XDcamEX vs JVC GY HD250

[Bob Grant]

Werner,
from our tests and the comments of others 1080i produces much better slomo than 1080p or 720p for that matter and that makes perfect sense scientifically. 1080i has double the temporal resolution to start with.

[Werner Wesp]

Originally Posted by Craig Seeman

I'd like to shoot 720p60 especially when I'm shooting fast action or material that may lend itself to slo-mo. I like having the option of shooting 1080p30 or 1080p24 though.

I agree to that, but I have seen in the last year or so that lots of people don't have the skills to be shooting in 25p (here in Europe). They keep insisting it is bad, which it isn't, but they can't produce anything in such a low temporal definition because of their camera techniques etc.

We'll also have to see if the CCD's are progressive 1080 CCD's - that hasn't always been the case. I believe the verical resolution of the Z1 was 1080 as well, but those CCD's weren't able of true progressive readout (ergo the 'frame' mode).

Actually I'm not saying anything on the quality of the SONY, I am merely reacting to some people that have never gotten the right info on p and i. the sony and the JVC aren't very comparible if you ask me. They are both designed for a segment in the market. The 16mm and 35mm adapters for the JVC go well e.g. and there's no substitute for that with this sony. Furthermore - JVC offers no handheld option. I personally think this sony model, just as the HVX200, is way to big and bulky for a handheld type camera, but nevertheless, sony and panasonic offer the option and some people like it.

[Werner Wesp]

Originally Posted by Bob Grant

Werner,
from our tests and the comments of others 1080i produces much better slomo than 1080p or 720p for that matter and that makes perfect sense scientifically. 1080i has double the temporal resolution to start with.

Sorry bob, 1080i50 and 720p50 have the same temporal resolution. 1080i needs deinterlacing before producing slow motion, therefore dropping in temporal resolution over 720p50 due to field removal. Obviously, spacial resolution drops too dus to field removal. (you are probably comparing to 720p25, which makes it still not true, as the higher temporal resolution of 1080i goes out the window as soon as you deinterlace. And you can't slow anything down without deintercaling first).

Don't believe what you hear - just really test it if you don't believe the numbers:

1/2 speed:
720p50 > 720p25
1080i50 > 540p12,5
(advanced deinterlacing techniques can make this a bit better, perhaps +/- 600p12,5 so to speak)


if you test it:
take 1080p50 fotage,
render it to 1080i50 and to 720p50,
then slow down both files,
compare

[Craig Seeman]

Shooting in 24p or 25p requires a different (improved?) set of skills due to the motion. Too many people think it's "flip a switch" and you can move the camera as before.

The EX1 is CMOS, not CCD BTW. The chips and the processing are Progressive coming from 1920x1080 (but there are various shooting modes).

For me, I need to shoot hand held frequently so I like the form factor. I've used shoulder mount and have found that awkward in some circumstances.
I don't think either is inherently "better." I think it's a matter of shooting style and technique. It looks like the EX1 rotating control grip should help wrist fatigue a bit.

Originally Posted by Werner Wesp

I agree to that, but I have seen in the last year or so that lots of people don't have the skills to be shooting in 25p (here in Europe). They keep insisting it is bad, which it isn't, but they can't produce anything in such a low temporal definition because of their camera techniques etc.

We'll also have to see if the CCD's are progressive 1080 CCD's - that hasn't always been the case. I believe the verical resolution of the Z1 was 1080 as well, but those CCD's weren't able of true progressive readout (ergo the 'frame' mode).

Actually I'm not saying anything on the quality of the SONY, I am merely reacting to some people that have never gotten the right info on p and i. the sony and the JVC aren't very comparible if you ask me. They are both designed for a segment in the market. The 16mm and 35mm adapters for the JVC go well e.g. and there's no substitute for that with this sony. Furthermore - JVC offers no handheld option. I personally think this sony model, just as the HVX200, is way to big and bulky for a handheld type camera, but nevertheless, sony and panasonic offer the option and some people like it.

[Alex Leith]

Originally Posted by Craig Seeman

Shooting in 24p or 25p requires a different (improved?) set of skills due to the motion. Too many people think it's "flip a switch" and you can move the camera as before...

Actually for 25p it's not really an issue. 24p is a challenge to work with because pull-down makes movement stutter.

I've been working with 25p for years with barely any special consideration. It would be just like going from 60i to 30p... It practically looks the same (only a little better IMHO)!

[Craig Seeman]

Not all 24p involves pulldown. Both the HVX200 and EX1 have modes that record 24p (23.98) natively to cards. It's one of the advantages of a card (solid state) based workflow.

