Hello, WOT (Way Off Topic) I decided to post here (risking flames) because many of the participants here are working on video implementations. I'm focused on Bandwith Minimization for video transmission over wide area networks. Futhermore, although I still have Debian and OpenBSD systems around me, I'm doing all of my newest work on Gentoo (yes I'm uncurable infected)....
Finding and testing cameras which acutally use very little bandwith, is a challenge. Furthermore, making adjustments to the equipment (cameras, encoders, software) is also obscure. What I'm specifically looking for is ways to test and verify that a given camera actually needs less than 30 kbps or 20kbps, for a given video stream. Working with Ethernet (either accurately measuring or constricting) has been problematic. Discussions with others seem to confirm this. I know there are new mechanisms in the 2.6 kernel series for such hacking, but, I'm looking for something I can use quickly. So I'm now going to sink some time into setting up ppp over a serial connection (ether synchronous or asynchronous). Asyncronous, like RS232 uses start and stop bits, so for every 7/8 bits of data you transmit, you have the overhead of 1/2 stop bits. Synchronous uses external clocking, so the overhead of start and stop bits is eliminated. Duplex issues are really minimal, since the cameras' and encoders' data output is one way, so half duplex is just fine. If I set an async serial port to 38.4 it's roughly equivalent to a 30kbps synchronous half duplex circuit(???). Later I can set the serial ports to 28.8 and then 19.2 kbps for refinement of test vectors. What I'm trying to do is set up ppp between two gentoo systems running ppp over a RS232 serial ports, set at 38.4, 8N1, so that a vendor can bring in their equipment and show it running H.264 video across the link. There will be 2 Ethernet switches connected to each dual Ethernet gentoo system (and NAT) and nothing else running on these sytems. The thinking is if their equipment works across this test link, then it's worth testing over 56kbps frame relay links that have 32k CIR (that is a synchronous port speed of 32 kbps). Has anyone tried anything like this? Any suggestions as to tweaking the ppp configuration/stack to to minimize overhead and latency? Any discussion or suggestion is most welcome. Is there an easier test methodology? confused and alone, James -- gentoo-user@gentoo.org mailing list
