SD vs down converted HD
 

Recently I've switched from shooting in SD to HDV then down converting after editing and burning a DVD. But I got tired of spending the extra time editing and down converting, so I decided to do some tests to see if there really is a difference.

My conclusion was no. Even though I wanted the down converted HD to be the winner, I honestly couldn't see a difference. I shot various subjects and switched back and forth, took screen captures (which I could post) and they looked virtually identical. I kept re doing the test with the same results.

I've read many attest to down converted HD to be better but has anyone really done a side by side test and can post evidence to back up the claim? To me I think there's psychological bias in favor of dc hd. I'm going back to shooting SD and only shoot HD when the client or I would like hd the footage for future use. But honestly I can't ever see myself ever going back and re-editing.

Pete, the only real benefit I see of shooting HD and going from there is that for whatever reason, you have an HD source should you need that in future.
If they're shots that you plan to wipe when done, then probably easier to shoot SD just for the drive space and CPU issues.
For the price of a tape which you probably won't re-use, I'd shoot HD everytime.

That is not accurate. It's camera dependant, so there's some models than gives a huge difference shoting on HD and downconverting to SD.

And besides that, keep in mind that if the SD mode is "standard DV", you can get better color resolution by downconverting. Just like having a 4:2:2 SD camera.

Another example: The goal of the 4k Red One is not to deliver a pristine 4k footage, but a 2k.

Of course, you have to balance the benefits of having larger renders and perhaps a harder editing with your actual equipment just for a little bit more quality.

Btw, this is with the Sony Z1u. I also didn't see a difference between down converting from the camera and the editor. Here are some stills the only difference I can tell is, SD yields a brighter exposure. Notice the blown license plate.

http://i43.tinypic.com/rlgphy.jpg
vs
http://i40.tinypic.com/2jct4cz.jpg

How were you downsizing the edited HDV to SD?

As far as I can tell, most NLEs do a rather poor job of downsizing, and I can imagine most NLEs are no better at downsizing than having a camera convert to DV, on the fly, during capture (downsizing with some NLEs might even be worse). The best way I know of to downsize HD footage, is to use VirtualDub or AviSynth with Lanczos3 resizing.

I just took an unedited frame from HDV footage (shot with an HV20 at 24p) and downsized to 720x480 images, with Edius and with VirtualDub/Lanczos3 (using no comprssion with either Edius or VDub). I was going to upload the resulting images (as lossless PNGs), but apparently I can't upload images here. The Edius downsized image is notably softer than the VirtualDub/Lanczos3 downsized image.

I downloaded and blew up your images. There isn't a big difference, but the first image does look slightly better to my eyes (magnified 250% on my 22" monitor). On a big screen TV, the difference might be perceptible, if looking closely (but not likely noticed if viewing casually).

The differences in the images I get from Edius and VDub/Lanczos3 is considerably greater.

I've pretty much concluded that it doesn't make much difference, downsizing HDV via camera or downsizing in an typical NLE, but sure does make a noticeable difference using Lanczos3 resizing to downscale (would be unmistakeable on something like a 60" HDTV).

The down converting was done when it was imported from the camera. I did a test prior to this comparing down convert from the camera vs the editor (I used MpegStream application which does a better job then FCP) and I didn't see a difference in quality and thats when it occurred to me to test it against SD.

I use TinyPic.com to post throw away images like this. Its free and you don't need to be a member.

I am with Robert on this one. I think the first pic looks slighlty better. But it could be down to exposure but I don't think so. It seems to be slightly sharper to me.

The SD would look better without the over exposure. The gamut on pc makes the grain more visible. Here are another scene.

http://i44.tinypic.com/bhn147.jpg
http://i43.tinypic.com/atw2fb.jpg

I'm confused about the source of these images. Can you tell us exactly how (the process) each were generated?

