Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

What you need to know before touching a video file

gist.github.com

Post reply on HN
Print view View original

91–100 of 251 posts

Re: What you need to know before touching a video file

#91

Post by mrguyorama »

yaur wrote: post #75
ramesh31 wrote: post #12

Earlier quoted context omitted.

technically correct is the best kind. who cares if it's obnoxious? take the opinions and agree or disagree with them.

When we switched from x264 to hardware based encoders it saved something like 90% on our customers' power and cooling bills. So while this essay might be "technically correct" in some very narrow sense the author is speaking with far more authority than they have the experience to justify, which is what makes it obnoxious in the first place.

The author is directing this at complete noobs who are subbing their first anime and you are complaining that it is not applicable to running a datacenter?

Re: What you need to know before touching a video file

#92

Post by derefr »

netsharc wrote: post #86

The second technical definition in this document is wrong. Great way to put the "the author is opinionated but is clueless" marker right near the top. > Actual video coding formats are formats like H.264 (also known as AVC) or H.265 (also known as HEVC). Sometimes they're also called codecs, short for "encode, decode". Codec is coder/decoder. It's not the format. There's a footnote claiming people mix the 2 terms up…

> If you want to educate, educate with precision, and don't spread your misinformation!

I would assert that the author was already being precise. A statement that X is "sometimes called" Y already conventionally carries the subtext that Y isn't actually the correct term; that Y is instead some kind of colloquial variant or corrupted layman's coinage for the more generally-agreed-upon term X.

Why mention the incorrect terminology Y at all, then?

Specifically in the case that pertains here, where far more laymen are already familiar with the Y term than the X term, giving Y as a synonym in the definition of X is a way to give people who are already familiar with this concept — but who only know it as Y — an immediate understanding of what is being discussed, by connecting their knowledge of "Y" over to the X term the author is defining. This is an extremely common practice in academic writing, especially in textbooks.

Re: What you need to know before touching a video file

#93

Post by abanana »

Waterluvian wrote: post #10
Jabrov wrote: post #6

What's wrong with VLC?

Making such a bold, unsubstantiated claim is a curious item in an otherwise detailed document. I went looking for other explanations and found this gem: https://www.reddit.com/r/mpv/comments/m1sxjo/it_is_better_mp... I think it might be one of those classic “everyone should just get good like me” style opinions you find polluting some subject matter communities.

Yes, absolutely. The top answer on that Reddit link starts with: "MPV is the ultimate video player on planet earth, all the others are junk in comparison" and doesn't mention VLC at all. That's not a helpful answer, it's just signalling that they're a huge fan of MPV, with nothing to suggest they've ever even tried anything else.

Re: What you need to know before touching a video file

#94

Post by ErroneousBosh »

memoriuaysj wrote: post #79
ErroneousBosh wrote: post #62

Earlier quoted context omitted.

> Is there a way to "undo" motion blur and get a sharp picture? Not really, no, any more than there is a way to unblur something that was shot out of focus. You can play clever tricks with motion estimation and neural networks but really all you're getting is a prediction of what it might have been like if the data had really been present. Once the information is gone, it's gone.

it's not gone, just more difficult to extract video has certain temporal statistics which can allow you to fit the missing information only true blurred white noise is impossible to recover

It really is gone. You can predict what you think it might have been, but you can't know what it was.

Re: What you need to know before touching a video file

#95

Post by unloader6118 »

echelon wrote: post #80
cnntth wrote: post #55

Earlier quoted context omitted.

OP makes zero comments about content generation, and the complaint is about upscaling introducing artifacts not in the original source. No different than hating a bad 4k remaster / sharpening.

That advice is not universal, and without context it's simply wrong. You wouldn't upscale a classic film in this way, but there are plenty of low-resolution shots that benefit. Especially with VGA resolution renders and modern AI workflows. Just looking at the Topaz marketing, you can see a lot of places where it indeed does work. And 20-year industry professionals are using it today for their day jobs. If you want t…

In any case, blindly apply upscaling is just wrong ..

You apply it to where it is needed. Not every scene need the same treatment.

Re: What you need to know before touching a video file

#96

Post by memoriuaysj »

ErroneousBosh wrote: post #94
memoriuaysj wrote: post #79

Earlier quoted context omitted.

it's not gone, just more difficult to extract video has certain temporal statistics which can allow you to fit the missing information only true blurred white noise is impossible to recover

It really is gone. You can predict what you think it might have been, but you can't know what it was.

it's gone in a single still frame

but across many consecutive frames, the information is spread out temporaly and can be recovered (partially)

the same principle of how you can get a high resolution image from a short video, by extracting the same patch from multiple frames

https://en.wikipedia.org/wiki/Video_super-resolution

Re: What you need to know before touching a video file

#97

Post by coppsilgold »

MPV plugins can actually do frame-perfect cuts and crops for you (+ whatever ffmpeg filters you want), something that would generally require the hassle of opening editing software. And those cuts can be done in h264 lossless (for additional processing later at no additional quality loss from this step).

https://github.com/occivink/mpv-scripts

There is also a way to losslessly cut preserving the original encoding but you give up the precision of the cuts due to keyframes. The MPV script above can do that too: script-opts/encode_slice.conf

Re: What you need to know before touching a video file

#98

Post by pomian »

dylan604 wrote: post #20
ramesh31 wrote: post #12

Earlier quoted context omitted.

technically correct is the best kind. who cares if it's obnoxious? take the opinions and agree or disagree with them.

How do you know it is technically correct without explanation. It's not much different from someone getting blown off for being annoying because they constantly question simple answers when seeking better understanding. I was fortunate to work with a group of engineers when I was very young that accepted my constant use of "why?" not as disrespectful questioning but realized I was actually learning so they naturally…

Why? Is the most simple test of a valid explanation. If you don't need to ask why any more, you've answered the question. Sometimes it takes 3 or 5 white in a row!

Re: What you need to know before touching a video file

#99

Post by rfl890 »

Etheryte wrote: post #17
embedding-shape wrote: post #9

It seems really weirdly written. It's written with a lot of authority, like saying "Don't use VLC" and "Don't use Y" yet provides no reasoning for those things. Just putting "Trust me, just don't" doesn't suddenly mean I trust the author more, it probably has the opposite effect. Some sections seem to differ based on if the reader knows/doesn't know something, but I thought the article was supposed to be for the latt…

Exactly, very hard to take the rest of it seriously after the VLC bit. VLC has literally never left me hanging, across I don't know how many decades. It's gonna take more than a trust me bro to challenge that.

VLC has always caused problems for me when seeking backwards (graphical glitches). mpv has never caused any issues in this regard.

Re: What you need to know before touching a video file

#100

Post by perching_aix »

memoriuaysj wrote: post #85
perching_aix wrote: post #84

Earlier quoted context omitted.

Drives me crazy but I'm glad to learn of it :D Makes a lot of sense in retrospect, to the extent it bothers me I haven't figured it out myself earlier.

this is exactly what "higher" compression levels do (among other things like bigger dictionary) - they try harder, more iterations, to find the optimum combination of available knobs for a particular chunk of data.

Yes, that much was always clear. I just always thought the way these software go about finding those combinations was also standardized on a high level rather than proprietary to each implementation. It is a fairly recent development for me to realize that the various encoder options and presets are specific to the encoder, not the format (and now, that the same is true for lossless formats too).
Post reply on HN