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Old March 24th, 2004, 06:44 PM   #1
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Another Possible use for HDV

I had an interesting idea the other day about the HDV format. I do not know all of the specs of the format yet and have not had the chance to see any footaqe shot with an HDV camera. Maybe some people can help me out with the specs.

I know the 1440 x 1080 format isn't fully out yet for HDV but when it is I thought of a way to use it for standard 4:4:4 video. Let me know if this makes any sense.

I am not sure if 1440 x 1080 is square pixels or not but if you resize the resolution by half you get 720 x 540 which would be the square pixel size of sd video. Now if you can get 4:2:2 1080 footage from the component outputs on the cam you can do the resize and now have 4:4:4 footage. The reason for this is that if 4:2:2 skips every other color sample then when you half the resolution you get rid of the missing samples. The same is true if you capture dv 4:1:1 footage and then half the resolution to 360 x 240. You would then have 4:2:2 footage at half the size.

Now that you have 720 x 540 4:4:4 footage you can do one more scale to the V. resolution to get the standard 720 x 480 and export as an uncompressed video file.

Of course this will only work if the 1440 x 1080 format is square pixels and if you can have a camera that would output component 1080 4:2:2 footage.

note. this would work with 1080p or 1080i footage because when it is scaled down to 540 the other field would be eliminated anyways so you would end up with 540p either way.

This would also work on 1280 x 720 footage but you would only get 640 x 360. You could then scale up the H. resolution to 720 to get a softer letterboxed 16x9 sd video.

This may seem a little useless to many but it was just a thought I came up with. Any thoughts?
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Old March 24th, 2004, 07:42 PM   #2
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I do beleive the 1440x1080 is anamorphic. i.e. will be in a 16x9 AR apon playback.
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Old March 25th, 2004, 01:00 AM   #3
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"Of course this will only work if the 1440 x 1080 format is square pixels and if you can have a camera that would output component 1080 4:2:2 footage."

I think that sums it up. So far we only have one cam and it can only component out at SD. Or 720p at 4:2:0. I am imagining cams that offer HD component out will cost a mint. This is where HDV steps on the toes of HD, and they aren't about to let that happen yet.
Ken
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Old March 25th, 2004, 08:27 PM   #4
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Even with only having 4:2:0 right now wouldn't you at least be able to get 4:2:2 from that assuming it works like pal?

4:2:0 doesn't mean 2 color samples and then 0 color samples. It is reffering to the samples alternating between the lines. With the 1/2 resize however this should also get rid of the color gaps and make 4:2:2. It still isn't 4:4:4 but 4:2:2 is a lot better to key with than 4:1:1. It would be an affordable way for people to basically get the same color resolution as dvcpro50 or digibeta.

the 18Mbit compression would also get enhanced as well in theory to a 36Mbit stream since the detail would be resampled to half the rez. Any image you take that looks ok and resize to half the rez will always look way better. You can capture VHS footage and it would look pretty good if it was scaled down to 360x240. This also starts to bring you a little closer to a 50 Mbit format. At least it is better than 25Mbit dv.

Now the only problem left is that 1440 x 1080 is anamorphic. In what way is it anamorphic? When it is unstretched what dimensions would it be. If it isn't to much we may still have a pretty good looking image.

If it is good then we would have a 720 x 480p 36Mbit 4:2:2 video that you could save to either an uncompressed format or a dvcpro50 codec.
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Old March 25th, 2004, 08:31 PM   #5
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Actually I just read somewhere that when the 1080 format does come to the next generation of HDV cameras that it will use a 25Mbit stream instead of the 18Mbit. This means in theory you could get a 720 x 480p 4:2:2 50Mbit video after scaling down by half.
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Old March 26th, 2004, 12:34 AM   #6
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"Even with only having 4:2:0 right now wouldn't you at least be able to get 4:2:2"

Yes.

"the 18Mbit compression would also get enhanced as well in theory to a 36Mbit stream since the detail would be resampled to half the rez."

Yes but so would the resolution so it would not theroretically double but stay the same 19Mbit. To get the equivalent of 4:2:2 colour space you have to drop to SD not HD res. This is fine, but should be done as a last stage for rendered output.

"Actually I just read somewhere that when the 1080 format does come to the next generation of HDV cameras that it will use a 25Mbit stream instead of the 18Mbit. This means in theory you could get a 720 x 480p 4:2:2 50Mbit video after scaling down by half."

Just theory at this point, and again it would stay at 25Mbit if you are 1/2'ing the resolution (720p is more like 2.4 times larger)

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Old March 26th, 2004, 09:09 AM   #7
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Is there a place where I can download a codec to use to do some tests or can I use any mpeg2 encoder and change the settings? I do not have an HDV camera right now but I will make some scenes in 3D Studio Max and render them out to the HDV format. I will then do some resampling tests to see if what I am thinking about is even worth it.

I know dropping a 1080 video to a 540 video wouldn't give a true 50Mbit video but with the smooting of the pixels it would be kind of like a psudo 50 Mbit video because a lot of the compression artifacts would get dissolved and the detail would be smoothed out better than it would be at 1080. Maybe it would only look a little bit better than 25 Mbit Dv but a little better is still better. At least it would be a way to have 4:2:2 SD on a budget. Although I don't know how much people would want to do a 4:2:2 SD when they can have HD. This only really aplies to those who want to do some serious graphics work.
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Old March 26th, 2004, 09:02 PM   #8
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Check out this thread
http://www.dvinfo.net/conf/showthread.php?s=&threadid=22833
In it are links to some mpeg2ts 720p footage and a player that will give you a codec.
Ken
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Old March 30th, 2004, 06:29 PM   #9
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Well I did a few tests and although I didn't test with actual HDV footage I rendered out some scenes in 3D Studio Max to 1440 x 1080 in anamorphic rez. I then brought a frame into photoshop and killed part of the color channels to simulate 4:2:2 video. When I scaled the video I can get a very high quality 864 x 480 4:4:4 video. This is the size of widescreen video without the anamorphic pixel size. When making a DVD just scale the video again to 720 x 480 and you would have a nice anamorphic DVD. We can keep it square for editing and compositing because it is higher quality.

Even though HDV is 4:2:0 I think we can still get 4:4:4 because 4:2:0 alternates 4:2 compression on every other line. So basically with the down rez we would get 4:4:0 and then because we cut the rez in half we get rid of the alternating color samples and end up with 4:4:4.

After doing some tests I come to conclude that if HDV used 4:1:1 it wouldn't be nearly as good as with it using 4:2:0.

I also did some tests with normal pal dv video which I rendered with 3D Studio Max since I am in NTSC land. When I scaled down the pal frames to 1/2, the u and v channels looked pretty close to 4:4:4.

This still however depends on a HDV camera coming out that supports 1080p. I did however do some tests of 720p footage scaled down to 640 x 360 to get 4:4:4 and then up scaled to either a 720 x 360 inside a letterboxed 480 frame or 864 x 480 for the square pixel widescreen format. It looked a little softer but since the footage is progressive it was still very good.

I will try to do some tests on the bitrate compression when I get a chance.
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