How to separate two videos playing simultaneously on both fields?

[Master Tape]

Never encountered a tape like this before, where two videos play at the same time, one in the top field, and the other in the bottom field, as both were filmed at the same time on two different cameras. When i pause the video in my machine, i get a full image.

[Sharc]

No idea what's the purpose of this, but you can separate like

AVISource("Fields.avi")
v=last.assumeTFF().QTGMC(lossless=1)
v1=v.selectevery(2,0)
v2=v.selectevery(2,1)

return v1 #or v2 vor video2

There will be some color crosstalk though.

[Master Tape]

No particular purpose, just fascinated to view the rest of the footage back so i can see what's going on, and for any tapes i encounter like this in future.

Thanks, that's great, i can switch between one or the other. Also how do i slow down the footage so it's playing at normal speed, and corresponds to the seconds on the clock, as it's playing a bit too fast.

[jagabo]

The given script does not change the frame rate. So if it's playing too fast it's because the source is too fast. You can use AssumeFPS() to lower it to whatever you want. You'll need to slow the audio too.

[Master Tape]

Yes i know it's the source and not the script that's causing the fast speed. It plays like that in my VCR. I'm guessing so they could fit more footage on a 3 hour tape. After reducing the FPS to match the timer, it only amounts to 5fps, yet you'd think it was more, amazing really.

[DB83]

TBH I am struggling to understand this.

Are you saying that you (or someone else) are feeding two independently recorded streams to one vcr and then capturing that ? Surely that is doomed to fail whatever.


The recording speed of the original has no bearing on the recording speed of the capture. That will, or should, be 25fps for PAL. But, of course, software such as vdub does allow you to reduce the recording speed of the capture. Yet even then you should get a pure capture.

[johnmeyer]

Pretty interesting video. It is obviously security camera footage and they got double the storage by using fields instead of frames. They actually got 4x the storage because each camera was sampled only once every 1/25 second. You can count, using the timecode and the seconds advance each 12.5 "frames," once you separatefields or bob.

I am surprised how clear the resulting video is.

I did my quick test using Vegas, but if I were to do it in AVISynth, I would avoid using QTGMC and just simply do a bob followed by a selecteven and selectodd.

This isn't tested, but it would be something like:

new=bob(0.0,1.0)
Camera1=selecteven(new).AssumeFPS(25.0/2)
Camera2-selectodd(new).AssumeFPS(25.0/2)

[jagabo]

Or something like:

AViSource("Fields.avi") 
SeparateFields()
nnedi3(dh=true)
StackHorizontal(SelectEven(), SelectOdd())

[Master Tape]

Here's some people in shot to give some perspective of motion.

[Master Tape]

Pretty interesting video. It is obviously security camera footage and they got double the storage by using fields instead of frames. They actually got 4x the storage because each camera was sampled only once every 1/25 second. You can count, using the timecode and the seconds advance each 12.5 "frames," once you separatefields or bob.

I am surprised how clear the resulting video is.

I did my quick test using Vegas, but if I were to do it in AVISynth, I would avoid using QTGMC and just simply do a bob followed by a selecteven and selectodd.

This isn't tested, but it would be something like:

new=bob(0.0,1.0)
Camera1=selecteven(new).AssumeFPS(25.0/2)
Camera2-selectodd(new).AssumeFPS(25.0/2)

Yeah it is quite clever actually. I believe they'd play correctly on a Time Lapse video player that security staff use, which have Rec/Play modes "Up" "Down" to display the corresponding field.

Why no QTGMC, wont it clean up the noise better? Saying that i don't notice much difference between the two.

12.5fps still seems a bit fast to my eyes, even half of that is still a little speedy. 5 frames looks to be the most normal speed. I think most old CCTV ran at low frame rates like this.

[johnmeyer]

12.5fps still seems a bit fast to my eyes, even half of that is still a little speedy. 5 frames looks to be the most normal speed. I think most old CCTV ran at low frame rates like this.

You have an on-screen timecode so unless I'm missing something, you just simply count the number of frames it takes until the one second digit changes. After I separated the video into two streams I pressed the frame advance button 12-13 times to get to the next second.

[jagabo]

Yes, the on-screen timecodes start at 09:42:26 and end at 09:44:56, a difference of 2:30 seconds -- so 150 seconds. The timecodes of the video frames shows a length of 30 seconds. So you need to slow by a factor of 5. 25 fps/5 = 5 fps.