The Ultimate 720p camera. at DVinfo.net

Thomas Smet · September 20th, 2007, 06:49 PM

One of my favorite things about the Ex1 is the fact that it will record 720p. Not only will it record the broadcast standard of 720p at 60p or 50p but they were smart enough to make the 720p record 24p as well.

Why is this important?

Well cause it offers less compression.

The EX1 in the HQ mode with record 35mbits no matter what framerate is used. If 35mbits is a great quality level for 60p then 24p will be even better yet. The same is true for 30p and 25p. 30p alone could look more like what 60p would look if it was encoded at 70mbits/s. Of course the motion prediction has to work harder because the frames are further apart but that still overall gives more bits to use per frame.

I predict that it will almost be impossible to break the codec on this camera when shooting 720p 24p.

The HVX200 ends up using around 40 mbits when shooting 720p 24p. 35mbits isn't that much less and it is interframe which makes the compression even better. If you use the same ratio the 720p 24p could look more like it has double the birtate over the HVX200.

When compared to the way JVC does 720p encoding the 35mbits is double the datarate of the JVC flavor of HDV which should lead to some very superior looking 720p video compared to JVC. The EX1 also down samples 1080 to 720 in the DSP which gives a level of detail that a raw 720p chip could never do. All that and the fact that it has 1/2" chips is going to make it hard to justify the $12,000 cost of a JVC 250 unless you really must have a shoulder mount camera.

Steven Thomas · September 20th, 2007, 08:09 PM

The more I hear about this camera, the better it sounds. Thomas, I like your thinking. You bring up some good points!

Barlow Elton · September 20th, 2007, 10:35 PM

Quote:

Originally Posted by Thomas Smet

The HVX200 ends up using around 40 mbits when shooting 720p 24p. 35mbits isn't that much less and it is interframe which makes the compression even better. If you use the same ratio the 720p 24p could look more like it has double the birtate over the HVX200.

Excellent observation. This thought had occurred to me as well--and it bears repeating that the HQ mode is VBR 35mbs, which would probably be the equivalent of at least another 10mbs if the recording were CBR.

Either way, I'm sure the image will look extremely clean.

Thomas Smet · September 20th, 2007, 11:58 PM

Another quick thing to point out.

80mbits/s is the max bitrate you can have with Main profile/high level HD. This is the 4:2:0 full resolution flavor of mpeg2. That is the best looking compression you can get for 1920x1080 or 720p 60p video. HD at 80mbits/s is like SD at 15mbits/s for main profile/main level. Encode some complex SD video at 15mbits and you will see just how good mpeg2 is at that bitrate. The only way to get mpeg2 to look any better is to use the 4:2:2 profile and encode with 4:2:2. It should be noted that after a certain bitrate all the higher bitrates do is make sure the B frames and some of the P frames don't fall apart in super complex video. The closer to that max level you reach the more you are sure every single frame even if it is a B frame will look perfect.

If 24p is 2.5x smaller then 60p that puts the max bitrate you would ever need for the best looking quality at 32mbits/s or slightly less then what you get on the EX1. This means it should be virtually impossible to break the codec no matter what situation you are in. Any other bitrate over 35mbits/s would be a total waste and it wouldn't help at all because the compression is already pretty darn near perfect.

Tim Polster · September 21st, 2007, 05:28 AM

I have a question about 720 60p.

How much storage does it take up compared to 1080 30p?

Not having a progressive camera now, one of the things I am looking forward to is in HD shooting is 60p and the motion control in post.

Thanks

Paul Cronin · September 21st, 2007, 06:42 AM

Thomas great points and easy to understand thanks.

Barlow Elton · September 21st, 2007, 12:15 PM

Quote:

Originally Posted by Tim Polster

I have a question about 720 60p.

How much storage does it take up compared to 1080 30p?

It should take up the same amount as 1080 30p because it has twice the temporal sampling but roughly half the spatial resolution. If you were shooting HQ mode with either format they should both be consuming the same 35 mbs bandwidth.

Emmanuel Plakiotis · September 21st, 2007, 02:10 PM

Those who are interested in 720p you will be pleased to know that EBU, after extensive testing with ordinary viewers, has urged the European broadcasters to adopt the 720p 50fps standard over the 1080i 25fps. Ultimately, when camera technology and bandwith permits everything will be standarised at 1080p 50fps.

Probably thats the reason for the sudden love affair between Sony's newer cameras and 720p.

