Re: unstable encoding bit rates...

On Mon, 10 Jul 2006 03:56:02 -0700, BusyBee
<BusyBee@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:


Here are the replies to your Qs:
a) the VGA2USB device is USB2, has no built-in hardware compression, and
works by default in YUY2 color space.
b) I got the same results on another computer


OK fair enough. Uncompressed VGA at 25fps is going to take a fair bit
of data transfer. Your systems may well have enough HP to encode DV
video, perhaps there's some bottleneck cause by reading the USB2
stream. You said the CPU usage was normal at this point ?

I did try to find some hotfix details, but nothing seemed relevant -
these were the closest support articles (they're not veru helpful
though in your case)

http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B298185
http://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B270873



My Comments:
- I have thus no further clues on what is going wrong ...
- I have diagnosed that the encoding bit rate is jittery: do you agree that
it is the symptom of something not going right ? Some people are telling that
if the requested encoding bit rate is too high for what has to be done, then
it will jump up and down all the time... Note that I am only requesting
93kbps... Could that be too much for VGA grabs ?


Well the more the data has to be compressed, oddly enough, the harder
the encoder has to work. I wonder if you do VGA to 259kbps whether you
can replicate the problem.

Perhaps if you look at the data within the WMV files created with
http://www.sliq.com/default.asp?view=wmsnoop you may see some extra
clues in the packet sizes.


I have been recently encoding live with WME on 2 machines, the first
receiving a video flow from a Sony camcorder through a 1394 connection, and
the other connected to a VGA2USB device receiving frame grabs from a
presentation computer.
I encoded the Sony output at around 250kbps, and the VGA grabs at a
requested 93kbps.
The Sony output got smoothly encoded at a stable bit rate not far from
250kbps, but the VGA slides were a catastrophy: the actual bit rate was
jumping all the time between 10-50kbps, the actual frame rate was lower than


I notice you're encoding slides here - have you tried (or are you
already using) the WM Screen Capture codec for that ?

It may give better results than WMV9 standard for slide data, but
there are a few gotchas.

One way for somebody to replicate your issue might be to use the
screen codec and have it switch unexpectedly between lossless and
lossy modes due to source video variations (details of this process :
http://support.microsoft.com/?kbid=837171)


You may wish to attach the PRX or WME files for both profiles to your
next post, in case there's something odd we haven't discussed about
the profiles in use.


HTH
Cheers - Neil
------------------------------------------------
Digital Media MVP : 2004-2006
http://mvp.support.microsoft.com/mvpfaqs
.

Relevant Pages

  • Re: unstable encoding bit rates...
    ... I realize I don't use and don't have this WM Screen Capture codec. ... Your systems may well have enough HP to encode DV ... Could that be too much for VGA grabs? ... I notice you're encoding slides here - have you tried (or are you ...
    (microsoft.public.windowsmedia.encoder)
  • Re: unstable encoding bit rates...
    ... The WME settings file I used is temporarily downloadable at ... Your systems may well have enough HP to encode DV ... Could that be too much for VGA grabs? ... I notice you're encoding slides here - have you tried (or are you ...
    (microsoft.public.windowsmedia.encoder)