Converting HD to SD for DVDs

[Martin Catt]

A quick search of the forum shows this to be an ongoing topic of discussion. I recently got a Canon XF300, which does NOT shoot in SD, and ran into some issues trying to downrez to SD 16:9. LOTS of issues with jaggies and shimmering thin lines.

I spent an afternoon searching the forum to see what solutions were available. They fell pretty much into two categories: A) spend almost a thousand dollars for Sorensen, or B) follow some vague instructions meant for a previous version of some freeware utilities, install a BUNCH of oddball stuff on an otherwise perfectly-functioning video editing system and hope it wouldn't unbalance the machine, and go through a series of additional steps to process the footage down to SD. I always get uneasy when the only instructions you can find are for the versions of the software two generations PREVIOUS to what's available now.

Anyhow, being perennially short on cash, I went looking for a solution using what I had on hand, using Premiere Pro CS5.

Alan Roberts' white paper on the XF300 pointed me in the right direction. He mentions jacking with the Noise Reduction setting in manual to reduce the resolution cleanly as a method to shoot for SD delivery with this camera. Unfortunately, this is if you plan on ONLY delivering in SD, and isn't much help if you need BOTH HD and SD versions. Still, it was a place to start.

I took a particularly troublesome sequence of a Mi-24 Hind helicopter, shot at a local airshow. In BluRay, it looks just fine, but when blown down to SD 16:9 using Premeire's standard conversion, the results are unacceptable. The gently-drooping rotor blades go jagged, made even more obvious as they move slightly in the wind. As the camera follows the aircraft as it's towed along the taxiway, the dark tarred expansion joints in the concrete wiggle and shimmer, taking the viewer's attention away from the main subject.

I laid copies of the sequence end-to-end on an SD Widescreen sequence, with the HD sequence scaled to fit the frame size through the right-click dropdown menu. Leaving the first sequence unchanged, I put Gaussian Blur on the following sequences, setting the blur levels to 2, 3, 4, 5, 7.5, and 10 each. The completed test sequence was sent to Encore and burned to DVD. The finished DVD was evaluated on a 46" LCD monitor using an upscaling BluRay player, knowing the upscaling process would make any imperfections look WORSE.

Results were in line with what I expected. The unaltered segment was unwatchable, with bad jaggies and shimmering lines. With increased blur, the footage became better, reaching an optimum for this particular footage at a blur setting of 5. At 5, the image remained acceptably sharp and crisp, typical of what you'd expect from a DVD playback. Moving beyond to 7.5 and 10 gave results that looked like they were shot out of focus to begin with.

Depending on the source HD footage, the sweet spot seems to be around 4 to 5 on the Gaussian Blur setting. The test footage was deliberately chosen because it was probably the WORST choice for downrezzing, with lots of straight lines at shallow angles and thin structures that shifted back and forth. The 5 setting gave the best overall correction for the less-demanding sections as well as the toughest ones. Comparing the 4 and 5 test sequences, if I was willing to go back to the source sequence and apply individual blur settings to each clip in the sequence, there would be a slight improvement in the final quality exported to DVD. The improvement is so small, however, I doubt the viewer would notice it unless they had the "blanket" correction alongside to compare to.

The process in simple steps:
1:Edit your sequence in HD. Apply all color corrections, gradings, and effects to this source sequence.

2: Open a new sequence in the timeline, DV-NTSC Widescreen, 48kHz, 720x480, 1.2121 pixel aspect ratio.

3: Import the source sequence into this new sequence as a nested sequence. Right-click the nested sequence and select "Scale to Frame Size."

4: Apply the Gaussian Blur effect to the nested sequence: Video Effects - Blur & Sharpen - Gaussian Blur.

5: Open the Gaussian Blur effect and set the Blurriness level to the desired level (4 to 5 or whatever works). Check that the Blur Dimensions dropdown is set to Horizontal and Vertical.

The sequence can now be exported to Encore for DVD output.

Note: I've only tried this with DV-NTSC. I see no reason why this shouldn't work with PAL, but until somebody tries this on the other side of the Atlantic, we won't know for sure.

