Re: [reSIProcate] rtp ringing
For the G711 ring tone - you can alter the frequencies slightly to
make the difference 100Hz,
e.g. 445Hz and 345Hz - which will give 100Hz separation and will
equate to an integer number
of 8kHz samples. From memory in the UK the frequency tolerance allowed is 5%.
I have done this in the past and it has worked well.
John
On 21/11/2007, Adam Roach <adam@xxxxxxxxxxx> wrote:
> For what you describe, a full RTP stack would be overkill. You can
> probably get by just sending your packets with an appropriately encoded
> RTP header every 20 ms. You'll also need to listen for incoming RTP
> packets and discard them. (Ideally, you'd calculate statistics based on
> these packets and generate proper RTCP; however, in practice, things
> will pretty much work just fine if you don't).
>
> Also: while what you're proposing will work _mostly_ fine for codecs
> that don't rely on prior frames for encoding (like G.711), you are very
> likely to run into difficulty coming up with a single G.729 or G.723
> packet to represent "ringing." Even with G.711, you'll run into problems
> because the standard North-American 350+440 ringback tone doesn't repeat
> neatly on 20 ms boundaries.
>
> You might try sending an RFC4733 representation of ringback (e.g., if
> you're targeting the US market: modulation = 0, volume = -6 dBm0,
> frequency = 350, frequency = 440, duration = 2 seconds; sent every 6
> seconds or so). Support for this approach may be more limited, so make
> sure you test it against all your target devices.
>
> /a
>
> On 11/20/07 10:37 AM, David Thompson wrote:
> >
> > Quick question if anyone has an idea for me:
> >
> > I have built an sbc using the reciprocate stack. (THANK YOU to all who
> > have worked on this stack)
> >
> > I want to provide my own "ringing" early media rtp for comfort
> > reasons. I know reciprocate does not offer an RTP stack but I was
> > wondering if someone could point me in the right direction on where I
> > could look.
> >
> > Basically I would already have the ringing file encoded in g729, g723,
> > g711 and would simply want to issue a 180 early media from the sip
> > stack then start transmitting the rtp in the proper codec. Once the
> > call completed I would then let the media pass from end point to
> > endpoint directly.
> >
> > Any thoughts would be appreciated……
> >
> > David
> >
> > ------------------------------------------------------------------------
> >
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--
John McBride
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