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  1. #1
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    Change codec from EVRC to 13k Vocoder for better call quality

    This was mentioned briefly in one of the "slot cycle" posts but I felt that it deserved a thread of its own.

    By default the codec used is Enhanced Variable Rate CODEC (EVRC). I believe the bandwidth on EVRC is 8kbs. By switching to the 13kbs Vocoder, call quality is theoretically better.

    As taken from wirelessadvisor:

    The 13kbps vocoder catches more of the nuances of a person's speech and generally sounds a good bit better, but when there are errors in the bit stream it makes people sound robotic. The 8kbps EVRC codec is more efficient, but looses a lot of the nuances of speech. It is better at handling bit errors so it doesn't make people sound so robotic or create the drastic shifts in tone that the 13kbps one does, but it does introduce the digital hiss that you hear in the background (it sounds like running water digitised at a very low bit rate) and when things get bad it drops frames (rather than creating such a dramatic shift in the speakers tone).

    That being said, it appears that EVRC handles/keeps calls better in low-signal areas.

    In case you wanted to change to 13k Vocoder:

    1. Dial **772
    2. Enter the Service Code 000000 (six 0's) and tap OK
    3. Push the directional pad down until you see a screen that says:

    SVC Mode NAM1
    End of BASIC NAM
    EXIT

    4. Push the directional pad right so that "Exit" bacomes "More"
    5. Press the action button (middle of directional pad) to enter the additional settings menu.
    6. Press down 1 time to get to the screen that says:

    SVC Mode NAM1
    Orig. SVC OPT
    EVRC

    7. The default is set to EVRC. To change to 13k Vocoder press right on the d-pad once.
    8. Then press the action button once to save the change.
    9. Finally, press the left soft key "Exit" to exit the service menu.

  2. #2
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    can anyone else confirm this?

  3. #3
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    The directions work, but I have yet to see whether it made a difference or not

    anybody know what all that other stuff is in the service menu?

  4. #4
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    Unlike the 730, 13k on the 760 makes a big difference. Callers tell me I sound very clear and they can't tell if I'm in a noisy environment. Callers sound much clearer to me as well.

  5. #5
    "WM2003SE fanatic..." RedBaronK's Avatar
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    Mrailing? superdave? can someone confirm this? Sometimes my calls get really echoey and this would be great if it works without any downfalls like affecting internet download speed etc....
    Mr. Belding's on speed dial #3, right after Screech.

  6. #6
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    Perhaps it is your calling area. I've had no problems with 13K in Dallas, Houston, or Miami. But Charlotte - do those people even use cell phones???

  7. #7
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    Smile

    Quote Originally Posted by eneltex View Post
    Perhaps it is your calling area. I've had no problems with 13K in Dallas, Houston, or Miami. But Charlotte - do those people even use cell phones???
    Yes, we do-Thank you very much. It's turn signals we don't use.

  8. #8
    Audio Gun For Hire HaoDaMao's Avatar
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    Hi all,

    I had a few open hours at the lab yesterday (I do audio and telecom work), I ran some PESQ (perceptual sound quality) measurements on the i760 with the standard CODEC and the 13K CODEC.

    The standard codec scored a 2.7; note that a typical wired landline is a 3.0, a good GSM is around 2.8, and a good CDMA is a 2.7. So we're right where it should be.

    The shocker was the switch to 13K; the PESQ score rose to a 3.2! So barring any issues with the network (echoes?), you should definitely use the 13K CODEC - it sounds better to my ear, and definitely measures better, pushing near wideband VOIP (3.5).

  9. #9
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    Quote Originally Posted by HaoDaMao View Post
    Hi all,

    I had a few open hours at the lab yesterday (I do audio and telecom work), I ran some PESQ (perceptual sound quality) measurements on the i760 with the standard CODEC and the 13K CODEC.

    The standard codec scored a 2.7; note that a typical wired landline is a 3.0, a good GSM is around 2.8, and a good CDMA is a 2.7. So we're right where it should be.

    The shocker was the switch to 13K; the PESQ score rose to a 3.2! So barring any issues with the network (echoes?), you should definitely use the 13K CODEC - it sounds better to my ear, and definitely measures better, pushing near wideband VOIP (3.5).
    It makes sense but yet I had no idea there was science behind perceptual sound quality. Awesome to have sound expert among us.
    Thanks
    - Andrew - PDAPhoneHome.com

  10. #10
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    Quote Originally Posted by HaoDaMao View Post
    The standard codec scored a 2.7; note that a typical wired landline is a 3.0, a good GSM is around 2.8, and a good CDMA is a 2.7. So we're right where it should be.
    Unless I'm mistaken, PESQ is analogous to the older MOS scores, which ranged from 1-5 in value. PESQ recognizes that nobody gives out 5's and caps at 4.5, but is otherwise identical. The average MOS score for a land line is a 4.0, not a 3.0. That's more in keeping with the average for cell phone conversations (you'll notice you can just about always tell.

