Rendering AVCHD to MPG2 - Upper or Lower Field 1st

Kevin Mc wrote on 4/13/2009, 4:43 PM
I am editing some AVCHD (1440x1080) footage shot on my new Panasonic AG-HMC70P. I am rendering this to MPG2 for a standard DVD. I noticed during rendering that it was letter-boxing the left and right sides of the screen. After a bit of research I discovered to use the settings of 704x480 instead of the standard 720x480.

When rendering should the Field Order be Lower First, or Upper First? It's been my understanding that lower applies to MPG2 and upper applies to HD, but I'm still learning about fields and am not sure what is correct when rendering AVCHD down to MPG2 for a standard DVD.

My target is to watch this on my 42" flat screen LCD tele.

Thanks!
--Kevin

Comments

musicvid10 wrote on 4/13/2009, 7:23 PM
"I am rendering this to MPG2 for a standard DVD. "
NTSC DVD is generally 720x480. Although 704x480 is supported, you have no way of knowing how a given player is going to handle it. A more practical solution is to keep it at 720x480 and check "Stretch output to fill frame" when rendering. You may get some difference of opinion on this.

BTW, the thin black bars you see are the result of slight (2%) differences between 1440x1080@1.333 and 720x480@1.2121.

"When rendering should the Field Order be Lower First, or Upper First?"
Both are supported, although there is no reason to change the default DVD templates which are lower first.

"...am not sure what is correct when rendering AVCHD down to MPG2 for a standard DVD."
This is something you need not concern yourself with. Vegas does all the work for you. In the unlikely chance the captured field order was wrong, you would know it instantly.



Kevin Mc wrote on 4/14/2009, 9:53 AM
musicvid ~ thanks for such a thorough reply!! Very helpful info. I considered using the stretch option and now that you mentioned it, I think this is the way to go.

Thanks again,
--Kevin
musicvid10 wrote on 4/14/2009, 10:35 AM
"...there is no reason to change the default DVD templates which are lower first."

I wanted to clarify one thing by qualifying this answer I gave you:

My set-top DVD recorder records files that can be renamed to .vob or .mpg and opened in the Vegas timeline. They are recorded Upper Field First.

In this case, after trimming and editing, adding chapter points, or whatever, I will change the DVDA render template to Upper First, and match the average and max bitrates exactly, so the project will smart-render in a few minutes. If I left the render template at Lower First, it would want to recompress the whole thing, taking much longer.

So, in this case of matching the source .mpg field order, it is an advantage to change the render field order as well to enable smart-rendering.

In your case of AVC to MPEG-2, it would make no difference, because the whole project gets re-rendered anyway, meaning changing the field order would have no effect on the rendering time.
Kevin Mc wrote on 4/14/2009, 12:03 PM
That makes perfect sense. I do render the MPG2 (LLF) and AC3 streams separately and just created a test DVD in Architect ~ no re-rendering required ~ burned the project in just a few minutes on my quad computer. Even though this video is converted down from my Pani AVCHD footage to MPG2, the quality is soooo superior to that of my Pani DV camera.

Regarding fields ~ are they more a function of the final playback device (i.e. my DVD player or TV)?

--Kevin
John_Cline wrote on 4/14/2009, 2:15 PM
As long as the MPEG2 encoder knows the correct field order of the original file, then it can encode either LFF or UFF and will set the appropriate flag in the MPEG2 file. You can use either LFF or UFF for DVD compliant MEG2 files.

Generally, HD files (HDV or AVCHD or broadcast Transport Streams) are UFF, SD is typically LFF, although there are some exceptions. DV is always LFF.
musicvid10 wrote on 4/14/2009, 4:48 PM
"Regarding fields ~ are they more a function of the final playback device (i.e. my DVD player or TV)?"

You would have to ask. Like I implied, there is quite a bit more to this than meets the eye. Here is just a beginning tutorial:

http://lurkertech.com/lg/fields/

The programs that can actually swap field orders are VirtualDub and AviSynth using various plugins designed for the purpose.

Again, as John reinforced, this is nothing you need to worry about to render successfully in Vegas.
John_Cline wrote on 4/14/2009, 8:10 PM
You can use Vegas to swap fields if that's what you really want to do. Just manually set the file's properties and intentionally tell it the opposite field order from what it actually is.
musicvid10 wrote on 4/14/2009, 8:25 PM
Sorry for the ambiguity, that isn't what I was aiming at.

I was talking about surgical correction of field order reversal as a result of improper capture, which results as horrible vertical oscillation from field transposition.

To my knowledge, Vegas is not able to accomplish this, and Virtualdub filters are able to accomplish this, just my experience.

And again, this is not a subject for concern in Vegas if the capture looks OK. Thanks for pointing this out.