QTGMC Deinterlacing Script (v3.384)

[Emulgator]

You may call me paranoid or seeing things that are not there. But I've had the imression that, back in a time when TVs internal deinterlacers were not yet so great, TGMC popped up here, and one or two years later those deinterlacers suddenly got much better!?

I am feeling the same, hihi. Somebody read up here from the Master, maybe ?

[Sharc]

Originally Posted by Emulgator

I am feeling the same, hihi. Somebody read up here from the Master, maybe ?

Remember Faroudja? Was a kind of game changer as well for TV deinterlacers.

[johnmeyer]

Originally Posted by Sharc

Remember Faroudja? Was a kind of game changer as well for TV deinterlacers.

Not only do I remember it, but I flew from San Jose to Las Vegas back in the early 1990s just to go to their suite and see their $15,000 line doubler. I did this because I was hanging around with people who were trying to create the "ultimate" home theater back in the early 1990s and they were planning to get an $80,000 Barco projector, a laserdisc player, and the Faroudia line doubler. I couldn't believe it would make that much difference but, given how marginal NTSC video looked like on a big screen, after seeing the demo at their hotel room suite, it did actually make a pretty big difference.

I never got one ... a little too rich for my blood.

[Sharc]

Originally Posted by johnmeyer

Not only do I remember it, but I flew from San Jose to Las Vegas back in the early 1990s just to go to their suite and see their $15,000 line doubler. I did this because I was hanging around with people who were trying to create the "ultimate" home theater back in the early 1990s and they were planning to get an $80,000 Barco projector, a laserdisc player, and the Faroudia line doubler. I couldn't believe it would make that much difference but, given how marginal NTSC video looked like on a big screen, after seeing the demo at their hotel room suite, it did actually make a pretty big difference.

I never got one ... a little too rich for my blood.

Legendary Faroudjas statement at an IBC 2004 session:
“I am amazed that anybody would consider launching new services based on interlace. I have spent all of my life working on conversion from interlace to progressive. Now that I have sold my successful company, I can tell you the truth: interlace to progressive does not work!”.

[johnmeyer]

Originally Posted by Sharc

Legendary Faroudjas statement at an IBC 2004 session:
“I am amazed that anybody would consider launching new services based on interlace. I have spent all of my life working on conversion from interlace to progressive. Now that I have sold my successful company, I can tell you the truth: interlace to progressive does not work!”.

I agree with half of that twenty-year-old quote. I agree that interlace to progressive does not work, and it is why I've spent 20+ years in this forum advising people to NOT deinterlace unless they have to.

However, interlacing exists for a reason. That reason existed in the 1930s and 1940s when TV was being invented. It existed when the world transitioned from HD to SD starting in the late 1990s. And it still exists today.

The reason? Cost. Interlacing was a brilliant engineering solution to the economics of creating, transmitting, receiving, and viewing an image that would be pleasing to watch, but at a cost that "the masses" could afford. It provides the fluidity of 60 fps, but in half the bandwidth. The implications for broadcast bandwidth (in the analog era), the cost of the TV receiver, and the cost of almost every other aspect of television engineering was, and is, massive.

Now that video is almost entirely streaming, with OTA broadcast, cable, and satellite TV on the inevitable decline to obscurity, the economics of bandwidth still remain. However, because frame rates are no longer fixed, the current solution to the bandwidth/cost problem is to simply degrade the frame rate, as we see everyday in videoconferencing, and often see in streaming services.

As a result, I would not have agreed, in 2004, that it would be crazy to introduce a service that was interlaced. The economics still favored that approach and indeed, when I got my first HD set in 2012 (yes, rather late), I noticed that most of the OTA and cable program material was either 720p or 1080i. Almost nothing was 1080p. Interlace was still widely used, long after his quote.

[Didée]

Originally Posted by johnmeyer

It existed when the world transitioned from HD to SD starting in the late 1990s.

In that sentence, swap HD<>SD, methinks that's the correct order.

In excuse for the general idea of "interlacing" -- it must be considered that back in that time, we only had CRT displays that inherently built up the image in an interlaced technique. That's why it made perfectly sense back in those times. In our modern times of progressive displays, of course interlacing should be considered an artificial relict ... but I think this has been discussed sufficiently in the past. It is like it is, some bad habits will stay forever.

[DTL]

Fast and UHD new displays can simulate interlaced scan good enough. Some convert script of SD interlaced to UHD progressive may be created with AVS. But for better simulation of CRT field fade it need 100..200+ fps output for 25i input.

[hippo88]

I tried to encode a .ts video (interlaced top field first) captured from TV into mp4 to 1080p with qtgmc setting = medium. The encoded video using megui x64 is slightly jerky when played on TV. But when I encode to 720p it plays fine. Does anyone know why. I tried with staxrip same result

[Trixter]

Inspect the output file (ffprobe, mediainfo, etc.) to ensure it really is 50/60p. If it is 25/30p, it will feel "jerky" when played. Ensure that megui or staxrip isn't cutting the framerate in half.

Try swapping the field order in case the fields are wrong. Put AssumeBFF() before QTGMC().

[hippo88]

Originally Posted by Trixter

Inspect the output file (ffprobe, mediainfo, etc.) to ensure it really is 50/60p. If it is 25/30p, it will feel "jerky" when played. Ensure that megui or staxrip isn't cutting the framerate in half.

Try swapping the field order in case the fields are wrong. Put AssumeBFF() before QTGMC().

I tried both, AssumeBFF & AssumeTFF video still jerky. It played fine on mpc on the pc. I have an older 1080 Samsung tv. I wonder if this is the problem.
Thank you for for your suggestion.

[wonkey_monkey]

I have an older 1080 Samsung tv. I wonder if this is the problem.

I think that's quite likely. I'm sure my old Samsung could only properly handle 1080i25/30, not 1080p50/60.

If you're playing over a network it could also be that it only has a 10mbit/s NIC and your 1080p file has too high a bitrate. It may also not support high USB speeds.

[hello_hello]

Originally Posted by hippo88

I tried to encode a .ts video (interlaced top field first) captured from TV into mp4 to 1080p with qtgmc setting = medium. The encoded video using megui x64 is slightly jerky when played on TV. But when I encode to 720p it plays fine. Does anyone know why. I tried with staxrip same result

The manual for my 2011 Samsung says it supports Level 4.1, although it also says 30fps is the maximum for 1080p.

It can play video at 50fps or 60fps if the resolution is lower, but it doesn't like long gops. If I remember correctly MeGUI adjusts x264's --keyint according to the frame rate, so for 60fps it'd probably set --keyint 600. The default for x264 is --keyint 250. If you try encoding at 1080p while making sure the keyint option is the default of 250, you might get lucky and find it'll make a difference.