Why are we still using Interlace?

[iwod]

In today's digital broadcast world, why are we still using Interlaced Video with Digital Broadcasting?

As far as i am concern it gives little to no benefits in bandwidth saving with H.264.

So why are we still using it?

[Ghitulescu]

For costs reasons. For you it may cost only 200€ to replace your old interlaced DVD player, for a studio it might very well cost millions to change all-of-the-sudden the equipment.

[sneaker_ger]

So why are we still using it?

A small anecdote: public German television opted for 720p50 H.264 HD broadcast. This resulted in an outrage of viewers, because they demand "Full HD" with 1080 lines. Since 1080p50 is (or was?) not specified for DVB, this would mean they'd need to switch to 1080i50 and indeed one of the channels announced that they'd switch to 1080i50 due to popular demand, after reasoning with the audiences failed. (But luckily they seem to have lied, as they are still using 720p50 at this point, and I doubt they'll switch to 1080i50)

[Ghitulescu]

I assumed the OP meant 1080i vs 1080p, not 1080i vs 720p (as in Germany). My comment was based on this assumption.

[ramicio]

In the US lack of bandwidth is still used as an excuse. It's still low bit rate 1080i MPEG2. Don't expect to see any infrastructure changes in the near future. There is no money for it anywhere in the world.

[Ghitulescu]

The second excuse is that the vast majority of the installed STBs cannot process 1080p (whihc BTW is true). That will incur additional costs for the consumer, it is said.

[smok3]

lack of bandwidth for 1080p50 and lack of cheap decoding chips? (also difficult to prepare material in 1080p50 from a broadcasters perspective)

[Blue_MiSfit]

Simple, because Joe Sixpack thinks "1080 is better than 720", and doesn't want to be told differently. So, we as broadcasters are only happy to oblige the customer demand - regardless of whether or not there is any technical merit. The placebo effect is a powerful thing.

/thread

Derek

[ramicio]

WTF is /thread? You're right about the average person...If you told an average person that most sports and even some networks were broadcast in 720p instead of 1080i they would not believe you. I don't quite understand what you mean on the technical merits. 1080 is superior to 720, you just need the bandwidth and source to back it up.

[hello_hello]

I don't quite understand what you mean on the technical merits. 1080 is superior to 720, you just need the bandwidth and source to back it up.

I assume he was referring to 1080i v 720p.

[sneaker_ger]

Blue_MisFit clearly talks about 720p vs. 1080i - and I have to agree with him: it's pure marketing. (That was also the point of my short anecdote)
And "just" needing good sources, when even Blu-Rays lack them, and bandwidth, when networks are known to use as little as possible, are both things we probably won't be seeing in a while.

[ramicio]

Just because some titles lack good scanning techniques doesn't make the rest of what is on the format unworthy of 1080p. Even if the quality is between 720 and 1080 most of these die-hard "objective" type people would rather just see a new resolution made for that than to just go with 1080. I've found most things don't need 1080 because of how they are scanned, but 720 would be degrading to them...so...yeah. I saw nowhere where he talked about an i or a p, so it wasn't clear to me.

[Blue_MiSfit]

Correct.

[sneaker_ger]

I won't deny that some titles do make use of 1080 lines (like CGI movies), but I guess this is getting off topic, as it's not about i vs. p anymore. I'm not against 1080p, even if only some movies and few viewers benefit from it.

[Blue_MiSfit]

I'm not arguing that 1080p isn't clearly superior for inherently progressive content, like film. Whether or not most HD masters utilize this potential is another discussion ;)

My only point is that the vast majority of people don't even know what interlacing is, let alone have a clue about its pros and cons. Given this fact, the only thing that matters to these people is the line count. Therefore, this is what matters the most to the decision makers when picking an HD format to broadcast.

I smile a little bit inside when I see a technically clever network broadcasting in 720p, like A&E.

Derek

[QBhd]

FOX and ABC also deliver 720p (OTA). Also some networks seem to do a better job of their 1080i than others. Take CBC for example, it could arguably be one of the best 1080i feeds I have seen. CBS on the other hand is just horrible.

