[nodes] KeyframeSelection: Flag outputExtension for video inputs

If at least one of the inputs is a video, then the `outputExtension`
attribute should never be set to "none": if it is, no frame will ever be
written on disk, and as a consequence, no SfMData file will be written,
meaning that the whole score computation and keyframe selection process
will have been done for nothing.

meshroom/nodes/aliceVision/KeyframeSelection.py

@@ -3,6 +3,9 @@
 import os
 from meshroom.core import desc
 
+# List of supported video extensions (provided by OpenImageIO)
+videoExts = [".avi", ".mov", ".mp4", ".m4a", ".m4v", ".3gp", ".3g2", ".mj2", ".m4v", ".mpg"]
+
 class KeyframeSelectionNodeSize(desc.DynamicNodeSize):
     def computeSize(self, node):
         inputPathsSize = super(KeyframeSelectionNodeSize, self).computeSize(node)
@@ -273,6 +276,8 @@ class KeyframeSelection(desc.AVCommandLineNode):
             value="none",
             values=["none", "exr", "jpg", "png"],
             exclusive=True,
+            validValue=lambda node: not (any(ext in input.value.lower() for ext in videoExts for input in node.inputPaths.value) and node.outputExtension.value == "none"),
+            errorMessage="A video input has been provided. The output extension should be different from 'none'.",
             uid=[0],
         ),
         desc.ChoiceParam(