| Best Movie/Animation Format for LARGE files [message #19018] |
Mon, 21 February 2000 00:00  |
wcapehar
Messages: 12
Registered: May 1998
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Junior Member |
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I have been working on some large image time series (long in time and
large in size) and am wondering what the best format (jpeg/mpeg) for
saving them with the least distortion to the frames.
Ideas? (I'm already breaking up the time series into smaller clips.)
Thanks much
Bill Capehart
Sent via Deja.com http://www.deja.com/
Before you buy.
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| Re: Best Movie/Animation Format for LARGE files [message #19065 is a reply to message #19018] |
Tue, 22 February 2000 00:00  |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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William Thompson (thompson@orpheus.nascom.nasa.gov) writes:
> I wonder if the larger movies "coarsen up" to be compatible with Microsoft
> Windows mpeg players. We've been making MPEG movies on our Unix workstations
> using mpeg_encode for some time now. The movies always play well on our
> workstations, but sometimes the movies don't play correctly on Windows
> machines. This problem has always been attributed in the past to the size of
> the individual frames. However, recently I was told that a movie which
> wouldn't play in Windows in its original format, was made to do so when it was
> regenerated at the same frame size, but with a lower quality parameter. The
> current theory is that Windows players refuse to play MPEGs unless they can
> decode them fast enough to play the frames at the correct frame rate.
Just five minutes ago I got a longish response from RSI
technical support on this topic, which seems to confirm
this theory. It's fairly technical, and I didn't understand
a lot of it on first reading, but I'll see what I can do
to clean it up and pass it along.
In the meantime, it would probably help to know which
*viewers* people are using when they notice problems.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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| Re: Best Movie/Animation Format for LARGE files [message #19066 is a reply to message #19018] |
Tue, 22 February 2000 00:00 |
Steve[2]
Messages: 7
Registered: January 1999
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Junior Member |
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wcapehar@my-deja.com wrote:
> I have been working on some large image time series (long in time and
> large in size) and am wondering what the best format (jpeg/mpeg) for
> saving them with the least distortion to the frames.
>
> Ideas? (I'm already breaking up the time series into smaller clips.)
>
> Thanks much
> Bill Capehart
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Hi Bill:
Well, this is the one issue in this NG that I can add something to
the discussion (though I program in IDL for 5 years or so, I'm no
expert). I use direct graphics (too lazy to learn Object graphics) and
make animations from 1 MB to 300MB (mpeg's and mjpeg's). I don't
know if you can fix IDL's image quality problems, but I do know that
there is a default 'quality' factor of 50 or 75 % written into the MPEG
routines provided with IDL. I use a separate encoder, already mentioned
by another poster here, and generate frames in IDL. The quality is much
better than those produced in IDL (btw, IDL makes MPEG-2, while the
Stanford encoder, is MPEG-1, an older standard, but more common).
I use PPM or GIF format for the frames, as I recall, JPEG didn't give as
nice of results. I think the reason is JPEG is a lossy compression, and
the
Stanford encoder will take that JPEG and convert it to PPM and then to
.Y .U .V component files, then use the MPEG compression, so you are
compressing something that has already undergone compression. I could
be wrong about that, but my experience is JPEG gave lower quality
MPEG's.
GIF gives you nice clean colors and a small file size. PPM is akin to
TIFF
in that it is not compressed and has the full color palette included,
but is
much larger that GIF. I didn't see a difference for my animations in
terms
of quality when using GIF instead of PPM, though the frame file size is
much reduced.
I got to the stage where I couldn't hold all the frames of my animations
on disk,
and began to use MJPEG. I make each frame and then have IDL run a
shell script that compresses each frame into MJPEG format. The MJPEG
compression does not use intra-frame statistics, like MPEG does, so you
can avoid having to save all the frames on disk before encoding, like
you
would need to do if you make an MPEG. The exact format of MJPEG
will depend on your playback hardware, and you would need that hardware
to view the animation. If you have $$$, you could write the MJPEG to
DVD, though I hear the DVD writer is a small fortune. The MJPEG will
ultimately not achieve any more compression than MPEG, but you can
avoid the huge slew of frames in production. For instance, for my
animations,
with 30 frames/second, 720x480-24bit frames, that's 1.8GB / minute !
You can use lower frame rates, smaller frames, maybe lower color quality
to conserve disk space. Generally MPEG gives you about 30:1 compression.
In an ideal world, I would always use MPEG, as the movies look the best.
Since MPEG only uses a few frames for statistics, it should in principle
be possible to generate only a short sequence of frames and send these
to your own custom-compiled mpeg encoder, and get around having
to generate all the frames beforehand, but I don't know of an encoder
you could use for this. I haven't looked in detail into the Stanford
encoder
source, but it is freely available.
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| Re: Best Movie/Animation Format for LARGE files [message #19068 is a reply to message #19018] |
Tue, 22 February 2000 00:00 |
thompson
Messages: 584
Registered: August 1991
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Senior Member |
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wcapehar@my-deja.com writes:
> In article <88rm7q$qqa$1@pukkie.phys.uu.nl>,
> P.Suetterlin@astro.uu.nl wrote:
>> In article <MPG.131a56a6dc21d88e989a3b@news.frii.com>,
>> davidf@dfanning.com (David Fanning) writes:
>>
>>>> I have been working on some large image time series (long in time and
>>>> large in size) and am wondering what the best format (jpeg/mpeg) for
>>>> saving them with the least distortion to the frames.
>>
>>>> Ideas? (I'm already breaking up the time series into smaller clips.)
>>> I've been getting reports--John Broccio's article today is
>>> only the latest--of poor resolution when making MPEG movies.
>> I had one try at the built-in MPEG creation of IDL and immediately
>> dumped it. I'm creating my mpegs using mpeg_encode (Version 1.5).
>> You have to store the single frames on disk, so no memory
>> limitations. Of course mpeg (and jpeg, too) are lossy compression
>> tools, I only use them if I only want to look at them, and don't
>> intend to do (e.g.) photometric work..
>> PS: That's under Unix. Not sure, but mpeg_encode might also compile
>> under other OS.
> I agree with the degradation issue. Small mpeg movies (in time steps
> and in the image sizes) are fine but larger ones, tend to "coarsen up."
I wonder if the larger movies "coarsen up" to be compatible with Microsoft
Windows mpeg players. We've been making MPEG movies on our Unix workstations
using mpeg_encode for some time now. The movies always play well on our
workstations, but sometimes the movies don't play correctly on Windows
machines. This problem has always been attributed in the past to the size of
the individual frames. However, recently I was told that a movie which
wouldn't play in Windows in its original format, was made to do so when it was
regenerated at the same frame size, but with a lower quality parameter. The
current theory is that Windows players refuse to play MPEGs unless they can
decode them fast enough to play the frames at the correct frame rate.
William Thompson
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