Best Downconversion workflow for 720P in FCP

[Brian Mills]

This should probably be in the DVD encoding section, but since I have a HD110, I wanted to address this specifically to other users.

I shoot HD 720P30, edit AIC in FCP. It looks gorgeous. When I make a QT movie out of FCP using the same settings, that looks gorgeous. But every time I try to downconvert the finshed piece to SD for DVD, it looks terrible. The graphics go soft and serious aliasing is introduced - and I don't ubnderstand since this is progressive footage. Is it the AIC intermediary codec that is messing me up? What do you guys find gives you the cleanest output to SD DVD using FCP and compressor?

[Scott Jaco]

Originally Posted by Brian Mills

This should probably be in the DVD encoding section, but since I have a HD110, I wanted to address this specifically to other users.

I shoot HD 720P30, edit AIC in FCP. It looks gorgeous. When I make a QT movie out of FCP using the same settings, that looks gorgeous. But every time I try to downconvert the finshed piece to SD for DVD, it looks terrible. The graphics go soft and serious aliasing is introduced - and I don't ubnderstand since this is progressive footage. Is it the AIC intermediary codec that is messing me up? What do you guys find gives you the cleanest output to SD DVD using FCP and compressor?

I output my timeline in QT format, then use Compressor "Best Quality 2-Pass" presets for video & Dolby 2.0 preset for Audio.

The way I understand it, all DVD compression codecs convert whatever you have to 480i wether it was originally progressive or not.

If there is in fact a way to keep it progressive, I would love to know how.
I know that DVD players are capable of outputing progressive for people with LCD/flatscreen displays but I think it's just using software to combine the 2 fields into a progressive stream.

Just my understanding. I could be wrong.

[Stephan Ahonen]

If you're editing 30p then your footage will "effectively" still be 30p even on a 60i DVD. Progressive displays will generally have fairly smart deinterlacers that can find the progressive picture in the interlaced stream and display that.

[Dennis Robinson]

Originally Posted by Brian Mills

This should probably be in the DVD encoding section, but since I have a HD110, I wanted to address this specifically to other users.

I shoot HD 720P30, edit AIC in FCP. It looks gorgeous. When I make a QT movie out of FCP using the same settings, that looks gorgeous. But every time I try to downconvert the finshed piece to SD for DVD, it looks terrible. The graphics go soft and serious aliasing is introduced - and I don't ubnderstand since this is progressive footage. Is it the AIC intermediary codec that is messing me up? What do you guys find gives you the cleanest output to SD DVD using FCP and compressor?

I used to simply make a Quicktime movie and import that into DVD SP thinking it was ok. After I tried using Compresser and best quality 90 mins it is a remarkable difference in quality. It takes a while but I am really happy with the workflow. I am in Pal land but should still be the same.

[Justin Ferar]

While we are on the subject- how does one go about creating a 480p DVD? Everytime I burn a DVD originating from 720p60 I get a 480i DVD no matter what.

[Stephan Ahonen]

There's no such thing as a "480p DVD." Progressive scan isn't in the DVD standard. The standard is very tied to the NTSC and PAL standards in which it was intended to be viewed.

If you're downconverting 720p60 for DVD I would recommend 480i60 to maintain the temporal resolution of your source material.

[Stephen L. Noe]

Originally Posted by Stephan Ahonen

There's no such thing as a "480p DVD." Progressive scan isn't in the DVD standard. The standard is very tied to the NTSC and PAL standards in which it was intended to be viewed.

If you're downconverting 720p60 for DVD I would recommend 480i60 to maintain the temporal resolution of your source material.

Actually 480p24 and 480p30 are in the DVD standard. I make progressive DVD's all the time.

Check this reference Click here

[Stephan Ahonen]

Originally Posted by Stephen L. Noe

Actually 480p24 and 480p30 are in the DVD standard. I make progressive DVD's all the time.

Check this reference Click here

What does the Wikipedia article have to do with what we're talking about? Maybe you meant to link to the DVD-Video article but it doesn't explain the issue either.

DVD video is 60i. Period. Okay, 50i in PAL. But it's never progressive. When you click the "encode progressive" option or whatever in your authoring software, it's not storing progressive frames on the disc. It's storing fields and using flags to indicate that they used to be frames, and in the case of 24p it uses repeat flags on the fields that don't change due to the 3:2 pulldown. A smart DVD player can look at the flags and recreate the progressive frames. A dumb DVD player doesn't have to look at the flags, it just has to decode the fields and spit them out to the TV. That's how Joe Blow can buy a $37 DVD player at Wal-Mart.

If the frames were actually progressive on the disc a dumb DVD player would have to be made more sophisticated (read expensive) in order to apply pullup to progressive material. While the ability to store progressive material natively would be nice, the added hardware complexity required makes it unsuitable for a consumer format.

[Stephen L. Noe]

Originally Posted by Stephan Ahonen

What does the Wikipedia article have to do with what we're talking about? Maybe you meant to link to the DVD-Video article but it doesn't explain the issue either.

