This is another of those
deeper newsletters, in which I muck around trying to learn something, and
say too much in hopes that some of it is of current interest to you,
and another part will be helpful someday... when you're ready for
it.
Not having access to the
program code, nor to a pool of Microsoft confidential info, I have to do much
of my learning experientially. However I get it, I try to sort things out a
bit and pass it along to you.
Next week I'll do a much
lighter topic, looking at some strange and some wonderful things you can do
by applying different special video effects to your clips... but that's
next week. Today is about the quality setting number in a custom profile,
somewhat an extension of last week's issue.
The Profile
Editor is a wizard for making or editing a custom profile... for
Photo Story 3 and Movie Maker 2, the custom profile working window
has two tabs... on the General tab you get to pick one of 4 modes, and a
codec... and on the second tab you can select various settings, one of
which can be the quality setting.
The first mode is CBR
(constant bit rate), and the other three are VBR (variable bit rate). We'll
be studying one of the VBR modes.
Wizards are great... pick a
mode and the choices of codecs are limited
to those appropriate for the mode, and the second tab of the window
gives you only the appropriate choices for the other settings.
With the dynamic nature of how the options change, I put together this flow
chart to help you see all the choices at one time.
The wizard also knows
what codecs are on your computer. For example, if your system doesn't
have the MPEG-4 Video V1 codec, you won't see that choice. The flow chart
is made of screen shots from the choices on my HP laptop.
For now, the path of
interest starts with the Quality VBR mode, then the Windows Media
Video 9 Advanced Profile, and finally the Video quality setting.
Other settings we'll enter are the video size, frame rate, Key frame
interval, and decoder complexity.
As a sequel to last
week's newsletter in which we used a Vista HD 1080 VC-1 movie to
determine appropriate settings for Photo Story 3 and Movie Maker 2 custom
profiles... I conveniently side-stepped the video quality setting for
Movie Maker 2 by using a CBR codec with a defined bit rate.
The video quality setting can
be anything from zero to 100. I guess it takes a programmer's mind to tell users
that a quality setting of zero isn't the same as 'no quality'... or that
given a choice of quality from 1 to 100, maybe 100 isn't the best
choice. I'm not a programmer, so my initial instinct is to opt for 100
and avoid the zero... I'll try to be open-minded.
The flow chart shows
that I ended up with a video quality of 90, and most
of this issue is about how I got to that number.
When I rolled out my
website page about custom profiles, I skipped the subject of Quality
VBR and the quality setting. Photo Story 3 wasn't part of the website at
that time, and as Quality VBR is the only profile option for a
story, it's time to do the homework and decide on a number.
... before getting into
it, here are a few notes...
Notes...
the Vista
Corner...
As usual, right after
distributing last week's newsletter I thought of other things to
check. Some more reading about the VC-1 codec showed
it's meant for use when heading toward TV viewing with HD
DVDs.... the blue-ray discs coming along soon.
When making the
custom profiles for PS3 and MM2 last week, I took a guess at the key
frame intervals, setting Photo Story's at 15 seconds and MM2's at
6 seconds. Using WMSnoop to check a couple VC-1 files
saved by Vista, I can see that key frames (bigger than the other frames around
them as they contain the full info rather than partial) are
spaced at 4 second intervals... I changed the two profiles to align
with Vista.
8 people attended my monthly MM2/PS3 class at my
local library on Monday. A quick opening poll showed that all 8 were
using XP, all were there to learn about Movie Maker, 2 had already tried it a
bit at home, and none of them had seen or heard of Photo Story.
The library classroom is equipped with a dozen laptops
so each student starts off in the driver's seat, doing hands-on learning
with me there to overview and guide. In almost a year of sessions, I
haven't seen one system hang or crash, such a common subject of newsgroups and
forums.
.... on to the main
topic...
the Quality
Setting
Let's go back to the story of Big
Ben used last week to check the VC-1 option in Vista, and take the
first cut at making comparable custom profiles for Photo Story 3 and Movie
Maker 2. With the 4 second key frame interval established, it's time
to go into the video quality setting.
