[Theora-dev] Re: PC-based video server
theora at elphel.com
Wed Jan 26 12:20:26 PST 2005
> Well, I've seen pretty good quality theora format video at less than 1
What was the resolution/frame/rate/type of the movie.
As I understand, in videosecurity in many cases most of the frame is
background that is perfectly stable, that will give significant advantage.
And this is why they usually use "motion detectors" - I don't think it is
needed in the case of Theora - whith proper adjustments there should be
very few data sent out ifnothing changes
> You are using high resolution sensors in your network cameras, so to
easy number to work with, I'm figuring 1 Mbps per network camera.
I have no experience so let's use this number
> It's great that the network cameras can output video in theora format.
When I decided I'm ready to implement videocompression I was planning to
use MPEG-2. What stopped me from that - I could not stand that Elphel name
will appear in the list http://www.mpegla.com/m2/m2-licensees.cfm :-)
> If you have ten network cameras attached to the PC-based video server,
> trying to save the output from all of the cameras at the same time, the
> camera(n+1) could be saved 1 minute after the stream from camera(n).
> cameras, you would be saving a total of 750 MB each ten minutes, or
about 108 GB
> every 24 hours.
What you mean by "after" - buffering the streams in memory? I thought OS
can handle it on it's own.
> A PC with two 400 GB drives could give you about a week's worth of storage.
I believe usually it's enough.
> I'm not sure what you would do when you run out of storage.
Usually they just start over again and overwrite older records.
> I'm also not sure how much traffic there would be accessing the
stored video, and how the server would keep up with the job of delivering
Initially that server should do 2 (or 3) parallel jobs:
1 - uninterruptedly store all the high-res video on disks (DVR);
2 - serve lower resolution video from live data in parallel with recording
with minimal delay.
Actually it will be possible to use 2 different servers for these 2 tasks
if neeedd - anyway there will be multicast stream.
and only the
3-d job will be to serve the stored video.
> If people wanted to watch the live video, they would just go to the address
> of that network camera, right? So, the PC-based video server
> would not be required to do much, if any, streaming video. People who want
> to watch the stored video could just download the desired files, right?
Not exactly - and here is the main point.
At the first stage all this high-performance GNU/Linux + Theora stuff is
confined to server+cameras. External interface of the system as a whole
will be MJPEG (other standard software codecs possible), "server push"
that majority of the video management software used in videosecuruity
business - the software they are currently using and don't want to get rid
of immediately. So the proposed server can be plugged in their system and
behave as a set of regular network cameras, not as a server+cameras.
That, from one side, will not scare off customers who got used to some
system immediately and will significanbtly simplify our job - security
systems have much more than cameras alone (i.e. other sensors) and many
companies work for a long time in this area and I don't think it is
possible to design something similar in short time and using limited
So I consider such server as intermediate step to get Theora into this
application area. It will be then next step to get rid of intermediate
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