FAXING with VoIP?, uncompressed VoIP?

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paradoxsm

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Topic # 7356 8-Apr-2006 14:20

Does anyone know of a good email-fax system available in NZ? Obviously Faxing does not work over VoIP. or any possibility of getting a NZ based "fax number" which then email to me. (I'm using Vodafone Faxmail but callers pay mobile charges)

another Q
Does anyone allow VoIP using uncompressed 64Kbps audio? (as per standard landlines) rather than the current Vocoders?

sbiddle

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Reply # 32575 8-Apr-2006 15:37

iTalk appears to offer some form of fax support, there have been people who say it works fine and others who have had trouble. I'll try and find out some more details for you.

MattD

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Reply # 33077 16-Apr-2006 10:15

I have been able to send faxes but unable to receive. At the moment not an issue as retain one land line.
Does anybody have any experience with T.38 or FoIP, that would like to share findings?

Curly

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Reply # 34058 26-Apr-2006 22:03

why would you need towo data cards ?
I thought they were unlimmited data ??

Curly

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Reply # 34061 26-Apr-2006 22:05

iTalk appears to offer some form of fax support, there have been people who say it works fine and others who have had trouble. I'll try and find out some more details for you.

where do we find out about the italk fax service ?
I've been using italk voice with 3x lines for 6 months now and its great

Fraktul

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Reply # 34217 28-Apr-2006 16:48

If you used g.711 and had a low jitter and reasonable latency to the softswitch in question it should work, or just use t.38 as other have pointed out

Curly

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Reply # 34219 28-Apr-2006 17:14

If you used g.711 and had a low jitter and reasonable latency to the softswitch in question it should work, or just use t.38 as other have pointed out
whats g711 and t38 ???

Fraktul

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Reply # 34224 28-Apr-2006 17:34

Codecs. Normally when I dont know what something is I try looking it up in wiki/foldoc/google first as they usually have a far better definition than some fob from a forum :P

They are both codecs, g.711 is uncompressed pcm, the stuff you used in a normal digital PSTN. t.38 is a codec designed for transporting fax over ip as VoIP codecs dont treat the fax modulation scheme nicely.

paradoxsm

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Reply # 34254 28-Apr-2006 23:33

I had researched some more since I last touched this....

G.711 has 10ms frame length with 64kbps bit rate; This is uncompressed PCM, just like a standard landline. Fax capable
G.722 has 10ms frame length with 64kbps bit rate; Another implemetation of uncompressed Landlibe PCM Fax capable
Compressed CODECS

G.726-32 (also referred as G.721) has 10ms frame length with 32kbps bit rate; V Good, Sounds like Vodafone 3g, Data/fax does not work
G.728 has 2.5ms frame length with 16kbps bit rate; Handleable, Quite cellphone like, Data does NOT work.
G.729 has 10ms frame length with 10kbps bit rate; OK, No fax, Impossible
G.723 has 30ms frame length with either 5.3kbps or 6.4kbps bit rate. Actually sounds good though robotic. No fax. No way
iLBC has 20ms or 30ms frame length with 15.2kbps or 13.3kbps bit rate; Very dated CODEC.

iTalk supports the high uncompressed bitrates and sounds fantastic.

FYI...Fraktul.. We are hardly "FOBS" here... We probably know as much or actually are the guys who UPDATE Wiki with it's relevant info.

Fraktul

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Reply # 34261 29-Apr-2006 02:34

Frame length is a strange term measured in ms from a networking background. I know they use this, just IMHO would rather use sample length.

Anyhow. Sample length/frame length is actually variable per codec on some of them (maybe all, not sure). Plenty use 20ms for g.729 for example.

Also to reduce overhead you can specify for example waiting for two 'sample lengths' before generating an Ethernet frame to reduce overhead slightly. Grandstream have this in a voiceframe per TX option I know however I am not 100% sure other vendors support this.