I've found the ONLY way to judge the results is to burn a DVD and play it. Watching the footage in Premiere will show SOME improvement, but it doesn't match exactly what you'll see once the footage is transferred to a DVD and played back.

There certainly are other and maybe better ways to handle downrezzing, but this method has worked well for me and doesn't involve additional software or expense.

Regards;
Martin

[Jay West]

Interesting post. I do not have an XF300, but I do use PPro (I'm on CS 6, now). In the past, I occasionally ran into some similar problems with very high motion, very high contrast footage even when encoding from native SD footage. My SD encoding solution back then was Procoder. Since then, I've moved to HD and the newer Adobe CS suites, and I've only run into the problem a couple of times, In both instances, I had to deliver the project before I could figure out how to fix it. (Fortunately, both problems were short duration pieces of much larger events and the artifacts didn't bother the customers when I pointed the clips out.)

For my curiousity, could you provide a bit more background information.

First, I was not clear if you first tried exporting or linking from a PPro HD timeline to Encore or if you always nested your HD sequence into a new SD timeline before exporting.

Second, what flavor of HD were you working from: 1080i, 1080p/30, 1080p/24 or 720p/60 and was it 50 mbps or 35 mbps?

How were you encoding to DVD? That is, when you sent your test sequence to Encore, were you exporting from PPro via AME to an MPEG2 DVD file that was imported into Encore or were you dynamic linking from your PPro SD timeline to Encore and then encoding from Encore?

Can you tell us what settings were used for encoding (bit rate, field order, VBR/CBR, single pass/2 pass, etc.)?

Finally, on alternative encoders. I believe Sorenson is "only" $650. ;-) I believe there is a downloadable trial, so, if you are in the mood to experiment, you might be able to find out if it would actually fix your problem or just give you different issues.

I still see mention of TEMPgenC and I believe there is a newish version of that available. Purchase price is a far more affordable $99. AFAIK, TEMPgenC will do multi-pass encoding (on beyond 2-pass) which sometimes can solve the problems you were seeing. It also is available in a trial version.

[Martin Catt]

Jay:

I've tried several avenues for moving the footage to Encore. Originally, I tried moving the HD sequence via Adobe Dynamic Link from inside PPro (under the file menu) and letting Encore take care of downrezzing to SD. The next attempt was creating a widescreen SD sequence, nesting the HD sequence in the new sequence and scaling it to fit the frame, THEN sending it to Encore via ADL. There was no appreciable difference in the final SD quality with either approach.

I've never had much problem moving UP in resolution, i.e. moving 16:9 SD footage from my XL2 to BluRay, and I haven't really done that much work trying to move HD material from my 5DMk2 to SD. Most of the 5DMk2 footage was handed directly over at the end of the days shooting, and I never saw it again until somebody else edited the finished product. I'm more in demand as a DP than editor, and frankly I think the DP is the worst choice to edit anyway, as they don't have the necessary emotional distance to evaluate the footage.

The source footage files were shot 1080p/30fps at the full 50mbps, standard Canon .mxf encoding. Once the HD sequence was edited and graded, it was nested in a new DV Widescreen sequence, 720x480 1.2121 PAR, and scaled to match the new frame size through the right-click option. The Gaussian blur was applied to the entire sequence, then the sequence sent to Encore via ADL.

The encoding settings were whatever Encore defaults to. A peek at the program setting dialog gives the following:
Codec: MPEG2, 720x480, 29.97 fps, lower field first. Max audio/video bitrate: 8 MBPS, Dolby Digital audio transcode scheme. No mention about variable/constant bit rate, single or 2 pass, nor could I see any options for setting them. As you can probably guess, my experience with Encore is limited mainly to sending it stuff through ADL and hoping for the best. Hey, I'm a camera guy that sometimes gets roped in to editing something! At least I'm a fairly decent color grader.

Last time I ran to the Sorenson site, I --THINK-- the price listed was $799, excluding any special offers. With my mindset, anything over six hundred bucks I tend to regard as a thousand (I'm cheap, what can I say?). If money was no object, I'd be shooting on a Red One. I damned near bankrupted myself getting the XF300.

