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Poor quality music on hold on external calls - SV9500

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phadobas

Technical User
Jul 30, 2005
607
US
I have an SV9500. It has 3 PIMs for some analog line cards and PRI cards, and otherwise the terminals are 90% IP terminals. The music on hold is played by an MP3 player and its output is punched down on the EXT/ALM cable.

On internal calls (IP-to-IP or IP-to-TDM) the music plays just fine. However on external calls, be it incoming or outgoing, which are handled by different routes and different telco-s, the music gets distorted. There are sections of the music that are playing OK, and other sections are just a distorted mess. It's alwaus the same sections that are distored.

Those incoming / outgoing routes have been handled by the same teclo and the same PA-PRT cards. I just did one more round of tests and actually noted that the problem occurs only if the external caller/called person is using a cell phone. If the external person is on a landline, the music sounds clean.

So I have:
MUSIC - TDSW - IPPAD card - IP phone - IP phone: sounds great
MUSIC - TDSW - PA PRT Card - Telco - landline: music sounds great
MUSIC - TDSW - PA PRT Card - Telco - mobile used: music is a distorted mess

Anybodo has any ideas?
 
Sounds like you may be a victim of VAD - Voice Activity Detection. If set on a VOIP connection, a router won't transmit RTP unless audio is detected. Could you turn up the source volume and see it it makes a difference, at least for a test?
 
I did increase the volume for testing, but unfortunately it didn't solve the problem. The music got louder and the distortion got louder.
 
With it apparently affecting the same sections of audio, only on cellular calls, my next thought would be a frequency problem, that is an inability for a cellular network to replicate those frequencies. What is particular about those audio sections that is not true of the good audio sections? Have you tried other music/audio? With it affecting only cellular calls, there aren't many things you can change to affect it.
 
I would try converting mp3 files on the player to 8-Bit, 8Khz, WAV file. Assuming their player can handle .wav format
 
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