XDcamEX vs JVC GY HD250

[Steven Thomas]

Specs are specs, but in the field myself, sometimes things can be somewhat different than a "black & white" description.
Without having the white paper or knowing the design engineers, looking at some specs is tough to call.

[Thomas Smet]

Originally Posted by Evan Donn

CBR = constant bit rate, VBR = variable bit rate

25mbs CBR means every second of video consumes 25 megabits - no more, no less.
35mbs VBR means every second of video may consume up to 35 megabits, but no more.

VBR primarily affects recording capacity - a static talking head shot may not need the full 35mbs and therefore your recording time may increase.

The picture quality difference comes mostly from the increased total data - 35mbs is 40% more data per second than 25mbs. However, as others have noted, the EX's full raster (1920x1080) mode has 33% more pixels than 25mbs HDV - so the difference might seem like it's not that big.

However modern compression doesn't scale linearly with resolution - a big part of the compression is eliminating redundancy between frames. So your I frame (first frame in your group of pictures, GOP) may be 33% larger, but the differences in the remaining frames are not necessarily that much larger than the corresponding frames in an HDV-resolution file, so the net quality improvement may be higher than the numbers would indicate. That gets hard to estimate though because so much of it depends on variables in the image itself like image detail, detail movement, and camera movement - so we can guess all we like but until we have a lot of sample footage under a variety of shooting conditions we won't really know.

If what Alex mentioned is true about peaking it may be that 35mbs is really an average data rate, not the maximum, and that situations where a scene moves between static and motion shots may be able to 'bank' data not needed during the simpler portions and apply it to go above 35mbs where needed as long as the average data rate over a given period (probably a few seconds) doesn't exceed 35mbs.

sure it is hard to calculate a value but if the redundant info helped that much then 1440x1080 wouldn't need that many more bits then 720x480. In fact you do need a lot more bits. Sure what you are saying is true that it isn't a 1:1 ratio but the encoder will have to work a lot harder. That is exactly why HDV and normal XDCAM HD is limited to 1440x1080. 1920x1080 would have pushed the 25mbits just a little too hard. There is also the fact that with 1920x1080 unique pixels your chances of redundant blocks of information is less because the overall image is sharper and more detailed. With the extra amount of pixels you have more blocks to deal with that could all be different. You end up with an opposite effect of how some encoders will apply a low pass filter to make the video compress easier. Well with more detail you make the compressor work harder.

I would say just giving a rough guess that 35 mbits from the EX1 will be about right in between 25 mbits HDV and 35 mbits XDCAM HD.

[David Heath]

Originally Posted by Thomas Smet

People just cannot seem to get out of the mind set that 720p 60p or 50p is just as good as 1440x1080 6oi or 50i.

I didn't hear a lot of people complaining about the World Series which was on FOX which uses 720p. In fact it looked pretty darn good.

But - and a big but - all those examples you give assume 50 or 60Hz motion, which I agree is needed for such as sport. The argument may be valid for a pure sport channel, but most aren't, and too often the fact that nearly all drama and films are shot at 24/25fps gets totally overlooked.

In which case, the choice is 720p/25 or 1080p/25 (carried psf), and here the 720 system is at an undeniable disadvantage. Which is why I understand many channels are choosing the 1080 approach - they can be 1080p(psf)/25 for drama material, or 1080i for such as sport.

But hopefully the future is 1080p, with framerates from 24 to 60Hz as appropiate, and both interlace AND 720 can be consigned to history.

[Thomas Smet]

Originally Posted by David Heath

But - and a big but - all those examples you give assume 50 or 60Hz motion, which I agree is needed for such as sport. The argument may be valid for a pure sport channel, but most aren't, and too often the fact that nearly all drama and films are shot at 24/25fps gets totally overlooked.

In which case, the choice is 720p/25 or 1080p/25 (carried psf), and here the 720 system is at an undeniable disadvantage. Which is why I understand many channels are choosing the 1080 approach - they can be 1080p(psf)/25 for drama material, or 1080i for such as sport.

