02-mediafrag-minutes.html
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<title>Media Fragments Working Group Teleconference -- 02 Dec
2009</title>
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<h1>Media Fragments Working Group Teleconference</h1>
<h2>02 Dec 2009</h2>
<p><a href=
'http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0003.html'>
Agenda</a></p>
<p>See also: <a href=
"http://www.w3.org/2009/12/02-mediafrag-irc">IRC log</a></p>
<h2><a name="attendees" id="attendees">Attendees</a></h2>
<div class="intro">
<dl>
<dt>Present</dt>
<dd>Raphael, Silvia, Yves, Philip_(irc), Michael</dd>
<dt>Regrets</dt>
<dd>Erik, Davy, Jack</dd>
<dt>Chair</dt>
<dd>Raphael</dd>
<dt>Scribe</dt>
<dd>Yves</dd>
</dl>
</div>
<h2>Contents</h2>
<ul>
<li>
<a href="#agenda">Topics</a>
<ol>
<li><a href="#item01">Specification</a></li>
<li><a href="#item02">Specific (cont.) - 2
roundtrips</a></li>
<li><a href="#item03">Rework of the section 5</a></li>
</ol>
</li>
<li><a href="#ActionSummary">Summary of Action Items</a></li>
</ul>
<hr />
<div class="meeting">
<p class='phone'> </p>
<p class='phone'> </p>
<p class='irc'><<cite>trackbot</cite>> Date: 02 December
2009</p>
<p class='irc'><<cite>scribe</cite>> Scribe: Yves</p>
<p class='irc'><<cite>raphael</cite>> Minutes from last
week: <a href=
"http://www.w3.org/2009/11/25-mediafrag-minutes.html">http://www.w3.org/2009/11/25-mediafrag-minutes.html</a></p>
<p class='irc'><<cite>raphael</cite>> +1 for
accepting</p>
<p class='phone'>no objection => accepted</p>
<p class='irc'><<cite>silvia</cite>> +1</p>
<h3 id="item01">Specification</h3>
<p class='irc'><<cite>raphael</cite>> ACTION-112?</p>
<p class='irc'><<cite>trackbot</cite>> ACTION-112 --
Raphaël Troncy to propose a digest of Conrad and current's
proposal regarding the use of existing and custom headers for
the communication UA server -- due 2009-09-25 -- OPEN</p>
<p class='irc'><<cite>trackbot</cite>> <a href=
"http://www.w3.org/2008/WebVideo/Fragments/tracker/actions/112">
http://www.w3.org/2008/WebVideo/Fragments/tracker/actions/112</a></p>
<p class='phone'>We have the one round trip version, and the
two round trips versions</p>
<p class='irc'><<cite>raphael</cite>> close
ACTION-112</p>
<p class='irc'><<cite>trackbot</cite>> ACTION-112 Propose
a digest of Conrad and current's proposal regarding the use of
existing and custom headers for the communication UA server
closed</p>
<p class='phone'><cite>Yves:</cite> what make you think that
the one-round trip version can't be cached?</p>
<p class='phone'><cite>Raphael:</cite> implementation issue
only, current implementation can't without knowing the unit</p>
<p class='phone'><cite>Yves:</cite> right, but implementation
can't exist before the spec is ready :)</p>
<p class='phone'><cite>Raphael:</cite> we can then document
expectation on client servers and proxies (wrt
support/implementation)</p>
<p class='phone'><cite>Yves:</cite> that would do it</p>
<p class='irc'><<cite>raphael</cite>> Silvia: there is a
optimal solution and then divergent cases ... this is how
section 3 is written</p>
<p class='irc'><<cite>raphael</cite>> Yves: changing the
UA is not easy</p>
<p class='phone'><cite>Silvia:</cite> changing servers and
clients is easy, proxies are not easy to update</p>
<p class='phone'><cite>Yves:</cite> By proxy you mean caches,
proxies will work perfectly well</p>
<p class='irc'><<cite>silvia</cite>> I mean caching
proxies indeed</p>
<p class='irc'><<cite>foolip</cite>> request to speak
