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In order to do this you'd need to know <i>in advance</i> exactly which
Ogg pages were audio and which were video so you could choose to only
download the vorbis pages. The upcoming Ogg Skeleton index does not
index pages at a high enough granularity to facilitate this. It could,
but then the index would be a lot bigger. I also wonder if the
time/server overhead of setting up new HTTP byte-range request for each
~4KB Ogg vorbis page wouldn't make this worth while. Especially over a
high latency connection. You'd be best to oggz-rip the streams you want
out in advance and serving them statically, as Conrad suggested.<br>
<br>
It's <i>impossible</i> to determine in advance which byte ranges to
download in order to download only one stream. You simply don't know
which stream a page belongs to or what size it is until you've
downloaded the page.<br>
<br>
Chris P.<br>
<br>
On 12/05/2010 11:18 a.m., Silvia Pfeiffer wrote:
<blockquote
cite="mid:AANLkTilomSJ18awbgi3GCXp9TTmfCwXAzTSKqU8XOxNF@mail.gmail.com"
type="cite">
<pre wrap="">Yeah, the track attribute of the media fragments specification that
Ralph links will in theory allow to just download the track-related
data. But it still requires implementation - either in the browser,
which will somehow need to identify which bytes belong to which track
and just request those byte ranges that are relevant, or on the
server, which will only deliver the relevant bytes when asked for the
audio track only.
None of this is implemented yet. In fact, the discovery of which bytes
in a Ogg stream belong to which track is a challenge. I am not sure
whether the new Skeleton Index format might actually allow for that...
Cheers,
Silvia.
On Wed, May 12, 2010 at 3:32 AM, Frank Barchard <a class="moz-txt-link-rfc2396E" href="mailto:fbarchard@google.com"><fbarchard@google.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">FWIW chromium does client side range requests that in theory would request
only the audio. But. the ogg demux reads the other tracks and discards
them.
A use case I've heard is listening to music videos and discard the video...
bit of a bandwidth waste.
On Tue, May 11, 2010 at 10:17 AM, Ralph Giles <a class="moz-txt-link-rfc2396E" href="mailto:giles@thaumas.net"><giles@thaumas.net></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">
On 11 May 2010 04:24, narendra sisodiya <a class="moz-txt-link-rfc2396E" href="mailto:narendra.sisodiya@gmail.com"><narendra.sisodiya@gmail.com></a>
wrote:
</pre>
<blockquote type="cite">
<pre wrap=""> It will be very good if HTML5 API specify this. I mean, Say, If we
use
<audio> tag , then It must stream only audio part of the file
irrespective
of the fact that the src field contains a video file.
</pre>
</blockquote>
<pre wrap="">
I don't think that's a practical option, since the server must
manipulate the file to return an audio-only subset of the data for
there to be any bandwidth advantage. That's not something that the
HTML5 specification, which documents browser behaviour, can describe.
Note that it's completely possible to use a server-size module or
script to do this, using a query url in the HTML5 media element's src
attribute. It's just part of a custom server config rather than the
HTML5 API. The Media Fragments Working Group at the W3C is currently
working on a standardized syntax for this. See
<a class="moz-txt-link-freetext" href="http://www.w3.org/2008/WebVideo/Fragments/WD-media-fragments-spec/">http://www.w3.org/2008/WebVideo/Fragments/WD-media-fragments-spec/</a> if
you're interested.
FWIW,
-r
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