Greg Boston · September 21st, 2007, 02:31 PM

Quote:

Originally Posted by Thomas Smet

they were smart enough to make the 720p record 24p as well.

Why is this important?

Well cause it offers less compression.

Thomas, that's a good point. Kind of the same thing we've talked about for awhile now with DVD authoring. Using 24P instead of a pulldown to 60i for DVD material, you can get more time or less compression with the same bit rate, and then allowing the player to do the pull down for you on output.

-gb-

Tim Polster · September 21st, 2007, 02:52 PM

Is there that much of a visual difference between 720p and 1080p?

A lot of folks can't tell the difference between SD & HD.

For those with a camera that does both, is this true in your experience?

If so, then I could see shooting everything in 60p and going home with a lot of options in post.

Piotr Wozniacki · September 21st, 2007, 03:03 PM

Quote:

Originally Posted by Tim Polster

Is there that much of a visual difference between 720p and 1080p?

A lot of folks can't tell the difference between SD & HD.

For those with a camera that does both, is this true in your experience?

If so, then I could see shooting everything in 60p and go home with a lot of options in post.

I can tell you this: when watching on a full HD (1920x1080) screen with pixel-to-pixel mapping (like a PC monitor for example), the 1080 material DOES look much better than 720p - but only when you *UPSCALE* the latter to view full screen. This should also be true with HDTVs: on a full HD screen, a 1080 stuff will generally look better than an upscaled 720p - but depending of the upscaler quality.

But this also brings forward another consideration: the real world resolution of a HD (1080) camera is 1000 TV lines at the best, so... Using EDTV (aka "HD ready" ones) in conjunction with 720p video could be worth trying!

Thomas Smet · September 21st, 2007, 10:35 PM

Quote:

Originally Posted by Tim Polster

I have a question about 720 60p.

How much storage does it take up compared to 1080 30p?

Not having a progressive camera now, one of the things I am looking forward to is in HD shooting is 60p and the motion control in post.

Thanks

This is why the quality gets better for lower framerates with 720p because the encoded datarate always stays the same.

720p 60p = 35mbits/s
720p 30p = 35mbits/s
720p 24p = 35mbits/s
1080i 60i = 35mbits/s

because there are less frames that means more bits can be used for each frame. So to answer your question 35mbits/s is used no matter what format you shoot in.

If it was an I frame only format such as DVCPROHD then the more frames there are per second means the size will be that much larger.

Evan Donn · September 22nd, 2007, 12:50 AM

Quote:

Originally Posted by Thomas Smet

This is why the quality gets better for lower framerates with 720p because the encoded datarate always stays the same.

Except that the 35mbit/s HQ rate is VBR - at this point we don't know that it actually tries to max out the available bit rate when shooting at a lower resolution/frame rate. It certainly makes sense that it might, and I hope that it does, but there's also always the possibility that Sony aimed for a lower average bit rate (while allowing it to spike to 35 for high motion scenes) in order to increase recording times in 720 mode.

Mark Kenfield · September 22nd, 2007, 10:15 PM

Quote:

Originally Posted by Piotr Wozniacki

I can tell you this: when watching on a full HD (1920x1080) screen with pixel-to-pixel mapping (like a PC monitor for example), the 1080 material DOES look much better than 720p - but only when you *UPSCALE* the latter to view full screen. This should also be true with HDTVs: on a full HD screen, a 1080 stuff will generally look better than an upscaled 720p - but depending of the upscaler quality.

But this also brings forward another consideration: the real world resolution of a HD (1080) camera is 1000 TV lines at the best, so... Using EDTV (aka "HD ready" ones) in conjunction with 720p video could be worth trying!

It's probably also worth noting considerably more 720p resolution plasma/lcd televisions get sold than full 1080p ones (well here in Australia at least, but I imagine the price difference between the two translates to similar sales figures elsewhere) so though extra resolution is always a good thing, the number of people who can actually appreciate full 1080p as opposed to 720p is still fairly small.

Tim Polster · September 23rd, 2007, 08:01 AM

Is there a compatability issue if one puts out a 1080p product and the television/player is 720p?

Whe Blu-Ray of HD-DVD get out there, are they spec'd at 1080p or will there be different variants that only play 720p?