One can certainly work from acquisition to master without using 29.97. Of course if you're heading for NTSC broadast the pulldown is going to happen at some point though.

Originally Posted by Alex Leith

Actually for 25p it's not really an issue. 24p is a challenge to work with because pull-down makes movement stutter.

I've been working with 25p for years with barely any special consideration. It would be just like going from 60i to 30p... It practically looks the same (only a little better IMHO)!

[Thomas Smet]

Originally Posted by Craig Seeman

Werner,

The EX1 shoots 1080p as well. While it doesn't shoot p50/p60 in that mode (it does shoot 720p60), it does shoot 1080p30, 1080p25, 1080p24. Also the EX1, in 35mbps, records FULL 1920x1080 from chips of the same size, even though other XDCAM HD cameras only record 1440x1080.

35mbps is more that "slightly" better than 25mbps. 25mbps is CBR and 35mbps is VBR. Fast moving images are allocated more bits making the codec MUCH HARDER TO BREAK than HDV.

True it's 4:2:0, to card, but as a "studio" camera it's uncompressed 4:2:2 (both SD and HD) out of HD-SDI before the MPEG2 codec touches it.

If you're talking about XDCAM HD in general, Sony will have a XDCAM MPEG2 4:2:2 50mbps format out soon in the highest end XDCAM HD.

You can ask people using the F355 if they're happy with the image and workflow. It works well.

I'd like to shoot 720p60 especially when I'm shooting fast action or material that may lend itself to slo-mo. I like having the option of shooting 1080p30 or 1080p24 though.

I agree it is a lot more. I just wanted to point out though that VBR isn't instant magic.

VBR just means it can adjust the bitrate depending on how complex the scene is. VBR 35 mbits will look just as good if you had CBR 35 mbits. VBR was more of a space saver then a quality booster. The only time the quality gets better is when you have to lower the bitrate. For example a DVD at 4.5 VBR will mostly still look as good as 4.5 CBR. It is just when it needs it it will bump the bitrate up to help.

With XDCAM the 35 VBR is the max so most of the time you might end up with bitrates lower then 35 mbits such as 25 or 30. So yes it looks better but not just because of VBR it looks better mainly for the reason it can go up to 35. 35 at CBR would look just as good but it would have been a waste of space because not all scenes would need 35 mbits. That is the key to VBR. Easy scenes can use lower bitrates. HDV isn't bad because it uses CBR. It is bad because sometimes 25 just isn't enough and it needs a little extra umphf.

With that said another thing I would like to point out is that with 35bmits on the EX1 it has to encode 1920x1080 instead of 1440x1080. It still uses a better quality encoder chip (I hope) but I think the 35mbit mode is going to look compression wise more like the 25mbit mode on the higher end XDCAM HD cameras. 1920x1080 has 1.33x more data to deal with so that almost cancels out the extra 1.4x worth of bits. Of course it isn't an exact science so it will still look better then 25 mbit HDV because most of the time a 1920x1080 image isn't going to have 100% unique pixels. My whole point is that 35mbits on the EX1 does have to work harder then 35mbits on other XDCAM HD cameras so do not expect a 1:1 quality compression between those cameras. Sure the EX1 is nicer because it is 1920x1080 but it will be slightly more compressed.

And that is why I may prefer shooting 720p with the EX1. Some of you may have seen my thread on 720p 24p and how awesome it is going to look on the EX1. Well even 60p or 50p is going to look great. Progressive is much easier to compress and 35mbits is about double of that of normal 720p broadcasts or what the JVC cameras use for their bitrates.

[Thomas Smet]

Originally Posted by Werner Wesp

Sorry bob, 1080i50 and 720p50 have the same temporal resolution. 1080i needs deinterlacing before producing slow motion, therefore dropping in temporal resolution over 720p50 due to field removal. Obviously, spacial resolution drops too dus to field removal. (you are probably comparing to 720p25, which makes it still not true, as the higher temporal resolution of 1080i goes out the window as soon as you deinterlace. And you can't slow anything down without deintercaling first).

Don't believe what you hear - just really test it if you don't believe the numbers:

1/2 speed:
720p50 > 720p25
1080i50 > 540p12,5
(advanced deinterlacing techniques can make this a bit better, perhaps +/- 600p12,5 so to speak)


if you test it:
take 1080p50 fotage,
render it to 1080i50 and to 720p50,
then slow down both files,
compare

Werner I totally agree with you. 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. Sure they are both good but they have different types of good. with interlaced if you have a perfectly still scene sure it may look like it has more detail but as soon as things move a little bit you loose a lot of that detail. 720p offers a clean compression with a consistant look no matter what type of scene you have. Good viewing of 1080i also depends on how good of a HDTV you have. Some just bob the interlaced video while others try to smart bob the video. Soem really advanced HDTVs will try to fill in the missing lines. Again we have inconsistant viewing experiences depending on who watches the video. With 720p everything looks clean all the time.

