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Video calls bandwidth calculation RRS feed

  • Question

  • Hi,

     

    we have a couple of sites distributed all over the world and connected via MPLS links with limited bandwidth. Does anybody know how to calculate required bandwidth for one site if there are X users. They would like to use video+voice?

    Thanks in advance. 

    Thursday, January 17, 2008 2:52 PM

All replies

  • Each audio stream uses 45 Kbps and each video stream uses 300 Kbps.  To calculate bandiwdth required, just multiply those numbers times the number of concurrent streams.

     

    There are the maximum numbers for full fidelity.  The RTAudio and RTVideo codecs and self-adjusting to the network conditions.  When bandwidth is degraded, the video stream is downgraded first to preserve audio quality.  If necessary, the video stream will be stopped completely to preserve audio.

     

    Thursday, January 17, 2008 3:06 PM
    Moderator
  • You should plan 57 Kbps for Audio and 320 Kbps for Video.

     The QoE document lists 45 Kbps for RTA-WB, but that does not include Ethernet or SRTP overhead.

    OC 2007 client uses RTAudio Wideband encoded at an average bit rate of 29 kbps in 20 ms packets. By default OC 2007 calls are encrypted using SRTP, the per-packet overhead is approximately Ethernet II =  14 byte header + 4 byte footer, IP = 20 byte header, UDP = 8 byte header, RTP = 12 byte header, SRTP = 12 byte footer. These numbers are the typical size for these headers.

     This results in 70 bytes per packet overhead per packet sent.  With payload at 29 kbps at 20ms packets, the average network bit rate for a fully utilized voice channel in a point to point call is:

    (70 [bytes/packet] * [8 bits/byte] * 50 [packet/s]) + 29000 [bits/s]  = 57 kbps

    In the web conference scenario with Round Table device, each user will consume 320Kbps for  Active Speaker, 320Kbps for paranomic video and 48Kbps.for Audio.......In Audio and Video conference, Audio codec is Siren so the bandwidth requirement for Audio is a little bit less.

    Friday, January 18, 2008 2:06 AM
  • Thanks for replies.

    The total required bandwidth will culculate as Number_of_users*bandwidth_per_video_stream. But if we install something like "dustribution server" at each site(local users will use this server instead of main) and these servers will be connected to main server via WAN will it mean that 
    Total_bandwidth=Number_Distr_servers*bandwidth_of_one_video stream. Is it correct?

    Thanks in advance.


    Friday, February 8, 2008 11:34 AM
  •  

    Here are some calculations I have used.  Similar values provided by the other posts; however the 300KBps is only video stream single direction.  Bidirectional video consists of two streams..

    The following formula can provide rough bandwidth consumption estimates for conferencing with Audio / Video.

    Note:  Calculation results will be displayed in Mbps

    CC = Concurrent Conferences

    PPC = Participants Per Conference

     

    Conference Type

    Bandwidth Consumption Mbps

    Audio with Application Sharing

    (((CC * PPC)*14KBps)+((CC *PPC)*90KBps))*10^-3

    Audio and Video

    (((CC * PPC)*14KBps)+((CC *PPC)*600KBps))*10^-3

     

    Tuesday, March 25, 2008 10:06 PM
  • Andrey,

    Did you ever get an answer on this?  I am doing the same thing (distributed servers) and would love to know if it cuts down on the amount of video streams across the WAN.

     

    Tuesday, August 26, 2008 8:12 PM