re-sizing HDV images

Ali Rasheed · January 17th, 2005, 11:52 AM

many thanks kyle...

49vm seems more contrasty so i'd go with the general consensus and say 30xs is the hi-def image...

but the quality change is so difficult to spot, which brings us back to the main issue here...

is the change in quality, when resized, enough to warrant an upgrade to hi-def?

Kyle Edwards · January 17th, 2005, 06:02 PM

d049vm.png is straight DV with no resize, while the d030x.png is HDV resized.

You can tell a difference, but it's very slight in these pictures. Once the weather clears up (maybe tomorrow) I'll do some motion scenes. One resized from HDV and another straight DV of the same scene.

Also the HDV was resized using the Lanczos filter.

Mike Tiffee · January 17th, 2005, 07:35 PM

<<<-- Originally posted by Ali Rasheed :

is the change in quality, when resized, enough to warrant an upgrade to hi-def? -->>>

No it's not. Upgrade to hi-def to shoot HD, not for better SD performance.

Brad Bodily · January 17th, 2005, 08:28 PM

There are some blocky "artifacts" in 49 (particularly the left edge of the main figure). Are those a product of the compression for hosting, or are they present in the original DV?

Steven Gotz · January 17th, 2005, 08:42 PM

Thanks for posting Kyle. It appears there is more of a difference than I expected. The question is still out there though. Which is better, resized HDV, or DV from a VX2100, or other really good SD camcorder?

Kyle Edwards · January 18th, 2005, 08:18 PM

I shot the 2 clips of the same scene, but now my computer is acting up. It refuses to see the Sony while it is in HDV mode. Very annoying. Hopefully soon there is a solution better than DVHS and cheaper than Aspect HD.

Once I get the footage on, I'll post the comparison.

Joonas Kiviharju · January 19th, 2005, 01:59 AM

Brad Bodily wrote:
"There are some blocky "artifacts" in 49 (particularly the left edge of the main figure). Are those a product of the compression for hosting, or are they present in the original DV?"

Yes, those blocks come from DV. I dare to say this even I haven't shot the footage. The web hosting has the files in PNG format, that in my information is lossles compression, so it doesn't affect the image in any way. NTSC DV is 4:1:1, so the luminance is sampled with full resolution, but color information isn't sampled that often. You can see that those blocks are all 4 pixels wide. This lack of color resolution is usually visible in the extreme reds. In fact, I've never seen it on another color. I've seen this behaviour many times on all DV cameras, as it's not a camera specific issue. It's there with DVX100A, XL2 and FX1 in DV mode.

One might wonder why isn't there those blocks in HDV as it is 4:2:0. Well, PAL DV is 4:2:0 too, and the blocks are there too in extreme reds. But HDV has much more resolution to start with, so you can't see the blocks when downsampled to SD resolution. Some said that it doesn't give you 4:4:4, but rather 4:2:2, but I don't know the details of this video color system so I can't confirm this is true. But, if you would re-encode HDV to DV the blocks would again be there as then it would be 4:1:1 or 4:2:0 with less resolution.

In my opinion there is a significant boost in SD quality when shooting HDV, atleast in still shots. (Motion is another thing, but in my experience it's handled pretty good too, so I wouldn't worry about it.) But it would require that you do your post processing in either uncompressed or atleast 4:2:2. And make a Digital betacam or DVCPRO master out of it. When you go to DV or DVD the quality boost would be lost.

Ben Buie · January 19th, 2005, 10:52 AM

Wow, some of the most obvious examples I've seen yet of the superiority of HDV down-rezzed vs. native DV. We have already seen this in practice for over a year with the HD10, but these posts really help drive the point forward.

Thanks guys, this confirms what the math already indicated, that starting with a higher resolution source and downconverting (with good software) should always yield better results than a low resolution original.

<<<-- Originally posted by Mike Tiffee : These are TIFF files, uncompressed- not resized in any way except where noted.

I put them in order of quality in my opinion. I place 16x9 DV as higher quality than 4x3 DV because it will look better on a 16x9 set.

Full size HDV frame:
http://www.miketiffee.com/hdv/HDV16x9.tif

HDV frame resized to 720x480 in photoshop:
http://www.miketiffee.com/hdv/HDVtoDVphotoshop.tif

HDV to DV conversion via 1394:
http://www.miketiffee.com/hdv/HDVtoDV1394.tif

16x9 native DV:
http://www.miketiffee.com/hdv/DV16x9.tif

4x3 native DV:
http://www.miketiffee.com/hdv/DV4x3.tif

I have no other DV camera to compare to, but in my opinion the photoshop resized image looks much better than the 16x9 native DV image... if you look at the stop sign, you'll notice the reds are handled much better. -->>>

Kyle Edwards · January 20th, 2005, 10:03 AM

http://s17.yousendit.com/d.aspx?id=1ACGW6D10K13K16TFF0HYTG91D

It's encoded to MPG4 (xvid), but you can still tell the difference. Each clip is labeled and a side by side comprasion is included.

