I noticed MKVToolnix is not warning us the fps will be set to 25 when opening .264 files (original source is MPEG-4 AVC). This one was extracted from a Blu-ray (I used TSMuxer GUI on a m2ts file), released in US. I usually informed this setting in the MKVToolnix fps tab:
Can you confirm if we need to keep doing that or if it's not necessary anymore?