QB

[Stereodude]

Take CBC for example, it could arguably be one of the best 1080i feeds I have seen. CBS on the other hand is just horrible.FWIW, CBS is the best 1080i channel where I live. They have 0 sub-channels and seem to put more effort into their picture quality.

[Stereodude]

In today's digital broadcast world, why are we still using Interlaced Video with Digital Broadcasting?

As far as i am concern it gives little to no benefits in bandwidth saving with H.264.

So why are we still using it?Because 1080i predates H.264. With a 6MHz 8VSB RF channel there isn't enough bitrate using MPEG-2 for 1080p60 (~19Mbit/sec), 1080p30 doesn't have adequate temporal resolution / motion capture capabilities, so they went with 1080i60 and 720p60.

The infrastructure is already in place and it's not going to change, so that's why 1080i60 is still with us. And, frankly speaking, it has better picture quality than 720p.

[Ghitulescu]

Some years ago, at one Consumer electronics Fair held in Germany (around the time when it was decided for public televisions to go 720p) a test was made upon a large batch of visitors (I think it ran into thousands). All of them clearly identified 720p better than 1080i for almost every type of video (sport, film, nature) - all of these in a blind test.
While I agree, the test could be faulty, Average Joe managed to forget Bigger is better, if he wasn't told this before :)

[iwod]

Correct me if I am wrong.

1080i60 and 1080p30 has little / negligible size difference with H.264 High Profile.
So in today's compressed, H.264 encoded digital video world, Interlace brings NO benefits what so ever. So i dont understand why we are still using it. Of coz Someone pointed out all these HDTV spec predates H.264 High Profile. And about the decoder not being powerful enough.

1080p30 doesn't have adequate temporal resolution / motion capture capabilities

How is p30 different from i60? Shouldn't both be the same?

[sneaker_ger]

No, because p30 means a temporal resolution of 30Hz, while i60 (also called i30) means a temporal resolution of 60Hz. Proper deinterlacing means bobbing/rate doubling, i.e. each field will result in a frame, not two fields into one frame.

[LoRd_MuldeR]

A small anecdote: public German television opted for 720p50 H.264 HD broadcast. This resulted in an outrage of viewers, because they demand "Full HD" with 1080 lines. Since 1080p50 is (or was?) not specified for DVB, this would mean they'd need to switch to 1080i50 and indeed one of the channels announced that they'd switch to 1080i50 due to popular demand, after reasoning with the audiences failed. (But luckily they seem to have lied, as they are still using 720p50 at this point, and I doubt they'll switch to 1080i50)

I also prefer 720p50 over 1080i50 for "true" 50 fps footage, like TV shows, sports broadcasting.

However for movies 720p50 is not the best choice. As the source is only 25 fps (actually 24 fps), they have to use frame doubling for 720p50.

If they could switch to 1080i50, at least for 25 fps movies, it would actually be 1080p25 (progressive with segmented fields) - higher resolution and no redundant frame doubling.

But much more annoying is the compression quality! Sometimes it looks really great, so the bandwidth or the final encoding stage cannot be the problem.

Unfortunately quite often it looks extremely blocky and washed out, just as they were broadcasting from low quality (low bitrate) master...

(Note that I am referring to German public broadcasting, not that HD+ crap. The latter, as far as I know, is 1080i50. But HD+ is a stillbirth - no PC support, not even planned)

[Stereodude]

Some years ago, at one Consumer electronics Fair held in Germany (around the time when it was decided for public televisions to go 720p) a test was made upon a large batch of visitors (I think it ran into thousands). All of them clearly identified 720p better than 1080i for almost every type of video (sport, film, nature) - all of these in a blind test.
While I agree, the test could be faulty, Average Joe managed to forget Bigger is better, if he wasn't told this before :)1080i60 can be turned into 1080p24 with a little IVTC magic for a lot of broadcast content. No matter what you do to 720p60 you can't turn it into 1080p24. Further most video processors aren't going to turn 720p60 into 720p24 so you end up with the ever lovely 3:2 judder even on a 120Hz display.

