1080 give us better 720???? at DVinfo.net

Thomas Smet · April 18th, 2005, 12:54 PM

This is just a random thought of my messed up brain.

if 720p gives us 960 x 720,

and 1080p gives us 1280 x 1080p,

We may actaully get slightly better 720p quality by shooting 1080p.

The reason is that if we shoot 1080p we will get the full Horizontal pixel count of the CCD's (only a theory so far) of 1280 instead of only 960 that goes on P2 in 720 mode.

The aspect is messed up but if you scale the vertical resolution from 1080p down to 720 you now have a 16x9 1280x720 instead of only 960x720. Clearly you wouldn't be able to use the DVCproHD codec for editing anymore but if you convert to an uncompressed codec this would give you a little bit more resolution for film transfer.

Just a silly thought since this would take a lot more work. You could edit in a 1080 timeline to keep the faster DVCproHD codec and then convert once finished.

Kevin Dooley · April 18th, 2005, 01:43 PM

Of course you're now using a larger image with the same amount of compression (thus there would actually be less compression on the 720 image on a per pixel basis right?). Plus you're capturing in interlace (unless of course you're using the 30 or 24p modes...

Thomas Smet · April 18th, 2005, 01:52 PM

Yeah I was talking about 24p or 30p 1080. Sorry. You do get a little bit more compression but at the same time 25% more pixels.

Steven White · April 18th, 2005, 02:52 PM

Actually:

1280 x 1080 pixels x 30 fps........960 x 720 pixels x 30 fps
-------------------------- = ------------------------
100 Mbps................................50 Mbps

The data rates are exactly the same per pixel for 1080i and 720p on the DVCProHD codec.

Therefore 1080p (30 and 24) will produce images with exactly the same colour fidelity, but with more resolution than 720p (30 and 24). If you stick with those framerates, it seems it would always be better to shoot 1080p and down-convert. I think storage and data rates on the limited capacity of P2 will be the larger issue.

Thomas Smet · April 18th, 2005, 05:33 PM

Now we just need to find out if the CCD's are a native 1280 or 960 horizontal pixels. If they are only 960 and the 1080 mode gets scaled up to the 1280 well then there isn't much of an advantage. If the CCD's are 1280 x 720 then this would be the only way to really get all of the 1280x720 pixels from the camera.

Peter Moore · April 18th, 2005, 08:46 PM

Wouldn't it be very odd for the CCDs to contain 1280 horizontal pixels but not use them in 720p mode? That doesn't make any sense.

Jeff Kilgroe · April 18th, 2005, 09:11 PM

Quote:

Originally Posted by Peter Moore

Wouldn't it be very odd for the CCDs to contain 1280 horizontal pixels but not use them in 720p mode? That doesn't make any sense.

I have been thinking the very same thing... In other words, if it has a full 1280x720 CCD block, and if it indeed encodes the video at 960x720 for 720p modes, there are two possible explainations. One being that Panasonic is crippling the resolution for some reason. Or the other reason is this could be a limitation of the DVCProHD codec. I'm not all that familiar with DVCProHD so perhaps someone who is more knowledgeable could shed some light on this. So far many seem to think that this camera will encode video with a crippled horizontal resolution - effectively encoding a 4:3 frame to be stretched in post. Why??? 960x720? 1280x1080?

I'm going to guess that this is a limitation of DVCProHD and that it was designed to run at these horizontally crunched resolutions. But then that begs the question of why would they design it that way to begin with...? Why not simply maintain the proper 16:9 aspect ratio of the intended format and allow for full representation of all the pixels within the encoding process? Even HDV encodes the full 1920x1080i or 1280x720p piexel array to tape. Yes, it's crappy 25Mbps MPEG2, but at least all the pixels are accounted for on cameras that have the CCD block to utilize them.

So far I'm thrilled over the HVX200 and will probably buy one to replace my DVX. However, I am a little less than thrilled of the prospect that this camera may just be throwing away 25% of it's acquired image before it encodes the video onto P2 or HDD or whatever the case may be. If the CCD block is in fact only 960x720, then I wouldn't feel so bad about it, knowing that I'm getting the full usable resolution of the camera in my 720p video. But if it does have a native 960x720 CCD, then shooting 1080i (and especially 1080p) with this camera would be almost totally pointless.

Kevin Dooley · April 18th, 2005, 09:36 PM

Quote:

Originally Posted by Jeff Kilgroe

Even HDV encodes the full 1920x1080i or 1280x720p piexel array to tape. Yes, it's crappy 25Mbps MPEG2, but at least all the pixels are accounted for on cameras that have the CCD block to utilize them.

Actually, the Sony cam's write 1440x1080 to tape, and start with (if I remember correctly) 960x1080 and use pixel shift to get to the 1440.

To my knowledge, there aren't any (except maybe HDCAM SR) cams/decks/codecs that write full resolution.

And you're right, it is the DVCPRO HD codec that specifies 960x720 and 1280x1080 of rectangular pixels as the resolutions.

Now one thing this cam might do is to sample 1280x720 and then write the files as 960x720 in 720p mode. Obviously for 1080 footage you're going to need some pixel shift to get to 1280x1080...

But anyways, all things considered, I think you'll end up with much better pics with this vs. the HDV cams (not to knock them or anything). I mean this is the same codec that the Varicam uses (obviously there are lot of other things that make this a different cam...)

