--- Forwarded Message from Michael Bush <[log in to unmask]> ---

>Date: Wed, 29 May 2002 23:03:59 -0600
>From: Michael Bush <[log in to unmask]>
>Subject: RE: #6688 Streaming video HELP!
>In-reply-to: <[log in to unmask]>
>Sender: [log in to unmask]
>To: "'Language Learning and Technology International Information Forum'"    <[log in to unmask]>
>Importance: Normal

------------------
Original message:
> Am I expecting too much to see mouths and sound synchronized 
> with next to no skips during play (at double size). At the 
> regular size it plays with no problems.

Subsequent message
> My problem has been with the RealPlayer and doubling the window size
of the player.

Do you mean that the image is 2 times the original size horizontally AND
vertically?  If that is indeed the case, then you must keep in mind that
the player has to handle FOUR times as many pixels as it did on the
original size. This puts a lot of load on the processor and graphics
sub-system of the client.

DVD for example relies on a bit rate that runs from about 3 mbps to
about 10 mbps in MPEG 2 and will usually average between 4 mbps and 6
mbps unless there is a lot of motion, and that is for an image that has
the data of a 720 x 480 resolution.  What that means in TV terms is more
nebulous than that of course, with the issue of fields and lower
effective TV resolution.  Nevertheless, if you only have 1 mbps
available, then you can see that you have a problem.  

As someone else mentioned, you also must consider the frame rate at
which the video was encoded.  You probably know that NTSC images run at
30 frames per second.  Film runs at 24 fps.  15 fps is perhaps the
lowest possible limit for video that looks halfway decent (depending on
how picky the viewers are) and of course requires the movement of a
heckuva lot fewer pixels.

And then there is the bandwidth of your server.  The number of
simultaneous streams that are you requiring it to handle can drastically
affect its performance, especially if it is not tuned for streaming
video.

As you can see, there is a good chance that you have more bottlenecks
than just the bandwidth of your wireless network.

Cheers,

Michael Bush
Associate Professor of French and
Instructional Psychology and Technology
Brigham Young University
http://baudelaire.byu.edu/digital/
[log in to unmask] 


-----Original Message-----
From: Language Learning and Technology International Information Forum
[mailto:[log in to unmask]] On Behalf Of LLTI-Editor
Sent: Friday, May 17, 2002 7:53 AM
To: [log in to unmask]
Subject: #6688 Streaming video HELP!


--- Forwarded Message from Beth Secrist <[log in to unmask]> ---

>Date: Wed, 15 May 2002 15:14:25 -0400
>From: Beth Secrist <[log in to unmask]>
>Reply-To: [log in to unmask]
>Organization: University of Tennessee
>To: LLTI-Editor <[log in to unmask]>
>Subject: Streaming video HELP!

Hello LLTIers!

Since we are *still* experiencing problems streaming video over our
wireless network (and probably over wired, but unable to test that
yet!), I would like your help in determining what could be expected of
streamed files.

We have both Real and QT files (although the QT is served from the Real
server). Our Digital Media Services encoded these files and they both
play at a "standard" size. Our throughput is 1 Mbps (athough there are
11 Mbps access points all over the place!). No matter where we set the
preferences for Real, there are still skips and halts when playing the
video at double size (double because the size is necessary when showing
the video in class through ceiling-mounted Proxima projectors).

Am I expecting too much to see mouths and sound synchronized with next
to no skips during play (at double size). At the regular size it plays
with no problems.

Also, the files look much better in QT, but it appears that the plugin
doesn't allow one to double the video size. Does anyone know if there is
a way to change that without re-digitizing everything?

Thank you for your help! Beth

Beth Secrist, Director
Language Resource Center
Dept. of Modern Foreign Langs. & Lits.
University of Tennessee
Knoxville, TN 37996
(865)974-6494; [log in to unmask]
http://web.utk.edu/~mfll/LRC/