Poor quality of audio files played by Asterisk - any idea

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darius
Posts: 8
Joined: Tue Jun 29, 2010 2:38 pm

Poor quality of audio files played by Asterisk - any idea

Post by darius »

re. Poor quality of audio files played by Asterisk via Celliax audio channel to a sound card -> headphone - any idea


The following wav file is audio stream coming from Asterisk, playing standard config files via Celliax audio channel to a sound card, saved in wav audio format by Audiocity.

Asterisk Celliax audio recorded by Audiocity in .wav file format

http://www.sendspace.com/file/nk6tb6

Please play the above wav file and tell me if such audio stream can be repaired by GoldWave to get clear sound, no echo.

I have already contacted developers of Oslec - echo canceller.

Thanks

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DougDbug
Posts: 2071
Joined: Wed Feb 16, 2005 3:33 pm
Location: Silicon Valley

Re: Poor quality of audio files played by Asterisk - any ide

Post by DougDbug »

:( I don't think GoldWave can help you...
...recorded by Audiocity...
I assume you mean Audacity? ;) The tools & features in GoldWave are somewhat similar to Audacity. GoldWave doesn't have an echo cancellation tool, and AFAIK, Audacity doesn't either...

I don't hear echo during the talking part, but I think I hear drop-outs. Do you have some echo cancelation enabled? I'm wondering if the drop-outs are the result of over-agressive (or malfunctioning) echo cancelation? I don't believe there is any software that can fix drop-outs... The "data" is missing.

I think I hear echo during the music, but I don't know what the music is supposed to sound like.

I don't know much about echo cancellation... I just know it's very common in telecommunications, and I have a vague idea of how it works... Hopefully someone here knows more than me...*


* You can also try posting your question on the HydrogenAudio.org forum. There is more activity on the Hydrogen Audio forum, and there are people with knowledge in many different audio specialty areas, and with knowledge of various audio software.
darius
Posts: 8
Joined: Tue Jun 29, 2010 2:38 pm

Re: Poor quality of audio files played by Asterisk - any ide

Post by darius »

[misquoted text removed]
==

Thanks DougDbug,

thank you very much for your kind reply.
Sorry for my typo in Audacity.

I have contacted Steve and David, developers of Oslec echo canceller for Linux, ported to Windows.
For echo canceller to work 2 signals should be compared and processed, tx and rx (I suppose so).
In case of recorded audio file or live audio stream to get echo removed,
one have to use pass-through adaptive filter, to let it learn in interactive mode, what echo pattern is ( signal level drop, echo interval or alike ) ( I suppose so).

So your reference to CD, DVD mastering is a good idea, as premastering involvs audio input filtering, processing.

In the meantime I am trying to learn what wav audio formats ( bitrate, frequency, single or dual , mono or stereo)
can Astersk play using its audio codecs

Ok. I have listed Asterisk installed audio codecs with
show audio codes command
as
g723, gsm, ulaw, alaw, g726, adpcm, slin, lpc10 g729, speex, ilbc

but need more detailed specification on wav file format to be played by Asterisk.


Mazzic just responded:

"
Basically the wav files are a mono, 8000Hz sample rate, 64 kbs.

http://wiki.kolmisoft.com/index.php/Con ... ble_format
"

So I am home.

Playing sample audio files ( one frequency peak level) more can be discovered soon about
true reasons staying behind the sound quality.

FFT should generate resonance frequency chart (I suppose so).

thanks

Darius
abhilash
Posts: 1
Joined: Fri Aug 27, 2010 5:58 am

Re: Poor quality of audio files played by Asterisk - any ide

Post by abhilash »

Are you people saying there is nothing which could be done possibly to solve this issue?. I had this same problem and thought it could be rectified somehow.
Regards
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DougDbug
Posts: 2071
Joined: Wed Feb 16, 2005 3:33 pm
Location: Silicon Valley

Re: Poor quality of audio files played by Asterisk - any ide

Post by DougDbug »

Are you people saying there is nothing which could be done possibly to solve this issue?
Echo? Right, there's nothing you can do. :(
I have contacted Steve and David, developers of Oslec echo canceller for Linux, ported to Windows.
For echo canceller to work 2 signals should be compared and processed, tx and rx (I suppose so).
He's saying that in order to cancel the echo, you need the pure signal without the echo. If the echo is being generated on the phone lines, then it's possible to "capture" the pure signal before the echo gets mixed in. But, that doesn't help us... If we had a file without the echo, we wouldn't have a problem! :D

A lot of things just can't be fixed. That's why professionals use good equipment and good talent in soundproof studios, and it's why most movie dialog is re-recorded in the studio.
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Re: Poor quality of audio files played by Asterisk - any ide

Post by GoldWave Inc. »

I believe abhilash is a spammer. His post is vague enough that it could apply to almost any topic. I've deleted the name of the company he is trying to advertise in his signature.

Chris
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