We've got three possibilities:

1 - Shot as DV and captured as DV
2 - Shot as HDV and captured as DV (camera converting on the fly)
3 - Shot as HDV, captured as HDV and converted to SD by an NLE (or other software, on a computer)

Those images are also 853x480, so I assume they have been re-sized from 720x480, and also compressed (via JPEG). That does alter the image, but as long as the methodology is the same, and of high enough quality, for both images being compared, should still make for close enough to an apple-apple comparison (less than very high quality, in resizing to 853x480 or in JPEG compression, could potentially narrow the differences between the images though).

Proper downconverting is a tricky little devil..Especially for 1080i sources. And it's as slow as molasses. I'm coming to the realization that one should shoot for the intended output..

But as mentioned earlier, my HDV projects can be called up at anytime for proper output..
That's the only thing pushing me to tape in HDV....

To do it properly, you need to BOB the fields to double framerate, resize, separate fields, choose the correct fields, and weave them back...

I just finished downconverting my first wedding, and the picture on a 50" Plasma was absolutely fantastic...I was shocked.
Would it have looked the same as my SD shoot?? I don't know...

But it's a pain to get a proper resize done...Anybody claiming resizing can be done on the fly, is throwing away information, and at that point, it becomes a subjective issue....

DO NOT Lanczos resize interlaced frames, without separating fields...It gives a deteriorated picture.....

If anybody's interested in my Avisynth script, just give me a holler.....

BTW, if there's issues in colour, you'll need to give workflow information to get to the bottom of any issues.

Virtual Dub has a switch for resizing interlaced footage, so you don't need to manually get into bobbing and weaving like a prize fighter. (I can't say I've really tested to see if it works correctly though.)

To do resizing with Lanczos on a regular basis, using AviSynth (with proper script) would be quicker and easier though.

Actually, I've found that resizing 1080i HDV to SD, with Lanzcos, treating the source as if it was progressive, isn't a bad way to deinterlace it to 30p while downsizing (kill two birds with one stone). It retains sharpness in static areas (extremely well), and usually blends motion areas pretty nicely. The beauty of it is there's no need for an algorithm to determine which areas of any given frame need to be deinterlaced (and thus, no mistaken deinterlacing occurs).

Robert, please load your .AVI, go to the status flydown, and tell me what kind of FPS you're getting back...
I don't quite understand....Treating interlaced footage as progressive needs some sort of deinterlacing....
I'm not familiar with your method....I'll post some screenshots via my method when i get back....

I just did a quick FPS test, with 1080i HDV (previously re-wrapped from an m2t container to an mpg container), using VirtualDub Mod (a version of VirtualDub that has been modified to be able to load MPEG-2 mpg files). Using Lanczos resizing (checking the box for resizing as interlaced content), it converted (to 720x480i60) at a little over 12fps, outputting as an AVI file using Canopus HQ as the output codec (the output codec will impact throughput considerably - H.264, for example, would obvously be much slower, but that has nothing to do with the resizing). This is with a Phenom 9500 (low end quad CPU).

If you don't check the box for resizing as interlaced content, you wind up with a result that has effectively been deinterlaced. Resizing 1080 lines to 480 lines that way, effectively blends the fields, rather than resizing them separately. The result is as sharp as you can get in areas where the image is static, and blends quite nicely in areas where there is motion. This works nicely for converting 1080i60 to 720p30 also. With AviSynth, you could effectively use similar methodology to convert 1080i60 to 720p60 (or 480p60).

I just did it again, using Panasonic's VFW DV codec for encoding the output file (literally converting HDV to DV). Speed was a little over 11fps.

One was shot in SD anamorphic and the other HD and down converted from the camera during import. The screen captures were done in MPEGstream Clip. I'm not really sure why they aren't 720x480 because I didn't resize them. Btw, I'd like to see stills comparing other people's down convert so I can see for myself any quality improvement over SD.
I don't use VitualDub because I'm on a Mac. If I remember correctly I once did a test down converting one frame in Photoshop and it really did a nice job but you'd have to be crazy to use it to downconvert a movie.