(write)</p>
<p class='irc'><<cite>raphael</cite>> Raphael: indeed my
asumption is that we have a UA conformant to the media fragment
spec (parse), a server like Davy's one that support MF URI and
that's it</p>
<p class='phone'><cite>Yves:</cite> just to mention that I am
not against the two round trip approach :)</p>
<p class='irc'><<cite>raphael</cite>> ... i.e. no caches
have been modified</p>
<p class='irc'><<cite>raphael</cite>> Raphael: do you
agree that the 2 round-trips approach allow to cache fragments
without changing cache implementation ?</p>
<p class='phone'><a href=
"http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0008.html">
http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0008.html</a></p>
<p class='phone'>GET /2008/WebVideo/Fragments/media/fragf2f.mp4
HTTP/1.1</p>
<p class='phone'><cite>Host:</cite> www.w3.org</p>
<p class='phone'><cite>Accept:</cite> video/*</p>
<p class='phone'><cite>Fragment:</cite> time:npt=12-21</p>
<p class='irc'><<cite>raphael</cite>> Yves: time ranges
are cacheable but need implementation. 2 rounds trip is a hack
to allow current proxies to cache</p>
<p class='phone'>HTTP 200 OK</p>
<p class='phone'><cite>Content-Length:</cite> 3571437</p>
<p class='phone'><cite>Content-Fragment:</cite>
time:npt=12-21</p>
<p class='phone'><cite>Vary:</cite> Fragment</p>
<p class='phone'>we should add Content-Location:
/2008/WebVideo/Fragments/media/fragf2f.mp4?t=12-21</p>
<p class='irc'><<cite>raphael</cite>> Yves: in Conrad's
proposal, case 1.2.b, we need to add a Content-Location header
in the response</p>
<p class='irc'><<cite>foolip</cite>> is there a speaker
queue?</p>
<p class='irc'><<cite>raphael</cite>> yes, Philip</p>
<p class='irc'><<cite>raphael</cite>> Yves: my concern is
that in the case of Conrad's proposal, if you have 2 request,
the second one will flush the cache of the first one</p>
<p class='irc'><<cite>foolip</cite>> I would like to note
that the NPT syntax in the HTTP headers examples are
inconsistent. Would it not be best to define a normalized form?
The UA would have to pick a formatting anyway unless it just
copies it verbatim (in which case it doesn't actually know
which offset it is requesting or if it's valid syntax).</p>
<p class='irc'><<cite>raphael</cite>> Philip, can you
point us to this inconsistency ?</p>
<p class='irc'><<cite>raphael</cite>> I don't see it</p>
<p class='irc'><<cite>foolip</cite>> "time:npt
11.85-21.16/36" vs "time:npt=12-21"</p>
<p class='phone'>ah it's the range reply syntax</p>
<p class='phone'>which is starting time -end time / total
time</p>
<p class='phone'>you have the same asymetry in byte ranges</p>
<p class='irc'><<cite>foolip</cite>> in either case, NPT
should be normalized, so that it isn't sometimes 0:00:12,
sometimes 12 and sometimes 12s</p>
<p class='irc'><<cite>raphael</cite>> Philip: we follow
the same pattern that the bytes range request ... with a
dissimetry between request and response</p>
<p class='irc'><<cite>raphael</cite>> it is not
0:00:12</p>
<p class='irc'><<cite>raphael</cite>> where did you see
this Philip ?</p>
<p class='irc'><<cite>foolip</cite>> raphael: some more
zeroes?</p>
<p class='irc'><<cite>silvia</cite>> foolip: the syntax
is given in <a href=
"http://www.w3.org/2008/WebVideo/Fragments/WD-media-fragments-spec/#naming-syntax">
http://www.w3.org/2008/WebVideo/Fragments/WD-media-fragments-spec/#naming-syntax</a></p>
<p class='irc'><<cite>raphael</cite>> I thought I have
normallized the npt syntax</p>
