W3C home > Mailing lists > Public > public-webrtc@w3.org > May 2018

Re: Raw data API - 3 - Encoded data

From: Harald Alvestrand <harald@alvestrand.no>
Date: Thu, 31 May 2018 12:02:10 +0200
To: public-webrtc@w3.org
Message-ID: <70abe632-db21-e5e0-596c-42caae22bf8c@alvestrand.no>
Den 30. mai 2018 21:49, skrev Randell Jesup:
> On 5/30/2018 12:29 PM, Peter Thatcher wrote:
>> This gets to my question I want to cover at the f2f (and which we now
>> have agenda time for): how low-level an API do we want?  With a
>> low-level RTP transport object, a JS/wasm app could implement a
>> high-level RtpSender on top.  But is that the right balance between
>> flexibility and ease of use?  How much do we want to rely on libraries
>> to fill in the higher-level stuff?  
>>
>> I feel like providing low-level components and letting the js/wasm
>> libraries fill in the higher-level stuff is the right way to go for
>> most things, but finding the right line is a bunch of tradeoffs and I
>> think there's a lot of the WG to consider.
> 
> Another thing to consider (and this applies to a lot of the discussions
> going on for the f2f): JS isn't realtime.  Not even close.  When you
> look at profiles like I do, and see JS pauses for GC/CC,
> layout/rendering, other things jumping in, etc...  When one page leaks
> (I'm looking at you adsafeprotected.com (anti-clickfraud provider) -
> though I poked them hard and they fixed it finally), you can see LONG
> GC/CC times.  Like 100's of ms.  or seconds.
> 
> Right now WebRTC is so isolated from JS land (at least in Firefox) that
> you can have a call continue for 10 minutes after the mainthread has
> deadlocked (until consent-refresh kills you, for example).  Push tons of
> stuff in to JS, and you're going to majorly destabilize timing and
> latency and framerate.  If you push most of this off into Workers
> running WASM, you may avoid the random latencies, but at some real costs
> in making everything multithreaded to the extreme.  And even if you can
> avoid adding delay or jitter to the media, you're going to be using more
> RAM and CPU especially on mobile devices.  WASM is good, true, but it's
> not a panacea.

WASM makes you able to do things faster, but not more consistently.

So yes, making something that works close to realtime requires getting
off the main thread.

Which means workers. Of some kind.
Received on Thursday, 31 May 2018 10:02:39 UTC

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