What is CBR (Constant bit rate),VBR(variable bit rate) and ABR (available bit rate)?

[tarakapraveen]

What is CBR (Constant bit rate),VBR(variable bit rate) and ABR (available bit rate) ?

How to differentiate those three?

Whether video comes under VBR or CBR ?

Thanks in advance,
Goud

 

[III]

CBR,VBR and ABR?

Well this came from ATM (Asimetrical Transfer Mode) This transfer mode like MPLS allowed for QOS.
in CBR the ATM swich reservs a constant amount of data for the trafic,
VBR - variable bit rate there is no constant bit rate availoble to a switch, if the trafic is low a user can get more bit rate, and if the trafic is high less.
ABR - averidge bit rate not availoble Well in ABR the QOS offered to the end user is an averidge usualy between a maxiun and a minimun bit rate this is simular as VBR but here the QOS is deffined better.
As for video, well in the begining of mpeg1 it's use to be defined for use in digital systems like atm, ant thet's where it's name comes from.
CBR - definative file size variable qualati
VBR - definative qualaty variable file size
ABR - something in between as the file size and the qualaty are defined with in reasnoble borders.

 

[mkhan]

Re: CBR,VBR and ABR?

Hi, in Telecom terms

CBR - Constant Bit Rate (For example a speech codec G.729 can work as all these three)

VBR - Variable Bit Rate (different BR for different applications for example for voice 8kbps and for CD 44.1Kbps)

ABR - Adaptive Bit Rate (again the example of G.729 whose algorithm is CS-ACELP i.e. conjugate strucutred algebraic code excited linear prediction)

or GSM codec is ABR as well, right now i cant remember its number and algorithm in my mind but it works on 13 Kbps (I m not sure about its BR, bro).

Hope this will help you.

Arif Khan

press helped me