MVP connected via wLAN-Bridge

[tivi]

Hi everybody!

First of all I would like to take the chance to thank Chris for VOMPserver.
Please go on with your great work! Thank you!!

Then, I would like to post my problem:

I have connected my MVP through wLAN using two routers in WDS.
I use the latest version of VOMPserver provided by c't-vdr v4.5 (kernel 2.6.12-ct).
MVP doesn't seem to get "enough" stream to decode. So, LiveTV is not possible.

The wLAN connection constantly provides 48MBit (gross).
100MBit through cable not tested yet.....

But, highbit MPGs (6-8 MBit) served by gbpvr work flawlessly.
So I think, wLAN capacity here is sufficient.

Any ideas? THX

tivi

[tivi]

No ideas? 

[Harry]

sorry...i'm not of much help.
..am using 100 MBit FD ...enough power.
i also have an 11 MBit WLAN... but would not dream of
trying to stream over that *g*.

it would surely be interesting to measure the throughput of
the liveTV stream.

cheers
Harry

[tivi]

Thanks for feedback, Harry.

I will do some testing, then I'll post again.

Can throughput be measured by console?
Is there a prog I could install?


THX

tivi

[Harry]

hmm...
i've never been tempted to measure throughput under Linux....
but one of these might be of help:
http://www.netperf.org/netperf/NetperfPage.html
http://www.pcausa.com/Utilities/pcattcp.htm
http://dast.nlanr.net/Projects/Iperf/
...there are many more.

it might be a little tricky though to measure between a server
and an MVP (->cross compiling needed)
but with any other client on your WLAN .. it shouldn't be a problem.
it should also work for unidirectional measurements.

cheers
Harry

[Chris]

I think this is the classic long running problem of the packet size used to send data to the MVP. The MVP's network chip is incapable of handling packets larger than 2-4 KB so vomp now sets it TCP receive window to 2 KB. This might be causing networks that can't get a lot of small packets through to fail to deliver enough data, even though the bandwidth numbers say they should. I will look into adding an option in the client for the next version to use a 2 KB receive window or say a 10 KB, or whatever a reasonable upper limit might be. Logically a larger packet size will fail and cause collision but we're not really dealing with a logical product here.

[Armin]

Hi,

that would be fine, thank you Chris.
I have the same problem when I use my Ehternet Bridge with MVP.
Sometimes my live tv or my records do not get enougth stream. When I view records, press the pause key for 2 seconds, after then in most of the records I have no problems. But there are some records with higher bitrate where this also failes after some more seconds.

Thank you!

Armin from (now) ice-cold germany

[tivi]

@Harry

Big THX for taking time! will test.....


@Chris

That would be great! Thank you!

BTW. I did an analog capture with 10Mbit/s videostream + 224kBit/s audiostream. The clip was about three minutes.
Served it to MVP by gbpvr without any problems.... Just to test my wLan.....

bye!

tivi

[argonaut32]

Hi Chris,

the new version of VOMP client and server 0.2.0 is gorgeous ! Thanks a million for the great work.

Since quite some time I have problems with stottering life TV and recordings via WLAN and I even had to switch
back to mediamvp vdr plugin because I was not able to watch any recordings without serious stottering.

But with version 0.2.0 all these problems are gone now since I realised that
it is now possible to adjust under "Advanced options" the TCP receive window in the client.

Boldly go where none has gone before I just set the TC receive window to 65565 ! Unfortunatly VOMP crashed
after accepting the settings.
So I loaded the dongle.bin once again and realised that now VOMP was showing 65565 as actual TC receive window.

Now I started to test my recordings and life TV and did not experience any stottering during playback nor when
watching Life TV via WLAN.

Thanks a lot that was great work well done. 

Best Regards,
                     argonaut32

[Chris]

I'm glad it now works for you. Just why it works can remain a mystery - packets that large over any network ought to screw up the MVP, but heh, whatever works. Also, it's amazing what bugs can be introduced in such a short time. I swear I tested every option on that menu including 64k, but now it crashes. I have added it as a bug to the SF tracker... it will be fixed in the next dongle.