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If given a youtube video, where one part of the video is normal, and the other part is sped up so slightly that it's hard to notice... is there a technical way of proving that it is sped up or not?

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Would you consider posting a link in your question to the Youtube vid you referenced? – filzilla Feb 24 '12 at 20:11
I would but I was hoping to not go the direction of having a debate about whether or not it is sped up by visual alone. I was hoping for some technical advice about how to analyze such a video. If it is deemed necessary to post the youtube link, I'll do so. – Vigrond Feb 24 '12 at 20:23
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Understood. As you know there are numerous ways time can be manipulated. It may start with time-lapse or slow motion right in the raw shot, and it may include further manipulation in the video editor, either compressing the timeline or stretching it. The range will depend on the video editor, e.g. Vegas Pro will allow a 4 x either way. When you have an instance where two things are in the same frame but moving in different time domains, aka bifurcated time, it should be obvious and usually the extreme as illustrated here: vimeo.com/29213923. However, your case suggests something close. – filzilla Feb 24 '12 at 20:41
Thanks for allowing me to review the video. One one hand the crane like shots are a reference for the motion, these seem to indicate that the video was not sped up as the crane motion is pretty consistent. On the other hand after 3:38 when the piece picks up tempo, the medium and close up shots of the lead guitar show more blurring, which does look a bit unnatural. I think that since this was shot in a studio (less light than outside), the camera has to drag the shutter a bit and so blur would be expected, and faster tempo is going to make a CU of a hand appear more slurred. – filzilla Feb 24 '12 at 23:37
@filzilla: if anything, there would be less motion blur in a sped-up video – which could actually be used to determine if it was sped up, albeit only very inaccurately (and, of course, it would be easy to add the lacking blur in post-processing). Those shutter settings really don't have anything to do with the studio setting, 1. in any professional studio there is enough lighting to allow good camera settings and 2. since the light doesn't change, neither need the shutter settings, and such change is all that could be used to give a positive answer here. – leftaroundabout Feb 25 '12 at 0:38
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4 Answers

up vote 1 down vote

Slowing down a video is a magic thing, but isn't cinema magical?

  1. What we are dealing with?

Video/cinema is a big lie. All we have there are photos, called frames.

  1. What we are looking for?

To "slowdown" a "video", you need more frames per second. Since they cannot be recorded again with a higher speed cam, the only way is to create intermediate frames, just repeating, or blending frames.

You should look for this(repeated or mixed frames), as a prove of the "slowdown" process, made by a computer. If you made the "slowdown" in the cam (shooting more frames per second) the process is smooth, and no prove can be extracted. Sure you should download the video to your computer to do this kind of observation.

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Decent slow-motion algorithms will use more clever interpolation than just blending between pictures, so even when the video is slowed down to 1/4 its original speed there are no repeated or "mixed" frames. — Anyway, the question was about sped up, not slowed down. – leftaroundabout Apr 2 '12 at 9:46
lol. You right. My mistake. So, no prove at all. Sped up just steal frames, how u gonna look for this? – H_7 Apr 2 '12 at 23:10
up vote 0 down vote

There is nothing in this that looks or sounds even slightly sped up. As @leftaroundabout said, the original is paced a bit faster all the way through, but also has that tempo increase halfway through.

While being a fairly fast piece, it is not challenging enough that I would anticipate speeding it up for any reason.

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up vote 1 down vote

Technical reason's why I think this video is both not sped up but looks unnatural.

Using the camera crane tracking shots as a time consent, I am pretty certain the video was not sped when the music tempo stepped up as the camera crane tracking shots that follow this appear to be consistent with the earlier shots. So for my eyes, I do not see a sped up video.

The key thing I think that is going on here is that this was shot in a studio with studio lighting. Even with bright studio lights the stage area is large enough to demand the iris to be stopped down to get the most depth of field but the trade off is a slower shutter speed. When the music tempo picks up the close ups of the hands playing the lead guitar appear to be more slurred which looks unnatural. The longer shutter time explains why there is this slurring or blurring.

Another element to consider in favor of the video not having been sped up: this looks like a live show, in other words, there was no post production, everything was done live as for broadcast. You can't speed up video in real time and match it with the sound unless maybe you have a whole chain of effects and delay lines which does not seem practical for this.

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I would like to mark this question as answered, or give some thumbs up out, but your answer still strays from my technical answer request. Again, I do not want answers based on visual alone. If I handed this video to the FBI and asked them to prove it was sped up in a court of law, how would they prove or disprove it? They would need some kind of technical proof to do so, and conversations about how it looks or about how its blurry or unnatural do not provide anything really meaningful. I was looking more for something along the lines of analyzing frames, but I suppose there is no answer. – Vigrond Feb 28 '12 at 1:59
@Vigrond No, there isn't.. :( – Friend of Kim Feb 28 '12 at 13:49
What you are looking for is perhaps beyond the expertise of this group, Forensic video analysis is not something I would expect to get a solid answer on in this forum. However, you never know, maybe one of the CIA or FBI Forensic Video experts hangs out here? It never hurts to ask. Conclusion: understanding time constants, depth of field, slow shutter speed, and the possibility that this was a live broadcast are not technical enough to satisfy your answer. – filzilla Feb 28 '12 at 19:05
up vote 1 down vote

There is unfortunally (or maybe fortunally) no way to see if it is slowed down or sped up if done properly. What you have to look for is their movements. I'm not a guitar player, so I can't tell if it is real, but I think it sounded and looked real.

If you study the people there you can see that they move pretty natural. You can see on several occations that they blink in normal speed, but you also see that the main guitar player looks from place to place pretty rapidly. But from my experience with the piano you do everything a little bit faster when you play fast. Because you need to look at what you do, and when you are working hard with your brain and "slowing" everything down to keep up the pace you do things fast. The left hand finger movement also looked pretty natural. If it was sped down it would probably have been unnaturally fast and awquard movements.

Everything looked like it goes in normal speed, even their foots. Normally you have a constant speed on your foot when you tramp the beat. Depending on how slow you play you just increase the time you have your foot flat on the ground. Their foots didn't look like they went up and down too fast. If they had sped it up they would probably have had a small brake holding their foots flat on the ground before tramping the beat again really fast.

Secondly I don't see why a spanish TV programme would slow down their footage or why a good guitarist wouldn't be able to play that.

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See my comments above, this is precisely the type of answer I would like to avoid. Technical answers only please. – Vigrond Feb 24 '12 at 22:06
Yes, I answered that, but I also wanted to help you out. :) "There is unfortunally (or maybe fortunally) no way to see if it is slowed down or sped up if done properly. What you have to look for is their movements. " – Friend of Kim Feb 24 '12 at 22:34
is there a particular reason why it is not possible 'if done properly'? – Vigrond Feb 24 '12 at 23:12
FYI: I am a guitarist, and the hand movements look spot on. – filzilla Feb 24 '12 at 23:44
Yupp, so if you play the guitar and you too think it looked natural I think it's not sped up. The reason is that if you speed a video up you can use good programs or cheap programs. If you use AE you could for example use KRONOS to slow things down a lot, and it still looks real. If you use the right software and don't overdo it you can't detect it. Just an awkward example: Go through the alphabet. Note down the letters you can't say without moving your mouth. A ventriloquist changes these letters to letters you don't have to move your mouth to say. Example: F - Fabulous. If you thay Th – Friend of Kim Feb 25 '12 at 8:21
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