streaming video over WLAN

[krisyok]

Hi,

I'm doing some experiment. I'm streaming a video over WLAN (802.11 b/g) in 2 modes: infrastructure and adhoc mode. My video bitrate is around 7Mbps. I'm trying to see some glitches on the video either when I share the bandwidth with other applications or when I interfere the channel being used for video streaming. The reason is that I want to better control either the wireless card (with custom driver) or control some other applications. So I need to have a scenario when VLC is really having a big problem with a lot of glitches in the video. My preliminary results are following.

1. Infrastructure mode
computer A <--> router <--> computer B

case 1: I start streaming VLC with 7Mbps and 3 downloading applications to share the bandwidth. I can see some glitches in the video.
case 2: I start streaming VLC with 7 Mbps. I use some other computer to generate background traffic on the same wireless channel to interfere this channel. I can see a lot of glitches in the video.

2. Adhoc mode
computer A <--> computer B

case 1: I start streaming VLC with 7Mbps and 3 downloading applications to share the bandwidth. I can see no glitches in the video. The video is still good but I only see some slow motion.
case 2: I start streaming VLC with 7 Mbps. I use some other computer to generate background traffic on the same wireless channel to interfere this channel. Again, I see no glitches in the video. I see only more slow motion.

I'm wondering why these 2 scenarios differ. What would be the main reason causing glitches in the video streaming?
My wild guess is the packet losses. But in both scenarios we should see packet losses due to packet collisions.
Did VLC do something to recover in the second scenario?
Any help/comments would be highly appreciated. Thanks!

[HumanBlade]

i may be incorrect, but as i understand it...

streaming over different protocols will give different effects. UDP for instance tries to go for less overhead, and so does not do normal stream signal handshaking and error packets. it's a case of 'i just want the stream constantly running. HTTP streaming uses the TCP stack and therefore does send error packets, so should be less glitches but you may suffer 'latency issues' even over adhoc as it negotiates the packets.

this doesn't necessarily explain what's going on with you however. it may be a simple case of the overhead of going through a router in infrastructure mode may force the client computer to choke on incoming packets. interesting experiment by the way.