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Re: RTT implementation = Real-Time Text implementation

From: Gunnar Hellström <gunnar.hellstrom@omnitor.se>
Date: Tue, 19 Jun 2018 11:27:06 +0200
To: Harald Alvestrand <harald@alvestrand.no>, public-webrtc@w3.org
Message-ID: <cc65ef24-4abc-4034-30c1-d8a32e8eaddf@omnitor.se>
This discussion started with RTT meaning "Real-Time Text" which is 
time-sampled text used in conversational sessions, often together with 
audio and video.

The time sampling is traditionally done in about 300 ms samples in order 
to not cause a lot of load. So any new text entered within 300 ms is 
transmitted in a chunk, regardless if the user has indicated any end of 
message or not. This way of sending text implies a much better sense of 
being connected between users in intensive conversations than the 
transmission in completed messages does.

Today, when bandwidth and processing is less expensive, it could be 
worth while decreasing the sample time, so that latencies close to what 
is used for audio and video in conversational sessions is achieved.

It should be possible to use WebRTC data channel for Real-Time Text.

The synchronism requirements versus video and audio are mild. Users 
barely notice an asynchronism of 500 ms or 1 second. Some applications,. 
like speech-to-text transmit in complete words, and that is also allowed.

So, I do not know if the implementation needs to build on the 
synchronized media use case. It may just be sufficient to use regular 
WebRTC data channels with suitable characteristics. I like the 
simplicity of the "reliable" transfer in data channels, but not the risk 
for long delays in case of transmission problems.

Since the topic is mentioned in the initial functionality goals for Data 
Channels, but not mentioned in RFC 7478, I suggest that it is included 
in the NV discussions.


Den 2018-06-19 kl. 10:07, skrev Harald Alvestrand:
> Existing RTT measurements:
> https://w3c.github.io/webrtc-stats/webrtc-stats.html#dom-rtcremoteinboundrtpstreamstats-roundtriptime
> https://w3c.github.io/webrtc-stats/webrtc-stats.html#dom-rtcicecandidatepairstats-totalroundtriptime
> On 06/19/2018 09:06 AM, Gunnar Hellström wrote:
>> Den 2018-06-19 kl. 08:46, skrev Bernard Aboba:
>>> In practice, the requirement for "synchronized data" can be supported
>>> by allowing applications to fill in the payload format defined in RFC
>>> 4103.
>>> This enables RTT to be implemented in Javascript on top of an "RTP
>>> data channel" transport, utilizing the existing RTCDataChannel
>>> interface.
>>> So in practice the need for RTT support can be included in a
>>> "synchronized data" requirement, if properly implemented.
>> Yes, it can be specified with current mechanisms, it is just a matter
>> of selecting some properties and values and getting it specified. A
>> standard is needed so that gateways and bridges can be developed
>> separately from user agents, and so that, as you say, it all gets
>> "properly implemented". So far, the latency requirements have been
>> slightly lower than for audio and video in conversational sessions,
>> when the user is typing the text, but now, with automatic speech to
>> text becoming useful, the requirement for short delays is becoming
>> more strict .
>> /Gunnar
>>> ________________________________________
>>> From: Peter Thatcher [pthatcher@google.com]
>>> Sent: Monday, June 18, 2018 10:49 PM
>>> To: Gunnar Hellström
>>> Cc: public-webrtc@w3.org
>>> Subject: Re: WebRTC NV Use Cases
>>> Thanks, I added that as a new requirement to the conferencing use case.
>>> On Mon, Jun 18, 2018 at 11:18 PM Gunnar Hellström
>>> <gunnar.hellstrom@omnitor.se<mailto:gunnar.hellstrom@omnitor.se>> wrote:
>>> I suggest to include real-time text (= text transmitted in the same rate
>>> as it is created so that it can be used for real conversational
>>> purposes) in the NV work.
>>> It is not included in RFC 7478, but included a U-C 5 in section 3.2 of
>>> https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-13<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Fdraft-ietf-rtcweb-data-channel-13&data=02%7C01%7CBernard.Aboba%40microsoft.com%7C4ecd480c191a456ac73d08d5d5a89c6f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636649842519679581&sdata=fEZV7O6vIb1m3bi6mIBmi%2Bbf6PeJCtKx3Jb3WeFjWbA%3D&reserved=0>
>>> It could possibly be done by continuing the work started in
>>> https://datatracker.ietf.org/doc/draft-schwarz-mmusic-t140-usage-data-channel/<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fdraft-schwarz-mmusic-t140-usage-data-channel%2F&data=02%7C01%7CBernard.Aboba%40microsoft.com%7C4ecd480c191a456ac73d08d5d5a89c6f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636649842519689589&sdata=KXNSeVQPxSLMa0%2FmzSQRio1W2p7Wgmn2oet%2FAoJTHjA%3D&reserved=0>
>>> Use cases are e.g.
>>> 1. conversational two-party sessions with video, audio and real-time
>>> text.
>>> 2. conversational multi-party sessions with video, audio and
>>> real-time text.
>>> 3. sessions with automatic speech - to - real-time text conversion in
>>> one or both directions.
>>> 4. interworking WebRTC with audio, video and real-time text and legacy
>>> SIP with audio, video and real-time text.
>>> /Gunnar
>>> Den 2018-05-09 kl. 21:29, skrev Bernard Aboba:
>>>> On June 19-20 the WebRTC WG will be holding a face-to-face meeting
>>>> in Stockholm, which will focus largely on WebRTC NV.
>>>> Early on in the discussion, we would like to have a discussion of
>>>> the use cases that WebRTC NV will address.
>>>> Since the IETF has already published RFC 7478, we are largely
>>>> interested in use cases that are either beyond those articulated in
>>>> RFC 7478, or use cases in the document that somehow can be done
>>>> better with WebRTC NV than they could with WebRTC 1.0.
>>>> As with any successful effort, we are looking for volunteers to
>>>> develop a presentation for the F2F, and perhaps even a document.
Received on Tuesday, 19 June 2018 09:27:46 UTC

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