Slight correction: the colour is noticeably less washed out on the Z1 downconverted from HDV compared to DV but HDV colour space is 4:2:0, NOT 4:2:2. This means that each "block" of colour information is 2 pixels by 2 pixels square, as opposed to DV which is 4 contiguous pixels on one line getting 1 unit of colour info.

4:2:2 colour has 2 pixels in a row sharing the same colour info, all on one row.

EDIT: Of course, the above assumes NTSC for DV. PAL DV uses 4:2:0 colour space, just like HDV does.

I think what he was trying to say is, even at 4:2:0, with HDV you have more chroma samples per frame than with DV. When you downsize the HDV to SD, you effectively get higher chroma resolution than DV records (somewhat similar to effectively getting 4:2:2 in SD - actually closer to 4:4:4, I think, but I haven't had my morning coffee yet so I'm still groggy).

You don't get MORE samples per frame. You get a different PATTERN: a 2 pixel by 2 pixel square instead of a 4 pixel x 1 pixel line.

Chroma subsampling - Wikipedia, the free encyclopedia

A great graphical representation of 4:2:0, 4:1:1, 4:2:2 and 4:4:4 can be found at the above address.

The number of SAMPLES of colour is identical in 4:1:1 and 4:2:0. The distribution is what makes the difference. And yes, 4:2:0 does have PERCEPTUALLY better colour representation (or at least less washed out) than 4:1:1, in my opinion.

When you shoot HDV, you get both more luminance samples and chroma samples per frame, than with DV. It's higher resolution video in both regards. With 1080i HDV, you get 1440x1080 luminance and 720x540 chroma resolution. With DV you get 720x480 luminance and 180x480 chroma. In theory, you can effectively wind up with 4:4:4 color sampling after downsizing 1080i HDV to SD.

Robert: INTERESTING... I'd never thought of it like that before. I'm sure that "in theory" comes into play somewhere. But of course, in downresing, you'd need to go to an intermediate codec that would support the increased colour sampling. Going to DV (4:1:1) would "throw away" all your gains by re-sampling to the 4 pixels by 1 pixel matrix.

Part of why I say "in theory" is that I think (but I don't know absolutely for sure) the 2x2 block (in 4:2:0 interlaced footage) is by field (rather than by frame). It almost has to be. I'm not sure (hurts my brain to think hard enough to figure it out), but I don't think downsizing 1080i HDV (to interlaced SD properly) will really yield 4:4:4 color. It is safe to say though, that downsizing HDV (of any flavor) to SD should certainly yield better than 4:2:0 or 4:1:1 color. Yes, if you then "recorded" the downsized footage (saved the result) as DV (for example), it would then be 4:1:1 color (essentially, that is downsizing the chroma portion of the image yet again).

Another part of why I say "in theory" is in recognition that the imaging system of the camera is a vital part of determining effective resolution. Just because a camera records an image in a particular format, doesn't mean the camera actually acquires at the resolution of that recording format (as a practical matter, the effective resolution never reaches 100% of the potential of the recording format - in the neighborhood of 70-80% is fairly typical).

I reckon Peter's nailed it. Don't forget that the Z1 (and any HDV camera for that matter) always shoots HDV. If you film in the SD mode the downconversion is taking place in real time, from chips to tape.

If you downconvert from an HDV tape so that DV exits via Firewire, the (presumably the same, and pretty cheap 'n' cheerful) downconverters are working to effect this.

But shooting for the intended output is very good advice, and if you're only ever going to make DVDs (by definition SD) then it's far safer to film in the SD mode. This is because dropouts are far less damaging (and individual frames can even be worked on in Photoshop) and of course the audio is uncompressed.

I too have difficulty seeing any real benefit in downconverting after I've done the HDV edit. There may be minute differences but hey - one HDV dropout is FAR more damaging from a visual pov.

tom.

That's exactly what I was talking about. Thanks.