<p class='irc'><<cite>silvia</cite>> foolip: if something
does not conform to that syntax, it is a typo</p>
<p class='irc'><<cite>raphael</cite>> Section 5 contains
indeed typos</p>
<p class='irc'><<cite>foolip</cite>> so which format is
normalized?</p>
<p class='irc'><<cite>silvia</cite>> I think section 5
still needs a general work-over</p>
<p class='irc'><<cite>foolip</cite>> the ABNF allows any
kind of variation</p>
<p class='irc'><<cite>foolip</cite>> not any, but many
variations of the same time</p>
<p class='irc'><<cite>silvia</cite>> ah, yes, we decided
to give the user the freedom to specify relatively freely, but
the syntax on the wire is fixed</p>
<p class='irc'><<cite>foolip</cite>> that's good, where
is it defined?</p>
<p class='irc'><<cite>silvia</cite>> not yet in the spec
- needs to go into section 5</p>
<p class='irc'><<cite>foolip</cite>> ok, so we are
already in agreement that this is neeed</p>
<p class='irc'><<cite>foolip</cite>> needed</p>
<p class='irc'><<cite>foolip</cite>> good</p>
<p class='irc'><<cite>silvia</cite>> yup, indeed</p>
<p class='irc'><<cite>foolip</cite>> I suggest
normalizing to seconds without s, but that's just me</p>
<p class='irc'><<cite>foolip</cite>> anything is fine</p>
<p class='irc'><<cite>foolip</cite>> as long as there can
only be one possible string output for each input (makes
writing conformance test suites lot easier too)</p>
<p class='irc'><<cite>silvia</cite>> yes, indeed</p>
<p class='irc'><<cite>raphael</cite>> OK, philip, I try
to solve your problem ...</p>
<p class='irc'><<cite>foolip</cite>> thanks</p>
<p class='irc'><<cite>raphael</cite>> what do you would
like to be changed in the spec?</p>
<p class='irc'><<cite>raphael</cite>> I'm not sure I
understand it :-(</p>
<p class='irc'><<cite>raphael</cite>> 1) The Media
Fragment URI syntax ? 2) The HTTP request header syntax ? 3)
The HTTP response header ?</p>
<p class='irc'><<cite>foolip</cite>> it should say that
when sending header X, the format MUST be Y, with Y
unambiguously defined</p>
<p class='irc'><<cite>raphael</cite>> ... for example in
the case of npt</p>
<p class='irc'><<cite>foolip</cite>> 2 and 3</p>
<p class='irc'><<cite>foolip</cite>> 1) is the parsing
end, which we'll get to later I think</p>
<p class='irc'><<cite>foolip</cite>> this should be a
conformance requirement of both UAs and servers</p>
<p class='irc'><<cite>raphael</cite>> OK Philip, now I
understand, indeed, we haven't specified yet the syntax for 2)
and 3)</p>
<p class='irc'><<cite>raphael</cite>> The only things we
have: <a href=
"http://www.w3.org/2008/WebVideo/Fragments/wiki/WG_Resolutions#Media_Fragment_Headers">
http://www.w3.org/2008/WebVideo/Fragments/wiki/WG_Resolutions#Media_Fragment_Headers</a></p>
<p class='irc'><<cite>foolip</cite>> OK, then it's just a
matter of time, I shall not worry any more :)</p>
<p class='irc'><<cite>raphael</cite>> +1</p>
<p class='irc'><<cite>raphael</cite>> ... or worry
later</p>
<p class='phone'>Silvia, we need some ABNF there as well</p>
<p class='phone'><cite>Yves:</cite> to summarize, lax URI
syntax, strict header</p>
<p class='irc'><<cite>silvia</cite>> part of the syntax
was started in <a href=
"http://lists.w3.org/Archives/Public/public-media-fragment/2009Sep/0099.html">
http://lists.w3.org/Archives/Public/public-media-fragment/2009Sep/0099.html</a></p>
<p class='phone'><a href=
"http://tools.ietf.org/html/draft-ietf-httpbis-p5-range-08">http://tools.ietf.org/html/draft-ietf-httpbis-p5-range-08</a></p>