    There are other PESQ scoring algorithms out there, so it's entirely possible that this isn't an accurate commentary.

    The shocker was the switch to 13K; the PESQ score rose to a 3.2! So barring any issues with the network (echoes?), you should definitely use the 13K CODEC - it sounds better to my ear, and definitely measures better, pushing near wideband VOIP (3.5).
    And this score confirms the above in my mind. VoIP typically is rated (on average) anywhere from .25-.5 lower on the MOS scale.

    But that result isn't surprising. The increase in bandwidth is probably due to less aggressive silence suppression and compression, which results in less clipping and can shorten latency (by not compressing, you save a few cycles). In VoIP parlance, nothing is equal in terms of overall quality to G.711, which is the 64Kbps payload used on voice ISDN lines. Others get close, but codec selection has a major impact on quality.

  11. #11
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    I might be missing something really basic, but when I dial **722, a voice comes on and says the call cannot be completed.

  12. #12
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    Quote Originally Posted by eleazar View Post
    I might be missing something really basic, but when I dial **722, a voice comes on and says the call cannot be completed.
    don't actually press the send key - just enter **772 and the quoted menus should pop up automatically. did for me anyway

    also, not sure if you made a typo in your post, but you wrote **722. the original post indicated it should be **772 (two sevens, not two twos)

  13. #13
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    Quote Originally Posted by eneltex View Post
    Perhaps it is your calling area. I've had no problems with 13K in Dallas, Houston, or Miami. But Charlotte - do those people even use cell phones???
    Are you serious? NC is the research capitol of the planet. We have more PHDs and MDs than anywhere... This state is not techno starved, we were one of the first areas with Rev-A.

    Speaking of research, you should learn to do some before spouting off stupid comments like that one.

  14. #14
    Peanut Butter eldersoul's Avatar
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  15. #15
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    so the consensus is that if you live in a decently populated area, switching would be worth your time?

    can anyone else confirm the better quality?

  16. #16
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    I don't know if that's the consensus, but it might be worth experimenting with.

    Where you might be concerned is how Verizon reacts to the switch. Changing codecs is something they can detect and might frown upon if they don't do it in their systems, since you're consuming more bandwidth and thereby reducing the number of calls each cell site can handle. They may not care, but then again they might.

    I guess I'm saying - be prepared to blame a friend of a friend you met at a party and play dumb if they call and ask about it or send you a letter.

  17. #17
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    I too can confirm that this improves the voice quality. It actually improved on both ends for me and the "lagging" in between when sending and receiving ends is also noticeably improved as well.

    I'm no sound expert, but as a general user, this was a welcome improvement. My signal area varies from zero to full depending on whether I'm at home or at work, but in my opinion, calls have been improved regardless.

    Nice find!

  18. #18
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    Quote Originally Posted by PerfAlbion View Post
    I don't know if that's the consensus, but it might be worth experimenting with.

    Where you might be concerned is how Verizon reacts to the switch. Changing codecs is something they can detect and might frown upon if they don't do it in their systems, since you're consuming more bandwidth and thereby reducing the number of calls each cell site can handle. They may not care, but then again they might.

    I guess I'm saying - be prepared to blame a friend of a friend you met at a party and play dumb if they call and ask about it or send you a letter.
    Verizon might do something. It's to good to be ignored

    If i hear something about this I will play dumb: "I have no idea what you are talking about"

    The quality is great... ppl I talked today immediately said something like: are you on a landline? or... did you switched phones?

    I hear them better to. Maybe it's just subjective, but the lag is almost gone. The sound is somehow... smooth

    Great find!

  19. #19
    PDAPhoneHome, IL fokis's Avatar
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    I Just made the changes but I haven't made a phone call with the new settings yet. Anyone in the Chicago Metro Area confirm the improved clarity of calls?
    "If pro is opposite of con, then what is the opposite of progress?"



  20. #20
    "WM2003SE fanatic..." RedBaronK's Avatar
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    my friend in verizon asked around, and he said no one there has heard of it in the data support team.....lmao
    Mr. Belding's on speed dial #3, right after Screech.

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