Maximizing HD to SD Quality

[Jim Snow]

There has been a lot of discussion about the poor quality SD video that results from a HD down conversion. The linked article describes a rather tedious procedure that is Premiere-centric. Precomposed Blog - HD to SD DVD - Best Methods Can anyone suggest a Vegas work flow for the same result? I also use Cineform NeoScene.

[Jeff Harper]

When you are required to shoot in HD for whatever reason, my suggestion is of no help: shoot in SD.

I maintain that when delivering in SD it is best to shoot in SD. Since there are times that you may be delivering on Bluray and also need to deliver additional copies of a project in SD, I believe simply rendering out m2t files to mpeg 2 is sufficient. No, the quality may not be the highest possible, but the difference, IMO is so slight that it truly means little to me or my clients. I think it is more important to acquire the highest quality to begin with, and these little nuances in post mean absolutely nothing. Just my two cents.

[Ken Diewert]

Jeff,

Thanks, but that's not what we wanted to hear.

I too am on a quest for better quality delivery. So much of my work ends up on the web, that I hadn't been delivering much DVD from HD source footage till this wedding season, and I must say the DVDA trancoding sucks. I haven't done many HD weddings til this year. The few I delivered over the last couple of years looked bad on dvd and I just assumed I hadn't tweaked my settings as well as I could have. I read thru the article Jim referenced and it confirms that the HD to SD workflow doesn't work.

I recently rendered a 28-minute piece, that is about 28gb, in very HQ(.avi). By the time I encode to mpeg2 for DVDA it's about 2.x gb and looks like absolute crap compared to the original.

I'm looking at the Procoder 3 route, but at $500, is it worth it.

I'm even thinking about offering an upgrade to the Western Digital HD Media Player and delivering on USB. YouTube - Western Digital WD TV HD Media Player

There has to be a better way, without a 15-step workflow (exaggerating).

[Jeff Harper]

You mention DVDA transcoding....I encode my mpeg so that is doesn't have to be re-encoded for DVDA, isn't that what you are doing? Or am I missing something?

[Ken Diewert]

Jeff,

Yes, I'm transcoding in Vegas 8 to mpeg2 for DVDA. I think it's the same process, but Vegas is quicker. In reading the article that Jim refers to, this HD-SD problem is inherent in most NLE.

I suppose if you're not looking at the very nice .avi files (I store a HQ .avi version for archive), you wouldn't be so sadly disappointed in the mpeg2 version.

[Eugene Kosarovich]

As the article points out, the issue is really the downconversion, not the MPEG-2 encoding itself.

In my own experience, I must concur that the best SD is from SD. But when that isn't possible, I've done something in Vegas that seemed to help my quality.

I shoot in XDCAM HD. To downconvert my project, I render it to IMX 50. That's a Sony I-frame only MPEG-2 mastering format at 50Mb/s. The downconversion in Vegas to that format seems cleaner than any other method I've tried, and I think the reason is that IMX is one of the few SD formats that is top field first, just like my HD (or HDV) is. And this seems to help in the quality of the downconversion in Vegas.

Then from the IMX file I can go to MPEG-2 any way I want, myself typically through the Frameserver to TMPGEnc. Note that NTSC IMX is a 720X486 format, so you need to match output aspect to 720X480 for your MPEG-2 render.

Also, be sure for all downconversions that you have the deinterlacer in project properties set to BLEND or INTERPOLATE and not NONE, since Vegas must deinterlace when scaling, though it will restore the interlace later, if it is needed for your format.

[Mike Calla]

I do HDV 1080 50i (I always have my in-camera colour desaturated a bit during filming, adding colour/saturation in post and have noticed it does help in the final product whether DV or HD)
> DI w/Cineform
- apply a almost unnoticeable sharpen
- render progressive w/interpolate enabled
> AVI uncompressed
> TMPGEnc mpg2

It’s fine but not perfect

But lately I’ve been a little interested in the HDV > IMX instead of cineform approach!

[Perrone Ford]

If the quality is important, I recommend a bicubic spline downcoverter. If you can't do that, then a Lanczos rescale is also very clean, and what I do for any of my projects that go from HD to SD.

Unlike some others, I find that my HD to SD downconversion yields superior results in every way possible. Frankly, they look stunning as I have demonstrated on this forum in the past. The workflow is a bit inconvenient, but gets the results I want.

