HDV problems gone?

[Ken Hodson]

That product will save render time if you want to use a different codec. Thats it. A software product like AspectHD that does intelligent up-sampling to 4:2:2 seems like a better option to me, rather then down-sampling to DVCproHD or the massive size of uncompressed.

[Spike Spiegel]

whoa, aspect HD does that ? It upsamples the HDV footage to 4:2:2 when you create a cineform 1080i project?

[Ben Winter]

Originally Posted by Spike Spiegel

whoa, aspect HD does that ? It upsamples the HDV footage to 4:2:2 when you create a cineform 1080i project?

Not when you create a project, when you convert your footage to the cineform .avi intermediate. The intermediate incorporates 4:2:2 colorspace for less artifacting when CC'ing and such.

[Spike Spiegel]

what do you guys think of capturing analog HD to a capture card? Any benefits to try out that method rather than thru firewire?

[Chris Hurd]

Analog HD capture has been discussed here many times... do a search on component video capture and respond directly to those threads, please. Thanks in advance,

[David Kennett]

Maybe a little clarification on some previous posts.

DV (standard definition) is 5:1 compression and uses INTRA-frame compression similar to JPEG.

HDV uses MPEG2 (a more efficient encoder than DV, whereby complete frames are sent only occasionally, and subsequent frames are derived from the complete frame. Each complete frame begins a Group Of Pictures.) This complicates editing because only a small percentage of frames are entities unto themselves. HDV is typically compressed more than 15:1.

With DV or HDV, the compression is done BEFORE recording data to tape (or whatever).

You can NEVER recover something which has been lost to compression, reduction of resolution, or reduction of color resolution.

ANY decompression and subsequent re-compression will ALWAYS result in further losses - even a lossless codec. There is loss in the conversion.

I feel there is too much concern about color resolution (4:2:2 vs 4:1:1). There are bigger fish to fry. Maybe 4:2:2 better for chroma key. In any case, you cannot make a 4:2:2 out of a 4:1:1.

This has already been said by other others, but various comments lead me to believe there is still some confusion. Hope this helps.

[Tim Brown]

Originally Posted by David Kennett

In any case, you cannot make a 4:2:2 out of a 4:1:1.

With all due respect David, of course you can. Transcoding DV through a capture card into any of the lessor compressed formats on another machine will greatly increase the color space of your original material "technically" changing 4:1:1 to 4:2:2 and greatly increasing the data used for color correction and graphics. But technically you are correct as you are unable to add anything to the original. Only increase the levels of gray in what was captured.

[Ken Hodson]

Now this seemed to have been made confusing again. Yes you can convert a 4:1:1( or 4:2:0) into a codec that is 4:2:2. It will not change your original colour space one bit. Essentially you will have a 4:1:1(or 4:2:0) frame held within a 4:2:2 frame. It will look the same and has no advantage at all until it is processed further such as colour correction. Then we have the case of 4:1:1(or 4:2:0) where it is processed to a codec such as AspectHD or Magic Bullet, that will intelligently upsample the chroma info to 4:2:2. This type of process does in fact change the image by filling in chroma info. So yes, technically adding to the origional.

[David Kennett]

Ken,

Kinda sounds like an upscaling DVD player to me. There are tricks to improve the appearance of an image as one converts to something better (resolution or whatever). But you simply cannot create something you never had in the first place. This isn't even hi-tech, it's just logic.

[Ken Hodson]

Yes you can create something that wasn't there. How well it does it depends on the software. It isn't creating luma info, it is using the original chroma info (4:2:0) and the luma values to fill the chroma info in an intelligent manner. Please check out Cineform.com for further explanation.
It is a little hard to find on their site so here is a link
http://www.cineform.com/technology/H...ysis051011.htm
Click on Original M2T file and then Cineform avi to see the difference.

