Is it True? Conversion Question

[ericbincat]

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[smrpix]

Take the example of a BBC documentary distributed on DVD in the US. It may have film clips at 24 fps, interviews shot in UK at 25fps, interviews shot in US at 29.97 fps, classsic television kinescoped 25fps->25fp or 29.97 fps->24fps->25fps, computer animation @2k 60p, or 50p, a Disney animated clip shot in 2's -- effectively 12fps... All of this reconciled with better or worse methods to 25i and converted by terenex to 29.97i

So yes, the DVD is generally going to be the best source you can get your hands on, but you have to go to the original source of each clip to find out what they really are.

Hope that's clear

[Selur]

If you want to know a file's (.mkv, .mp4., .avi etc) true media information,...

then you will have to write a lot of code yourself.
Why? Because to get reliable information about a file, quite a bit of analysis has to be made.
Most tools simply stick to the infos provided in the headers of the file (if that is enough use MediaInfo and be happy).
If you want reliable infos about interlace patterns, time codes, color metrics,.. you have to analyse the whole source, frame-by-frame which takes quite some time and isn't easy. For interlacing MeGui and similar tools have Avisynth based interlaced detection routines, which are not 100% reliable, but a good step in the right direction. (Side note: I tried to implement something similar mplayer based, but it isn't as reliable and informative as the Avisynth based analysis, but good enough for the content I normally encounter.)

-> I'm not aware of any tool which does a reliable in-depth media analysis of files and I doubt that there is one. Especially if it comes to colors and interlacing there is a lot of stuff that can go wrong.

For most users a 'simple' header analysis like MediaInfo does is enough.
(btw. DVDs are also not always properly flagged, which sometimes seems to be a part of some sketchy copy-protection scheme, which things that providing false informations in headers and dummy or broken tracks will prevent users from copying their content; on Blu-rays this and similar is more and more common practice)

[hello_hello]

DVDs are always constant frame rate. Whether they're interlaced, or in the case of NTSC, use 3:2 pulldown (telecine), is another story. And of course NTSC can be a combination of both. The frame rate is always 29.970 though. PAL is generally either interlaced or progressive.

That's best case scenario in a way. For DVDs the framerate will always be constant and in theory they're either interlaced, telecined or progressive, but all sorts of horrible things can be done in order to get there, depending on the frame rate of the source video etc.

MKVs and MP4s are usually encoded after de-interlacing and more often than not they're progressive with a constant frame rate, but there's no guarantee if they're encoded from interlaced/telecined video it was done correctly, or the best way, and of course one of the more popular encoder GUIs (Handbrake) spits out variable frame rate video by default, so anything's possible.

[ericbincat]

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[smrpix]

Not the answers OP was hoping for, I guess.