Video over 802.11?

[JimGeier]

Has anyone had any experiences running video applications over 802.11? What was the quality of video? How many users could support?

[Sumaryo]

I have been designing and implementing a 4 CAMERA real time two-way digital video transmission over 802.11.

The capture devices basically a DVR (Digital Video recorder) system with 4 NTSC/PAL camera input with combine frame rate 120 fps. The remote system is an IP based PC viewer that normally attached to the DVR with a LAN system. The DVR uses MPEG (MPEG-4 ?) for the compression of the analog video signal.
The remote viewer may interact with PTZ-F (Pan-Tilt-Zooming and manual Focusing) camera in real time (hence, the "viewers" may choose/select what they want to see/zoom/focus etc)

Due to geographically/topografically difficult area, we have to split to two link from camera/server to remote viewer, one measured at 2.6 km (1.7 mile) and the other 0.9 km (0.6 mile)

Initially we are using a 802.11b wirelessbridge system on both link.
The quality is acceptable (good fps) at only one CAMERA input. If more than one camera were activated, the frame rate drop significantly.

However due to interference during day time on longer (2.6 km) link, the wireless throughput, hence the frame rates become unpleasantly low, if not frozen at all.

Then we replaced the shorter link (0.6 mile) with 802.11a system (with ext antenna to increase range) and with laserlink 10 Mbps system on the longer (1.7 mile) link. The throughput (hence the frame rates) are excellent.

Due to impracticality of the laser setup, the customer request us to build the all 802.11a system end to end, which is still going on right now.

[JimGeier]

Great feedback. Thanks.

Anyone have experiences that they can share related to transmitting video over 802.11a enterprise networks?

[computeradam]

I have seen on TechTV a reciever called Moxi. It hooks up to your TV, Computer and Digital Cable. You can share video and Things on your computer to a "Moxi Extension" connected to your second TV threw 802.11b. The Computer connection is also 802.11b I think. You can record movies with it also.

This was a prototype they showed on TechTV a while back, but I am not sure if they actually built it. Just look for "Moxi Digital" on the internet to get more info.

Ahh, I found a link... http://www.digeo.com/ <--- This is who makes Moxi

But it looks like they only make it for Digital Cable now

[JimGeier]

Thanks. I've been looking at MPEG-2 vs. MPEG-4 for transmitting video over wireless. I've had some experiences with MPEG-2, but MPEG-4 is new to me. I understand that MPEG-4 will carry video at about half the data rate of MPEG-2.

Does anyone know if any of the pocketPCs (Windows CE) devices support MPEG-4? Has anyone tested MPEG-4 over 802.11a or 802.11b?

[fintheman]

I was running a Jornada and a Compaq IPAQ and played mpeg4 on them if that helps answer your question.

[Jim Lin]

Hi Jim Geier,

Forget about MPEG-2, it can't be fully carried even by 11a ad-hoc.
MPEG-4 Part 10: H.264 seems to be good solution currently.

My question is how to transmit different video streams to multiple receivers from a server?

[JimGeier]

Thanks. That's what I've been finding out. MPEG-4 seems to be the best way to go with video over wireless LANs. It sounds like enough devices support it, and it seems to provide the most optimum compression for wireless.

To send a video stream to multiple 802.11 receiving devices, you'll need to implement multicast or broadcast addressing at the MAC layer. With multicasting, 802.11 doesn't utilize acknowledgements, which isn't an issue with video. In fact, it saves considerable throughput by not needing to expend the overhead of acknowledging each frame as you would with unicast addressing (as if you were going to send a different video stream to each receiving device).

[Jim Lin]

That's exact what our engineers thinking of.
Because we are software company.
Do you think we should cooperate with chip vendor to have multi-casting mechanism implemented inside chip?

[JimGeier]

That would certainly be a feature that would best support many video type applications.

[John Klein]

Sony makes a device in Japan (http://www.ecat.sony.co.jp/vaio/acc/acc.cfm?pd=9760) for streaming MPEG2 over 802.11a

[Jim Lin]

I think the most important thing for video over WLAN is the limitation of bandwidth.
There are two key points.
One is the improving of wlreless technologies such as 802.11a/b/g or UWB...
The other is the improving of streaming and its codec.
Even though Sony has this kind of product, but it still has limitation when receiver become more and more.
When the request come, Sony may get rid of MPEG2 unless MPEG2 has better solution available.

[JimGeier]

Does anyone know of using 802.11 for distributing video for home theater applications?

[Gilbo]

I am new to the forum and hope you can possibly direct me in the right direction. Although this topic is dated back to 2002 is it rather relavent to what I am attemptiong to do currently which is to run a proof of concept for video streaming distribution over 802.11g/b to fixed mobile clients equipped with laptops or pocket PC's.

To summarize how far we've gotten:

- Video encoders are connected to the switch port of a wireless router/access point.
- Laptop and Pocket PC (iPAQ hx2790 series) are used as wireless clients and loaded with appropriate video viewing software.
- Video encoding is full motion 25/30fps MPEG2 tried at various rates and SIF or QSIF resolutions.

