720 vs. 1080 debate

[Mark Grant]

There is almost no difference in detail between 1280x720 scaled up to 1440x1080p and 1440x1080i deinterlaced to 1080p.

Good for you. Now, rather than throwing away half of the resolution of your 1080i footage, try watching it on a 1080i display, or deinterlace the fields and play them at twice the frame rate.

Why is anyone in their right mind going to choose to deinterlace 1080i footage just to make 720p look better? 1080i/30 vs 720p/30 will give you 70% more pixels on an interlaced display or 85% of the pixels _and twice the frame-rate_ on a progressive display.

About the only reason I can see to deinterlace would be to output to film. So why are you even comparing it that way?

[Thomas Smet]

yes film out is exactly right. My whole point along with a good portion of this thread is comparing 720p to 1080i in terms of getting a 1080p.

I was not saying that 1080i is bad but actually saying that they are both just as good as each other. I even stated that if you like the higher framerate motion of 60i then 1080i has the clear advantage. If however you prefer progressive footage then 720p may have the advantage.

1080i also gives you the advantage of creating a 720p 60p. That however doesn't mean anything if you are shooting 24p. There is no such thing as 48p for double framerate 24p.


It is going to be tough in my opinion to get a 60p HDV format as we know it right now. To jump from 30p to 60p would require double the bandwidth. That would mean a datarate of at least 38 Mbits/s if you wanted to keep the same level of quality as 30p. Current DV tapes would have a hard time dealing with 38 to 50 Mbits/s. The only way I could see a 60p HDV version would either be to hard drive only, new tape format, or double the compression level. Those extra 30 frames per second have to go somewhere. Bumping up to 25Mbits/s for 60p in my opinion would not be enough to handle double the data.

[Greg Boston]

Originally Posted by Thomas Smet

It is going to be tough in my opinion to get a 60p HDV format as we know it right now. To jump from 30p to 60p would require double the bandwidth. That would mean a datarate of at least 38 Mbits/s if you wanted to keep the same level of quality as 30p. Current DV tapes would have a hard time dealing with 38 to 50 Mbits/s. The only way I could see a 60p HDV version would either be to hard drive only, new tape format, or double the compression level. Those extra 30 frames per second have to go somewhere. Bumping up to 25Mbits/s for 60p in my opinion would not be enough to handle double the data.

You forgot to mention P2 technology, writing to flash memory in a raid configuration which could very well give 60p capabilities in the not too distant future. Where technology is concerned, "never say never" is my mantra. After all, there were many in the early 1980's who said we would 'never' be able to go faster than 1200 baud on standard copper wire phone lines. And yet, I am sitting here typing over a 1.5mbs up/3mbs+ down phone line. My line has been tested and could handle close to 6mbs.

Just food for thought.

-gb-

[Thomas Smet]

I was using the term hard drive to mean any other type of recording other than tape. This could include P2, Hard Drive, Optical media, direct capture from firewire.

My main point is that with tape itself it will be hard to get 60p. It can happen it just will not be as easy.

[Greg Boston]

Originally Posted by Thomas Smet

I was using the term hard drive to mean any other type of recording other than tape. This could include P2, Hard Drive, Optical media, direct capture from firewire.

My main point is that with tape itself it will be hard to get 60p. It can happen it just will not be as easy.

Gotcha! Just one of those little communication glitches. I thought you literally were speaking of hard drive only. Yeah, for now, tape is pretty much out of the question until they figure out a way to make head gap smaller and/or tape transport faster.

-gb-

[Ken Hodson]

Thomas, good point about the lens.
Are we to believe that somehow companies are using 2x better lens to match the resolution? My belief is that JVC stuggles to provide adequate lens for 720p never mind trying to adopt a prosumer cam to a 1080i lens. The costs just don't work out.
Sony has taken the Intel route. Speed sell's, or at least bigger numbers. Regardless if your prosumer cam is even coming close to capturing half of your advertised 1080i. Logic would say that a lens capable of that should cost more than the cam! I have no respect for a company that pixel shifts then up-rez's a 960x1080 capture to 1080, strictly for maketing reasons. Although it is still a mighty nice cam ;>)

[Ken Hodson]

" tape is pretty much out of the question until they figure out a way to make head gap smaller and/or tape transport faster."

I think they will just double the capture to 38/50 Mbps. Like DV50. Old tech for new HDV. Combine that with 2/3" chips and there will be no need to buy a Varicam. Heck, it will be sucking some of Cinealta's market.

[Barry Green]

Originally Posted by Thomas Smet

It is going to be tough in my opinion to get a 60p HDV format as we know it right now. To jump from 30p to 60p would require double the bandwidth.

Or double the compression. The HDV spec calls for 60p, but still maintaining the 19mb/s data rate. Actually, if you want to get technical, the new 24P HDV mode of the HD100 *is* a 60p data rate -- it's 24p with 2-3 frame duplication carried within a 60p data stream, at 19mb/s.

The only way I could see a 60p HDV version would either be to hard drive only, new tape format, or double the compression level.