Here's some guidance
from the help file of the Profile Editor:
Video quality
Specify the image quality that you want to
maintain by typing a value from 0 through 100. While encoding, the bit rate is
adjusted as necessary to achieve the quality level that you specify without
dropping any frames.
Currently, there are 30 discrete quality
settings, so several quality levels refer to each quality setting. The
following quality levels equate to discrete quality settings: 1, 4, 8, 11, 15,
18, 22, 25, 29, 33, 36, 40, 43, 47, 50, 54, 58, 61, 65, 68, 72, 75, 79, 83,
86, 90, 93, 97, and 100. The numbers between two values equate to the same
quality setting as the lower number. For example, 2 and 3 both equate to the
same quality setting as 1.
And I found that a setting of 0 is
the same as using number 1. Let's use the listed discrete settings and
check the video quality... first with Photo Story 3, and then with Movie Maker
2.
Photo Story 3
Profile
I rendered the same story over and over,
changing only the quality setting. The composite image shows
the change in visual quality as the setting goes from 100 to
0.
The steps taken to make the
composite:
- added my URL to the minute hand of the Big Ben clock
tower, a high quality 11 megapixel image
- used the picture in a Photo Story and zoomed into
the area
- rendered the story using the 1440x1080
custom profile that emulates the VC-1 file settings... changed the
quality setting for each render to get a set of files that ranged
from a quality setting of 100 to 0
- used Movie
Maker to take snapshots from the last frame of each story
- cropped
the section of the minute hand with IrfanView
- put the cropped sections together in Paint.NET for the composite
image at the right (shown at 1/4 original
size)
You can see
from the composite how the URL dissolves into highly
jagged pixilated images as the quality setting goes from 100 to 0.
Obviously
the quality setting drives the visual quality, the bit rate, and the file
size....
Here's a list of the video bit rate
and file size for each of the discrete quality points. The
quality setting of 72 was curious, as it's the only one to break
the pattern of increasing bit rate and file size as the setting moves
up from 0 to 100. I don't know why... if you use 72, then your file will be a
higher bit rate and bigger than if you use 75 or 79. Curious, but enough so to
warrant digging into it.
| Quality |
Video Bit Rate |
File Size |
| |
kbps |
MB |
| 1 |
25 |
1.7 |
| 4 |
26 |
1.8 |
| 8 |
27 |
1.8 |
| 11 |
28 |
1.8 |
| 15 |
29 |
1.9 |
| 18 |
30 |
1.9 |
| 22 |
31 |
1.9 |
| 25 |
32 |
2 |
| 29 |
33 |
2 |
| 33 |
35 |
2 |
| 36 |
36 |
2.1 |
| 40 |
38 |
2.1 |
| 43 |
40 |
2.2 |
| 47 |
43 |
2.3 |
| 50 |
46 |
2.4 |
| 54 |
49 |
2.5 |
| 58 |
53 |
2.6 |
| 61 |
58 |
2.7 |
| 65 |
63 |
2.9 |
| 68 |
71 |
3.1 |
| 72 |
79 |
3.4 |
| 75 |
71 |
3.1 |
| 79 |
78 |
3.3 |
| 83 |
86 |
3.6 |
| 86 |
98 |
3.9 |
| 90 |
114 |
4.4 |
| 93 |
138 |
5.1 |
| 97 |
183 |
6.5 |
| 100 |
284 |
9.6 |
The help file says you can also use zero (0) as the
setting... I tried it and got the same result as using a quality of
1... the story viewing quality didn't fall through the floor, so a setting of
zero doesn't mean 'no quality'. If you need the smallest file size, then a
setting of zero might be best.
All of the stories played smoothly on my laptop, and
with file sizes so small compared to movie files, there wasn't any need or
desire to go with something less than 100.
