_FORMAT_RGB565},
             {"yuyv",        DRM_OPTS_FORMAT_YUYV})},
         {"drm-draw-surface-size", OPT_SIZE_BOX(draw_surface_size)},
         {"drm-vrr-enabled", OPT_CHOICE(vrr_enabled,

video/out/drm_common.h

@@ -34,6 +34,7 @@ enum {
     DRM_OPTS_FORMAT_XRGB2101010,
     DRM_OPTS_FORMAT_XBGR8888,
     DRM_OPTS_FORMAT_XBGR2101010,
+    DRM_OPTS_FORMAT_RGB565,
     DRM_OPTS_FORMAT_YUYV,
 };
 

video/out/opengl/context_drm_egl.c

@@ -594,6 +594,10 @@ static bool drm_egl_init(struct ra_ctx *ctx)
         argb_format = GBM_FORMAT_ABGR8888;
         xrgb_format = GBM_FORMAT_XBGR8888;
         break;
+    case DRM_OPTS_FORMAT_RGB565:
+        argb_format = GBM_FORMAT_RGB565;
+        xrgb_format = GBM_FORMAT_RGB565;
+        break;
     default:
         if (drm->opts->drm_format != DRM_OPTS_FORMAT_XRGB8888) {
             MP_VERBOSE(ctx->vo, "Requested format not supported by context, "

video/out/vo_drm.c

@@ -109,6 +109,10 @@ static struct framebuffer *setup_framebuffer(struct vo *vo)
         p->drm_format = DRM_FORMAT_XBGR8888;
         p->imgfmt = IMGFMT_RGB0;
         break;
+    case DRM_OPTS_FORMAT_RGB565:
+        p->drm_format = DRM_FORMAT_RGB565;
+        p->imgfmt = IMGFMT_RGB565;
+        break;
     case DRM_OPTS_FORMAT_YUYV:
         p->drm_format = DRM_FORMAT_YUYV;
         p->imgfmt = pixfmt2imgfmt(AV_PIX_FMT_YUYV422);