Smooth accelerated video

[Bluelemmy]

I shoot on a Panasonic GH2. I travel regularly between London and Languedoc in the south of France, a drive which takes about 12 hours. The GH2 is hacked and does not have the 30 minute recording limitation and I can power it from the car rather than battery. I use a Manfrotto clamp to secure the camera to photograph through the windscreen. All of this works fine. I shoot 720p avchd. All works well. BUT....

I can happily shoot the entire journey on video but wish to reduce the play time from the full 12 hours to about one half of an hour. I can shoot a frame every couple of seconds using the GH2's electronic shutter but this gives very jerky and unrefined results. I can vIdeo the whole journey and speed it up in Sony Vegas but this seems a bit extreme.

How can I best achieve a half hour record of a 12 hour journey?

[transporterfan]

https://forum.videohelp.com/threads/344497-Best-method-for-time-lapse-video

[Bluelemmy]

Thanks for that. I hadn't thought to search on time lapse since I associate that with flowers opening and so on.

After a life time as a pro stills photographer with all it's associated jargon and methodology, I now have another lifetime's worth to learn for video

[intracube]

I can shoot a frame every couple of seconds using the GH2's electronic shutter but this gives very jerky and unrefined results.

This is probably because you haven't got much motion blur, which will make any movement stutter. What's the shutter been set to so far?

For example if you keep a 1/50th shutter but take a frame every 2 seconds and speed back up to 25fps, the shutter is effectively a 1/2,500. What you want to do is make the shutter half the framerate. If the framerate is 0.5fps, the shutter should be 1 second.

Background; because of mechanical limitations of cine cameras, the shutter couldn't be open much more than than 1/2 the duration of each frame (when shooting at traditional speeds) - because each frame of film takes time to be pulled through the gate. The shutter is synchronised to block the light while the film is moved on.
http://en.wikipedia.org/wiki/Rotary_disc_shutter

So shooting at normal speeds (24 or 25fps), the shutter would be something like 1/48 or 1/50th of a second. Video cameras don't have this limitation and the shutter can match the framerate - 50fps video might also have a 1/50th shutter.

*even though you could set the shutter to be the same as the framerate, it might make the footage look 'video like' and the movement smear too much - especially if you're filming at 24 or 25fps.

A strong neutral density filter to control exposure would be needed when shooting in daylight.

I can vIdeo the whole journey and speed it up in Sony Vegas but this seems a bit extreme.

How can I best achieve a half hour record of a 12 hour journey?

One advantage of recording the whole journey at a normal frame-rate is you'd have better control over the speed-up. You could choose to drop every other frame (2x speedup), only keep one out of every four frames (4x speedup), one out of every 8 frames (8x speedup) etc.

A complication of this method (which I don't think was discussed in the links transporterfan posted) is you'd run into the problem of stuttery video. It would be better to blend some frames together in addition to dropping others. This would give motion blur. So if you film this journey at a normal video framerate (50fps) with a 1/50 shutter, the first 25 frames would be mixed together in equal amount, the next 25 would be discarded. The process would then be repeated for the next 50 frames. Avisynth could probably automate this - I don't know if it can be done within Vegas.

[jagabo]

A simple AviSynth script to speed up your video and simulate motion blur:

WhateverSource("filename.ext") 
Merge(selectEven(), SelectOdd()) #2x
Merge(selectEven(), SelectOdd()) #4x
Merge(selectEven(), SelectOdd()) #8x
AssumeFPS(60000,1001)

A random dash cam video from Youtube using this script is attached (h.264 in MKV).

[Bluelemmy]

This is fascinating stuff which I need a while to absorb. I'm a stills man, thinking of movie as just being a stream of stills, so the concepts you mention are new (and exciting) to me. I don't find it intuitive that blur on a frame will look like anything other than blur on a still......in principle bad.

But this is moving pictures and the brain interprets it differently is what I glean from what you say and the example. I have to get my head around what you say and do a bit of experimentation.

I like the idea that I can shoot an original movie conventionally and then blend to get the result I want. Highly flexible. In a way, it reminds me of shooting RAW which I have since I went to digital cameras, in that you keep everything the sensor can give you and extract what you want but you can always go back to re-interpret or improve using the latest software.