There's a shimmering of horizontal lines during
the zooming that's been the subject of some recent newsgroup and forum
posts... why is it there and what can be done about it? I didn't see enough
changing of the condition as the quality was lowered to conclude that it's
something that drives the selection of the quality setting. One person
testing it feels that applying a dose or two of Gaussian blur to the still
picture before bringing it into Photo Story is the solution. He may be right,
but the checking is on-going and not yet conclusive.
After going through all these renderings and viewing
the stories, I left the custom story profile from last week at
a quality setting of 100. I saw no reason to lower it.
If you get into custom story profiles, consider
the settings used in the profiles that came from Microsoft in
the PhotoStory 3 software installation package:
- the 5 profiles for computer playback use a
quality setting of 95
- the 4 profiles to use when heading toward DVD or
VCD discs are 98
- the smaller 2 email choices use 75, and
the largest for email uses 90
- Pocket PC and Portable Media Center files are set
to 90
- stories for Smartphones use 75
Discs and computer playback are the types of
files I most often use, so the higher quality settings are
appropriate.
Movie Maker 2 Quality Based
VBR Profile
We know from the file properties that the Vista
VC-1 files are VBR... we know the file
size, bit rate, and key frame interval, but we don't
know the quality setting for a comparable Quality VBR profile for MM2.
Of course we could just use a constant bit rate profile and go to it directly
like we did last week, but that wouldn't fit into this week's topic. So we'll
need figure it out.
Let's check the properties of files rendered
by MM2 when using different quality based VBR settings, and
compare the files to Vista's... using the same input Big-Ben story file
that we've been using. If things work out OK, we should be able
to home in on the right quality setting.
Our benchmark is the Vista VC-1 file with a video
bit rate of 15,816 kbps and a file size of 62.1 MB.
Starting with a quality setting of
100, the MM2 file has a video bit rate of 58,529
kbps and a file size of 226.3 MB.... that's way too high. With
that high a bit rate, I can't play it smoothly on my
laptop.
The next break point,
a quality setting of 97, results in an MM2 file
with a video bit rate of 31,782 kbps and a file size of 123.9 MB....
about half of the quality 100 file, but still too high. I can almost
play it smoothly, but not quite.
With a quality setting of
93, the MM2 file has a
video bit rate of 21,227 kbps and a file size of 83.9 MB... and plays smoothly
on my laptop. If I didn't know the Vista file info, and only wanted files to
play well on my laptop, I'd probably stop here.
With a quality setting of 90, the MM2 file has a video
bit rate of 15,787 kbps and a file size of 61.9 MB... it plays smoothly
and aligns almost exactly with the properties of the VC-1 file
from Vista... looks like 90 is the setting.
How is the visual quality of the movie when using 90 as the quality
setting compared to the story itself made from a profile set at 100?
The image at the right is a full size segment of the last frame... and
the image below is the same segment from the last frame of source file, the
story with a setting of 100. It's interesting that the story set to a quality of
90 is of less visual quality than the movie set to that number.
I see them as being comparable and used 90 in my
revised custom MM2 profile...
Our exercise leaves us with a story, an MM2 movie,
and a Vista movie of comparable quality... each aligned with the properties
of the HD 1080 VC-1 file, and each starting with a Photo
Story.
Conclusions and Closing
For the most part, this week is just
an exercise to learn more about the quality setting
in quality-based VBR profiles.
I changed last week's PS3
and MM2 custom profiles, and rolled copies out to the regular
download folder of the site. They'll be permanent downloads and I'll
be adding these links soon:
The subject isn't finished... not
when it comes to the aspect ratio of the viewed movies rendered with the Vista
profile. Mine all play at standard 4:3 mode when I give it widescreen 16:9 files
and use a Movie Maker setting of 16:9.... Microsoft told me today there's a bug
in my version of Vista which is resolved in the next one.
If you're read this all the way
through, I hope you got at least a little out of it.... see you next week with
some fun special video effects.
Have a great week...
PapaJohn
