W3C home > Mailing lists > Public > public-media-capture@w3.org > December 2012

Re: revised recording proposal

From: Robert O'Callahan <robert@ocallahan.org>
Date: Mon, 10 Dec 2012 22:55:58 +1300
Message-ID: <CAOp6jLZHF6K9AqKJ5hf9YsyFeaqyzK67B4Gj=3YJ3qX+7k7RjA@mail.gmail.com>
To: Travis Leithead <travis.leithead@microsoft.com>
Cc: Jim Barnett <Jim.Barnett@genesyslab.com>, "Mandyam, Giridhar" <mandyam@quicinc.com>, "public-media-capture@w3.org" <public-media-capture@w3.org>
On Fri, Dec 7, 2012 at 8:37 AM, Travis Leithead <
travis.leithead@microsoft.com> wrote:

>   I am still not convinced time-sliced data is better returned as a blob
> versus an ArrayBuffer, particularly if latency is an critical concern (i.e.
> “reliable” streaming).  At very least you will need the extra step of
> invoking the FileReader I/F (
> http://www.w3.org/TR/FileAPI/#FileReader-interface) to get at Blob data.
>

I'm convinced that returning a Blob is better than an ArrayBuffer. Blobs
have been designed so the UA need not store them in CPU-addressable memory.
ArrayBuffers have not. As Tim observed, this freedom is especially useful
in this case, where the data could be very large.

And I agree with others that returning a Blob is better than returning a
File (because a File is just a Blob with extra attributes that aren't
needed here).

My only concern about using Blobs is this: what is the MIME type of a Blob
which is the second slice of, say, a Wave file? Is it even OK to set the
expected MIME type on the first slice of a resource, if it's not a complete
resource of that type? I think the latter is probably OK, but perhaps we
should say that the first Blob gets the MIME type of the whole resource and
the types of later Blobs are just the empty string.

Rob
-- 
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Gentiles lord it over them, and their high officials exercise authority
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you must be your servant, and whoever wants to be first must be your
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as the Son of Man did not come to be served, but to serve, and to give his
life as a ransom for many.” [Matthew 20:25-28]
Received on Monday, 10 December 2012 09:56:32 UTC

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