Doing this, I find I need to add no sharpening when going to Mpeg2. When I am going from SD to Mpeg2, I add just a bit of an edge with sharpening knowing that the compression will knock nearly all of it back off.

I'd be happy to post screenshots of downconverts for you guys. It CAN be done very cleanly.

[Perrone Ford]

Ok, so here's an example.

I took 2 frames of a RED 4k file and laid it onto a timeline. I conformed that timeline to 1024x512 to preserve the 2:1 layout of the original. I took a frameshot of that 1024x512 file. I then went back to a 4k timeline, rendered that 4k RED file to a 4k uncompressed AVI file. Pulled that into virtualdub, did a lanczos resize to 720x360, and rendered back out uncompressed. Put that onto a 720x360 timeline, and took another frameshot.

So here, we have an SD sized frame derived from a 4k source. This site won't let you upload a real HD sized image, so I had to pass on that.

Look at the clean edges on the signs in the background and the engine. The clean edges of the lines on the car. All those problematic things people say you can't get on a downscale from HD. If coming down from HD was a problem, then coming down from 4k should be terrible. Judge for yourself.

There is a color space shift that happened that I didn't bother to correct for. Sorry. Other than that, this photo got zero processing. Just laid on the timeline and a frame shot taken.

[Jim Snow]

Simple question - - Since much higher quality HD to SD (MPEG-2) conversion is possible, why don't the so-called "Pro" editing software companies such as Adobe, Sony, Avid, Grass Valley et al offer it? Has anyone asked these companies? If so, what did they say? Personally I think it is ridiculous to ignore something like this in products that cost many hundreds of dollars each.

[Perrone Ford]

I believe Apple's "Compressor" program includes the Lanczos rescaler, but you have to know the setting to use it. In typical Apple fashion, the underlying choice is hidden from the user, so it's not obvious how to turn it on. There was a long thread here about it.

As to why this option is not available in NLE's, that I couldn't tell you. Perhaps they see down conversion as something not many people would want. Certainly Lanczos and Bicubic Spline algorithms are well understood and free to implement. They do take quite a lot of time to do what they do and as is proven time and time again, 99% of people are more interested in speed than quality of results. So they seem to be hitting their targets quite well.

[Jim Snow]

Originally Posted by Perrone Ford

Perhaps they see down conversion as something not many people would want.

I just can't see that rationale. If they are that disconnected from their users, maybe they need to find a new line of work. I believe the NLE market is ripe for a new company with a keen desire to capitalize on the state of the NLE industry. The current NLE suppliers are bloated with everything from the internal politics of massive companies to kissing up to stockholders.

I suspect one aspect of the problem is that they don't have the skill set in-house to fix the problems. Adobe and Sony license the Main Concepts encoder. If they were that "skilled" with encoding, they wouldn't need to go out-house would they. I believe they are all more focused on the superficial glitz and glitter of their products and aren't nearly as concerned about the "hidden" functionality of the core elements of their products.

[Marc Salvatore]

I've been fairly happy using TMPEG enc. for downscaling and converting my Cineform 1080i masters to MPEG-2. Inside of TMPEG in the filters section it lists Lanczos-3 as the default picture resize methed. This is probably why the downscale looks good.

Marc

[Jim Snow]

Originally Posted by Marc Salvatore

I've been fairly happy using TMPEG enc. for downscaling and converting my Cineform 1080i masters to MPEG-2. Inside of TMPEG in the filters section it lists Lanczos-3 as the default picture resize methed. This is probably why the downscale looks good.

Marc

Thanks Marc. You may have just given me a practical work flow. I use Cineform. If all I need to do is output my final edit as Cineform and then encode it to MPEG-2 with TMPEG, that's a reasonable work flow.

[Kenneth Fisher]

When you are required to shoot in HD for whatever reason, my suggestion is of no help: shoot in SD.

From my experience in the print and web production world, it is almost always is better to start with higher-resolution source material then "down-res" to a lower resolution.

This does not seem to be the case starting with HD footage then going to SD...or is it? As recently as last night I watch a television program, half on the HD1080P television in my living room, then switch to my old SD television in my bedroom. The program looked great in HD, and it looked great in SD.

I would assume that the show was shot only once in HD, then "down-resed" for SD viewing. Is this technology not available or easily in reach of desktop editors?

I just started mixing HD with SD footage. I thought the big issue was going to be differing aspect ratios, but it seems to be more complex than that.

Ken