The main idea was to come up with a solution that worked well using what was on hand. With the solution I've found, I can shoot and edit in HD, then blow the completed HD footage down to SD and be able to deliver in either format with relatively little extra effort.

It's more a stop-gap measure. I can see the requirement to deliver in HD becoming standard in the near future. DVD's appear to be going the way of VHS tapes, where VHS used to be the standard delivery, while including a DVD version was a selling point. I'm watching the number of DVD titles shrinking in the store racks, while the number of BluRay offerings gets larger and larger. Pretty soon DVD's will be considered quaint. I expect to see steampunkers wearing them any day now. ;)

Martin

[Jay West]

Anything over $600 might as well be $1000. Pretty much how I look at add-ons, too.

What you described in the footage sounds like motion artifacts from the DVD encoding, so here are a couple of suggestions that may help.

First, I would try redoing the transcode -- from either the original HD timeline or the nested SD, or both, if you have time --- and change the transcode settings to 2 pass VBR with higher bit rate settings. It has been a while since I used CS5, but my recollection is that Encore CS5 defaulted to encoding at 4 MBps with single pass VBR. With dance recitals, I've found that likely to produce motion artifacts. Higher bit rates and 2-pass VBR seem to mostly avoid them.

It takes a bit of digging to find the settings. In the Encore CS5 project panel (not the the timeline display below), the sequence that you've imported from PPro will probably say "Automatic" in the column for transcode settings. If it says "trancoded - Do not Transcode," right click and choose "revert to original." Then, right click again, choose the DVD menu (top item) and select 7mb 2-Pass VBR High Qualit" then click on the "edit presets" button on the right. This will give you the AME window. If you are not seeing any real settings, you might need to click on the "advanced" button which will be on the far right side. (It has been a while since I used CS5 and that might have been the case with CS4.) If I recall correctly, the AME window will come up with a Blu-ray preset. You need to change that to Mpeg2-DVD. You may be able to select a pre-set, and you should pick of 7Mbps High Quality NTSC 2 pass VBR. Then go the box at the lower left of the window, select the video tab (that's probably the default.) Scroll down. Set quality to "5" (all the way to the right). Below that, you should be able to find settings for bit-rate settings. My recollection is that that the defaults of the 7Mbps High Quality will be something like 1.5 minimum, 7 target and 9 high, or 1.5/4/7, or something like that. Try resetting them to 5, 6.5 and 8. (Don't go over 8 as some players will not properly recognize the disk if the bit rate is over 8.) The program may ask you to save this as a modified preset. If so, do it. Then do your encode and see if that does not help with twinkling in the block-strips and the jaggies on the rotor blades.

As an aside, is your CS5 using hardware MPE or software MPE? With Hardware MPE, you auomatically get maximum render quality. (Don't check the boxes for MRQ and Maximum Bit Depth because that forces software mode which will slow things down.) However, if you are working with software MPE, then I suggest you try checking the boxes for MRQ and maximum bit depth. Choosing these may improve the encode although it will greatly lengthen the time it takes to complete the trancode.

Second, I suspect (but do not know) that shooting in 1080p/30 might also be playing a role here. Did you have a choice on shooting 1080p/30? If you do, next time I suggest you try shooting at 720p or 1080i, which will give you smoother motion capture and improve the conversion to 480i SD DVD. There are numbers of postings here recommending shooting in 720p for downconversion to DVD via Adobe PPro/Encore and explaining how 720p seems to downconvert most smoothly. I've only used 720p on a couple of projects -- for which it worked quite well -- but I mostly do multi-cam projects with HD cams that do not record 720p. If you need to shoot a 1080 format, I would use 1080i.

I have just gone through the end-of-the-school year dance recitals which are often high-motion-high contrast. (Though, I doubt they are as as severe as the rotors on the Hind going down a runway on a bright Texas day.) Still, I very rarely run into motion artifacts with downconverting from 1080i to DVD.

Next time I do, though, I'll try your gaussian blur and see if that does not fix things.

As for DVDs getting replaced by Blu-ray disks, it does not seem to be happening very quickly here. I've been offering Blu-rays as an option for recitals, events and weddings for the last four years. I've sold a grand total of 7. I get more calls for web conversions.

