HD to SD Downconversion

Bill Ravens · December 20th, 2008, 08:01 AM

Perrone...

I really hesitate to post much of my own experiences here, but, I'll give it a try. As of late, it seems people on this forum have become quite rude and intolerant of opposing viewpoints.
Having said this, I've played with both Vdub workflow scenarios, as well as other techniques. As far as vegas is concerned, I can achieve results with Vegas that are comparable with Vdub downrezzing by generating the HD .veg file, then opening an SD project and bringing the HD.veg file into the SD project, then rendering in SD.

Also, many people, here, seem to like to use sharpening when shooting with the EX1. As you know, a DETAIL setting of '0' adds sharpening to the captured images. Sharpening done in-camera, is to be avoided as it significantly adds to the twitter problem people experience. For some reason, they refuse to accept that better results can be obtained by turning DETAIL off and sharpening in post. It doesn't help, also, that in camera sharpening adds to the work done by the camera compressor algorithm, sucking up bandwidth that would be better used on image detail, not compression/DETAIL artifacts. There are supposed "experts" here that really believe there are no compression /motion artifacts with the EX1 codec.

Perrone Ford · December 20th, 2008, 08:39 AM

Quote:

Originally Posted by Jay Gladwell

Perrone, maybe I missed something along the way in your explanation. When making DVDs, why not render straight from the HD timeline (mfx) using MainConcept MP2/DVD Architect NTSC Widescreen Video Stream?

Because it means that the encoder has to do two jobs. It has to downres the video, and it has to encode it. I don't know what method the Mainconcept encoder uses to downres, so I like to control that step myself and use the best rescaler available.

Perrone Ford · December 20th, 2008, 08:42 AM

Quote:

Originally Posted by Dominik Seibold

Absolutely. Btw, did you know that your choice of the lanczos-rescaler is a very good one, because the lanczos-rescaler is the best rescaler actually programmable? :)

Well, after much research and testing, I settled on it. Though I would like to find a bicubic spline rescaler to test againt but no one seems to have one. It would not be nearly as fast though. The lanczos also adds some subtle sharpening, so I wouldn't use it for everything.

Clark Peters · December 20th, 2008, 08:45 AM

Dominik-
Instead of taking potshots at Perrone's method, please give us your version of a step-by-step process of converting HD to SD. I'd love to see how you do it.
Pete

Perrone Ford · December 20th, 2008, 08:49 AM

Quote:

Originally Posted by Bill Ravens

As far as vegas is concerned, I can achieve results with Vegas that are comparable with Vdub downrezzing by generating the HD .veg file, then opening an SD project and bringing the HD.veg file into the SD project, then rendering in SD.

This doesn't surprise me. But I tend to like to know what's happening behind the scenes so I use VDub. There are likely a number of ways to solve these issues and get good SD results. I merely posted mine as I have not had any negative results from deriving SD from the XDCamEX cameras.

Quote:

Originally Posted by Bill Ravens

Also, many people, here, seem to like to use sharpening when shooting with the EX1.

This is a shame. The EX1 is the sharpest camera in it's class. It needs no sharpening in the camera at all. My results are with sharpening off, and I don't do any in post either.

Quote:

Originally Posted by Bill Ravens

There are supposed "experts" here that really believe there are no compression /motion artifacts with the EX1 codec.

Well that's silly. That's why it's called compression. And artifacting is clear and obvious under motion. Just grab a still and zoom in 400%. You'll see all you want. My interview footage is a great example. As I adjust in my chair, you can see the codec get overwhelmed and go soft.

Perrone Ford · December 20th, 2008, 08:52 AM

Quote:

Originally Posted by Clark Peters

Dominik-
Instead of taking potshots at Perrone's method, please give us your version of a step-by-step process of converting HD to SD. I'd love to see how you do it.
Pete

It's ok Clark. I know why he was on my back. But I would love for him to share his method here.

Dominik Seibold · December 20th, 2008, 09:39 AM

Quote:

Originally Posted by Perrone Ford

Well, after much research and testing, I settled on it. Though I would like to find a bicubic spline rescaler to test againt but no one seems to have one. It would not be nearly as fast though. The lanczos also adds some subtle sharpening, so I wouldn't use it for everything.

Lanczos is the best because it approximates closest to the Nyquist-Limit without aliasing. That sharper look isn't actually sharpening but just real unboosted high-frequency-information which can't be seen by more high-frequency-muffling methods.

Quote:

Originally Posted by Clark Peters

Dominik-
Instead of taking potshots at Perrone's method, please give us your version of a step-by-step process of converting HD to SD. I'd love to see how you do it.
Pete

I'm sorry, I initally misunderstood his intention.
My method is actually very simple, because I'm in the lucky position to use Apples Final Cut Studio Pro. Its Compressor Application does in one step excellent rescaling and good mpeg2-compression. What I've actually to do is to pick a dvd-preset, set up an appropriate bitrate, set the rescaling quality to best and press start.

Jay Gladwell · December 20th, 2008, 10:08 AM

Quote:

Originally Posted by Perrone Ford

Because it means that the encoder has to do two jobs. It has to downres the video, and it has to encode it. I don't know what method the Mainconcept encoder uses to downres, so I like to control that step myself and use the best rescaler available.

One would think that after all those various generations that one would be moving farther away from the images original quality. Something has to be lost in the process.