But hopefully the future is 1080p, with framerates from 24 to 60Hz as appropiate, and both interlace AND 720 can be consigned to history.

I do not agree at all. watching a 24p movie on a 1080i channel is still 1080i which means the same reduction in detail I listed above. Sure maybe 720p 30p has a disadvantage to 1080i 60i but you are talking similar framerates. If framerates are the same then the same exact rules I gave above apply.

What about ABC? They are 720p and they have a lot of primetime drama shows. Ugly Betty, Pushing Daisies, Grey's Anatomy, Desperate House Wives, Brothers and Sisters and many other examples of highend 24p productions. Again not very many people complain about how those shows look and in fact they are some very popular shows. FOX has a lot of 24p based drama shows as well and some of those shows are very popular. I have never heard of anybody knocking the quality of any of those channels.

So why is 720 25p or 24p at a disadvantage? If it has the same framerate and the same lack of artifacts compared to 1080i 25p then I am sorry but I don't see how that is the case. 25p sitting inside of 50i still has to have a certain level of filtering and bad HDTV's will still bob the heck out of it. HDCAM, DVCPROHD and HDV cameras still shoot it at 1440x1080 pixels that are filtered so you only gain a small edge of detail. 1440 is not that was larger then 1280 and filtered 1080 isn't that much sharper then 720p. The same rules I gave for consistancy also apply to 25p or 24p. No matter what the image will look the same and what you see is what you get.

[Werner Wesp]

Originally Posted by Evan Donn

The deinterlacing should occur naturally as part of the process of slowing it down.

Of course it doesn't. Normal, un-supersampled slow mo (supersampling induces blur anyway) asks for deinterlacing first. Leaving 720p50 at 50fps, but making 1080i50 into 540p25. Slowed down that gives respectively 25 and 12,5 fps.

[David Heath]

Originally Posted by Thomas Smet

I do not agree at all. watching a 24p movie on a 1080i channel is still 1080i which means the same reduction in detail I listed above.

Depends on the receiver. Good ones should make use of the psf flag and resurrect the true p image, and keep the full resolution etc. Cheaper ones may not do such a good job, but at least the potential is there.

Sure maybe 720p 30p has a disadvantage to 1080i 60i but you are talking similar framerates.

My comparison here was 720p/25 to 1080psf/25, and yes, they are the same framerates. The ones applicable to drama, films etc if not sport.

What about ABC? They are 720p and they have a lot of primetime drama shows........... I have never heard of anybody knocking the quality of any of those channels.

I can only say we are at the beginning of broadcast HDTV, and in the UK only one broadcaster is providing a general service, though that's likely to change next year. Most of the sets that have been available so far have had resolutions typically around the 1360x768 mark, but that is now changing rapidly with 1920x1080 fast becoming the norm.

Together with better electronics inside the sets, the bar is being raised, and the potential differences between 720p/25 and 1080psf/25 are increasingly likely to be evident to the viewer.

So why is 720 25p or 24p at a disadvantage? If it has the same framerate and the same lack of artifacts compared to 1080i 25p then I am sorry but I don't see how that is the case

Resolution. 1280x720 pixels versus 1920x1080. Otherwise both the same - both 25fps, both progressive, but 1080p(psf)/25 potentially much sharper - dependent on receiver. And it's only now with 1920x1080 displays becoming the norm that it's really beginning to matter.

For the same reason 1080p/50 would be far superior to 720p/50, but the former is too much for most current technology. The same isn't true of 1080p(psf)/25.

[Werner Wesp]

Originally Posted by David Heath

For the same reason 1080p/50 would be far superior to 720p/50, but the former is too much for most current technology.

Quite true. So it's waiting for a camcorder/system to come out with 1920x1080, 1080p50... A JVC HD400 or something? the GY-HD7000 perhaps? The Pana HPX3000 with AVC-intra is there, but still quite expensive.

[Mike Marriage]

Aren't we a little off topic?

Could we split to a thread of 1080 vs 720 because the argument of whether 1080 is worth it over 720 can be interesting.