Thanks for your generosity and expertise intercube and jagabo. Instead of feeling adrift, I now have a direction to travel.

[intracube]

A random dash cam video from Youtube using this script is attached (h.264 in MKV).

Nice example.

There are some artefacts on fast moving objects - probably because the original video was shot with a fast shutter. If the shutter had been set to match the framerate, fast moving objects would be blurred smoothly:

I don't find it intuitive that blur on a frame will look like anything other than blur on a still......in principle bad.

It depends if the whole frame is blurred uniformly (bad) or if the blur is limited to specific objects within the scene - a moving ball, someone waving their arms, etc (good). In the video jagabo posted, the main area of interest (the centre of the image) is free from blur - only the peripheral area is blurred.

Of course motion blur can be used purposefully in still photography too:
http://www.flickr.com/photos/mattzel/3875699410/

But this is moving pictures and the brain interprets it differently is what I glean from what you say and the example.

In the real world the eye/brain produce their own motion blur. Try waving your hand in front of your face (especially in low light). If TV/film ran natively at much higher framerates, the viewer's eye/brain would generate it. But because framerates are much lower (for film especially) motion blur needs to be part of the recorded image for it to look natural.

I like the idea that I can shoot an original movie conventionally and then blend to get the result I want. Highly flexible.

It would also mean you could temporarily drop back to normal speed (or even slow-motion) to highlight any interesting landmarks.

[jagabo]

A random dash cam video from Youtube using this script is attached (h.264 in MKV).

Nice example.

There are some artefacts on fast moving objects

Of course. Merge() simply blends pairs of frames together. If there's no motion blur in the source you get a multiple exposure look. The OP should use 1/50 second exposure and a 1/50 second frame or field rate. Then apply a similar script.

The OP could also try using one of the motion interpolation frame rate changers to increase the frame rate then several interations of Merge(). That would look more like motion blur. But the interopolators sometimes introduce artifacts.

Simple Merge() as above:


Three DoubleFPS() and three more Merge():

ffVideoSource("video.flv") 
Crop(0,0,640,360)
DoubleFPS2()
DoubleFPS2()
DoubleFPS2()
Merge(selectEven(), SelectOdd())
Merge(selectEven(), SelectOdd())
Merge(selectEven(), SelectOdd())
Merge(selectEven(), SelectOdd())
Merge(selectEven(), SelectOdd())
Merge(selectEven(), SelectOdd())
AssumeFPS(60000,1001)

[Bluelemmy]

Enough

I have plenty to mull over and learn here but you've given me a starting point to launch on my own discovery path . I's better than I had hoped for and thanks again.

Today, a novice. Tomorrow, riches, Oscars and a knighthood!

[Bluelemmy]

I've put my first attempt here - filmed from my bicycle going round Richmond Park in west London.

It's at 1/50th sec, shutter priority GH2 with ND filter and Olympus 12mm f2 lens. I shot it at 1280x720 25fps in cinema mode. I've cut it down to 640x480 so it is out of proportion but I'm only interested in the motion effect at this moment.

I took the avchd file, converted it to .mov and brought it into Quicktime. This was half an hour long. The I loaded another video of 2 mins length and copied the first video into it using paste and scale and deleted the shorter video, leaving the original 30 minute video showing over 2 minutes. It seems to work pretty well but I'd appreciate any comments. Just to reiterate, it's movement that interests me, I've been a pro stills man all my life, so the other technicalities (colour/ sharpness etc) I can sort out.

I find that on my 20Mb cable connection, the first part of the video is jerky due to streamning reasons I suppose,so it may be better to download it and view.

Comments appreciated....

http://www.dthorpe.net/viewing/park_ride.htm

[intracube]

I'm not familiar with Quicktime, but the way it's speeding up the video is by dropping/deleting frames (rather than combining them).

To get a better quality result, you'd need to use a method that combines/merges a number of frames down to one - like jagabo's suggestion in post #5.

If you're filming at 25fps, the shutter speed should also be 1/25th sec. That way, blurred objects will be blurred smoothly.

Because the original footage isn't particularly stable, using this method might make the speeded up video excessively blurred. Using image stabilization software on the source before speed conversion will help.

After Effects can probably do something comparable to avisynth.

