Movie Maker 2 and Photo Story
PapaJohn's Newsletter #54 - May 21, 2005

Interlaced versus Progressive
I'll assume you're familiar enough with "interlaced" and "progressive", the two methods of advancing along the visual images in a video or movie.
Interlacing 'jaggies' are seen Interlaced - closeupwhen you look at a frame made of 2 overlapping half frames, each half frame showing every other horizontal line...  
Progressive - CloseupProgressive 'blurriness' is seen when you look at a moving subject in a picture taken with a slow shutter speed of 1/25 or 1/30 of a second...
Sometimes the technology dictates which of the two to use. Sometimes you get to pick.
We'll get into the jags and blurs this week... let's first take a fun look at some of the macro factors that helped us get to our current state of having a choice.

If you take a sill picture with a camera and snap it at 1/24 of a second, you would have a slightly to heavily smudged or blurred image if there was any kind of movement. Stopping at any frame and looking closely would show the blurring. We don't usually get to see a frame stopped on screen, so it's not an issue. 
Which is better? I've read that interlacing is considered a sign of being associated with TV and VCR tapes, a lower class of viewers than Hollywood and movie-goers. 
The technology of CRT computer monitors and TVs needs the interlacing, but the goal is not to see jaggies when viewing there. One issue, which really isn't an issue, is seeing the interlacing during the editing phase. Many extrapolate the editing environment to the final movies, assuming what they see in the project previewing will be what they see in the saved movie.
Newer LCD and plasma screens use a different technology one more akin to computers... they can display whatever is played on them. Viewing progressive home video is becoming more normal.
In home movie-making activities, here are some places that you run into interlaced or progressive:
When using the Profile Editor and TMPGEnc, I'm starting to pay more attention to such options, trying to choose more knowlegeably and wisely. 
In this newsletter, I'll go into my camcorder to see how interlacing differs from progressive. 
some notes... before going further 

I attended a Microsoft MSDN seminar in Kalamazoo on Tuesday, and stopped by this Microsoft 'Across America' truck. 
Across America
A reader suggested the topic of 'Video Blogging (Vlogging) using Moving Maker' as a very timely topic. I added it to the schedule.
There were some hurdles to my work during the week. On Monday the server went down for its 'longest ever' outage of 2+ days... a network card going bad. Then my main working computer, a Toshiba laptop, had it's screen stop lighting and is off to the CompUSA repair center in Texas. When I brought my old Dell laptop back into service, the power adapter chord had problems and I had to get a new one... with all these hurdles, the content of this newsletter might take a slight hit... hope it's not noticed.
Last night I was checking an uncompressed NTSC AVI clip that has each frame numbered. I was curious about which frames I could see in MM1 and MM2, which frames were dropped in the generational issues of DV-AVI files, which frames were used if I opted to render from an NTSC file (30 fps) to a PAL file (25 fps), and other things like that. With the Toshiba still in Texas, I thought it would be a good topic for next week's newsletter... the subject won't focus on the dropped frames, but more on which frames you see. If one second of NTSC video has 30 frames and you render a PAL video from it, which 25 of the 30 frames are used? Send me any guesses.
.... back to the main topic

I wondered, if the world is moving from interlaced to progressive in the high definition area, why shouldn't I flip the switch in my camcorder and do all my recording as progressive? I asked on the SimplyDV forum, where movie and video experts tend to go... and I read my camcorder manual.
The manual has a single page with an interesting title: "Recording with all the Pixels - Progressive Recording Mode". You would think that using all the pixels is better than fewer. But a footnote says the camcorder won't do a couple things as it records progressive... one is widescreen, and another is 'steadyshot' compensation for normal camcorder movement. It also says the progressive recording will be a slightly larger field of view.
The comments I received at SimplyDV included a caution about losing the 'steadyshot' feature, advice to stay with interlaced if the video is to be played on TV, use progressive if you want clearly defined stills, interlacing  looks smoother on TV than progressive, and the image quality is far better in progressive mode...
To check the manual and advice at SimplyDV, I shot some footage using one mode and then the other.
3 Sets of Clips - First Impression
Here are snapshots from 3 sets of clips, using the MM2 snapshot feature with the clips being previewed in the collection...
The first and most obvious thing is the field of view. I routinely shoot with a wide-angle lens on the camcorder, but the only change I made between the clips at the left and right was to change the option for interlaced versus progressive. The Sony manual said something about it using more pixels when it shoots in progressive mode, but I hadn't expected the difference to be as significant as this. The progressive option adds considerably more wide-angle to the already wide-angle view.
If you don't have a wide angle lens but you have a progressive option, then maybe you also have a built-in wide angle lens.
It's pretty easy to determine how much the pictures at the right differ from those at the left... the left image is comparable to cropping 480x360 pixels and resizing it to 640x480, a 33% magnification in each direction.
    Interlaced Clips at Left                                      Progressive Clips at Right
Camcorder steadied on arm-rest of big cushy chair... pointing straight ahead... partially zoomed
Maximum 10x optical zoom... steadied on arm-rest but panning the shelves for minor movement
interlaced - pan booksprogressive - pan books
No zoom... wide-angle lens on camcorder, hand-held with the Toshiba on my lap
interlaced - laptopprogressive - laptop

