[AG-TECH] High res video streams, in AG VIC session

Andrew Swan aswan at cs.berkeley.edu
Fri Jan 24 14:44:54 CST 2003


Osland, CD (Chris)  wrote:
> We're interested in sending and receiving video streams, preferably
> as part of a regular AG VIC session, that run at higher than the
> AG default VIC resolution (388x288 or somesuch?).  We would be
> interested in 640x480, 768x576 and 1024x768.
> 
> [...]
> 
> 3.  Has anyone a concise idea of the current state of VIC and
> OpenMASH in this area?  I don't know what has already been
> written or what remains to be done.

the only realistic codec options for higher resolution are
jpeg and h.263.  (this is not an implementation issue, the
h.261 bitstream syntax simply does not permit any resolution
other than cif or qcif).

the h.263 spec expands the allowed resolutions so it is a
possible option.  {ucl,ag}vic have an h.263 codec but for
some reason, it is limited to cif (the underlying code
seems to be capable of encoding larger images but the tcl
code that glues vic together forces the capture pipeline
in to cif for h.26*).  we are also working on building a
reliable h.263 codec for openmash which ought to be usable
soon but if you want to start experimenting right now, its
not there yet..

so that leaves jpeg.  jpeg is of course more expensive in
terms of bandwidth and cpu cycles.  but the good news is
you can actually use it today.  if you're willing to spend
a few hundred dollars on new hardware (a linux media labs
hardware jpeg codec) and are willing to run some non-standard
ag software, you can get great quality with rtptv:

  http://bmrc.berkeley.edu/~delco/rtptv/

if you have another machine with an lml board, you can decode
in hardware quite cheaply.  alternatively, you can decode in
software with openmash vic but may not be able to keep up with
a full 30 fps stream (although if you have a new top of the
line cpu you'll probably come pretty close)

if you don't want to buy hardware or run rtptv, you can still
get higher resolution images with software encoded jpeg.
this definitely works in openmash vic -- i don't know if it
works or how well it works in agvic.

that's just a random braindump -- if you have any questions
about openmash or rtptv, i'll be happy to try to answer them...

-Andrew




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