September 20th, 2007, 06:49 PM	#1
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	The Ultimate 720p camera. One of my favorite things about the Ex1 is the fact that it will record 720p. Not only will it record the broadcast standard of 720p at 60p or 50p but they were smart enough to make the 720p record 24p as well. Why is this important? Well cause it offers less compression. The EX1 in the HQ mode with record 35mbits no matter what framerate is used. If 35mbits is a great quality level for 60p then 24p will be even better yet. The same is true for 30p and 25p. 30p alone could look more like what 60p would look if it was encoded at 70mbits/s. Of course the motion prediction has to work harder because the frames are further apart but that still overall gives more bits to use per frame. I predict that it will almost be impossible to break the codec on this camera when shooting 720p 24p. The HVX200 ends up using around 40 mbits when shooting 720p 24p. 35mbits isn't that much less and it is interframe which makes the compression even better. If you use the same ratio the 720p 24p could look more like it has double the birtate over the HVX200. When compared to the way JVC does 720p encoding the 35mbits is double the datarate of the JVC flavor of HDV which should lead to some very superior looking 720p video compared to JVC. The EX1 also down samples 1080 to 720 in the DSP which gives a level of detail that a raw 720p chip could never do. All that and the fact that it has 1/2" chips is going to make it hard to justify the $12,000 cost of a JVC 250 unless you really must have a shoulder mount camera. Last edited by Thomas Smet; September 20th, 2007 at 11:28 PM.

September 21st, 2007, 06:42 AM	#6
Paul Cronin Inner Circle Join Date: Dec 2005 Location: Rhode Island Posts: 4,048	Thomas great points and easy to understand thanks. __________________ Paul Cronin www.paulcroninstudios.com

September 20th, 2007, 08:09 PM	#2
Steven Thomas Trustee Join Date: Sep 2005 Location: Gilbert, AZ Posts: 1,896	The more I hear about this camera, the better it sounds. Thomas, I like your thinking. You bring up some good points!

September 20th, 2007, 11:58 PM	#4
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	Another quick thing to point out. 80mbits/s is the max bitrate you can have with Main profile/high level HD. This is the 4:2:0 full resolution flavor of mpeg2. That is the best looking compression you can get for 1920x1080 or 720p 60p video. HD at 80mbits/s is like SD at 15mbits/s for main profile/main level. Encode some complex SD video at 15mbits and you will see just how good mpeg2 is at that bitrate. The only way to get mpeg2 to look any better is to use the 4:2:2 profile and encode with 4:2:2. It should be noted that after a certain bitrate all the higher bitrates do is make sure the B frames and some of the P frames don't fall apart in super complex video. The closer to that max level you reach the more you are sure every single frame even if it is a B frame will look perfect. If 24p is 2.5x smaller then 60p that puts the max bitrate you would ever need for the best looking quality at 32mbits/s or slightly less then what you get on the EX1. This means it should be virtually impossible to break the codec no matter what situation you are in. Any other bitrate over 35mbits/s would be a total waste and it wouldn't help at all because the compression is already pretty darn near perfect.

September 21st, 2007, 05:28 AM	#5
Tim Polster Inner Circle Join Date: Dec 2004 Location: Arlington, TX Posts: 2,231	I have a question about 720 60p. How much storage does it take up compared to 1080 30p? Not having a progressive camera now, one of the things I am looking forward to is in HD shooting is 60p and the motion control in post. Thanks

September 21st, 2007, 02:10 PM	#8
Emmanuel Plakiotis Major Player Join Date: Sep 2006 Location: Athens, Greece Posts: 344	Those who are interested in 720p you will be pleased to know that EBU, after extensive testing with ordinary viewers, has urged the European broadcasters to adopt the 720p 50fps standard over the 1080i 25fps. Ultimately, when camera technology and bandwith permits everything will be standarised at 1080p 50fps. Probably thats the reason for the sudden love affair between Sony's newer cameras and 720p.

September 21st, 2007, 02:52 PM	#10
Tim Polster Inner Circle Join Date: Dec 2004 Location: Arlington, TX Posts: 2,231	Is there that much of a visual difference between 720p and 1080p? A lot of folks can't tell the difference between SD & HD. For those with a camera that does both, is this true in your experience? If so, then I could see shooting everything in 60p and going home with a lot of options in post.

September 23rd, 2007, 08:01 AM	#15
Tim Polster Inner Circle Join Date: Dec 2004 Location: Arlington, TX Posts: 2,231	Is there a compatability issue if one puts out a 1080p product and the television/player is 720p? Whe Blu-Ray of HD-DVD get out there, are they spec'd at 1080p or will there be different variants that only play 720p?