The frame size is an inherent codec capability, independent of the application
level framing protocol (like RTP, AAL2, FR, 3GPP FPs, etc).
Right, the packetization time for G.711 is basically 5 ms for short packet
technologies like AAL2, see ITU-T I.366.2.
However, you may also find proposals for < 5 ms or like 5.5 ms (e.g. in ATM-F
proposals).
For RTP I would suspect 10 ms due to the packet overhead.
________________________________
From: Jagan Mohan [mailto:[EMAIL PROTECTED]
Sent: Montag, 22. September 2008 20:32
To: Schwarz Albrecht
Cc: Aneesh Naik; [email protected]
Subject: Re: [Sip-implementors] Should 'ptime' value be multiple of 5
or 10
AFAIK, there is no standard which tells that the 5ms samples per frame,
need to be used for G.711 codec.
Since G.711 codec involves just sampling and quantization, its more
implementation specific.
Certain implementations of G.711 codec operate on sample intervals of
5ms. Hence, encoding of 5ms of G.711 samples in one frame. Here, ptime can be
multiples of 5ms.
Some implementations operate on sample intervals of 10ms. Hence,
encoding of 10ms of G.711 samples in one frame. Here, ptime would be multiples
of 10ms.
Thanks,
Jagan
On Mon, Sep 22, 2008 at 9:18 PM, Schwarz Albrecht <[EMAIL PROTECTED]>
wrote:
I know that 125 µs relates to the sample period, which is
however identical to the frame size in case of G.711 IMHO.
Could you provide your reference concerning the 5 ms definition?
Thanks, Albrecht
________________________________
From: Aneesh Naik [mailto:[EMAIL PROTECTED]
Sent: Montag, 22. September 2008 14:45
To: Schwarz Albrecht
Cc: Sachin Rastogi;
[email protected]
Subject: Re: [Sip-implementors] Should 'ptime' value be
multiple of 5 or 10
125 µs is not the frame size of G.711. It is the time
sampling rate.
8000 samples in 1 sec.
1 sample in 125 µs.
Number of such samples are combined to form a frame of
data.
This frame size for G.711 is 5ms.
Hope this clears your understanding.
Thanks,
Aneesh
On Mon, Sep 22, 2008 at 5:43 PM, Schwarz Albrecht
<[EMAIL PROTECTED]> wrote:
> > The frame size for g.711 is 5ms
G.711 has a frame size of 125 µs in my
understanding.
See ITU-T G.711.
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On
> Behalf Of Sachin Rastogi
> Sent: Montag, 22. September 2008 13:45
> To: Aneesh Naik
> Cc: [email protected]
> Subject: Re: [Sip-implementors] Should 'ptime'
value be
> multiple of 5 or 10
>
> Thanks Aneesh,Alex for quick reply.
>
>
> Sachin
>
> On Mon, Sep 22, 2008 at 3:03 PM, Aneesh Naik
> <[EMAIL PROTECTED]> wrote:
>
> > Yes, as explained by alex the ptime depend
on the frame size...
> > The frame size for g.711 is 5ms, for g.729
is 10ms and for
> g.723 it is
> > 30 ms.
> > So the ptime for 711 and 729 can be 10, 20,
30... and for
> 723 it can
> > be 30,60....
> >
> > -Aneesh
> >
> > On Mon, Sep 22, 2008 at 1:50 PM, Alex
Balashov
> > <[EMAIL PROTECTED]
> > >wrote:
> >
> > > There are no drafts or recommendations
mandating that ptime be a
> > > particular value because the desired
packetisation duration is
> > > closely related to the frame size and other
> characteristics of particular codecs.
> > >
> > > However, almost no media gateway equipment
out there will support
> > > anything other than the usual 10-30 ms for
the usual suspects -
> > > G.711u/A, G.729A, etc.
> > >
> > > There are certain recommendations or
mandates for ptime
> values based
> > > on particular codecs. For instance, 20 ms
is recommended
> when using
> > > Speex
> > >
(http://www.speex.org/docs/manual/speex-manual/node14.html):
> > >
> > > ---
> > >
> > > 4.1.1. <http://4.1.1./> Registration of
media type audio/speex
> > >
> > > Media type name: audio
> > >
> > > Media subtype name: speex
> > >
> > > Required parameters:
> > >
> > > None
> > >
> > > Optional parameters:
> > >
> > > ptime: see RFC 4566. SHOULD be a
multiple of 20 msec.
> > >
> > > maxptime: see RFC 4566. SHOULD be a
multiple of 20 msec.
> > >
> > >
> > >
> > > Sachin Rastogi wrote:
> > >
> > > > Hi All,
> > > > Is there any rfc/draft or recommendation
which suggests
> that 'ptime'
> > > > value should multiple of 5 or 10? Can I
use 'ptime'
> value as 11 or
> > > > 12
> > or
> > > 18
> > > > or 19?
> > > >
> > > >
> > > >
> > > > Thanks
> > > > Sachin Rastogi
> > > >
_______________________________________________
> > > > Sip-implementors mailing list
> > > > [email protected]
> > > >
>
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
> > >
> > >
> > > --
> > > Alex Balashov
> > > Evariste Systems
> > > Web : http://www.evaristesys.com/
> > > Tel : (+1) (678) 954-0670
> > > Direct : (+1) (678) 954-0671
> > > Mobile : (+1) (706) 338-8599
> > >
_______________________________________________
> > > Sip-implementors mailing list
> > > [email protected]
> > >
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
> > >
> >
> >
> >
> > --
> > Aneesh
> >
_______________________________________________
> > Sip-implementors mailing list
> > [email protected]
> >
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
> >
> _______________________________________________
> Sip-implementors mailing list
> [email protected]
>
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>
--
Aneesh
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