fix(server): fix DPB corruption on NVIDIA

Using UNDEFINED as the source layout when transitioning the DPB buffer for
access causes the driver to discard the DPB contents, which results in
corruption when the image is used as a reference for a future frame.

mm-server/src/compositor/video/vulkan_encode.rs

@@ -508,7 +508,7 @@ impl EncoderInner {
                         .src_access_mask(vk::AccessFlags2::NONE)
                         .dst_stage_mask(vk::PipelineStageFlags2::VIDEO_ENCODE_KHR)
                         .dst_access_mask(vk::AccessFlags2::VIDEO_ENCODE_READ_KHR)
-                        .old_layout(vk::ImageLayout::UNDEFINED)
+                        .old_layout(vk::ImageLayout::VIDEO_ENCODE_DPB_KHR)
                         .new_layout(vk::ImageLayout::VIDEO_ENCODE_DPB_KHR)
                         .image(pic.image)
                         .subresource_range(vk::ImageSubresourceRange {
@@ -531,7 +531,7 @@ impl EncoderInner {
                         vk::AccessFlags2::VIDEO_ENCODE_WRITE_KHR
                             | vk::AccessFlags2::VIDEO_ENCODE_READ_KHR,
                     )
-                    .old_layout(vk::ImageLayout::UNDEFINED)
+                    .old_layout(vk::ImageLayout::VIDEO_ENCODE_DPB_KHR)
                     .new_layout(vk::ImageLayout::VIDEO_ENCODE_DPB_KHR)
                     .image(setup_pic.image)
                     .subresource_range(vk::ImageSubresourceRange {
@@ -1014,9 +1014,11 @@ fn default_structure(
     // let mut layers = std::cmp::min(4, max_layers);
     let mut layers = 1;
 
-    const DEFAULT_GOP_SIZE: u32 = 32;
-    let gop_size = if device_vendor == Vendor::Nvidia {
-        1
+    const DEFAULT_GOP_SIZE: u32 = 256;
+
+    // TODO: Radv has a bug that causes the encoder to truncate POC.
+    let gop_size = if device_vendor == Vendor::Amd {
+        32
     } else {
         DEFAULT_GOP_SIZE
     };