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Re: RTT implementation = Real-Time Text implementation

From: Lennart Grahl <lennart.grahl@gmail.com>
Date: Tue, 19 Jun 2018 18:36:46 +0200
To: public-webrtc@w3.org
Cc: Gunnar Hellström <gunnar.hellstrom@omnitor.se>
Message-ID: <080000bb-fdb7-4d6a-45b8-1d24ec5969db@gmail.com>
This may benefit from having more knobs to control SCTP-specific timers
such as the retransmission interval. It might actually be the first use
case I've encountered that could make some use out of `maxRetransmits:
<some carefully chosen value above 0>` along with a specific
retransmission interval.

Cheers
Lennart


On 19.06.2018 11:27, Gunnar Hellström wrote:
> 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.
> 
> /Gunnar
> 
> 
> 
> 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 16:37:10 UTC

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