720p50 to 1080p25 conversion

[minchjp]

Hi,
I have a transport stream with a 720p50 hdtv format which i want to convert to 1080p25. The broadcast was sourced from a 1080p25 tape, and before broadcasting, bobed to 540p50 and then resized to 720p50. Does anyone know what programs i can use to reverse the process?

Thanks

[edDV]

Hi,
I have a transport stream with a 720p50 hdtv format which i want to convert to 1080p25. The broadcast was sourced from a 1080p25 tape, and before broadcasting, bobed to 540p50 and then resized to 720p50. Does anyone know what programs i can use to reverse the process?

Thanks

When you cut resolution to 540p, you probably tossed a field from 1080i. So odd or even fields were dropped leaving a 25 fps field of some width 1920 or less. Was this it?

I'm unaware of a 1080p50 tape explain that. If you did have a 1080p50 source, it would be possible to halve the vertical for 960 to 1920x540p/50 but then converting to 1280x720p50 would interpolate new vertical lines while reducing horizontal 1/3. Why upscale again?

Once you cut down to 1280x540 or whatever minimum, that is where the image resolution will stay even it you do upscale back to 1920x1080. You can't recover the resolution that you tossed earlier.

[manono]

Yeah, I don't see the point of this exercise either, and I also doubt your explanation of how your TS was created. Assuming each frame is shown twice, and you're familiar with AviSynth:

SelectEven()
Lanczos4Resize(1920,1080)

[edDV]

Rereading this I see minchjp started with 1080i/25, bobed the fields to 540p/50 and scaled to 720p50. Converting this to 1080i probably will degrade the image but it is possible to interpolate new pixels and reinterlace. If the display accepts 720p/50, it will rescale internally.

[minchjp]

When you cut resolution to 540p, you probably tossed a field from 1080i. So odd or even fields were dropped leaving a 25 fps field of some width 1920 or less. Was this it?

No, it was bobed from a progressive source, and both frames were kept. In the resultent 720p broadcast, there is 50 frames/second, with 25 frames of motion per second. However, if you take 2 repeated frames, you can notice that the image moves up and down between frames.

I'm unaware of a 1080p50 tape explain that. If you did have a 1080p50 source, it would be possible to halve the vertical for 960 to 1920x540p/50 but then converting to 1280x720p50 would interpolate new vertical lines while reducing horizontal 1/3. Why upscale again?

The source was a 1080i tape - but with 25 progressive frames per second.

You can't recover the resolution that you tossed earlier.

Not me! The ABC.

My reasoning behind trying to 'recover' some lost resolution is that the odd lines and even lines from the original tape - the progressive source was bobed, so i should be able to reconstruct a 1080p25 copy.

Thanks for your help

[edDV]

Was this film or a 1080i live source? If film, a field toss would get you back to native progressive 540p/24fps (adjusted for speed). If live action, the bob would preserve 50 Hz. motion resolution.

Too bad it wasn't a normal 1080i -> 720p conversion. That could be reversed with reasonable quality. Going down to 540p put vertical resolution into SD territory. If square pixels were maintained, 16:9 would produce 960 horizontal pixels or 720 pixels for 4:3.

That doesn't give much resolution to recover.

[manono]

If what you say is correct about the fields being bobbed (and the evidence you present is good), and if I'm understanding correctly that you want to make it 1080p@25fps by resizing and reinterleaving the fields, then:

Lanczos4Resize(1920,1080)
SeparateFields()
SelectEvery(4,0,3)#if TFF
Weave()

AviSynth is absolutely the best way to handle the kinds of things required here, and if you're going to make a habit of playing with TS streams in this way, it's in your best interests to learn it.