[ramicio]

Putting 24 FPS into a 60 Hz thing will always result in some sort of judder, I don't care if you interlace it into 60 fields or just progressively distribute the frames, 24 doesn't divide into 60. It doesn't matter if either are on a 120 Hz display because any inputs are limited to 60 Hz anyway.

[kurkosdr]

For costs reasons. For you it may cost only 200 to replace your old interlaced DVD player, for a studio it might very well cost millions to change all-of-the-sudden the equipment.

You 've got a point, but why 1080 sports content is often broadcast at 50i/60i?

If you ask me, i am suprised that all content is NOT interlaced (at least the content not originating from film), because, with a nice deinterlacing filter, it allows for 50p/60p-like temporal resolutions while using 25p/30p bitrates.

Sure, that involves signal processing, but interpolating 25p/30p for 50Hz/60Hz etc monitors does too.

I blame it on the laziness of the open source guys. The year is 2011, and VLC still doesn't automatically de-interlace by default. Hence, many treat interlacing as a desease that must be cured. When did the times people prefered to pay for software that works instead of downloading freebies have gone?

P.S. 720 at 50p/60p only looks better that 1080i when a bad de-interlacing filter is used, which unfortunately is the kind of de-interlacing filters most TVs have. But since televisions shouldn't have quality filters?

[sneaker_ger]

If you ask me, i am suprised that all content is NOT interlaced (at least the content not originating from film), because, with a nice deinterlacing filter, it allows for 50p/60p-like temporal resolutions while using 25p/30p bitrates.

I guess that's disputed.

I still remember when the x264 team made a Blu-Ray demo disc. At first they encoded one of the movies using 1080i30, but then opted for 720p60. 1080i30 only has some 11% more pixels. If you count in the loss of compression efficiency of interlaced H.264 and potential artifacts introduced by interlacing and deinterlacing, I don't think it pays off.

Sure, that involves signal processing, but interpolating 25p/30p for 50Hz/60Hz etc monitors does too.

I don't know any channel that uses p25 or p30.

[Ghitulescu]

You 've got a point, but why 1080 sports content is often broadcast at 50i/60i?

I have no idea, in Germany all public channels broadcast in 720p50 (like the WM this month). I don't like the business method of Murdoch so I don't have Sky HD, I cannot comment on this, but I've heard it's 1080i.

1080p cameras are quite new. I'm not talking, I think you noticed, about consumer camcorders, whose visual resolution is still at or a bit above the level of a [semi]pro SD camcorder, but about the TV ones.

My impression is that the studios still use the "old" 720p cameras (JVC, Panasonic) and upscale the material to 1080i (needed for DVB-S2) for two main reasons:
1. "placebo" - average Joe was "taught" (via countless ads and commercials) that "bigger is better" - that also explains the reactions in Germany after the public broadcasters decided to go 720p (the case ARTE HD is even nicer, they emit 1080i for France but 720p for Germany).
2. the same Average Joe has also some "Scottish roots" when it comes to buying things. Most cheap TVs do have bad upscalers and deinterlacers (this also explains the frenzy with upscaling/deinterlacing methods, here, at doom9), so performing this in studio, using S&W grade upscalers provides him with quite a good image (in spite his efforts to ruin it). I know only 3 models of pure 720p TVs, the others being something like 768p (HDready) or 1080p (FullHD).

There are probably also other reasons ....

[iwod]

If you ask me, i am suprised that all content is NOT interlaced (at least the content not originating from film), because, with a nice deinterlacing filter, it allows for 50p/60p-like temporal resolutions while using 25p/30p bitrates.

Sure, that involves signal processing, but interpolating 25p/30p for 50Hz/60Hz etc monitors does too.

Arh.. very true... something i haven't thought of, may be i need to do a bit more reading on the subject. May be i need to rethink the whole thing again

May be with a VERY good deinterlacing filter, everything *should" be interlaced?

[ramicio]

Frame doubling is not interpolating.