PapaJohn's Newsletter #10 - Movie
Maker 2 and Photo Story 2 - July 17, 2004
About: Compression, Codecs, and the
Windows Media Encoder
This week's topic was requested by a newsletter reader.
It's always a good one to discuss, and I appreciate getting requests to
cover specific topics.
All video files are compressed. They need to be in order to
be more easily stored and transmitted. The codecs are the underlying
hardware or software devices that do the compression or decompression. And
software such as Movie Maker, PhotoStory and the Encoder help you pick
appropriate compression settings and produce your movies.
Codecs achieve compression by removing redundant info in the file.... and
even more compression by eliminating some of the video/audio info that
it thinks you won't miss, or will miss the least...
And of course, everyone feels their codec is better than the
others. There are thousands of codecs. You might be familiar
with Divx AVI files, Apple's MOV files, MPEG1 and 2, and Windows Media
Video and Audio (WMV and WMA files). You might not be familiar
with Panasonic's Digital Video, Cinepak, Huffy or even Microsoft Video
1.
Windows Media version 9 codecs are newer and better than the
others!!!! That's one of the reasons we use Movie Maker and PhotoStory.
In this newsletter, I'll explore video file compression, the topic of
compression versus quality, spend some time on bit rate (a measure of
compression and quality), the Windows Media 9 codecs, and a mini-tutorial on
using the Windows Media Encoder to convert a file.
Notices
How about a poll this
week? I'm curious about your knowledge and
skill levels. I don't want to overwhelm newbies, nor
do I want to hold back info for advanced users. So I'll warn you
up front that I might not change my subject matter or style, but I'll share the
statistics with you in the next newsletter.... and use the results as
guidance.
Pick from the following the one that most closely aligns with you.
Just send an email to
papajohn@chartermi.net and tell me what
letter you pick:
A - I'm a newbie to video editing and computers, learning about
digital movie editing but not yet into doing it. For now, I'd just like to
read and think.
B - I'm a newbie to video editing and computers, and dabbling in the
early phases of doing digital movie editing. Any topic is great, but
most of what I read goes over my head.
C - I'm skilled in digital video editing but not with computers.
D - I have high computer skills but digital video editing is
new to me.
E - I have moderate skills with both computers and video
editing. I'd like to read more about advanced topics.
F - I am very skilled with computers, and would like to bring my
video editing knowledge up to that level.
G - I know more about computers and digital video editing than you do. I
just read your newsletters for fun.
If it's hard to choose between a couple, give me both.
Some Basics About Video
File Compression
99.99% of the video files that we
use on our computers are compressed. The rare person who is working with
uncompressed video files probably isn't using Movie Maker or reading these
newsletters, so I'll make the statement a bit stronger and say that all
video files we use are compressed. Some are more compressed than
others.
Compression is a process for removing
redundant data from a digital media file or stream to reduce its size or the
bandwidth used.
The closest we get to
uncompressed is the Digital Video file that is recorded on the tape of our
mini-digital or digital8 camcorder. There's about a 5:1 compression ratio from
the info captured by the camcorder versus what it can lay down on the tape as
the tape moves through the camcorder in standard play mode. In a recent post,
I called DV-AVI uncompressed and was promptly corrected.... it's
compressed.... but it's still pretty big.
It's actually easier to start
with the basis that all video files we work with are compressed because
that leads directly into the next part of the topic.... the compression format
and the amount.
Digital video files are compressed to
make them more easily stored or transmitted. They need compression when heading
for storage, and decompression when being viewed.
Some compression can be done by
hardware... a camcorder or some sort of hardware capture device are a couple
examples. Other compression is done by software
using codecs.
We've all heard of codecs by now. Many
of us got part of our orientation with Movie Maker by learning that
some codecs clashed with Movie Maker, and Movie Maker lost and
crashed.
There are thousands of audio and video
codecs, and many of the codecs have adjustable settings.... so the possibilities
are almost endless. Look at the GSpot utility (see the Setup > Software page
of the website for a link to GSpot) and the info it has about video
compression codecs. Here's the list of known video compression formats sorted
alphabetically by codec. I'm just showing you the 28 in the list that start with
the letter 'A'... I'm not even wanting to count how many there are in the full
GSpot list.
The full GSpot list of audio
codecs isn't near as long. Here's the GSpot listing of the audio
codecs currently installed on my laptop.
It would be complex enough if there
was only one video or audio codec associated with a video file, but there are
usually two, one used for the video and the other for audio. And they
might be mixed or matched.