In my mind that's what's so revolutionary about this cam. With the DV revolution, pro's knocked the DV format at first because it was technically inferior to the "broadcast standard" at the time. HDV is in the same boat when you compare it to DVCPRO HD or HDCAM... but this cam... it uses the same encoding, bit rate, and colorspace as one of the world's most popular HD cameras. And at this point, people are used to the limitations of a 3 1/3" CCD blocks with fixed lenses... they're used to it, and they know that it can do amazing things... Plus they're doing away with tape/linear-based acquisition??? Wow. Honestly, when I heard the rumours of this camera... I became a lot less interested in HDV--again, not to knock it, but at this price range, I have my choice between a hamburger (XL2/DVX), a 10 oz. NY strip (HDV cams), or the 24 oz. Prime Rib... Guess which one I'm most interested in...

Thomas Smet · April 18th, 2005, 10:15 PM

The codec forces the 960x720 resolution for 720p. Thats just the way it is. I don't really like it but hey it worked for the Varicam just fine. My whole point to this post however is that it just so happens that the 1080 mode does have exactly the 1280 horizontal pixels. This means we can use every pixel from the CCD to get to 720p. 720p does use every pixel but then it gets downsampeld to 960. Think of it as how on DV cameras when you record 16x9 it still gets recorded onto tape at 720x480 even though it should be 853x480. Using the 1080 to 720 method does have a lot of drawbacks of course. It uses the full 100 Mb/s so half the record time on P2, faster system to edit with, need more hard drive space to edit, after editing you will have to convert and render to remove the pulldown and scale from 1080 down to 720 which could take some time. You would however end up with 25% more pixels compared to just the 960x720 DVCproHD codec. This would only really matter if you were going to film since you would have a hard time telling the difference on a HD monitor. Might be an option to keep in mind for the film people. Of course if they were going to shoot 1080 why not just keep it at that then? I don't know it was just a silly thought. I'm always thinking of ways to use images in ways they were not meant to be used.

April 18th, 2005, 12:54 PM	#1
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	1080 give us better 720???? This is just a random thought of my messed up brain. if 720p gives us 960 x 720, and 1080p gives us 1280 x 1080p, We may actaully get slightly better 720p quality by shooting 1080p. The reason is that if we shoot 1080p we will get the full Horizontal pixel count of the CCD's (only a theory so far) of 1280 instead of only 960 that goes on P2 in 720 mode. The aspect is messed up but if you scale the vertical resolution from 1080p down to 720 you now have a 16x9 1280x720 instead of only 960x720. Clearly you wouldn't be able to use the DVCproHD codec for editing anymore but if you convert to an uncompressed codec this would give you a little bit more resolution for film transfer. Just a silly thought since this would take a lot more work. You could edit in a 1080 timeline to keep the faster DVCproHD codec and then convert once finished.

April 18th, 2005, 01:43 PM	#2
Kevin Dooley Major Player Join Date: Dec 2003 Location: Fort Worth, TX Posts: 414	Of course you're now using a larger image with the same amount of compression (thus there would actually be less compression on the 720 image on a per pixel basis right?). Plus you're capturing in interlace (unless of course you're using the 30 or 24p modes... __________________ Kevin Dooley Media Director, Pantego Bible Church

April 18th, 2005, 01:52 PM	#3
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	Yeah I was talking about 24p or 30p 1080. Sorry. You do get a little bit more compression but at the same time 25% more pixels.

April 18th, 2005, 02:52 PM	#4
Steven White Major Player Join Date: Nov 2004 Location: Canada Posts: 547	Actually: 1280 x 1080 pixels x 30 fps........960 x 720 pixels x 30 fps -------------------------- = ------------------------ 100 Mbps................................50 Mbps The data rates are exactly the same per pixel for 1080i and 720p on the DVCProHD codec. Therefore 1080p (30 and 24) will produce images with exactly the same colour fidelity, but with more resolution than 720p (30 and 24). If you stick with those framerates, it seems it would always be better to shoot 1080p and down-convert. I think storage and data rates on the limited capacity of P2 will be the larger issue.

April 18th, 2005, 05:33 PM	#5
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	Now we just need to find out if the CCD's are a native 1280 or 960 horizontal pixels. If they are only 960 and the 1080 mode gets scaled up to the 1280 well then there isn't much of an advantage. If the CCD's are 1280 x 720 then this would be the only way to really get all of the 1280x720 pixels from the camera.

April 18th, 2005, 08:46 PM	#6
Peter Moore Trustee Join Date: Oct 2002 Location: Arlington VA Posts: 1,034	Wouldn't it be very odd for the CCDs to contain 1280 horizontal pixels but not use them in 720p mode? That doesn't make any sense.

April 18th, 2005, 10:15 PM	#9
Thomas Smet Trustee Join Date: Mar 2004 Location: Milwaukee, WI Posts: 1,719	The codec forces the 960x720 resolution for 720p. Thats just the way it is. I don't really like it but hey it worked for the Varicam just fine. My whole point to this post however is that it just so happens that the 1080 mode does have exactly the 1280 horizontal pixels. This means we can use every pixel from the CCD to get to 720p. 720p does use every pixel but then it gets downsampeld to 960. Think of it as how on DV cameras when you record 16x9 it still gets recorded onto tape at 720x480 even though it should be 853x480. Using the 1080 to 720 method does have a lot of drawbacks of course. It uses the full 100 Mb/s so half the record time on P2, faster system to edit with, need more hard drive space to edit, after editing you will have to convert and render to remove the pulldown and scale from 1080 down to 720 which could take some time. You would however end up with 25% more pixels compared to just the 960x720 DVCproHD codec. This would only really matter if you were going to film since you would have a hard time telling the difference on a HD monitor. Might be an option to keep in mind for the film people. Of course if they were going to shoot 1080 why not just keep it at that then? I don't know it was just a silly thought. I'm always thinking of ways to use images in ways they were not meant to be used.