My advice is to shoot always in HDV, edit in HDV and let the final step do the downconversion. This allows you to mantain the maximun quality of your original footage even with color correction, fx, and preview renders (second generations). Also, you can reframe when you needed up to a certain degree without loosing quality in your final SD master.

peter,

is the SD you shot showing up s 16:9?? I was wondering this myself because im buying a FX1 to shoot weddings with and want to know if its still widescreen 16:9 SD????? or anamorphic

thanks

Jason

The FX1 has 16:9 CCDs, so everything you shoot will be widescreen unless you pillarbox it for 4:3 in the menu.

Maybe we're just getting confused with terminology, but all standard definition widescreen 16:9 is anamorphic. That is the only standard definition widescreen format. It is recorded at 720x480 (or 720x576 PAL), then it is stretched to fill the 16:9 monitor when you play it back. The Z1 conforms to this standard when you set it for DV (or use the camera to downconvert from HDV).

That's not correct. Wide screen was first achieved by cropping SD and putting black bars on the top and bottom. As they advanced they switched to anamorphic which used all of the vertical resolution by squeezing the image when filmed, then was expanded by the dvd player. This then was called "true" wide screen.

I believe what Boyd is referring to is that all 16:9 SD DV is RECORDED as "anamorphic", which is a "new" take on the original filmic process of placing a "squeezing" lens on the camera and a "stretching" lens on the projector.

By this I mean that REGARDLESS of whether one has native 16:9 sensors or a centre crop of a 4:3 sensor is performed (lowering resolution), BOTH are recorded to tape the same way which is writing the information to a 720 x 480 frame size (ASSUMING NTSC) with a pixel aspect ratio conversion so that during play back, the 720 x 480 (which is NOT 16:9 if you do the math...) BECOMES 16:9.

Of course, Pete knows this and my dissertation is solely for the benefit of future readers.

Actually, the process was to take a 16:9 shaped "bite" out of a 4:3 image and then stretch that vertically to fill 4:3 frame and record to tape.

Shaun's considered reply is correct but I have a small quibble about 'a centre crop of a 4:3 sensor is performed, lowering resolution.'

In fact the resolution isn't affected at all - a road sign is just as readable in the middle of a 4:3 frame as it is in a masked down 4:3 frame. On a 4:3 TV this is very clearly so - but if you then expand this cropped image vertically to fill a 16:9 TV it does appear to have less resolution. But the resolution is actually unchanged; sit further away and the sign is just as legible.

Pete's argument (anamorphic uses all of the vertical resolution) is not borne out in practice and the DVX100B clearly proves this. It's a 4:3 chipped camcorder that has the option of masking to produce 16:9 (whereupon the v'finder image is undistorted) or squeezing the image (then the v'finders show vertical expansion)

Both give the same end result on DVD - in resolution and aspect ratio.

tom.

Again, my bad for not being clearer: resolution of a 4:3 sensor cropped to 16:9 is reduced COMPARED TO a 16:9 native sensor in SD when viewing on a 16:9 display (NOT letterboxed in a 4:3 display).

Another benefit to shooting in HD and converting to SD after editing is the ability to crop footage (zoom) to optimize framing and composition without losing SD definition. You can safely go in 20% without perceptible SD softening.

Re: SD vs down converted HD
 

I agree with Jim Snow about downloading HDV in HD, editing in HD, and converting as the last step.

What is still confusing to me is what method (workflow) of converting from HDV to SD is the best method before burning an SD DVD. I've tried exporting to Quicktime, then to Compressor/DVD Studio Pro. Have also used MPEG Streamclip and Toast.

The reason this is especially critical at this point in time is that I was hired to video tape series of fast paced soccer games. Just want to reduce the blur and get the best clarity to SD DVD.

Many thanks, everyone.

Leon

Re: SD vs down converted HD
 

Hi Leon, you might want to check whichever editing forum we have that best suits your workflow (Vegas / Adobe / Final Cut etc.) because I think you'll find much more info there rather than this camera-specific board. Hope this helps,