'Flash
forward' - you preview a clip in your collection and it plays great....
Movie Maker only needs to deal only with a
couple codecs for the single source file..... then
you have 50 video and music/audio clips on the timeline and preview
your movie. With the many codecs involved, previewing the timeline is that much
more complex, so Movie Maker has to shift gears to preview things differently.
Sometimes a clip plays fine in the collection but not on the timeline.... that's
how things work or don't with codecs.
An interesting thing about codecs is
that a number of them on your computer might be used to play a particular
file. Movie Maker will start at the top of the list to pick one that will
probably work. If the first one doesn't, it'll go to the second, and then the
next, etc.
File Compression Versus
Video Quality
I'll generalize again. The bigger the
file size, the less it is compressed. The smaller the file size, the more
it is compressed.
Bigger, less compressed files, have
higher quality. Smaller, more compressed files have lower quality.
I have a whole website page devoted to showing dozens of
different versions of the same file... it's the Saving Movies > Sample Video
Clips page. The original DV-AVI file runs 21 seconds and is 70 MB in size.
Scroll the page and see that the compressed files made from it run from 84K
to 57 MB.
You want both smaller files and higher quality. That's the quest
for compression processes. What's a good tradeoff of file size versus
quality? From the perspective of a Movie Maker 2 user, you get two
file format choices - DV-AVI and WMV.
If you are heading toward showing your movie on a TV, then
DV-AVI is your preferred path.... it might look or play poorer
on your computer, but a little faith says it's the best
choice when it gets to a TV. Your choice of compression is taken care
of... whatever the Digital Video codec gives you. Of course the next step to
convert the DV-AVI file to an MPEG2 one will be a significant compression
process that will determine the viewing quality, more so than the starting
DV-AVI file.... but that's beyond Movie Maker.
If you'll be viewing your movie on your computer, or via discs
or the internet on other computers, then WMV is the preferred format. But
it won't be as easy as picking DV-AVI; you'll have lots of options for
settings to deal with.
If some of your audience will watch it on a TV,
others on a disc on their computers, and still others via downloads or
streaming video from an internet server, you might want to render the movie a
few times and give each the best choice for their viewing.
About Bit Rates
A good practical indicator of quality is bit
rate. Consider two aspects of your viewers' assessment of quality....
(1) the visual/audio quality, and (2) the smoothness of playback.
When discussing bit rate, we're usually talking
about the total bit rate... that's the bits for the video and
the audio, and a few more bits for 'overhead'. The
figure we'll see in MM2 is the total.
Playing a High Definition movie on a low end computer isn't a
good experience, as the bits of data overwhelm the system and the
movie pauses, hesitates, misses frames, etc. The computer tries its
best, but there is too much data flowing into it to give a good quality
presentation. You might think the file is bad, but it's the ability of the
computer to play it smoothly.
And using a high end computer to view a highly pixilated video
made from poor quality video and audio inputs isn't pleasant either,
no matter how smoothly it plays.
Movie Maker 2 provides an easy way to gauge how many bits of
data the saved movie will need to flow each second to be able to see
the rendered movie play smoothly... regardless of visual/audio
quality.
This screen of the Save
Movie Wizard shows the highest bit rate I've dealt for WMV
files so far in MM2, the 8.4 Mbps rate for my emulated 1080p high
definition movies. It's easy to see what the bit rate will be, even before
committing to rendering the movie. Movie Maker tells you (unless you
picked a Variable Bit Rate option). Change the option in the pick list and
see the change in the bit rate figure.
A computer with a 3.0 GHz CPU is needed to play a
1080p file smoothly. Most people don't have one.
And, with the same project on the timeline as for the above
figure, here's the situation if I select a good setting
for those viewing on a dial up modem. See the 38 Kbps figure, which is
over 2000 times less bits per second than the high quality choice above.
Two extreme choices for saving the same movie.
For the same playing time, the measure of file size versus
quality between these two choices is: 274+ MB for 1080p and 1.3 MB for a dial up
modem.
Custom profiles for use with MM2 must have video target bit
rates between 4 Kbps and 20 Mbps.... note that Digital Video (DV-AVI)
is 25 Mbps for both NTSC and PAL.
What's a Good Bit Rate?
Look for your personal sweet spot in bit rate for each movie you
render... a rate that depends on your usual methods of distribution and
your viewers ability to play your movies smoothly.
