Re: [codec] #1: Application: 2.1. Point to point calls supporting transcoding?

["Christian Hoene" <[e-mail]>]

Hi James,

>-----Original Message-----
>From: James Rafferty [mailto:[e-mail]]
...
>Vendors of products on these network edges will take the steps needed to get endpoints to communicate
>(as driven by their service provider customers), even if it requires a codec change to complete the
>call.

So, the main requirement in these cases is the interoperability. Conversational quality is of lesser importance.
Thus, we need not particular quality requirements beside that it works OK?

Christian

>
>James
>
>-----Original Message-----
>From: Christian Hoene [mailto:[e-mail]]
>Sent: Wednesday, March 24, 2010 9:08 AM
>To: James Rafferty; [e-mail]
>Subject: RE: [codec] #1: Application: 2.1. Point to point calls supporting transcoding?
>
>Hi all,
>
>the well known reasons for avoiding transcoding/tandem-coding are:
>
>1) It decreases the conversational quality by decreasing speech quality and increasing transmission
>delay. Thus, it is in the interest of users/customers to avoid transcoding.
>2) It violates Internet's end-to-end principle and thus increasing system complexity and costs. Thus,
>an Internet codec shall not consider operation modes of transcoding, typically.
>3) Codecs must be optimized towards transcoding, which is a time consuming tasks. Thus, it is in the
>interest of codec developers and tester to avoid the additional cost of verifying the transcoding
>scenarios.
>
>Of course, we are not living in an perfect world and there are many valid reasons to install
>transcoding gateways to manage proper interaction between two remote sides/operators. If it is
>required to do so, there are multiple options:
>
>1) The gateway tries to negotiate a proper codec that is supported by both sides.
>2) Two ITU-T codecs, which are very well optimized towards tandem-coding conditions, are selected.
>3) Only, as a last resort, it might be needed to transcode between an Internet-codec and other codecs.
>
>I am not yet convinced that option 3) will happen frequently, especially considering the facts that
>the Internet codec is intended towards IP-to-IP use cases.  Also, it is quite easy to include
>additional traditional codecs beside the Internet codec into a phone or gateways. In addition, the
>costs of updating the software of a phone or gateway to support the Internet codec might not be very
>high because of the lack of IPR fees.
>
>Thus, I would recommend to consider transcoding as a requirement of very low priority, as it is going
>to be used seldom. It shall be ensured that the Internet codecs does not "fail" during tandeming but
>that not particular effort is invested to make the Internet codec work particular well for
>transcoding.
>
>Having this say, it is appreciate if volunteers will test the Internet codec in tandem conditions so
>that the codec design can be influenced.
>
>With best regards,
>
> Christian
>
>---------------------------------------------------------------
>Dr.-Ing. Christian Hoene
>Interactive Communication Systems (ICS), University of Tübingen
>Sand 13, 72076 Tübingen, Germany, Phone [phone]
>http://www.net.uni-tuebingen.de/
>
>>-----Original Message-----
>>From: James Rafferty [mailto:[e-mail]]
>>Sent: Tuesday, March 23, 2010 4:14 PM
>>To: Christian Hoene
>>Cc: [e-mail]
>>Subject: RE: [codec] #1: Application: 2.1. Point to point calls supporting transcoding?
>>
>>Christian,
>>
>>Please see my comments below.
>>
>>James
>>
>>-----Original Message-----
>>From: Christian Hoene [mailto:[e-mail]]
>>Sent: Tuesday, March 23, 2010 2:53 PM
>>To: James Rafferty
>>Cc: [e-mail]
>>Subject: RE: [codec] #1: Application: 2.1. Point to point calls supporting transcoding?
>>
>>Hi James,
>>
>>>In my view, this is dodging the real issue.  I believe there WILL be transcoding for point to point
>>>calls between wireline and wireless networks, where the connection is IP on both sides and multiple
>>>wide band codecs are used.
>>
>>Could you elaborate a bit more on this scenario? Do you mean that the wireline has -for example-
>Skype
>>phone with the Internet codec and the wireless end will have an LTE codec? Of course, both sides will
>>use IP.
>>
>>JR - Yes, the example of Skype from the desktop connecting to a mobile phone with wideband audio (say
>>G.722.2) is an example.  In order for that to happen, there would likely be a border element at the
>>network edge (what the Speermint architecture calls a Data Border Element) which negotiates the
>>transcoding to take place in real time.  Another use case example would be where an enterprise IP
>>phone uses a wideband codec when calling to a mobile phone, again requiring transcoding to take place
>>to complete the call, if the two handsets do not support a common HD codec.
>>
>>>For that matter, there will also be cases where a PSTN - IP gateway is needed, but that's not
>usually
>>>defined as transcoding.
>>
>>As a manufacturer of IP-to-IP gateways your insight knowledge is highly appreciated.
>>
>>With best regards,
>>
>>  Christian Hoene
>>
>>
>>
>>>
>>>James
>>>
>>>James Rafferty
>>>Product Line Director, Integrated Media Gateways
>>>Dialogic, Inc.
>>>15 Crawford Street
>>>Needham, MA 02494
>>>USA
>>>
>>>Tel:    [phone]
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>>>Web:    www.dialogic.com
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>>>-----Original Message-----
>>>From: [e-mail] [mailto:[e-mail]] On Behalf Of codec issue tracker
>>>Sent: Tuesday, March 23, 2010 10:20 AM
>>>To: [e-mail]
>>>Cc: [e-mail]
>>>Subject: [codec] #1: Application: 2.1. Point to point calls supporting transcoding?
>>>
>>>#1: Application: 2.1.  Point to point calls supporting transcoding?
>>>------------------------------------+---------------------------------------
>>> Reporter:  hoene@…                 |       Owner:
>>>     Type:  enhancement             |      Status:  new
>>> Priority:  major                   |   Milestone:
>>>Component:  requirements            |     Version:
>>> Severity:  Active WG Document      |    Keywords:
>>>------------------------------------+---------------------------------------
>>> Question: Shall the point-to-point call support transcoding?
>>>
>>> If not, please add something like
>>> "This scenario does not include the use case of using a VoIP-PSTN gateway
>>> to connected to legacy telephone systems. In those cases, the gateway
>>> would make an audio conversion from broadband Internet voice to the frugal
>>> 1930’s 3.1 kHz audio bandwidth. Interconnections to the PSTN will most
>>> likely stick with its legacy codecs to avoid transcoding."
>>>
>>>--
>>>Ticket URL: <http://tools.ietf.org/wg/codec/trac/ticket/1>
>>>codec <http://tools.ietf.org/codec/>
>>>
>>>_______________________________________________
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>