Re: The Image Stream Processing pipeline/s

Hi all, 

A maybe related question. The draft of Image Capture says both getFrame() and takePhoto() capture a single still frame/image at one call, and the API also provides some options to manipulate the capture result. So should the Image Capture need to handle the preview of settings change in streaming mode? Like the camera preview window. Or this kind of streaming preview should be handled at user level, using setTimeout() or requestAnimationFrame()? 

Thanks, 
Shelly 

----- Original Message -----

From: "Greg Billock" <gbillock@google.com> 
To: "Rob Manson" <roBman@mob-labs.com> 
Cc: public-media-capture@w3.org 
Sent: Friday, September 6, 2013 12:12:20 AM 
Subject: Re: The Image Stream Processing pipeline/s 

I think compute-intensive image processing will not want to use the MediaRecorder pathway. It will likely not be presenting a frame-based chunk, and depending on what options are available you'd have to decode the stream. I think using something more like stream->video->canvas (although admittedly chewy) is better. 


On Thu, Sep 5, 2013 at 8:51 AM, Rob Manson < roBman@mob-labs.com > wrote: 


So is the recommendation that we should use the Media Recording Blob based API? 

stream -> media recorder -> blob -> file reader -> array buffer 

As compared to the current de-facto pipeline? 

stream -> <video> -> <canvas> -> image data -> array buffer 

And Image Capture? Giri has just published the latest version of that. 


roBman 



On 06/09/13 01:21, Harald Alvestrand wrote: 

<blockquote>
On 09/05/2013 07:37 AM, Rob Manson wrote: 

<blockquote>
Hi Adam, 

that's true. But Transferable objects avoid the copy overhead so 
there is a real performance benefit in that. 

Unless I'm missing something? 


That's actually only true for browsers using shared memory between 
entities. 


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roBman 


On 05/09/13 15:14, Adam Bergkvist wrote: 

<blockquote>
On 2013-09-05 04:50, Rob Manson wrote: 

<blockquote>
Also since I don't believe Blob's are Transferable[9] then choosing B 
has performance implications for processes that want to shift work off 
into a Web Worker too (see comment above about B's secondary pipeline). 

</blockquote>

It's true that Blob's aren't Transferable (since they are immutable and 
easy to share it doesn't add much), but you can send them as the first 
(message) argument to postMessage() [1]. 

/Adam 

[1] http://dev.w3.org/html5/ postmsg/#dom-window- postmessage 


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