[Asterisk-Users] FAX, IAX and *....Maybe I'm dreaming...:-)

[Olle E. Johansson]

Tilghman Lesher wrote:

> On Friday 12 December 2003 07:25, Dan wrote:
> 
>>Hi,
>>
>>It would be great if the IAX protocol will be able to tranfer fax
>>data (even converted in another format) between Asterisk boxes,
>>using low bandwidth codecs like GSM.
>>I know that this is possible only with the G.711 now (passing faxes
>>using the audio stream), but.... maybe in the future...some native
>>support will permit this.
> 
> 
> You're not going to get that working because GSM is a lossy codec.
> It is able to get extreme savings in size, because it optimizes out
> parts of the sound that most humans don't hear.  However, that same
> bandwidth that humans don't hear is exactly the bandwidth that the fax
> application uses to transmit valuable portions of the image.
> 
> Therefore, the GSM codec is never going to be appropriate for sending
> faxes.  Besides, if you need low bitrates for your IP connection,
> you're likely to experience delays in the fax negotiation -- which
> will probably result in a failed fax attempt.  If you want to be able
> to send faxes in this way, then negotiate the fax at one end, and
> email the resulting TIFF to the other end.
Added to FAQ and
http://www.voip-info.org/tiki-index.php?page=Asterisk+fax

Thank you both!

/O