A compression algorith that is tuned for low bandwidth would be better in one way but eveb that would eventually encounter the congestion problem we found as explained below. We do intend to move to MPEG4 and better still to MPEG4-AVC (H.264) very soon.


Results with Unicast Video streaming towards the client
Laptop - seems to have no end, have tried up 6Mbps video traffic, full D1 res, excellent video at 2Mbps

iPAQ - maxes out at approx 1.2Mbps SIF resolution - This was somehwat expected as a limitation of the CPU capabilities of a Pocket PC and very acceptable for our POC. In fact SIF at 500Mbps is quite acceptable for 30 fps and significant scene changes. Even QCIF can be veru useful. It would be safe to assume that several unicast sessions approaching 20 to 25Mbps could be handled without impacting the video quality.

Resuilts with Multicast Video streaming towards the client

Laptop and Pocket PC - max video throughput is 500Mbps, router ping response becomes erractic ranging from 10ms to 1500ms.


We checked with the router supplier and confirmed all settings are optimum and they cannot explain why we see such poor results with multicast streaming.
One of your articles about using multicast video streaming appeared to describe an application for multicast from a wireless device towards the access station as would be the case for a wireless camera. BTW we have tried confirming the Power Save option is off and the DTIM and Beacon intervals are optimized as you've pointed out.

In our case the application is streaming over the wireless towards the clients. The problem we see is similar to projects that attempt to use ADSL lines to stream video. ADSL of course is great for downloading but not so great for uploading so the ADSL service has to be quite large to get sufficient upload bandwidth.

Woudl appreciate any insight you could provide on the problem. One again, sorry for stepping in on a old topic and being so verbose.

[M/Q]

You did not mention what radios you were using and if they had QoS capabilities. Or if you have researched any QoS standards for Ethernet or 802.11. Looking into that might be to your advantage and help with the congestion problem.

This link is just one approach.

http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1521523

[Gilbo]

Thanks for the reply M/Q. I'm not sure what you mean by radio. I'll assume this refers to the 802.11 or other protocol. The wireless setup is an 802.11g Access Point router running combined b/g. It apparently supports several types of QoS including port and application based but none of these options change anything for the throughput of the multicast streams. Thanks for the link though, I'll check it out.

[dentalan]

I think I should mention that in here. I used WIndows Media encoder 9 to stream a USB webcam over my network (a wireless & 4 4port ethernet router)
It worked fine, allthough the picture quality of the webcam was bad.
It had a delay about 4 seconds. I was viewing the video stream just by opening in Windows Media player the IP:port ( 192.169.xxx.xxx:xxxxport)

[ariel884]

I am new to the forum and hope you can possibly direct me in the right direction. Although this topic is dated back to 2002 is it rather relavent to what I am attemptiong to do currently which is to run a proof of concept for video streaming distribution over 802.11g/b to fixed mobile clients equipped with laptops or pocket PC's.

To summarize how far we've gotten:

- Video encoders are connected to the switch port of a wireless router/access point.
- Laptop and Pocket PC (iPAQ hx2790 series) are used as wireless clients and loaded with appropriate video viewing software.
- Video encoding is full motion 25/30fps MPEG2 tried at various rates and SIF or QSIF resolutions.

A compression algorith that is tuned for low bandwidth would be better in one way but eveb that would eventually encounter the congestion problem we found as explained below. We do intend to move to MPEG4 and better still to MPEG4-AVC (H.264) very soon.


Results with Unicast Video streaming towards the client
Laptop - seems to have no end, have tried up 6Mbps video traffic, full D1 res, excellent video at 2Mbps

iPAQ - maxes out at approx 1.2Mbps SIF resolution - This was somehwat expected as a limitation of the CPU capabilities of a Pocket PC and very acceptable for our POC. In fact SIF at 500Mbps is quite acceptable for 30 fps and significant scene changes. Even QCIF can be veru useful. It would be safe to assume that several unicast sessions approaching 20 to 25Mbps could be handled without impacting the video quality.

Resuilts with Multicast Video streaming towards the client

Laptop and Pocket PC - max video throughput is 500Mbps, router ping response becomes erractic ranging from 10ms to 1500ms.


We checked with the router supplier and confirmed all settings are optimum and they cannot explain why we see such poor results with multicast streaming.
One of your articles about using multicast video streaming appeared to describe an application for multicast from a wireless device towards the access station as would be the case for a wireless camera. BTW we have tried confirming the Power Save option is off and the DTIM and Beacon intervals are optimized as you've pointed out.

In our case the application is streaming over the wireless towards the clients. The problem we see is similar to projects that attempt to use ADSL lines to stream video. ADSL of course is great for downloading but not so great for uploading so the ADSL service has to be quite large to get sufficient upload bandwidth.

Woudl appreciate any insight you could provide on the problem. One again, sorry for stepping in on a old topic and being so verbose.

I will thank you if u can write the software u used in the pocket PC and the Laptop.