January 19th, 2005, 10:52 AM	#23
Ben Buie Regular Crew Join Date: Mar 2004 Location: Atlanta, GA Posts: 184	Wow, some of the most obvious examples I've seen yet of the superiority of HDV down-rezzed vs. native DV. We have already seen this in practice for over a year with the HD10, but these posts really help drive the point forward. Thanks guys, this confirms what the math already indicated, that starting with a higher resolution source and downconverting (with good software) should always yield better results than a low resolution original. <<<-- Originally posted by Mike Tiffee : These are TIFF files, uncompressed- not resized in any way except where noted. I put them in order of quality in my opinion. I place 16x9 DV as higher quality than 4x3 DV because it will look better on a 16x9 set. Full size HDV frame: http://www.miketiffee.com/hdv/HDV16x9.tif HDV frame resized to 720x480 in photoshop: http://www.miketiffee.com/hdv/HDVtoDVphotoshop.tif HDV to DV conversion via 1394: http://www.miketiffee.com/hdv/HDVtoDV1394.tif 16x9 native DV: http://www.miketiffee.com/hdv/DV16x9.tif 4x3 native DV: http://www.miketiffee.com/hdv/DV4x3.tif I have no other DV camera to compare to, but in my opinion the photoshop resized image looks much better than the 16x9 native DV image... if you look at the stop sign, you'll notice the reds are handled much better. -->>> __________________ Ben Buie, Producer "On Our Way Up" - Shot Completely in HDV http://www.onourwayup.com HD Articles and Reviews at HDSource! http://hdsource.highlydef.com

January 17th, 2005, 11:52 AM	#16
Ali Rasheed Tourist Join Date: Jan 2005 Location: Maldives Posts: 2	many thanks kyle... 49vm seems more contrasty so i'd go with the general consensus and say 30xs is the hi-def image... but the quality change is so difficult to spot, which brings us back to the main issue here... is the change in quality, when resized, enough to warrant an upgrade to hi-def?

January 17th, 2005, 06:02 PM	#17
Kyle Edwards Major Player Join Date: Nov 2004 Location: LI, NY Posts: 274	d049vm.png is straight DV with no resize, while the d030x.png is HDV resized. You can tell a difference, but it's very slight in these pictures. Once the weather clears up (maybe tomorrow) I'll do some motion scenes. One resized from HDV and another straight DV of the same scene. Also the HDV was resized using the Lanczos filter.

January 17th, 2005, 07:35 PM	#18
Mike Tiffee Regular Crew Join Date: Oct 2004 Posts: 150	<<<-- Originally posted by Ali Rasheed : is the change in quality, when resized, enough to warrant an upgrade to hi-def? -->>> No it's not. Upgrade to hi-def to shoot HD, not for better SD performance.

January 17th, 2005, 08:28 PM	#19
Brad Bodily New Boot Join Date: Jan 2005 Location: Boise, ID Posts: 21	There are some blocky "artifacts" in 49 (particularly the left edge of the main figure). Are those a product of the compression for hosting, or are they present in the original DV?

January 17th, 2005, 08:42 PM	#20
Steven Gotz Trustee Join Date: May 2002 Location: Clermont, FL Posts: 1,520	Thanks for posting Kyle. It appears there is more of a difference than I expected. The question is still out there though. Which is better, resized HDV, or DV from a VX2100, or other really good SD camcorder?

January 18th, 2005, 08:18 PM	#21
Kyle Edwards Major Player Join Date: Nov 2004 Location: LI, NY Posts: 274	I shot the 2 clips of the same scene, but now my computer is acting up. It refuses to see the Sony while it is in HDV mode. Very annoying. Hopefully soon there is a solution better than DVHS and cheaper than Aspect HD. Once I get the footage on, I'll post the comparison.

January 19th, 2005, 01:59 AM	#22
Joonas Kiviharju Regular Crew Join Date: Jul 2004 Location: Helsinki, Finland Posts: 52	Brad Bodily wrote: "There are some blocky "artifacts" in 49 (particularly the left edge of the main figure). Are those a product of the compression for hosting, or are they present in the original DV?" Yes, those blocks come from DV. I dare to say this even I haven't shot the footage. The web hosting has the files in PNG format, that in my information is lossles compression, so it doesn't affect the image in any way. NTSC DV is 4:1:1, so the luminance is sampled with full resolution, but color information isn't sampled that often. You can see that those blocks are all 4 pixels wide. This lack of color resolution is usually visible in the extreme reds. In fact, I've never seen it on another color. I've seen this behaviour many times on all DV cameras, as it's not a camera specific issue. It's there with DVX100A, XL2 and FX1 in DV mode. One might wonder why isn't there those blocks in HDV as it is 4:2:0. Well, PAL DV is 4:2:0 too, and the blocks are there too in extreme reds. But HDV has much more resolution to start with, so you can't see the blocks when downsampled to SD resolution. Some said that it doesn't give you 4:4:4, but rather 4:2:2, but I don't know the details of this video color system so I can't confirm this is true. But, if you would re-encode HDV to DV the blocks would again be there as then it would be 4:1:1 or 4:2:0 with less resolution. In my opinion there is a significant boost in SD quality when shooting HDV, atleast in still shots. (Motion is another thing, but in my experience it's handled pretty good too, so I wouldn't worry about it.) But it would require that you do your post processing in either uncompressed or atleast 4:2:2. And make a Digital betacam or DVCPRO master out of it. When you go to DV or DVD the quality boost would be lost.

January 20th, 2005, 10:03 AM	#24
Kyle Edwards Major Player Join Date: Nov 2004 Location: LI, NY Posts: 274	http://s17.yousendit.com/d.aspx?id=1ACGW6D10K13K16TFF0HYTG91D It's encoded to MPG4 (xvid), but you can still tell the difference. Each clip is labeled and a side by side comprasion is included.