I did some testing on my end and think this is related to the AVC decoder running slower than it should. We use the same decoder to decode other AVC files like Canon 5d/7d, GoPro etc. If I run the XAVC file through that code I get 100% CPU usage, but I also almost max out my memory. I have 16 GB and was using 15.8 GB.
To me this points to the decoder not being setup properly when used with the Sony SDK. We could very easily switch the code so XAVC files go through the same path as other AVC files, but I think we should use the Sony SDK to read metadata from the files. I’ll see what I can do to get the decoder to behave as expected with the Sony SDK.