One thing people forget about interlaced video is that it has to low pass filter the video so there isn't any interlace flickering. So yes you may have 1080 lines but those 1080 lines are slightly softened to the point where they only have a tiny tiny bit of extra detail in still scenes. Like you pointed out most 1080 video even from HDCAM tape is 1440 which isn't all that much higher then 1280. Although to be fair until there was HDV 720p tape only used 960x720 pixels which is why some people may notice a lack of detail in some 720p shows. True 720p however is just as good if not better then normal 1080i video. Sure 1920x1080 may have a little bit of an edge over 1440x1080 but it is still interlaced and it still has a low pass filter. Even shooting progressive with a 1080i camera you have to be carefull. Sure the video may be progressive but a lot of HDTV's and a lot of HDV formats will still play this back as 1080i. 1080p material still has to have low pass filters or as soon as you watch it as 1080i you will get flickering. Again why 1080i or 1080p can give a lot of inconsistant results.

I like to think of HD in terms of a sliding scale. On one end you have dirty detail and the other end you have clean softness. It kind of depends on what you like but to me quality equals clean video with as few of artifacts as possible.

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.

[Evan Donn]

Originally Posted by Werner Wesp

Don't believe what you hear - just really test it if you don't believe the numbers:

1/2 speed:
720p50 > 720p25
1080i50 > 540p12,5
(advanced deinterlacing techniques can make this a bit better, perhaps +/- 600p12,5 so to speak)

Your numbers don't make sense - both formats start with 50 samples a second. Cut that in half, and both formats now have 25 samples a second.

What your numbers describe is de-interlacing first to produce a progressive frame and then slowing it down - but that's simply a bad workflow, not a limitation of interlaced video. The deinterlacing should occur naturally as part of the process of slowing it down. Drop 50i/60i footage into AE, tell it to separate fields and conform to 50/60fps in the interpret footage dialogue and each field will be scaled to a progressive frame, retaining your full temporal resolution at the expense of up to half of your spatial resolution (depending on motion levels).

Now you're back to comparing 50x1280x720 to 50x1440x540, which is a 15% difference - certainly significant but close enough that the I'd argue the deciding factor in which looks better comes down more to the lens and imaging system of the cameras than the format.

[Joel Brooks]

Would someone exlpain the definition and diferrence between 25mbx CBR and 35mbs VBR terminology. Thanks.
Joel

[G.A. Kokes]

Originally Posted by Thomas Smet

With that said another thing I would like to point out is that with 35bmits on the EX1 it has to encode 1920x1080 instead of 1440x1080. It still uses a better quality encoder chip (I hope) but I think the 35mbit mode is going to look compression wise more like the 25mbit mode on the higher end XDCAM HD cameras. 1920x1080 has 1.33x more data to deal with so that almost cancels out the extra 1.4x worth of bits.

Thomas,

Keep in mind that the EX uses only 2 channels of audio whereas the XDCAM HD uses 4. The 2 channel difference may help even the score you are talking about above.

Cheers,
G

[Alex Leith]

And if XDCAM HD on the EX1 behaves anything like XDCAM on the F330/350/355, etc. then (according to a Sony Engineer who talked to Greg Boston) that the data rate can actually peak slightly above 35mbps.

[Evan Donn]

Originally Posted by Joel Brooks

Would someone exlpain the definition and diferrence between 25mbx CBR and 35mbs VBR terminology. Thanks.
Joel

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.

[Thomas Smet]

Originally Posted by G.A. Kokes

Thomas,

Keep in mind that the EX uses only 2 channels of audio whereas the XDCAM HD uses 4. The 2 channel difference may help even the score you are talking about above.

Cheers,
G

The audio plays no part in that bitrate. In fact the audio is uncompressed and sits apart from the video bitrate. You could have 16 channels of audio and the video bitrate would still be the same.

[Thomas Smet]

Originally Posted by Alex Leith

And if XDCAM HD on the EX1 behaves anything like XDCAM on the F330/350/355, etc. then (according to a Sony Engineer who talked to Greg Boston) that the data rate can actually peak slightly above 35mbps.

yes peak slightly but not by a whole lot. Maybe 1 or 2 mbits/s is what I heard.