Handling 720p Captures of Orginally 24 FPS Content

[blazerqb11]

I was wondering if someone could give me some advice on how to deal with re-encoding 720p TV captures of videos that were originally 24 fps, such as animation. I'm not really sure what the process is for converting 24p to 60p for broadcasting, so I don't know how I should proceed with lowering the frame rate.

[blazerqb11]

Did I post this in the wrong section? If so, where should I have posted it?

[reepa]

You should have better luck at the AviSynth subforum. Ask a moderator to move the topic there.

[Guest]

You should post a link to an unprocessed sample stream.

Probably you just need an appropriate decimation function. Something like this works for straightforward streams:

TDecimate(cycle=5,cycleR=3)

or more clumsily:

Decimate(2)
Decimate(5)

But it depends on the specifics of your source material.

[blazerqb11]

Actually, looking at it I'm not totally sure it was originally 24 fps. Is American animation typically 24 or 30 fps? Whenever I use decimate or IVTC(either Telecide or TFM(which I thought shouldn't be necessary but I saw at least one interlaced frame in there)) or simply ChangeFPS(24000,1001), I end up with a video that looks like it's shaking up and down. Even Decimate(2) by it self results in this; however, ChangeFPS(30000,1001) does not.

[Guest]

It's all speculation until you post a link to an unprocessed source sample. Please do so if you want meaningful help.

[blazerqb11]

OK, here is a 100MB sample(took me a while because of numerous failed uploads):
http://www.megaupload.com/?d=TOBQ1HED
The "shaking" can especially be seen in the house's windows right after the opening credits.

[Guest]

The shaking appears to be there because this was created by bobbing and upsizing an interlaced SD stream.

Where did you get that stream?

[blazerqb11]

I used a Pinnacle 880e Ultimate Stick as a tuner card to record it off Fox(to be clear, I mean the TV channel) in Windows Media Center. Then I converted it from wtv>dvr-ms>mpg.

[Guest]

The "shaking" is not caused by the decimation. It is caused by the bobbing/upsampling.

[blazerqb11]

Alright, but it seems much more pronounced after decimation(I'm not just imagining that, am I?)

So what is the best course of action for dealing with this stream? My goal is to bring it back to its original frame rate(is it 24 or 30?), scale it back down to something like 640X480 and then re-encode in AVC.

[Guest]

Originally Posted by blazerqb11

Alright, but it seems much more pronounced after decimation(I'm not just imagining that, am I?)

I fail to see how tossing out frames can alter the remaining ones.

I can't answer about "best" and anyway I'm not particularly skilled at dealing with such horrible source material. In fact, I avoid it like the plague!

[blazerqb11]

Yea, I see what you mean. And after further study it seems that my eye is some how mis-perceiving the shaking when I watch it at 60 fps: sometimes I will see it and other times it doesn't seem to be there. In fact, it seems that most of the time I don't see it when playing the same scene over and over again. However, when I watch it with Decimate(2) Decimate(5), I always see it. Whether this is all the result of an optical illusion of some kind I really can't say.

I did some research on bobbing and I wondered if I'm understanding it correctly. If I understand it right they re-separate the fields(if they had been combined) of an interlaced video and then double the lines or scale each separate field back up to the original resolution. The fact that ever other resultant frame is shifted by a line of pixels is what causes the video to "bob" up and down.

[wonkey_monkey]

The fact that ever other resultant frame is shifted by a line of pixels is what causes the video to "bob" up and down.

That didn't seem to be quite the problem when I had a look, although it's related. Each frame is based on an alternate field - the shift is being compensated for, but that doesn't stop the "shimmer", because in one picture the even lines were real, and in the next the odd lines are real - if the video hadn't been bobbed correctly, as you were thinking, the result would be much worse.

David

[blazerqb11]

Well, after a little bit of experimentation I came up with something that seems to work reasonably well. I basically just reversed the line doubling(or motion compensated line doubling) which left me with a telecined stream. The result was actually pretty good. Let me know if anyone sees a better way of doing something.

AssumeFieldBased()

BilinearResize(1280,360)

Weave()

Tfm().TDecimate()

Crop(164, 6, -164 ,-10)

LanczosResize(640,480)

Here is a sample: http://www.megaupload.com/?d=IDAZCA79

Or, now after some more experimentation, what I was really trying to do:

SeparateFields()

video1 = SelectEvery(4,1)

video2 = SelectEvery(4,2)

Interleave(video1,video2)

Weave()

Tfm().TDecimate()

Crop(164, 6, -164 ,-10)

LanczosResize(640,480)

Though I'm not sure whether to use the above or
video1 = SelectEvery(4,0)
video2 = SelectEvery(4,3)

I can't tell a difference in the output.