Personally I'd prefer less compression and less resolution. Even SD on a 42" screen looks fine to me, as long as the compression is mild. In a perfect world, I'd go for 1080 every time, but it does require compromises elsewhere. I heard that testing with your average layman showed preference of 720p50 over 1080i50.

[Greg Boston]

Originally Posted by Mike Marriage

Aren't we a little off topic?

Could we split to a thread of 1080 vs 720 because the argument of whether 1080 is worth it over 720 can be interesting.

Personally I'd prefer less compression and less resolution. Even SD on a 42" screen looks fine to me, as long as the compression is mild. In a perfect world, I'd go for 1080 every time, but it does require compromises elsewhere. I heard that testing with your average layman showed preference of 720p50 over 1080i50.

Agreed. Gentlemen, you have drifted off topic a bit.

Mike, your comment about SD looking good on a 42" looking good brings up another point that is often overlooked.

The PAL system has enjoyed superior vertical resolution to the NTSC system and I often hear Europeans comment that HD isn't that much better. I can see why. But in the world of NTSC with only 480 visible lines of resolution, the difference in SD to HD is quite apparent.

-gb-

[Thomas Smet]

Originally Posted by Greg Boston

Agreed. Gentlemen, you have drifted off topic a bit.

Mike, your comment about SD looking good on a 42" looking good brings up another point that is often overlooked.

The PAL system has enjoyed superior vertical resolution to the NTSC system and I often hear Europeans comment that HD isn't that much better. I can see why. But in the world of NTSC with only 480 visible lines of resolution, the difference in SD to HD is quite apparent.

-gb-

It all depends on the screen size and viewing distance. 42" and smaller at a decent viewing distance 480p will still look very good. In fact a lot of consumers think they are watching HD when they watch a 480p DVD on their HDTV's. I bought my parents a 32" HDTV and when sitting on their couch 480p DVD's look just as good as HD channels. Of course the closer I get the more that changes but bumping up to 720p gives that little extra boost for when you are really close.

Resolution is not the only factor in quality.

How did we get in this debate anyway? I thought we were talking about shooting 720p with two different cameras?

[Steven Thomas]

Originally Posted by Thomas Smet

I bought my parents a 32" HDTV and when sitting on their couch 480p DVD's look just as good as HD channels. Of course the closer I get the more that changes but bumping up to 720p gives that little extra boost for when you are really close.

Of course, distance is a perception factor, but it sure looks "day and night" to me when switching from the same movie playing 480P DVD, verses HD.
Looking at a 50" plasma from about 15 ft.

It's really not until you can do a direct comparison where things become more obvious.

[Jody Eldred]

Originally Posted by Werner Wesp

Sometimes I wonder...

How many people actually know that 720p50 is far superior to 1080i50? Or how many even know that 1080i is NOT full HD? And yet - it is just a matter of the easiest mathematics:

50 x 1280 x 720 pps or 50 x 1440 x 540 pps is kinda obvious. (and that's not even taking into account the interlaced filter you need to keep the image from being jittery)

Not to mention all HD screens nowadays are progressive, so you can not watch 1080i optimally.

choosing 1080i and 720p might be difficult, but not as an aquisition format: you can aquire 720p and make perfect slow motions and whatever you want to do and then convert it to 1080i if a client asks for 1080i. If you would choose 1080i as an aquisition format, you can't make any serious slow motions (they'll have almost half the resolution and just half the temporal definition) or any other effect that uses deinterlacing. Furthermore, you cannot supply a client with seriously good looking 720p. Pretty simple if you ask me. But some people will be holding on to 1080i, and as a mathematician and image processing expert, I can only say: I suppose they're let by the fact that 1080 sounds larger then 720 ... ?