[jagabo]

Yes, using image stabilization should help. If you blend multiple frames you may have to deshake before and after blending. Sometimes video can look worse after deshaking. When the camera is shaking a lot you get motion blur. After deshaking the motion may go away but you still have blurry frames. It's disconcerting to see those blurry frames when there's no motion!

It's not clear to me that blending multiple frames is better than simple decimation. It's just a different look.

[Bluelemmy]

With the bike videos, I have rigged up a frame that sits on my shoulders. It's the stablest way of getting cycle video I can find because any mounting on the bike itself, which has suspension, is unbearable jittery plus I doubt the cams would survive for long. I could avoid some of the effect by cutting out the brake cables or handlebars but that tends to make the video look bland with no sense of perspective or travel.

Video from my car will be more stable, of course, though the windscreen. The car most of the time will be travelling at fairly high speed on the French autoroute and it may be that a 25th sec shutter speed Would provide enough blur without frame blending. But I shall try both.

Given the amount of jitter and the nature of it, I'm not convinced that any stabilisation would improve things. Again, an area to explore. Thanks for the input, all very helpful and welcome.

[intracube]

After deshaking the motion may go away but you still have blurry frames. It's disconcerting to see those blurry frames when there's no motion!

Yep. I've seen post stabilised footage which has this effect. It looks like someone has applied a directional blur intermittently throughout the video. Quite disconcerting. The only way to know if this will be an issue with the bike footage is to try applying stabilisation.

It's not clear to me that blending multiple frames is better than simple decimation. It's just a different look.

As you know, most video has significant motion blur. Video will often have a shutter speed the same duration as each frame (50fps video, 1/50th sec). Film shutter is usually half the duration of each frame (24fps, 1/48th sec). Having video with effectively no motion blur is at odds with this. An exception to this rule is stop frame animation which doesn't (usually) have motion blur.

Having little or no motion blur can be used (carefully) as an effect:

Given the amount of jitter and the nature of it, I'm not convinced that any stabilisation would improve things.

I think it could help quite a bit. Only way to know for sure is to try.

[jagabo]

I know the difference between motion and no motion blur. I'm saying I don't consider one or the other to be superior with this type of application, just different, a personal preference. Motion blur does reduce apparent flicker at low frame rates.

[Cornucopia]

If it were me, I'd take the shots with NO motion blur, then apply MB in post. More controllable for whatever situation, and you have other options down the road. Much like what's done with Sports cams doing Slo-mo instant replays - they're using fast shutter cams and applying a digital post-MB at playback.

I like that you can quickly and easily (and freely) do this in AVISynth, but it's much more fun to do it in AE with time remapping, as then you can do fancy ramp-ups and -downs to get the pacing exactly as you want.

AFA stabilization goes: on a bike, the most stable place is probably your head or shoulders, so you're guessing smartly. On cars, you need both stabilization from the BIG shocks and DAMPING of the little jitters (wow & flutter). A rig bolted to the chassis and then damped with rubberized mat/cushion or similar works well. (I have a custom Sand/Water/Air bag that does the trick)

I think what you want is ~1FPS capturing. Assuming you had 24fps capturing (I know you really have 25, but for the sake of argument), and you are dropping from 12 hours (aka 720 minutes) to 30 minutes, that's 720/30 = 24:1. So capping at 1Fps should give you the look you want. Using intercube's rules, that would mean having a shutter speed of 1/2 sec. But as was mentioned, you probably can't go that slow with cams like that, so you could do what I suggest and keep the ShutterSpeed short and MB in post (by merging frames, or similar options metioned by jagabo).

Alternatively, you could try the AVISynth:

AVISource("video.avi")
SelectEvery(25)
AssumeFPS(25)

...and see which one you like better.

Scott

[Bluelemmy]

After much experimentation, I've found that I can get a pretty good effect using VirtualDub (thanks for the recommendation!) and increasing the frame rate from 25 to 250.

Basically, I bought a 32GB Class 10 SD card for the GH2 and can get over 5 hours recording at 720p.With my other 16GB cards (and car power source instead of battery) I can get the whole trip on video.

I presume that when I increase the frame rate to 250 I cannot really see that, given the refresh rate of a computer monitor?

Am I missing anything? Increasing the frame rate seems all I need if I elect to video at normal frame rate. Should I drop some frames and lower the frame rate?