<p class='irc'><<cite>silvia</cite>> but needs to go into
ABNF</p>
<p class='irc'><<cite>raphael</cite>> Silvia, yes, it is
even better summarized in <a href=
"http://www.w3.org/2008/WebVideo/Fragments/wiki/WG_Resolutions#Media_Fragment_Headers">
http://www.w3.org/2008/WebVideo/Fragments/wiki/WG_Resolutions#Media_Fragment_Headers</a></p>
<p class='phone'><a href=
"http://tools.ietf.org/html/draft-ietf-httpbis-p5-range-08#section-5.4.2">
http://tools.ietf.org/html/draft-ietf-httpbis-p5-range-08#section-5.4.2</a></p>
<p class='phone'>other-ranges-specifier = other-range-unit "="
other-range-set</p>
<p class='phone'>other-range-set = 1*CHAR</p>
<p class='phone'>other-range-unit = token</p><a name="action01"
id="action01"></a>
<p class='irc'><<cite>scribe</cite>>
<strong>ACTION:</strong> Yves to come up with ABNF for header
syntax [recorded in <a href=
"http://www.w3.org/2009/12/02-mediafrag-minutes.html#action01">http://www.w3.org/2009/12/02-mediafrag-minutes.html#action01</a>]</p>
<p class='irc'><<cite>trackbot</cite>> Created ACTION-123
- Come up with ABNF for header syntax [on Yves Lafon - due
2009-12-09].</p>
<p class='irc'><<cite>foolip</cite>> ABNF syntax without
any use of " / " to that.</p>
<h3 id="item02">Specific (cont.) - 2 roundtrips</h3>
<p class='phone'><cite>Yves:</cite> on the two round trip I
have some reservation with the first 200 OK reply</p>
<p class='irc'><<cite>raphael</cite>> Yves: In the case
of 2.1, first roundtrip response should be a 307 instead of
200</p>
<p class='phone'>may be better to have a 307 and redirect to
itself with the right headers</p>
<p class='phone'>will followup by email</p>
<p class='phone'><cite>Raphael:</cite> we need to update
section 5</p>
<p class='phone'><cite>Silvia:</cite> happy to work on it</p>
<h3 id="item03">Rework of the section 5</h3>
<p class='irc'><<cite>raphael</cite>> See: <a href=
"http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html">
http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html</a></p>
<p class='phone'><cite>Silvia:</cite> what you summarized is in
sync with what I had in mind, writing this will clarify
things<br />
... not clear that we need the Fragment: header, but don't
remember what Conrad wanted it for<br />
... but good that the email thread restarted</p>
<p class='phone'><cite>Raphael:</cite> I proposed a
restructuration plan for section 5</p>
<p class='irc'><<cite>mhausenblas</cite>> +1</p>
<p class='phone'><cite>Raphael:</cite> Silvia, do you want to
work on specific sections? or all of them?</p>
<p class='phone'><cite>Silvia:</cite> better if it is
consistent</p><a name="action02" id="action02"></a>
<p class='irc'><<cite>scribe</cite>>
<strong>ACTION:</strong> Silvia to rework section 5 according
to Raphael's restructuration plan <a href=
"http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html">
http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html</a>
due 2009-12-15 [recorded in <a href=
"http://www.w3.org/2009/12/02-mediafrag-minutes.html#action02">http://www.w3.org/2009/12/02-mediafrag-minutes.html#action02</a>]</p>
<p class='irc'><<cite>trackbot</cite>> Created ACTION-124
- Rework section 5 according to Raphael's restructuration plan
<a href=
"http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html">
http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html</a>
due 2009-12-15 [on Silvia Pfeiffer - due 2009-12-09].</p>
<p class='irc'><<cite>foolip</cite>> where in section 5
will the processing requirements (parsing) go? part of MF
