13K Or Evrc Or Evrc-B

[gaurangbhartia 19]

What is EVRC ?

"Enhanced Variable Rate CODEC (EVRC) is a speech codec used in CDMA networks. It was developed in 1995 to replace the QCELP vocoder which used more bandwidth on the carrier's network, thus EVRC's primary goal was to offer the mobile carriers more capacity on their networks while not increasing the amount of bandwidth or wireless spectrum needed.[1]. EVRC uses RCELP technology, which Qualcomm claims improves speech quality with lower bit rates.[citation needed]

EVRC compresses each 20 milliseconds of 8000 Hz, 16-bit sampled speech input into output frames of one of three different sizes: full rate – 171 bits (8.55 kbit/s), half rate – 80 bits (4.0 kbit/s), eighth rate – 16 bits (0.8 kbit/s). A quarter rate was not included in the original EVRC specification and eventually became part of EVRC-B."

-Taken from Wikipedia : http://en.wikipedia.org/wiki/EVRC

Now to talk in layman's language, I will skip what are vocoders and blah blah blah and come down to the point !

Recenty, I started reading about it and found that we can use different vocoders by changing setting on the phone. You can find the settings on your phone or use QPST to change it.

Here are the advantages and the disadvantages of the different vocoders based on my testing and/or other 100s of pages I read on the internet. (I would like to thank all the unnamed people in various forums for posting their experience)

13K :

Intro :

This is an old method of coding the voice and uses 13k bandwidth.

Advantages :

Many people claim that the voice is more clearer by using this codec. Theoretically since this uses 13k bandwidth, as against 8k of EVRC, voice should be clearer and nuances of human sound should be better reproduced. Some people have also commented that although it was clearer in a quite environment, it was worse than EVRC in noisy environment as it does not have any kind of noise suppression. However, I didn't not find any significant improvement in clarity when I changed to this codec.

Disadvantages :

It does not contain any noise suppression technique, and since it is fixed bitrate, it uses more bandwidth of the operator (which means, theoretically in case all of the people change to this codec, it might create a network congestion) . In noisy environment, noise is also picked up. In case of network congestion, data gets dropped more frequently as this method does not employ a very good error correction technique. In congested areas, your data might drop more frequently if you choose this codec.

(Some very few people have commented that their signal stability has increased). Although I did FEEL that my connections were getting dropped more, I cannot be very sure as it was by an insignificant margin.

EVRC :

Intro :

This is a variable rate Codec with maximum bandwidth of 8k.

Advantages :

It is supposed to be a variable rate codec, where 0 bits are transmitted when silence is detected, therefore uses less bandwidth. This codec claims to achieve this with maintaining a good voice quality. It is also claimed that this codec has noise suppression and error correction algorithms, hence more stability. ( I did not find any significant stability increase/decrease)

Disadvantages :

The voice clarity is supposed to be lesser than that of 13K & EVRC-B.

EVRC-B :

Intro :

It is the newest method similar to original EVRC with employment of quarter rate.

Advantages :

It employs better error correction techniques and a quarter rate. Hence Voice clarity and stability should increase. It also helps achieve better bandwidth allocation for the operators. After changing to this method, I did notice that my connection was a bit more stable, however only slightly.

Note :

Please do note that the Cell tower that you are connected to CAN control your phone's settings for codec and override your settings in QPST (May or may not depending on how the operator has deployed/configured their towers)

This post is for informative purpose so that the users can try EVRC-B, and if they have any luck, it may improve their call quality.

Suggestion :

Since towers can control this setting, I suggest that you can try changing to EVRC-B. If the tower lets you use your settings, you might get a better call quality.If the tower overrides the settings, then you will not feel any difference.

However, if you are in a rural area, EVRC-B may not be deployed. Just check the settings, and if it works for you, keep it, else revert back to default.

Warning :

Please do this at your own risk. I do not take any responsibility whatsoever if anything gets spoilt !

[dkaile 1,051]

Reliance works perfectly with EVRC-B also, as well as EVRC... already tested and posted in Incredible topic...

[gaurangbhartia 19]

^

Sorry for the repost, but I dont think comparison had been done before.. ... I tested on Tata connection and posted the above....

Edited November 12, 2010 by gaurangbhartia