[Cornucopia]

You want the FINAL framerate to be NORMAL (50i, 25p, 50p, etc). So you start with 50p (or 50i, deinterlacing if needed) of 5 hours and modify the FR header to 250p, giving you ~30min?
Then you apply the right kind of Frame-Averaging Motion blur and bring the FR back down (by dropping frames, after they've been "averaged") to 50i or 50p (depending on how you expect to view it).
This should keep the length of program @ ~30min.

*Note: if you do want to keep interlaced, you'll have to be careful to maintain field structure during those intermediate stages, like avoiding resizing & maintaining cadence. I might even consider doing a 2-path workflow, one path for each field.

Scott

[berenger]

I like that you can quickly and easily (and freely) do this in AVISynth, but it's much more fun to do it in AE with time remapping, as then you can do fancy ramp-ups and -downs to get the pacing exactly as you want.

Hello, I try AVISynth and it's very cool alternative, but for my workflow, and for my brain, i would like know how you make this effect with After-effects and the time remapping please.

Sorry for my bad English, I'm French..

[poisondeathray]

I like that you can quickly and easily (and freely) do this in AVISynth, but it's much more fun to do it in AE with time remapping, as then you can do fancy ramp-ups and -downs to get the pacing exactly as you want.

Hello, I try AVISynth and it's very cool alternative, but for my workflow, and for my brain, i would like know how you make this effect with After-effects and the time remapping please.

Sorry for my bad English, I'm French..

Which one specifically? Exactly what do you want to do ? Cornucopia was talking about ramping (speed up, speed down, go reverse, that sort of thing)

AE is capable of many different methods and "looks" for time manipulations, had many different "time" plugins as well (you can do this as a plugin as well with the CC Time plugins) . You can add motion blur with CC Force Motion Blur

[berenger]

Recreate a motion blur with acceleration in video, like the exemple in a car.

[poisondeathray]

Recreate a motion blur with acceleration in video, like the exemple in a car.

OK, that's not specific enough - there are several of different ways you might do this . Look at the screenshots above - there are many different types of blurs

If you want one way - enable time remapping for the layer , and move the last keyframe. Enable both frame blend for the layer, and for the composition

Other ways - you can use timewarp plugin with CC Force Motion Blur , or other effects like CC Wide Time etc...

[as264]

As done above, in MVTools2 it is possible to increase the framerate, then merge these frames together. This seems inefficient to keep performing motion analyses and merging them, and there will still be "gaps" between the frames that are being merged. Is there no way to, in effect, set the shutter speed (to increase it to effect motion blur) for the frames that are being generated?

I'm also thinking this would be useful for reducing 60/50fps to 30/25fps - ie give MVTools2 the 60fps content for motion analysis and ask it to output 30/25fps with each frame having a shutter speed of 1/60 or 1/50 (to obey the 180 degrees shutter rule).

At the moment I'm thinking I'd have to increase the framerate to say 4 times the input (which would then be 8 times the output framerate), and alternate between merging 4 consecutive frames and deleting the next 4, to achieve the gap for 180 degrees shutter. Even then it's not going to look perfect and will take a lot of processor power.


PS - I also found this function (http://avisynth.nl/index.php/SmoothFreezeFrame) which seems to feature another way of merging frames, using TemporalSoften:

function SmoothFreezeFrame(clip clip, int start, int end) {
  replace = clip.trim(start,end)
  smooth = replace.TemporalSoften(round((end-start)/2),255,255,255,2)
  insert = smooth.FreezeFrame(0,end-start,round((end-start)/2))
  return clip.Trim(0,start-1)+insert+clip.Trim(end+1,0)
}

[jagabo]

QTGMC() has motion blur ability. One example: https://forum.videohelp.com/threads/361756-Converting-50p-to-25p-without-simply-droppin...=1#post2295927

[racer-x]

Reading through this thread gave me an inspiration to shoot my own Dashboard video and speed it up. I used a simple Compact digital camera and shot video in auto mode. I didn't have any mounting brackets and just sat the camera on my hat on the dashboard, it almost fell twice.

I use variable speed ramps effect with full speed at 8x. I didn't add any blur or frame blending. What you see is what I got minus the resizing and compression. I think it looks pretty good on it's own, maybe next time I'll wash the windshield........