gstreamer-encoder: Add video metadata for DMA-BUF

Include video metadata when using DMA-BUF to provide stride and
offset. Without this metadata, GStreamer may incorrectly interpret
the buffer layout, leading to corrupted image output—especially
when the framebuffer includes padding.

server/gstreamer-encoder.c

@@ -1805,6 +1805,15 @@ spice_gst_encoder_encode_dmabuf(VideoEncoder *video_encoder,
         }
         gst_buffer_append_memory(buffer, mem);
     }
+    
+    gst_buffer_add_video_meta_full(buffer,
+        GST_VIDEO_FRAME_FLAG_NONE,
+        encoder->format->gst_format,
+        dmabuf_data->width,
+        dmabuf_data->height,
+        dmabuf_data->num_planes,
+        dmabuf_data->offset,
+        dmabuf_data->stride);
 
     gst_mini_object_weak_ref(GST_MINI_OBJECT(buffer),
                              (GstMiniObjectNotify)spice_gst_mem_free_cb,