Update README and CMake scripts

- Add VPI library introduction to README
- Update minimum Holoscan version to 2.1.0
- Update CMake scripts to download precompiled libraries in build time

Signed-off-by: Mehmet Umut Demircin <mdemircin@nvidia.com>

Author: mdemircin

applications/precompiled_pva/README.md

@@ -25,7 +25,7 @@ The PreCompiledPVAExecutor operator performs an image sharpening operation in th
 2. Apply a 5x5 unsharp mask filter on the luminance color plane.
 3. Convert the enhanced image back to the RGB format.
 
-The [VPI library](https://developer.nvidia.com/embedded/vpi) offers numerous algorithm examples that leverage the PVA as the backend.
+Numerous algorithm examples leveraging the PVA can be found in the [Vision Programming Interface (VPI) library](https://developer.nvidia.com/embedded/vpi). VPI enables computer vision software developers to utilize multiple compute engines simultaneously—including CPU, GPU, PVA, VIC, NVENC, and OFA—through a unified interface. For comprehensive details, please refer to the [VPI Documentation](https://docs.nvidia.com/vpi/index.html).
 
 ## Compiling the application
 

applications/precompiled_pva/cpp/CMakeLists.txt

@@ -8,7 +8,7 @@
 # license agreement from NVIDIA Corporation is strictly prohibited.
 #
 
-find_package(holoscan 1.0.3 REQUIRED CONFIG
+find_package(holoscan 2.1.0 REQUIRED CONFIG
              PATHS "/opt/nvidia/holoscan" "/workspace/holoscan-sdk/install")
 
 add_executable(precompiled_pva
@@ -35,16 +35,24 @@ set(PVA_UNSHARP_MASK_URL "https://edge.urm.nvidia.com/artifactory/sw-holoscan-th
 # Define the URL for downloading cupva_allowlist_pva_unsharp_mask
 set(CUPVA_ALLOWLIST_URL "https://edge.urm.nvidia.com/artifactory/sw-holoscan-thirdparty-generic-local/pva/cupva_allowlist_pva_unsharp_mask")
 
-# Define a custom target for preparing libpva_unsharp_mask.a and cupva_allowlist_pva_unsharp_mask
-add_custom_target(prepare_pva_dependencies
+# Define a custom command for preparing libpva_unsharp_mask.a and cupva_allowlist_pva_unsharp_mask
+add_custom_command(
+  OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/pva_unsharp_mask/prepared.stamp"
   COMMAND ${CMAKE_COMMAND} -E cmake_echo_color --cyan "Preparing PVA dependencies..."
   COMMAND ${CMAKE_COMMAND} -E make_directory "${CMAKE_CURRENT_BINARY_DIR}/pva_unsharp_mask"
   COMMAND ${CMAKE_COMMAND} -E cmake_echo_color --green "Directory ensured at ${CMAKE_CURRENT_BINARY_DIR}/pva_unsharp_mask"
   COMMAND ${CMAKE_COMMAND} -D PVA_UNSHARP_MASK_LIB_DEST="${PVA_UNSHARP_MASK_LIB_DEST}" -D PVA_UNSHARP_MASK_URL="${PVA_UNSHARP_MASK_URL}" -D CUPVA_ALLOWLIST_URL="${CUPVA_ALLOWLIST_URL}" -D CUPVA_ALLOWLIST_DEST="${CUPVA_ALLOWLIST_DEST}" -P "${CMAKE_CURRENT_LIST_DIR}/PreparePVADependencies.cmake"
+  COMMAND ${CMAKE_COMMAND} -E touch "${CMAKE_CURRENT_BINARY_DIR}/pva_unsharp_mask/prepared.stamp"
   COMMENT "Preparing libpva_unsharp_mask.a and cupva_allowlist_pva_unsharp_mask"
 )
 
-add_dependencies(pva_unsharp_mask prepare_pva_dependencies)
+# Define a custom target that depends on the custom command
+add_custom_target(prepare_pva_dependencies ALL
+  DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/pva_unsharp_mask/prepared.stamp"
+)
+
+# Ensure the custom target is built before the main target
+add_dependencies(precompiled_pva prepare_pva_dependencies)
 
 # Update the IMPORTED_LOCATION to the new path in the build directory
 set_target_properties(pva_unsharp_mask PROPERTIES IMPORTED_LOCATION ${PVA_UNSHARP_MASK_LIB_DEST})