DVD video is 60i. Period. Okay, 50i in PAL. But it's never progressive. When you click the "encode progressive" option or whatever in your authoring software, it's not storing progressive frames on the disc. It's storing fields and using flags to indicate that they used to be frames, and in the case of 24p it uses repeat flags on the fields that don't change due to the 3:2 pulldown. A smart DVD player can look at the flags and recreate the progressive frames. A dumb DVD player doesn't have to look at the flags, it just has to decode the fields and spit them out to the TV. That's how Joe Blow can buy a $37 DVD player at Wal-Mart.

If the frames were actually progressive on the disc a dumb DVD player would have to be made more sophisticated (read expensive) in order to apply pullup to progressive material. While the ability to store progressive material natively would be nice, the added hardware complexity required makes it unsuitable for a consumer format.

Are we going to get into this again? We went through this last year. There is DVD progressive. If the DVD player is connected via Y/C or Composite it will ouput interlace only. If the DVD player is connected Component it will ouput progressive to a progressive capable TV (ie flat panel).

S

[Stephan Ahonen]

If you could find a link to that thread I'd like to see it.

Just because a smart DVD player can produce progressive output doesn't make the format itself progressive. Deinterlacing video doesn't make the original video progressive. The video is stored on the disc as 60i and any processing done by the DVD player doesn't change that.

[Jack Walker]

Originally Posted by Stephan Ahonen

If you could find a link to that thread I'd like to see it.

Just because a smart DVD player can produce progressive output doesn't make the format itself progressive. Deinterlacing video doesn't make the original video progressive. The video is stored on the disc as 60i and any processing done by the DVD player doesn't change that.

This is all obfuscatorated. Is it perhaps like the Sony V1? where the stream is 60i but the video encoded within the 60i stream is truly progressive?

That is the progressive frames are imbedded into a 60i stream... then a cheap player just plays the 60i but a progressive player pulls the progressive frames out of the 60i stream and they are displayed as the original progressive frames.

???

[Stephan Ahonen]

Originally Posted by Jack Walker

This is all obfuscatorated. Is it perhaps like the Sony V1? where the stream is 60i but the video encoded within the 60i stream is truly progressive?

That is the progressive frames are imbedded into a 60i stream... then a cheap player just plays the 60i but a progressive player pulls the progressive frames out of the 60i stream and they are displayed as the original progressive frames.

???

That's exactly it. There are flags in the bitstream that indicate that certain pairs of fields were originally part of a single frame, and a smart DVD player can use those flags as hints to build progressive output. It was done this way precisely so that a cheap player could be as simple (cheap) as possible, while still allowing for more sophisticated players to produce progressive output painlessly.

It's also similar to how the HDxxx records 24p and 30p to tape when HDV is natively 60p. Repeat flags are used to duplicate frames without taking up more bandwidth.

[Antony Michael Wilson]

Exactly. The basic video on a DVD Video is either 625/50 or 525/60, just like progressively scanned SD video is recorded to either 625/50 or 525/50. Metadata for handling that image within the DVD player for prog scan output via component is another matter.

[Sean Adair]

Techies arguing is such a great opportunity to learn!
So, putting aside the semantics of the dispute, it would seem that:

•All dvd's have a 60i signal which is inherently "interlaced".
•Flags can be added to the encoding, allowing "smart" players to decode "true" progressive.

What I assume however, is that since 2 interlaced fields are still required to make a frame, 60p cannot be recreated. So 60p footage could be encoded for 30p playback (temporal loss, possible motion issues not seen at 60p), or 60i (temporal speed unchanged, less sharp on LCD/Plasma displays). Same effect with different numbers for 50p shooters.

Interesting (tough) choice for those of us in the HD200 series camp shooting 60p/50p, (or HD100 shooting SD 50/60p). For HD100 series owners (or other 24p/25p/30p sources), encoding "progressive flags" would appear to be a no brainer for HDV sources converted to SD for DVD.

I think this has been covered before, but one of the clear issues in keeping quality going to DVD from HDV is with quality re-sizing / downconverting prior to mpeg encoding. Search for exact workflows...

Stephen sez:
"It's also similar to how the HDxxx records 24p and 30p to tape when HDV is natively 60p. Repeat flags are used to duplicate frames without taking up more bandwidth."

Flags are definitely used to differentiate the 24/30p frames, but 6 frame GOP mpg2 HDV isn't "natively 60p" I believe. The camera is native 60p, but sends to tape 30p or 24p with 6 unused additional frames. Using a firestore with 24p actually discards those frames and uses less space. The 12 frame GOP of true 60p is natively 60p, and can be interpreted in post to other frame rates, although we don't have the flags that a varicam creates while recording, which allow preview of the effect.

Preparing for fireworks...

[Stephan Ahonen]

I can't find my source but I'm very sure I've read that the HDV used by the HD100 operates at 60fps and uses repeat flags on 24 and 30p material. Yeah, useful, I know.

720p60 downconversion for standard def is a no-brainer. 60i, not 30p. By going wtih 30p you're losing half your temporal resolution and making it look juddery. And I've mentioned before that going 30p will not result in any more vertical sharpness because 30p in standard def is treated exactly the same as 60i.

When you watch standard def TV (especially sports), often times you're looking at downconverted 720p60. I can't name a single broadcaster that chooses to maintain a progressive look in downconversion at the expense of temporal resolution. They all downconvert to 60i.