[David Kennett]

Don't know how you can say that, Ken. If you "make something up", then you "make something up", no matter how slick you are. They state "For many production needs the quality of CineForm intermediate is actually higher in it's first generation than the original". They did not state it IS actually higher! I see some color streaks pointed out by the arrows. I don't know where they came from, but they do not come from 4:2:0 chroma sampling. It's possible that their technique to fill in the missing data could inadvertantly fill in these small color streaks. I have difficulty finding any artifacts due to 4:2:0 sampling, as many analog errors are there before digitizing, which can easily mask the 4:2:0. I think the jaggies on the purple hat at the bottom of the cropped frame are far more objectionable. They are caused by interlaced scanning.

They show you the deterioration with TEN generations of HDV decoding and recoding, which I would expect to be degraded somewhat. It DOES make sense upscaling to a less compressed format THEN degrade by ten generations. My editing is done with NO recoding, or at the most two generations.

They make some statement as to 4:2:0 errors being more apparent for deeply saturated colors. If you have ANY color errors, they're going to be more apparent on saturated colors! Keep in mind that any errors caused by reducing the color sampling will ONLY show up at the edges, and I can't see anywhere where they have improved the chroma detail.

The original idea of reducing chroma resolution came from tests, showing that the human eye could not percieve fine chroma detail - only luminance. Since 4:2:0 is reducing chroma detail more than 4:2:2, it would seem to me that some pretty scientific tests would have to be done to show that we can actually percieve the difference.

There are worse "picture demons" than 4:2:0, and while the CineForm codec has it's advantages, it cannot "improve" 4:2:0.

[A. J. deLange]

Once high frequency picture (or sound for that matter) information is lost (removed by an atialiasing filter) prior to sampling or resampling it is gone forever and cannot be restored. It can, however, be replaced by information synthesized by an up-rezzing algorithm and, if that is done properly, we may well perceive the new picture to be better than the original. An outstanding example of this is sharpening by algorithms such as USM. The sharpness we see in a USM doctored picture is not the sharpness of the original thus the distortion of the original has been increased but the edges are more distinct and thus the picture looks sharper and more pleasing up to the point where we start to notice the halo along the edge. Another example is when SD video is uprezzed to play on an HD set. If, instead of just doubling pixels we average adjacent ones and display [original1][average][original2] the jaggies are suppressed even though no new picture information has been generated. [average] is not what appeared in the corresponding spot on the CCD (which couldn't resolve it) and thus represents distortion though in this case, as in USM what we see is more pleasing.

So it's a perception thing. Downsampling and then uprezzing increases mathematically measured distortion but the picture may look better.

[Ken Hodson]

A.J- We are talking chroma not luma. And we are not talking about uprezing. Two completely different things. Intelligent upsampling.

David- Yes it is making it up, that is the whole point. But when you have all of the luma info and a 0:2 chroma already, it does a very good job. It isn't so much that the human eye can see much different, it is the fact that when you start to CC or other FX work such as chroma key, then the difference is far more noticeable, and the primary reason why people were considering working in uncompressed to begin with.

[A. J. deLange]

When you double the number of chroma samples you are upping the chroma resolution. Intelligent upsampling it is and my comments still apply. Granted both my examples are both best understood with respect to luma but the color difference signals are sharpened and interpolated as well. Anyway, a signal is a signal and the principals are the same. It may look better (and or work better for some applications) but it isn't real.

But aren't you all demphasizing the main reason for converting HDV to a less compressed CODEC i.e. interpolation (uprezzing) in time? Instead of the very compressed combination of 1 I frame per second and motion vectors you get the P and B frames encoded as I frames so that you can step through them one at a time, cut between them etc. Again, it's not the real data - that got thrown away when the HDV compression was done - but rather something that looks credibly like the original stuff to the point that you can't tell whether an HDVPRO frame came from an I, B or P frame.

[Ken Hodson]

When you up-rez luma it is is unknown territory, being it has to completely guess what information would be there. When up-sampling chroma the outline of where information goes is already mapped out by the luma info. Based on this luma info and recorded surrounding chroma, the HDV frame gives a very logical path of where chroma info should go and good software can figure it out quite well. I have been more then impressed. It gives HDV footage, especially progressive, a great head start on overcoming its deficiencies, especially if you move to uncompressed for high end CC.

As to the second part of your post, I really can't tell what you mean. For one I frames are 5 times per second for 720pHDV and twice per second for 1080iHDV. Not one per second.