For my web-based movies, I use a bit rate of about 350 Mbps
as a rule of thumb. I'll usually pick my option by using the choice 'Best fit to
file size ___', toggling the file size figure and watching the
bit rate at the lower left of the wizard. When the display size is
right for web-based movies (320x240 is good for my standard aspect ratio
ones), and the bit rate is about 350 Mbps, that's what I'll go with.
The standard profiles in MM2 go as high as 2.1 Mbps.... you
can drive the rate up higher with custom profiles, as I've done in
my simulated High Resolution ones.
Windows Media 9
Codecs
There are seven Windows Media Audio and
Video 9 Series codecs.
| Codec |
Description |
| Windows Media Audio 9 |
Audio codec for general use in encoding complex audio,
such as music. (the normal one used by Movie Maker 2) |
| Windows Media Audio 9 Professional |
Audio codec for encoding complex audio, such as music.
Supports multichannel and 24-bit encoding. (used by the Encoder) |
| Windows Media Audio 9 Lossless |
Audio codec for lossless encoding. |
| Windows Media Audio 9 Voice |
Audio codec optimized for encoding the human voice at high
compression ratios. This is the preferred codec for streams consisting
mostly of spoken words. For content that is mixed music and speech, this
codec can dynamically change the encoding algorithm used to get optimal
quality. |
| Windows Media Video 9 |
Video codec for general use in encoding complex video,
such as movies. (used by Movie Maker 2 - with a few exceptions for the
Pocket PC choices) |
| Windows Media Video 9 Screen |
Video codec optimized for encoding sequential screenshots.
This codec is often used for software training or support by recording
monitor images as computer applications are used. (used by Encoder when
doing screen capture) |
| Windows Media Video 9 Image |
Video codec for converting bitmap images (still photographs) with
deformation information into compressed video. (used by PhotoStory)
|
Seven Media Series 9 codecs. But we know from MM2 experience that
there are lots of choices when using these seven.... the choices are in the
settings.
The profiles we select from in MM2, or the custom ones we create by
tweaking the settings in the Profile Editor, are all dealing with the
settings within these codecs.
Think of the hundreds or thousands of codecs that we saw in GSpot.... many
of those have as many possible settings as those presented by the Windows Media
series codecs.
Some Windows Media
Products
Movie Maker is
good for capturing video from camcorders or recorded analog
tapes, making a movie with a single bit rate, and mono or
stereo audio. It was intended for home or casual
users.
For businesses, Microsoft Producer
enters the scene, allowing you to render a movie to a number of
different bit rates at the same time, and to integrate info from Power Point
presentations with other material such as a video of the person doing the
presentation.
For professionals (and anyone else who wants to
use it), the Windows Media Encoder also supports features such
as screen capture, live video capture, multiple-data streams in one
file, and surround sound audio.
Windows Media Encoder -
Mini-Tutorial
Let's quickly step through the Encoder, using it
to convert a file. I'll take a high definition trailer file of the
Magic of Flight and convert it to a DVD quality file.
Here's the opening window of the Encoder.
Once you pick Convert File, you get this screen to specify the
source file and the output. I'm picking the Magic of Flight trailer and making a
copy of it in the same folder.
Next is your choice of distribution method. Let's pick the
one that includes a DVD.
Then use the Video and Audio pick lists to select something
appropriate for a DVD.
See the Tip at the bottom of the window about being able to
adjust the settings after completing the wizard. The wizard sets you up with a
good balance of settings, but the Encoder lets you tweak them further.
I'm not going into tweaking the settings.... let's just render
the new file from the source file. See that the Encoder shows both the source
file being used and the new file being rendered (for the second pass of a two
pass VBR process).
After the rendering is done, the Encoder shows you the
tally of the results. I aborted this rendering before it was finished,
as I was doing it just to get some screen shots for this newsletter, so
don't look too closely at the figures.
Note that the above info includes such things as
dropped video frames and audio samples.
There are different approaches that users of Movie Maker can
use. The person who requested this topic saves his movies as
DV-AVI and then uses the Encoder to tweak the settings of his WMV files. My
approach is to learn about profile settings, make custom profiles and use
them with Movie Maker 2... skipping the step of saving the movie to a DV-AVI
file. Both approaches work.
My personal interest is in the 82 profiles in the
c:\Program Files\Windows Media Components\encoder\Settings subfolder. They have
been setup by Microsoft to achieve a good balance in the various
profile settings, a great starting point to make custom profiles
for MM2. Use any of them with the Profile Editor to make additional choices for
Movie Maker 2.
That's more than enough for this
newsletter. See you on the newsgroup and forums. Don't forget to respond to
the poll.
PapaJohn
