Anything with a mix of TFF and BFF?... yes, the VOB files on a
DVD made by Vista's DVD Maker from recorded TV files.
When going online to check the DV standard, I got as far as
finding a website that sells you a copy of the DV-AVI spec for 50,000
yen... a bit too steep for my needs, whatever the exchange rate.
Changing the Field Order
Some video apps let you select the field order, and others take
care of it for you.
TMPGEnc lets you set the field order of saved MPEG
files as TFF or BFF... if you bring in a BFF DV-AVI file made by Movie Maker,
you can make the MPEG-2 files needed for a disc as either BFF or
TFF.
A bit more checking indicates that MPEG files are TFF by
default, unless changed by the user... while DV-AVI files are always BFF.
Collecting Sample Clips
As anything I shot with my camcorder or ran through Movie Maker
to DV-AVI files was automatically made BFF to align with the DV spec, I had
to satisfy my quest to do some testing by checking interlaced versus
non-interlaced clips.
I turned to my camcorder and digicam, and had Aeromouse
walk around in front of a blue screen (RGB of 0,0,255 in Paint)... I did green
and red ones too, but the blue ones give the best results, so
the rest of this newsletter is about bluescreening.
My Sony TRV80 mini-DV camcorder can shoot in
the usual interlaced mode or in progressive. But when connecting with firewire
to the computer, the only thing I can capture is an interlaced DV-AVI
files. I tried both modes anyway.
My Canon PowerShot SD 750 shoots video in
Motion JPEG format and when connecting by USB to the computer, there's no
conversion. The file is a series of JPG images, not
interlaced.
I put the cameras on a tripod and shot my laptop's LCD
screen. That puts some sort of analog encoding processes between
the pure blueness of the Paint screen and the digital file on the tape or
card... actually I kind of like the added complexity of the analog
steps.
Here's what the pure blueness of the screen in Paint looks
like... to compare to the different background patterns you'll see below. The
differences didn't effect things as much as I expected.
Bluescreening in XP and Vista
The custom XML code for bluescreening in MM2.1 is on
my website (the Persian Gal's code) and in the forum library of custom
transitions (Blaine's code). Both of them use the same settings.
The code for bluescreen transitions in Vista isn't
in the forum library yet, but Rehan's Shader
TFX package includes 10 different bluescreen transitions. I
used two of the five Chroma blue B ones for these
samples.
I packaged the results in a couple 2-1/2
minute clips. Each is of the same series of clips, the only real
differences being the making of one in MM2.1 and the other in MM6, so the
bluescreening technology is different.
These images show you a bit of what's happening in the videos.
There are pairs of clips, the first of which shows the bluescreen clip
before it's used as an overlay... with Aeromouse over the blue
background. The next clip shows what you see when you put the video clip
over a black still picture. The blackness could be any picture or video
clip, still or moving. I usually use pictures or video clips as backgrounds, but
it's easier to see what you get of Aeromouse when it's over a solid colored
background.
The Motion JPEG clips easily win over the mini-DV interlaced or
progressive ones. In XP you can hardly see anything from the progressive clip.
Vista is considerably better but falls short of the MJPEG files.
Inerlaced DV-AVI clips work better than progressive... I
don't know why.
Thinking that Vista was doing a better job of bluescreeing than
XP, and Movie Maker automatically de-interlaces when making WMV files, I
decided to make a test file in Vista, letting it do the de-interlacing. I
used Vista's profile of 3 Mbps, and then used it in XP and Vista to get
some more to ponder when watching the bluescreening clips.
That series of clips starts half way through the sample
videos, and shows...
-
the wmv clip made from an interlaced DV-AVI one
-
one made from a DV-AVI clip de-interlaced
and 'enhanced' using VirtualDub (there's an editorial error in the
wording of the clip... where it says 'interlaced...' it should say
'de-interlaced' by VirtualDub
-
a wmv clip made from a progressive DV-AVI
clip
-
one made from the MJPEG clip
My quest of the week started with Mark's email asking about
Movie Maker converting TFF source files into BFF, and ended with more of a study
of bluescreening using various interlaced and non-interlaced files.
There's the technology of compression, and interlacing TFF
and BFF fit into it. I've always wanted a copy of the book Digital
Video Compression by Peter Symes. I ordered it in the middle of writing
this newsletter... it's in the mail.
Then there's the application of the technology. If you're
putting low quality on YouTube, I'm sure you won't care about which field is
first in a video. But if you're looking at your new Hi-Def 60 inch screen
and playing a DVD, you might get better results by aligning the fields all the
way through the process. If you start with BFF files from your mini-DV
camcorder, and don't take steps to change it, you might have TFF files on your
discs and wondering what's causing the flickering. Maybe your flickering
is 'jittering' and you can fix it.
