"Who designed this user interface, Stevie Wonder?" Actual statement from a LE technician, and point well taken when it comes to proprietary DCCTV players. They're often horribly designed, and like all multimedia players/editors/tools regardless of who makes them, they are time & resource dependent (e.g. hardware resources, drivers, frameworks, codecs, etc.).
As I say in every one of our training classes, ALL software has strengths & weaknesses. Not just Proprietary DCCTV players, but software from Microsoft, Adobe, and even software designed by & for specific markets or niches. All software, period.
When it comes to multimedia evidence there are more variables to consider than with any other type of digital evidence. When a couple pixels in one frame of video really matters, hopefully you're not trusting a single tool.
Furthermore, I don't recommend that anyone goes to court without having reviewed their video evidence in the Proprietary DCCTV player specifically designed to playback that evidence. That'd be sort of like a ballistics expert choosing to compare a 9mm casing & round to their controlled tests that were done using a S&W .38 Special. Dumb, IMHO.
For investigative processing, both Open Source and specialized software & tools can and do save tremendous amounts of time. Like it or not though, they too have shortcomings, which a properly trained & equipped Forensic Analyst should be further investigating in the controlled environment of their lab.
Are you missing entire streams of evidence? What about the GPS, Velocity or PoS data stored in that proprietary In-Car or DCCTV file? Other text or metadata that FFmpeg or your specialized tool can't parse?
Tools are vital at every stage of criminal prosecution, from evidence collection through court presentation. Regardless of who you work for, Analysts should seek knowledge & truth, not the path of least resistance. Be safe out there my friends!