Newsletter #175 - Nov 10, 2007
I got into this
newsletter subject in a Support Space session a week ago with Mark,
about how Movie Maker handles interlaced files... TFF versus BFF. He was
seeing it converting TFF files to BFF, something I had only read about
but not tested.
What happens when you
have the wrong field first during playback. From what I read, the
official word is visual 'jittering'.
Each frame of an interlaced
file is made of two 'half-frames', half the lines on the first part and the
other half on the second. The 30 frames per second of an NTSC video are made of
60 half frames. Similarly the 25 fps of PAL video are 50 half frames per
When it comes to Movie Maker
and interlacing, my notes boil down to this short
If you edit in DV-AVI
and save to DV-AVI, WMM2 will preserve the interlace present in your original
video (and publish will be much slower as it works in a field-based mode
instead of a frame-based mode). In all other cases it de-interlaces
using an adaptive de-interlacing filter that will preserve vertical resolution
for still and slow moving images but for fast moving images will be closer to
That may be so, but what it
doesn't tell you is that if your source file is an MPEG-2 file with TFF,
and you save it to a DV-AVI file, it'll come out BFF, not preserving the
interlacing. When it switches the fields without your
involvement... you'll end up with some
One of the filters in VirtualDub is named
'field bob'... which compensates for field jumping in field-split video by
applying bob-deinterlacing techniques. How it does it is on page 148 of
'Learning VirtualDub' by Georgios Diamantopoulos, Sohail Salehi, and
Here's a screen grab of part
of a clip in VirtualDub, magnified 4x. At the left is how it
looks in the interlaced DV-AVI file captured from my mini-DV camcorder. The
adjusted one at the right is after applying VirtualDub's field bob filter
(with Smoothing). It gets rid of the 'jaggies' but leaves
If you work with DV-AVI or
other interlaced files, the 'jaggies' will stay until you save the movie to
a wmv which de-de-interlaces it, or view it on a TV where the
hardware does the same. Saving to a WMV file will be similar to using the field
bob filter of VirtualDub.
Enough background. What does
it all mean and what options do you have if you see a video clip that you think
could be handled better when it comes to?
As I mostly work with and
distribute wmv files that are not interlaced, I'm not ready yet to see and show
you what happens when you input a TFF file and get a BFF one back. This week's
newsletter is more about interlaced or not, and takes a look at how the
different files effect bluescreening in XP and Vista. I'm really doing a
jump-shift from the TFF/BFF subject.
Before doing it, here are...
Support Space entered the next
phase of starting up... charging a standard $25 fee for a session... with
the first one free to new customers. The expert gets $20 and the house gets
Customers I know
have been extremely pleased with the service when it was a free ride though the
early beta phase. We'll see how many keep going when they have to ante up a
Over at my other
startup, my 11 software reviews are now online at BrightHub and I'll be
attending the first writers' conference call next week with Bill Phelan,
.... back to the main
Interlaced - TFF or BFF
Mark and I were checking video files all week... are
they TFF or BFF?
Here's a picture showing GSpot looking at the file
that started Mark's quest.
It's a Tivo file, an MPEG-2 one that GSpot says is a SVCD (Super
VCD). I marked it to show where GSpot says it's an interlaced TFF
file... which seems to be the 'normal' for MPEG files.
I used MM2.1 to convert it to DV-AVI and saw the same
thing Mark had. It goes in as TFF and comes out BFF. As Mark suspected when
he contacted me, Movie Maker and the Microsoft DV codec are changing the
We haven't found a DV-AVI file that is TFF, so it seems the
standard for the file type is BFF. So it wouldn't be Movie Maker
doing the changing as much as it would be the codec applying the standard,
something we need to be aware of and live with.
Here's a sampling of files I've checked.
Files that are TFF...
MPEG-2 files recorded by a Sony DCR-SR42 HDD (hard
Sony Mini-DVD camcorder files - VOB (MPEG-2)
M2V files extracted from the Sony mini-DVD camcorder files by
TMPGEnc... preserving the TFF
VOB files on DVDs made by Vista's DVD Maker... by the
quick automatic process from tape to disc.
Files that are BFF...
DV-AVI files, NTSC and PAL, made by Movie Maker 2.1 and
DV-AVI files made by VirtualDubMod when using the Panasonic DV
codec for compression... even if the input file is a TFF MPEG-2 file.
Pinnacle Studio MPEG-2 files heading to DVDs
SVCD files made by TMPGEnc
VOB files on a DVD made by MyDVD
VOB files on a DVD made by Premiere Elements
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
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
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
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
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
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
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
one made from the MJPEG clip
Conclusion and Closing... and What's
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.
Have a great week!!