It's hard to judge on the Web, but the video samples on both YouTube and Vimeo look soft on my monitor.

Perrone Ford · December 20th, 2008, 10:10 AM

Quote:

Originally Posted by Jay Gladwell

One would think that after all those various generations and renders (6) that one would be moving farther away from the images original quality. Something has to be lost in the process.

Then you clearly don't understand what "uncompressed" means. If I copy a data file from computer to computer 6 times, does it mean it changes from what I started with? This is no different.

Jay Gladwell · December 20th, 2008, 10:16 AM

Yes, Perrone, I know what "uncompressed" means. But thanks anyway. As I said, above, your Web samples do not support your methods.

Dominik Seibold · December 20th, 2008, 10:18 AM

Quote:

Originally Posted by Vincent Oliver

I use Premierre Pro CS3 (Windows) and Encore CS3.

Adobes MediaEncoders downscaling produces some visible aliasing. Apply gaussian blur with a strength of about 3.0 on the timeline (not in the mediaencoder-settings) and try again. That should result in better results.

Bill Ravens · December 20th, 2008, 10:18 AM

hmmm..I would distinguish between "soft" images and images that demonstrate twitter or flicker. Perhaps I misunderstand the nature of people's discontent. "Softness" is acceptable, to me, provided it isn't as soft as DV material, but on an SD display, some softness is understandable. Twitter or flicker, OTOH, is extremely distracting, annoying and unacceptable for a quality presentation. Even native progressive footage will show twitter/flicker in SD, if one isn't careful.

Perrone Ford · December 20th, 2008, 10:24 AM

Quote:

Originally Posted by Jay Gladwell

Yes, Perrone, I know what "uncompressed" means. But thanks anyway. As I said, above, your Web samples do not support your methods.

Well, ANY codec is going to soften footage when going from 1080 to 480. Especially given that your monitor can resolve more than SD can offer. But output that footage to an SD TV and it looks marvelous. Laying my footage back onto the timeline and scrubbing it while looking at my SD broadcast monitor is very nice. I also wonder if you have closely looked at the 720p version. The original footage was "soft" because the focus was out. But the SD looks remarkably true to the original footage. Download all the files and view for yourself.

And if you do understand uncompressed and generational loss, why are we discussing it?

Vincent Oliver · December 20th, 2008, 10:29 AM

Quote:

Originally Posted by Dominik Seibold

Adobes MediaEncoders downscaling produces some visible aliasing. Apply gaussian blur with a strength of about 3.0 on the timeline (not in the mediaencoder-settings) and try again. That should result in better results.

Thanks, will give this a go

Peter Kraft · December 20th, 2008, 10:32 AM

Quote:

Originally Posted by Dominik Seibold

My method is actually very simple, because I'm in the lucky position to use Apples Final Cut Studio Pro. Its Compressor Application does in one step excellent rescaling and good mpeg2-compression. What I've actually to do is to pick a dvd-preset, set up an appropriate bitrate, set the rescaling quality to best and press start.

Dominik, would you say that MpegStreamClip also does a good downscaling HD > SD? Do you know which algorithm is applied (the famous Lanczos)?

I am asking coz I intend the use Cinema Craft encoder right after New Year, they offer a Compressor plug in now.

December 20th, 2008, 08:01 AM	#16
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	Perrone... I really hesitate to post much of my own experiences here, but, I'll give it a try. As of late, it seems people on this forum have become quite rude and intolerant of opposing viewpoints. Having said this, I've played with both Vdub workflow scenarios, as well as other techniques. As far as vegas is concerned, I can achieve results with Vegas that are comparable with Vdub downrezzing by generating the HD .veg file, then opening an SD project and bringing the HD.veg file into the SD project, then rendering in SD. Also, many people, here, seem to like to use sharpening when shooting with the EX1. As you know, a DETAIL setting of '0' adds sharpening to the captured images. Sharpening done in-camera, is to be avoided as it significantly adds to the twitter problem people experience. For some reason, they refuse to accept that better results can be obtained by turning DETAIL off and sharpening in post. It doesn't help, also, that in camera sharpening adds to the work done by the camera compressor algorithm, sucking up bandwidth that would be better used on image detail, not compression/DETAIL artifacts. There are supposed "experts" here that really believe there are no compression /motion artifacts with the EX1 codec.

December 20th, 2008, 08:45 AM	#19
Clark Peters Regular Crew Join Date: Nov 2007 Location: Manhattan, Kansas Posts: 123	Dominik- Instead of taking potshots at Perrone's method, please give us your version of a step-by-step process of converting HD to SD. I'd love to see how you do it. Pete

December 20th, 2008, 10:16 AM	#25
Jay Gladwell Join Date: Jul 2002 Posts: 1,244	Yes, Perrone, I know what "uncompressed" means. But thanks anyway. As I said, above, your Web samples do not support your methods.

December 20th, 2008, 10:18 AM	#27
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	hmmm..I would distinguish between "soft" images and images that demonstrate twitter or flicker. Perhaps I misunderstand the nature of people's discontent. "Softness" is acceptable, to me, provided it isn't as soft as DV material, but on an SD display, some softness is understandable. Twitter or flicker, OTOH, is extremely distracting, annoying and unacceptable for a quality presentation. Even native progressive footage will show twitter/flicker in SD, if one isn't careful.