MoH poor quality

Discussion in '3CX Phone System - General' started by schmooot, Sep 7, 2011.

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  1. schmooot

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    I've made up some Music on Hold files for the very limited system...eagerly awaiting some simple genius work from the programmers :eek: . Anyways the files sound great on my machine, they also sound fine when I upload into the repository and preview them through the management console (it sends the file to a line and I can answer and listen to my onhold music) Clear and crisp and an appropriate volume (I have reduced the volume of my tracks by quite a bit because the system feels the need to amplify them to an ear-splitting volume)

    However when actually using the hold music it comes through horrible. It is scratchy and super low volume and its volume fluxuates constantly.

    Is this an issue with my files? (Note they are identical to the sample wav provided in all aspects like sample rate and bit per sample)
    or is my gateway configured improperly? codec issue maybe?

    Again it works fine from the management console to the phone but actually out over the air it deteriorates significantly.

    Any ideas?
     
  2. schmooot

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    Nevermind I managed to get it working reasonably well

    http://www.3cx.com/forums/music-on-hold-workarounds-and-tips-v8-x-13580.html?highlight=music+on+hold#p75747

    I followed this guy's advice about using high and low pass filters and cutting everything above and below certain frequencies. Seems to have cleaned it up quite a bit.

    Thanks for that anonymous guy
     
  3. captivateglobal

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    It's a common problem when using WAV files as a base for music on hold, since WAV is only a waveform representation which doesn't contain info about the actual volume (dB), just a sort of 'reference' to how loud the part should be (like 0 to 100%, the 'wider/taller' the waveform the louder it is). So first of all, check that your waveform has enough amplitude by opening it up in some kind of WAV editor (there's a decent free trial one called WavePad you could try). If the waveform doesn't expand to about 80-90% of the field, then run a normalize operation.

    After that, make sure that you downsample the wave file correctly. When taking a file from CD, the original waveform is 44100 16-bit samples a second - what you want is 8000 16-bit samples a second. Obviously there's a major amount (try 36000 per second) of 'extra samples' to throw out, and the downsampler will not know what from what, so it will just throw out every Nth sample.

    Make sure it gets the samples it wants by cutting off high and lows (you want a bandpass, basically, between 250hz and 3khz for voice recordings, probably 200Hz to 8khz for stuff with music backgrounds). Depending on the production samples and voices used those could vary - but as a general rule shave off <200hz and >8khz as most stuff outside those ranges can't be transmitted down a phone line.

    Also, when downsampling, use a dithering downsampler if you have one available (should be a checkbox in the GUI if available). This will result in less 'noise' which translates to better quality on the line.

    Finally, make sure your original production/recording is done in 8000hz 16-bit signed linear PCM. If you must rip a cd, make sure it outputs at that quality. That will sort most issues to begin with.

    As always though, if you're doing this for a business you should look at getting professional services. While 3CX v9 doesn't support a digital player setup, most MOH companies will provide you with a wave file you can load in - and you can specifically request they produce it with that format.
     
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