Yep - double the compression level. And we'll see it implemented next year, according to JVC's schedule -- they say June 2006 for the GY-HD7000U, the 2/3" 3-CMOS camera. It's listed as supporting 720/50p and 720/60p HDV.

[Thomas Smet]

Barry are you sure the 24p will be carried in a 60p stream? I thought the mpeg2 could be written to tape as 24p. Although this does make sense since that is how the analog output would work. So that might mean then that 24p isn't slightly better in quality than 30p but may be slightly worse.

I always thought for the HD7000U they would actually raise the bitrate and not the compression. If they just raise the compression it is going to be hard to sell this as a high end $27,000.00 camera.

If they bumped up the datarate to 25Mbits/s that would give us around the compression of a 4.7 Mb/s DVD which is ok but not perfect. If it stays at 19.7 Mb/s to keep the uncompressed audio track we are looking at a 3.7 Mb/s DVD. Yuck!

Could they maybe run the tape to cover 1.5 the area like with DVCAM to maybe get 37.5 Mb/s with only 40 minutes of recording time?

[Barry Green]

Originally Posted by Thomas Smet

Barry are you sure the 24p will be carried in a 60p stream? I thought the mpeg2 could be written to tape as 24p.

The HDV specification doesn't allow for 24p. HDV is 720/25p, 720/30p, 720/50p and 720/60p. So to do 24p, and still call it "HDV", they'd have to carry the 24p within a 60p stream using 2-3 frame duplication.

Also, it is my understanding that the Lumiere folks have footage on tape from the HD100, and that they've said that it is indeed a 60p data stream.

So that might mean then that 24p isn't slightly better in quality than 30p but may be slightly worse.

Not necessarily. MPEG-2 can be famously efficient with duplicate frames. It's possible that the totally-duplicate frames may not impact the compression one bit (well, okay, they have to take up at least one "bit"!) ;)

But because the frames are exact duplicates, I expect that MPEG-2 will be extremely efficient, and I would expect that the 24p would actually have more bits to spread around to the actual frames than even 30p does.

I always thought for the HD7000U they would actually raise the bitrate and not the compression.

They may. But if they do, it won't be HDV. And the specs on their website say "HDV recording" and list 60p.

They do have plans for ProHD XE, which includes a "higher bitrate". But that's not HDV, that's a new format. HDV is defined as 720p in 19 megabits, at either 25p, 30p, 50p or 60p. Anything outside that would be, by definition, outside the format.

The JVC specs do list 1080i recording, but it does *not* say HDV, it says "mpeg-2" for that. So perhaps that's where the higher bitrate format would be used?

If they just raise the compression it is going to be hard to sell this as a high end $27,000.00 camera.

It's a year away, and anything can change between now and then. A simple terminology change on the spec sheet could make all the difference (i.e., they could change the wording so it says "HDV: 720/25p 720/30p; ProHD XE: 720/50p 720/60p". I wouldn't read too much into it at this point.

Could they maybe run the tape to cover 1.5 the area like with DVCAM to maybe get 37.5 Mb/s with only 40 minutes of recording time?

Not and still call it HDV. That would be a new format (just like DVCAM is a different format than DV). So if they change the naming of the format, perhaps that would be possible. And they do plan on ProHD XE. But if they do that, it will not be HDV, that's all I'm saying -- it wouldn't be compatible with anything with an HDV logo on it, so they'd have to make a new format and call it something new. And that's not what the currently existing spec sheet says, that's all I'm saying. As it's worded now, they're saying 60p in HDV. And that means 19mb/s.

[Greg Boston]

Barry,

Isn't that why JVC is calling their format 'ProHD', so that they can work around the HDV spec limitations? I was thinking the same with Panasonic but they are just bringing a high end camera format down to an entry level camera with P2.

Just wondering...

-gb-

[Barry Green]

Originally that's what we thought -- that ProHD was a new format. But then Dave Walton clarified and said that ProHD is *not* a format, that the format is indeed HDV.

ProHD is their take on the idea that they're making professional gear that uses HDV, pretty much the same idea as behind the JVC DV500 -- it was the first in their "Professional DV" lineup. It still used regular DV, it wasn't a new format, but they had a different name for it to differentiate it from their consumer gear.

I believe that's the same thing they're doing here. The ProHD name is a name for the product line, not a different format.

[Thomas Smet]

Thanks for the data Barry.

Do you know how much more of a chanllenge is it going to be to capture the 24p video? I did not notice if any current HDV tool can capture and remove duplicate frames on the fly. I did notice Cineform mentioned support for the HD100 when it comes out but thats about it.

Any editing tool will have to not only be able to pull out the duplicate frames but also add them back in to record back to tape.

[Barry Green]

I'm certain that all the HDV editors will need an update, but I'm also pretty sure it'll be minor. Lumiere is apparently already at work on it, and I'm sure CineForm will be able to implement it quickly.

Once they update it, Vegas will probably do it on the fly, like they do with 2-3-3-2 and 2-3 DV footage, so the user probably won't even notice that anything happened.

[Thomas Smet]

If ProHD is not any different how can they add a second set of uncompressed audio or was that always in the 720p specs and they just finally made a camera that can do it?