[Mike Beckett]

Martin,

I don't think you should have to jump through so many hoops just to get a good SD export. What a nightmare for you!

I'm on Windows, and I was never particularly impressed with the media encoder output on CS5, particularly when scaling to SD.

As an aside, even exporting HD h264 MP4 files introduced crazy noise, especially in blacks. A friend with a Mac and a PC tried the same process on a CS5 trial on each computer, and the Mac was clean. Go figure. Even upping the quality and setting the bit rate at crazily high levels wouldn't fix this issue.

I ended up buying TMPGEnc Mastering Works for $100, exporting uncompressed from CS5 and using TMPGEnc to export to DVD, as well as for normal HD exports.

Now with CS6, on exactly the same computer, with no hardware changes, I get perfect exports without that horrible noise. I presume they fixed something, or another improvement to Media Encoder got round some bug on my system.

Also, there used to be a problem in older versions of Premiere Pro where if you tried to downscale to SD and export in one step, you would get absolutely ghastly quality. This bugged me in UWOL contests a few years ago. The answer for that was to export uncompressed at your smaller size, then import that new file back into an SD timeline in Premiere Pro and export THAT one compressed. It was as if doing it all in a single step was just too much for it.

I thought that was fixed in CS5, but maybe it depends on your settings. It might be worth a go.

The only thing I can say for certain is that your export shouldn't be quite so painful!

[Martin Catt]

It's not that hard, ONCE you know how to do it. One effect applied to a nested sequence, and you're done. It's certainly a LOT easier than the other solutions I found while searching the forum.

I'm not going to beat this one to death. Discussing favorite tricks for converting from HD to SD is like discussing recipes for chili: everyone has their favorite, and will defend it to the death. This one works for me, and I thought I'd share it.

Martin

[Randall Leong]

Martin,

I feel your pain on how to get downscaled DVD video right. However, the method that you used only works for 30p source video. I tried this method with 59.94i (interlaced) video, only to end up with a flickery final result.

What went wrong there? Big reason: Field order flipping. Nesting an upper-field-first HD sequence into a lower-field-first SD timeline just does not work because the field order gets flipped, and then exporting/encoding only makes the field-flipping artifacts more noticeable. One way to fix this would be to make the SD timeline upper-field-first - but then, Encore CS5.x will flip the field order of any Adobe Dynamic Linked SD sequence back to lower-field-first (and this cannot be changed at all whatsoever). The only way to circumvent this would be to export from the modified SD upper-field-first timeline to a new lower-field-first encoded file, then import that into Encore. (Encore CS6 fixed the field-flipping problem by allowing SD upper-field-first files to be imported without field-flipping.)

[Martin Catt]

Randall:

Good to know that. I shoot primarily in 1080p 30fps, and edit in PPro 5, so I'm not familiar with the ins and outs of other frame rates and other PPro versions. Eventually I'll upgrade to 6, couldn't see any advantage to moving up a half-version. Thank you for providing both the symptoms and the workaround for CS5 so I can get through it if I ever encounter the problem.

I'm printing out you post and putting it in my notebook for future reference.

Martin

[Martin Catt]

Just so you can see the difference, here's a blowup of two frame-grabs of the same frame showing the rotor head of the Mi-24 Hind. The top half is from the straight HD sequence import, while the bottom half is the same frame with a 5 Gaussian Blur effect added.

The thin rotors make a particularly tough item to downrez because of their high contrast with the sky and because they curve gently away from horizontal, exaggerating the stair-step appearance. The jaggies are even worse when the video is played, as the rotor bounces up and down slightly as the aircraft is towed past, making the edges of the rotor "crawl" like an escalator.

As with any applied blur, there's a slight drop in contrast, but it isn't noticeable during playback.

[Christopher Young]

Interesting, the rotor blades, a great example of just off horizontal aliasing, not nice! Any chance you can post a few seconds of the rotors online for download. Would love to see how I would deal with it.

In most of the material I shoot, humans, these sorts of fine aliasing issues don't seem to arise but it would be nice to have some answers should the problem arise on a down-conversion.