Selected Closer Views - Magnified
I used TMPGEnc to extract each frame of the clips to sets of BMP images, and browsed the pictures with IrfanView to see the differences.
Items of interest were cropped and considerably magnified to better see the jaggies of the interlaced clips versus the blurriness of progressive.
                             interlaced                                                         Progressive
Interlaced - closeup
Progressive - Closeup
Interlaced - pan books
Progressive -closeup
Interlaced - laptop
Progressive - laptop

Low Light Conditions
With the camcorder on a tripod, in a low light situation... night-time, shooting toward a closet that had darker crooks and crannies... Because the progressive mode adds to the wide-angle view, I magnified the cropped area of the progressive frame an additional 33%.
I'm not seeing any differences to indicate one is better than the other.
                               Interlaced                                       Progressive - magnified additional 33%
Interlaced - darknessProgressive -darkness

Custom Profiles...
After checking the camcorder, I tried making a custom WMV profile that passed the interlacing of an interlaced DV-AVI file to a WMV. Could I? The Profile Editor only let me pick that option with the Media Video 9 Advanced Profile, but then it did let me.
WMV Interlaced - CropI made a profile with settings comparable to a high quality MPEG-2 file for a DVD... the picture at the left shows a cropped section of the saved WMV movie. It doesn't look like the jaggies were passed along.WMV - Interlace Not Allowed
As a check, I opted to not 'allow interlacing' and rendered it again... it's the picture at the right.
The results are similar and the profile/codec doesn't result in interlacing being passed along to the WMV file. Checking or unchecking the option doesn't matter.
Doing this exercise left me off at a good starting point toward 2 new custom profiles as WMV alternatives to DV-AVI files.

Conclusions and Closing
I'm going to continue shooting in interlaced mode. I like widescreen and prefer steadier video.
The manual doesn't come right out and say it, but gives hints about progressive frames being taken at 1/30 of a second and interlaced at 1/60 in order to get the two half-frames. If so, I'd expect the interlaced frames to be sharper than progressive... but if the shutter is open twice as long for a frame, why isn't it better in low light? I'd guess it's because of the step back to a wider angle view, which uses the extra light rather than giving it to the selection. That means zooming in tighter would give the pixels back to the area of interest and the lower light situation might be better... I need to do some more testing. The next 'last dance' at a wedding might be better shot in progressive mode.
While playing with the WMV profile to see if the interlacing of a DV-AVI source file would be passed through to a WMV file, I noticed that the profile I made emulated a high quality MPEG-2 file. Pulling on that thread a bit, I used TMPGEnc to convert the 10 second WMV file into files needed for a DVD and compared the file sizes (the WMV file was 10.7 MB.... the .m2v was 8.9 MB with an associated 1.9 MB .wav file = 10.8 MB total). If bit-rate correlates to quality and file size, then the WMV made with the profile correlates to high quality DVD MPEG-2 files.
Could this be a better work-around of the generational loss issues with DV-AVI files, and the audio issues in DV-AVI files... avoid rendering to DV-AVI by rendering to a single high-quality WMV file that aligns with the bit-rate and other parameters of an MPEG-2 file made for a DVD? The bit-rate is 4 times as high as the highest WMV profile included in Movie Maker 2.
I made custom profiles to use when saving a WMV file headed for a DVD, for both NTSC and PAL. The settings include quality-based VBR audio and video, a quality setting of 95 for the video, and lossless audio. If you want to try them, there are new links on the Saving Movies > Custom WMV Profiles page of the website. I checked them by rendering WMV files and running them thru TMPGEnc to get MPEG-2 files.

Have a great week...