Wireshark-users: Re: [Wireshark-users] Bandwidth calculation
From: "Anders Broman" <[email protected]>
Date: Fri, 12 Mar 2010 20:17:55 +0100

 

 


Från: [email protected] [mailto:[email protected]] För Salvatore Frandina
Skickat: den 12 mars 2010 19:38
Till: [email protected]
Ämne: Re: [Wireshark-users] Bandwidth calculation

 

Hi,


I'm still trying to calculate the bandwidth. I have a problem with the video bandwidth values. The audio bandwidth is correct. G711a requires 64 Kbps Bit rate and 87.2 Kbps Ethernet bandwidth (27% overhead) as reported here http://www.voip-info.org/wiki/view/Bandwidth+consumption.
For video I use H263p and H264. The picture format is CIF with a fps = 1 and profile 4:2:0 so the total video bandwidth without compression is about 355*288*8*1 + 176*144*8*1*(2) = 1.25 Mbits.


I know that H264 codec can reduce the video bandwidth up to 50-60 kbps and 70-80 kbps Ethernet bandwidth. H263p is wore than H264 about 2 times so requires 140-160 kbps Ethernet bandwidth.

I have analyzed with Wireshark 1.2.6 RTP->stream analysis the RTP flow. I have taken in account the six column IP BW with Matlab and I have extract the PDF function. The mean and max bandwidth values are very high respect how I'm expecting. For H263p 343 kbps and 555 kbps...

I’m not sure what you mean by profile 4:2:0

ITU H.263

X.4 Levels of performance capability

:

3) Level 30 Support of CIF, QCIF and sub-QCIF resolution decoding, capable of operation

with a bit rate up to 6·(64 000) = 384 000 bits per second with a picture decoding rate up to

(30 000)/1001 pictures per second.

4) Level 40 Support of CIF, QCIF and sub-QCIF resolution decoding, capable of operation

with a bit rate up to 32·(64 000) = 2 048 000 bits per second with a picture decoding rate up

to (30 000)/1001 pictures per second.



In the video CSV files of Wireshark I see a lot of incorrect timestamps while in the audio CSV file there are not of these values.

 

Where could be the problem?

See my previous answer:

The RTP Analysis is designed with voice in mind, time stamps and marker bit is used differently in

Voice and video I think. For video the marker bit is set for the last packet belonging to the same

Picture and the timestamp will be the same for all packets making up one picture (if memory serves).

 

 

Thank

 

NB Wireshark calculates IP bandwidth it should be lower that Ethernet bandwidth

 

 

-- 

_______________________________________
Salvatore Frandina
website: http://frandinas.altervista.org
mail: [email protected]

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