resolution?</p>
<p class='phone'>depends on the author :)</p>
<p class='irc'><<cite>silvia</cite>> I think it should be
section 5.5 ABNF for HTTPrequest & response
headers</p><a name="action03" id="action03"></a>
<p class='irc'><<cite>scribe</cite>>
<strong>ACTION:</strong> Michael to revisit his ednote in
section 5 [recorded in <a href=
"http://www.w3.org/2009/12/02-mediafrag-minutes.html#action03">http://www.w3.org/2009/12/02-mediafrag-minutes.html#action03</a>]</p>
<p class='irc'><<cite>trackbot</cite>> Created ACTION-125
- Revisit his ednote in section 5 [on Michael Hausenblas - due
2009-12-09].</p>
<p class='irc'><<cite>foolip</cite>> I agree that most
parts can be given as ABNF, but not all of it</p>
<p class='irc'><<cite>foolip</cite>> I can elaborate if
it's not clear why.</p>
<p class='irc'><<cite>silvia</cite>> why not?</p>
<p class='irc'><<cite>raphael</cite>> Yes please Philip,
I suggest we wait for Silvia's input and then complain what is
not sufficiently specified</p>
<p class='phone'><cite>Raphael:</cite> on the test cases, lots
of action. postpone?</p>
<p class='irc'><<cite>foolip</cite>> sorry, difficult to
guess who's talking over IRC</p>
<p class='irc'><<cite>scribe</cite>> => postponed</p>
<p class='irc'><<cite>raphael</cite>> ACTION-119?</p>
<p class='irc'><<cite>trackbot</cite>> ACTION-119 -- Yves
Lafon to request admins to set up a cvs notifications mailing
list and notifications -- due 2009-10-14 -- OPEN</p>
<p class='irc'><<cite>trackbot</cite>> <a href=
"http://www.w3.org/2008/WebVideo/Fragments/tracker/actions/119">
http://www.w3.org/2008/WebVideo/Fragments/tracker/actions/119</a></p>
<p class='phone'><cite>Yves:</cite> oops, will work on this</p>
<p class='irc'><<cite>silvia</cite>> foolip, can you
clarify your opinion on ABNF via email?</p>
<p class='irc'><<cite>foolip</cite>> silvia: to you or
the list?</p>
<p class='irc'><<cite>silvia</cite>> the list</p>
<p class='irc'><<cite>foolip</cite>> will do</p>
<p class='phone'>ADJOURNED</p>
<p class='phone'>tracker, end telcon</p>
<p class='irc'><<cite>raphael</cite>> Raphael: I will
make sure we follow-up the current thread of dicussion so we
can converge rapidly between Conrad's and current's
proposal</p>
<p class='phone'>trackbot, end telcon</p>
</div>
<h2><a name="ActionSummary" id="ActionSummary">Summary of Action
Items</a></h2><!-- Action Items -->
<strong>[NEW]</strong> <strong>ACTION:</strong> Michael to
revisit his ednote in section 5 [recorded in <a href=
"http://www.w3.org/2009/12/02-mediafrag-minutes.html#action03">http://www.w3.org/2009/12/02-mediafrag-minutes.html#action03</a>]<br />
<strong>[NEW]</strong> <strong>ACTION:</strong> Silvia to rework
section 5 according to Raphael's restructuration plan <a href=
"http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html">
http://lists.w3.org/Archives/Public/public-media-fragment/2009Dec/0009.html</a>
due 2009-12-15 [recorded in <a href=
"http://www.w3.org/2009/12/02-mediafrag-minutes.html#action02">http://www.w3.org/2009/12/02-mediafrag-minutes.html#action02</a>]<br />
<strong>[NEW]</strong> <strong>ACTION:</strong> Yves to come up
with ABNF for header syntax [recorded in <a href=
"http://www.w3.org/2009/12/02-mediafrag-minutes.html#action01">http://www.w3.org/2009/12/02-mediafrag-minutes.html#action01</a>]<br />
<br />
[End of minutes]<br />
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$Date: 2009/12/02 11:00:15 $
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