Chris Young
Sydney

[Randall Leong]

Originally Posted by Randall Leong

Martin,

I feel your pain on how to get downscaled DVD video right. However, the method that you used only works for 30p source video. I tried this method with 59.94i (interlaced) video, only to end up with a flickery final result.

What went wrong there? Big reason: Field order flipping. Nesting an upper-field-first HD sequence into a lower-field-first SD timeline just does not work because the field order gets flipped, and then exporting/encoding only makes the field-flipping artifacts more noticeable. One way to fix this would be to make the SD timeline upper-field-first - but then, Encore CS5.x will flip the field order of any Adobe Dynamic Linked SD sequence back to lower-field-first (and this cannot be changed at all whatsoever). The only way to circumvent this would be to export from the modified SD upper-field-first timeline to a new lower-field-first encoded file, then import that into Encore. (Encore CS6 fixed the field-flipping problem by allowing SD upper-field-first files to be imported without field-flipping.)

I am trying this again. It turned out that portions of my HD-to-SD conversions using any software were very choppy and stuttery because the video source files had non-drop-frame time scales but the new 29.97 timelines defaulted to drop-frame time scales. As a result, some of the frames did get dropped on the encodes/transcodes! Worse, portions also played back with the wrong field first.

And I did try Gaussian blur. A setting of 4.0 in CS6 turned out to be way too strong for the material I used, and the images were way too soft even when viewed on an old SD analog CRT set.

[Peter Manojlovic]

Sorry guys, i dont' wanna beat a dead horse here. But if i can save anybody the hours of pain i've endured, then i'll be glad to mention it again.
If you're planning on downrezzing HD material, make sure it's a progressive source, and not HDV interlaced.
Progressive sources are a simple scaledown. AME does a fairly good job of this.

The pain of acceptable downrezzed HDV interlaced sources cannot be done within Premiere or AME without the help of outside software or hardware.
Knowing the basics of separating the fields, bob deinterlacing the frames, resizing, and then reweaving those frames is essential. This is the only way of getting a true downrez.

The only software that i know that does this is AVISynth.
Again, it's painstaking to learn, and takes a while, but in the end, is the only accepbable method. Fortunately, google is your friend, and if you're on a mission, this is a good place to start.

If Premiere had a folder for different deinterlacing filters as they do for outdated "Stylized" plugins, then i'd be the first to congratulate them.

[Randall Leong]

Originally Posted by Peter Manojlovic

Sorry guys, i dont' wanna beat a dead horse here. But if i can save anybody the hours of pain i've endured, then i'll be glad to mention it again.
If you're planning on downrezzing HD material, make sure it's a progressive source, and not HDV interlaced.
Progressive sources are a simple scaledown. AME does a fairly good job of this.

The pain of acceptable downrezzed HDV interlaced sources cannot be done within Premiere or AME without the help of outside software or hardware.
Knowing the basics of separating the fields, bob deinterlacing the frames, resizing, and then reweaving those frames is essential. This is the only way of getting a true downrez.

The only software that i know that does this is AVISynth.
Again, it's painstaking to learn, and takes a while, but in the end, is the only accepbable method. Fortunately, google is your friend, and if you're on a mission, this is a good place to start.

If Premiere had a folder for different deinterlacing filters as they do for outdated "Stylized" plugins, then i'd be the first to congratulate them.

Actually, downrezzing progressive video from HD to SD is not as easy as you stated it is: You'd have to deal with the different pixel aspect ratios (SD does not use square pixels like most HD video does). And the only way to properly get progressive video with a frame rate higher than 24 fps to a playable, nominally interlaced DVD is, well, to transcode from progressive to interlaced. Unfortunately, many MPEG-2 encoders actually drop half the fields and duplicate the remaining fields in the progressive-to-interlaced transcodes, leaving the viewer with only half the vertical resolution and also introducing aliasing artifacts on straight lines (especially diagonal ones).

By the way, the MainConcept MPEG-2 encoder included with Premiere/Encore and many other NLEs and authoring programs does a rather poor job of converting progressive to interlaced: The encoder simply drops half of the lines that were in the progressive original and replaces them with interpolated lines. This creates artifacts big time, especially on lines. It also leaves the viewer with an effective resolution of only 288i or 240i.