Hi all,

I've been learning my way around R4V5 for a few weeks and finally did a clean install with R5A9 a few nights ago. What a difference! (I like the 2.6.x kernel much better... Kudos to the development team!)

Anyway, I have my KnoppMyth box connected to my home network consisting of some Windows PC's and a NASLite server via a 802.11G wireless link. I've noticed that when I play an MPEG4 (DivX or whatever) file in mplayer from an SMB share on any machine in my network, the video has frequent pauses in it (approximately 1 per second lasting a couple of frames), but the audio is fine. When I 'rewind' the video in mplayer, it plays smoothly up to the point where I left off, then starts pausing again.

My current guess is that I've got some network latency or buffering issues with the wireless link.

'iwconfig ath0' reports that I have good signal strength and quality and that I'm operating at 54 Mbps.

I've tried swapping back to a 100 Mbit wired connection for comparison and the video playback issues go away.

Here's my hardware profile:

Athlon XP 2200+
Asus A7V333
512 MB SDRAM, 266 MHz FSB
Chaintech GeForce FX5200 (NV34) w/128 MB
Onboard AC97 audio (C-Media Electronics Inc CM8738 (rev 10))
D-Link DWL-G520 wirelss PCI card
Linksys NC100 Network Everywhere Fast Ethernet 10/100

Also, my wireless AP is a D-Link DWL-2000AP, connected to my home 100BaseT network through a switch.

Does anyone have any thoughts?

Regards,

~ Terrin

I have been playing MPEG4 as well as recorded shows over 802.11b. It works well... most of the time.

Positioning makes a difference, as I guess 54Mbps (in theory) is just enough to work smoothly, but only if you have good signal. So try to use it from different locations, or different orientations even.

In my setup, I am connecting wirelessly from the server to the AP and from the AP to a client on a laptop.

54Mbps is in theory 5 times as much bandwith as the 802.11b you are talking about it working with. If you are getting good signal and little interference then 802.11g should be plenty of bandwith. my guess would be the driver. I haven't played with g much, but many of the b drivers just weren't all that stable, and consistant.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

I had a similar problem and think it has to do with the link quality. When my laptop is facing one direction in my bedroom I get smooth motion video. When its in another direction the same video goes smoothly then freeze frames then continues smootly again and so on. Based on the signal strength indicator, it seems to coincide with reduced signal strength.

Everyone,

Thanks for the input. I'll experiment with the antenna placement/orientation and try to associate some signal strength/quality numbers with my results and post them here.

The driver I am using is the MadWifi that is included in the kernel for KnoppMyth R5A9. (not sure what the precise version number is.)

Thanks again,

~ Terrin

Wireless networking is inherently prone to any number of issues that can severely degrade it's throughput and even more so the reliability and consistency of that thoughput. While streaming video around the house isn't all that demanding (10Mbs is fast enough) you've really got to have that data delivered like clockwork in a nice smooth stream. Chunky style just won't cut it.

That said, you may be able to improve the situation in your front end to a certain extent by choosing the "extra buffering" or "agressive buffering" options.

Greetings!

After much tinkering, I think that I have found a solution to my choppy playback problems.

The problem appears to be twofold:

* Multi-second dropouts in the wireless link
* Lack of buffering on the client (MythTV box)

Here's what I figured out about the first issue. I'm using Madwifi with a D-LINK DWL-G520 PCI wireless card. My /etc/network/interfaces file used to look like the following. Some of the names have been changed to protect the innocent.



I figured this would work fine. Well, it worked but not very well. Signal levels and signal quality were good, except when data was being transferred. What I discovered was madwifi was actually using the wrong channel! My AP was set to use channel 6 and madwifi was using channel 5. Apparently, this was just close enough to make things work until lots of traffic showed up. The solution to this problem is to simply specify the channel number that your AP is set to.

At the same time, I did a little 'survey' of all the available channel numbers and picked the one that gave me the best signal level and link quality. In my case, this turned out to be channel 2. I set my AP to channel 2, then modified my /etc/network/interfaces file in the following manner:



First, I set the mode value in the first line to '0'. This allows the driver to pick which mode (A, B, G) is best for the conditions, assuming your hardware is capable. As you can see, I also changed the rate value in the second line to 'auto' but I don't think that had a noticable effect, other than to let the rate 'float' to whatever level it could best achieve according to the signal conditions. The most important setting is the channel number in the second line, of course.

By ensuring the channel numbers matched, my connection became rock steady with no dropouts.

To address the second problem, I forced my MythTV box to buffer the videostream by doing the following:

Then add this line to the file:

This forces mplayer to attempt to keep a 1 meg buffer of your file at all times. This is useful for slow media as well as network connections with latency issues. The only tradeoff here is a slight pause when starting to play a file. There is also a (very) slight pause when fast forwarding in the file.

Additional info:
I bought a couple of inexpensive antennae for my wireless AP and my PCI client from Newegg. These boosted my signal level and link quality each by 10 dB. (The PCI card's antenna boosted the signal by 8 dB, the AP's antenna by an additional 2 dB).

On a slightly sadder note, even with all the above tweaks I can only get a maximum throughput of around 10 megabits/s. I think that the madwifi driver still needs a bit of work to improve it's efficiency. Maybe turbo/superG will help.

Anyways, I sure hope that helps! Here's what 'iwconfig ath0' is reporting as I write this:



Regards,

~ Terrin