Anyhow. That's not even taking into account that the MPEG2 compression scheme has no higher order for interlaced images, thus losing efficiency in 1080i. 1080i in MPEG2 at 35 Mbps can't be compressed better then 720p at MPEG2 at 20 Mbps. I'm not especially promoting JVC here (although I know they have the better product here), but I cannot agree to Sony for what they are doing: They are making XDCAM look like it is a higher end format, but any scientist (as I am) know they are marketing HDV on a different format: it is also 420 - 18 and 25 Mbps is HDV. 35 Mbps is just SLIGHTLY superior standard Z1 HDV. It is obviously all long GOP. XDCAM HD is HDV in 18 and 25 Mbps mode and it is just very slightly better in 35 Mbps, while retaining all disadvantages for it not to be a high end format: long GOP mpeg2, interlaced, just 35Mbps in interlaced, 4:2:0, ....

Quality of the camera and lens, we'll have to see. If the EX wanders onto my desk, and I want to get the best out of it, I'm recording in 720p. Needless to say - that's what I do with the Panasonic HPX-500 that I have as well and with the JVC GY-HD201 (athough, there I have no choice).

Sure is a lot of math being talked about here. Strange, because not too many viewers watch TV with a calculator and test equipment in their hand...

;-)

Here's a simple test for you:

Shot a scene in 720P, and upconvert it to 1080i and 1080P.
Shoot the identical scene in 10801i and 1080P.
Compare the two.
Native 1080 will CLEARLY look superior to upconverted 720.

Downconvert the 1080 footage to 720.
Compare it to the natively shot 720.
It will match or look superior to the native 720 footage.

Sorry lads. The proof is in the pudding, not in the mathematics.

I'll put the XDCAM EX against any 720P camera out there.

[Tim Polster]

I think Werner still has a valid point.

Aquiring in 60p gives one more options in post if those options are needed.

Jody, you are correct as well, 1080p will have more resolution than 720p, therefore the chance to show more detail.

But I would be careful using 1080p and 1080i in the same sentence as 1080i & 720p are very similar.

So yes, shooting at 24 or 30fps, 1080p would be a great choice, so the nod would go to the EX over the 720p cameras.

But, only the video folks will notice the difference. odds are "normal" viewers will not see much if any difference.

[David Heath]

The EBUs stance is not that 720p is better than 1080i, period, but rather that it COMPRESSES far better, being progressive. And is therefore more suitable as a broadcast standard. That's a different matter to which may look the best straight out of the camera.

I'll accept they're right as far as it goes, but the problem with their stance is that it takes no account of 1080p/25 (broadcast psf). Strange, as so much material is made and transmitted that way.

[Thomas Smet]

Originally Posted by Jody Eldred

Sure is a lot of math being talked about here. Strange, because not too many viewers watch TV with a calculator and test equipment in their hand...

;-)

Here's a simple test for you:

Shot a scene in 720P, and upconvert it to 1080i and 1080P.
Shoot the identical scene in 10801i and 1080P.
Compare the two.
Native 1080 will CLEARLY look superior to upconverted 720.

Downconvert the 1080 footage to 720.
Compare it to the natively shot 720.
It will match or look superior to the native 720 footage.

Sorry lads. The proof is in the pudding, not in the mathematics.

I'll put the XDCAM EX against any 720P camera out there.

Ok, and sorry I do not agree at all. A lot of people enjoy 720p broadcasts and have never once complained watching shows in HD on ABC or FOX. I'm talking about film source shows as well such as Grey's Anatomy and other drama shows.

Here is a image I made exactly like you said I should test it. I took a Canon D20 still image and cropped it at 1920x1080 pixels. I then down scaled a 720p version and scaled it back up. I faked a 1080i version by adding in a slight softness for reducing the interlace flicker and low pass filtering. Sure maybe true 1080p when watched as true 1080p is sharper but it is not "clearly" better and only tech heads watching it on a computer monitor would ever notice.

This image does not give any numbers at all because I do not use numbers. I use my eyes and my eyes tell me that at the end of the day there is very little difference between 1080i and 720p. If you have a better example please show me because no matter what type of images I start with be it 3D rendered, digital still or actual 1080i still shots from HDV I find always the same to be true. It isn't exactly fair to compare 720p from DVCPROHD tape either since it only uses 960x720 pixels. We are talking true 1280x720 pixels.