NEC 2000 IPS Plays distorted Music, but Clear Voice

[MoHGurue]

Hello Yall,
One of our clients is using an NEC 2000IPS PBX. We have a Message on Hold Player attached to this PBX through the MoH port. Here is the issue we are having:

1- When placed on hold, we can hear the "voice" portion of the Message crystal clear
2- However; the "Music" portion of the message plays distorted and staticy

We tried different sample and bit rates, but it is always the same. The client is using AT&T IP Flex service. Does anyone know what the solution is to this problem?

Thank you for your tips in advance.

Ollie
Spectrio, LLC
800-584-4653 ext 6440

 

[MoHGurue]

Another question:

Does the NEC 2000 IPS have the ability to store and play MoH audio files internally? If so, what is the supported file format, and is there a maximum audio file size limit?

Thank you again

Ollie

 

[belevedere]

IP phones have the capability to have their own MOH. Each phone would have to be set up individually. There are documents on the NTAC web site on how to download the music files. TDM phones cannot do this. They rely on the central MOH source.

 

[MoHGurue]

The client does not believe his NEC 2000 supports storing and playing MoH audio files internally. Would anyone be able to confirm that? Here is what the client is saying:

"Unfortunately, most of the early PBX models did not fully support VoIP. They also typically did not support flash memory or USB devices. Most only had ROMs, EPROMs or EEPROMs back then, which could only be updated (on a limited level) at the command line or via a ROM Burner or by purchasing a replacement. I believe this to be the case with ours. It is a fairly old NEC 2000 system, which was upgraded to IPS several years ago by our inside phone contractor."

If that is the case, then does anyone know why the MoH plays clear during voice playback, but sounds distorted during "Music" playback and how to correct this issue? Again, the client is using AT&T IP Flex service.

Thank you

 

[OzzieGeorge]

Ok so firstly have you actually put a test phone across the jack of the music player to make sure it's output is clear? secondly are you using SIP trunks and if so what compression are you using as some compression codecs are designed for voice only and struggle with music (I would have to read up which)!

 

[3racefan3]

On the CPU there is the Variable resistor wheel that adjusts MOH you can try to adjust it and see what happens, it has helped me in the past. It is below the MOH jack on the CPU.

 

[MoHGurue]

Thank you both for the tips, I already notified the client about both of your tips and I will post his reply as soon as I get it

Thanks again

 

[OzzieGeorge]

Ok so I checked and if you are using g728, g729 or g729a you will have issues with distorted music as the codecs use a sort of human voice cookbook to achieve the compression rates and it is a known problem with music and more specifically music on hold! Problem is that if it passes through any link using these codecs, you will experience this problem (sometimes it can be so bad all you hear is a hissing)!

 

[MoHGurue]

Thank you so much for the info OzzieGeorge, that definitely describes the issue. Is there a fix for this issue?

 

[MoHGurue]

I have a couple more question, and please forgive for not being that familiar with the NEC phone system:

1- What does "G728, G729 and G729a" stand for? Is that an add on card, a firmware, hardware platform...etc.?
2- Where would the client look for it on the phone system to confirm whether they have it or not?

I need to be able to describe it to my sales team so they can ask the client the right question in order to identify NEC systems that will fall into these three categories. This way we can tell the client in advance about the "Music distorsion" issue and let them make up their own minds...Unless there is a known solution to this issue by now!

Thanks again

 

[belevedere]

G728/729/729a are compression standards in the data/IP world. Do an internet search on them. They have nothing to do with a specific phone system. Each manufacturer strives to meet the standards so they are compatible with each other.

 

[OzzieGeorge]

Unfortunately this is a consequence of the Voip era. in order to gain clear speech with the minimum of bandwidth useage people are using these compression codecs and they do make massive differences to the amount of bandwidth required for very small degredation in speech quality. however they are designed for use with voice and not music. They use a codebook to predict the changes in speech but can't predict the changes in music (some use as little as 2 bits to indicate the change from the preceeding information) and most people don't consider music on hold when deciding on using compression. Add to that the possibility that the carrier may use compression over some links and you actually lose control of the quality of your music on hold. The best you can do is make the customer aware of the issue and let them decide on whether they want to pay for increased bandwidth.

There is a place in the system programming where you can check the compression codec being used but off the top of my head I can't tell you where it is as I don't work on many Voip systems. Belvedere may be more conversant with this.

 

[MoHGurue]

Thank you so much for your reply, now I know. AT&T confirmed that the client has the following: PRI with 2210 Ohms at g729 compression and fail-over to g711. AT&T is recommending the following audio file format: PCM, 8kHz 16-bit, mono

It is harder said than done, because most MoH players require a much better audio file format in order to sound good. I'll have to experiment with a few units and different format to see if I can come close enough. AT&T said their IP Flex requires the G729 compression standard, so they won't do anything for us.

If anyone knows of a workaround, I would really appreciate you letting me

Thanks again

 

[belevedere]

Command 6700 combined with those listed below deal with adjusting codecs. Note that at default all of the location data is set to 00, so you may not have to adjust all of the listed commands.
CM42
CM12 Y=39/50
CM8A Y=5000-5255: 173
CM0A Y=09
CMAD Y=29

 

[OzzieGeorge]

Ok so I have to admit first off that I am really technically out of my depth here as I don't do much NEC voip (I changed jobs to a Mitel company around the time NEC started bringing in Voip) however I believe the NEC can negotiate the preferred codec and you put them in against the item using the codec. So you can for example tell an extension or a line that normally it will use g729a but if it connects to an item that can only use g711 then it will switch to that! So if you put your lines as g729 as required but then set the second option to g711 then only give the MOH source permission to use G711, they should use g711 and as the carrier says they have failover to g711 this may rectify the problem.

Again I have to add the rider that this is just my understanding of the way this works and I have no direct experience of it, I will defer to others to confirm this is the case. However you need to understand that this will impact on the customers bandwidth useage!

 

[mikibri]

Analog trunks will fix it

 

[Billz66]

I agree with ozzie , sounds like you have a E1/T1 connected to an IAD (AT&T) which is then compressing to g729)

I suspect the only fix is to get them to provide it as uncompressed g711 , (they wont like it as it will use more bandwidth).

To confirm it
Is the distortion only noticeable on trunk calls?
Are there TDM phones connected to the Main site where the MOH is connected - if so if 2 of these call each other internally and one puts the other on hold is it distorted.

If the MOH is working internally without distortion then its most likely a carrier issue.

If I never did anything I'd never done before , I'd never do anything.....

 

[MoHGurue]

The music distorsion is heard only one a caller is placed on hold when they call. The voice portion of the message sounds crystal clear, but the music that plays between the voice announcements is the part that plays distorted. The whole audio file (music and voice) was stitched together as one audio file. We tried loading music only with different format, but the music always played with distorsion.

I forwarded your reply to the client for accurate answers. I'll post as soon as I hear back

Thank you so much for your thoughts

 

[OzzieGeorge]

Am I correct in assuming your company supplies the music on hold and does not maintain the system?

If this is the case then you or your customer needs to contact both NEC and the carrier. You need to know if the carrier's trunks can switch to g711 as needed and you need to check with NEC if my suggestion that setting the MOH source to g711 only and allowing the trunks to switch as needed will work (I am fairly sure it will). If you get a yes to both then the problem is solveable. A no to either will necessitate a rethink of the customer's configuration!

 

[MoHGurue]

You are correct sir, we are the MoH provider, we do not manage their phone system, or their service with AT&T. We have been working with their IT team who has been working with their own phone vendor. I have been passing every single tip from this forum to them

Thanks again