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Merge pull request #141 from w3c/issue-125
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Allow remote playback device to choose the remote playback source.
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@markafoltz
markafoltz authored Nov 10, 2020
2 parents b0ecc12 + 852e47e commit 1612ad8
Showing 1 changed file with 48 additions and 43 deletions.
91 changes: 48 additions & 43 deletions index.html
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Expand Up @@ -571,30 +571,47 @@ <h5>
<dfn>availability sources set</dfn>.
</p>
<p>
The <a data-cite="HTML#media-resource">media resource</a>
of a <a>media element</a>, that is used to
<a>initiate remote playback</a> on the selected <a>remote
playback device</a> is called <dfn>remote playback source</dfn>.
Remote playback source MUST belong to <a>availability sources
The <a data-cite="HTML#media-resource">media resource</a> of
a <a>media element</a> that is used to <a>initiate remote
playback</a> on the selected <a>remote playback device</a> is
called the <dfn>remote playback source</dfn>. A remote playback
source MUST belong to the media element's <a>availability sources
set</a>.
</p>
<p>
The mechanism of picking the <a>availability sources set</a> and
the <a>remote playback source</a> is implementation-specific. For
example, the user agent MUST either use the
{{HTMLMediaElement/currentSrc}} of the <a>media element</a>
for both availability monitoring and remote playback or use all the
<a data-cite="HTML#media-resource">media resources</a>
associated with the <a>media element</a> as the
<a>availability sources set</a> and pick one of the resources as
the <a>remote playback source</a> after user selects the
<a>remote playback device</a>.
The mechanism to choose the <a>remote playback source</a> from
the <a>availability sources set</a> is implementation-specific,
but the user agent SHOULD consider every resource in
the <a>availability sources set</a> as a potential <a>remote
playback source</a>.
</p>
<div class="note">
The algorithm to select the <a>remote playback source</a> for a
selected device depends on the user agent and supported <a>remote
playback device</a> types. For example, in case of <a>media
mirroring</a> the user agent can simply follow the
{{HTMLMediaElement}}'s <a data-cite="HTML#concept-media-load-algorithm">
resource selection algorithm</a>. However, if <a>media
remoting</a> or <a>media flinging</a> is used, the best media
source can depend on the selected <a>remote playback device</a>
fetch and playback capabilities.
</div>
<p>
If the user agent cannot determine a <a>remote playback source</a>
appropriate for the <a>remote playback device</a>, it is
RECOMMENDED that the user agent send metadata (for example,
the <a data-cite="HTML#attr-source-type">extended MIME type</a>)
about all resources in the <a>availability sources set</a> to
the <a>remote playback device</a> so it can run its own
<a data-cite="HTML#concept-media-load-algorithm">resource
selection algorithm</a> and choose the <a>remote playback
source</a>.
</p>
<p>
Remote playback is said to be <dfn>unavailable</dfn> for the
<a>media element</a> if the <a>list of available remote playback
devices</a> is empty or none of them is compatible with any
source from <a>availability sources set</a> for the <a>media
devices</a> is empty or none of them is compatible with any source
from <a>availability sources set</a> for the <a>media
element</a>. The remote playback is said to be
<dfn>available</dfn> otherwise. A `boolean` set to
`false` if the remote playback is <a>unavailable</a>
Expand Down Expand Up @@ -1009,17 +1026,6 @@ <h4>
this user friendly name, using its locale and text direction when
they are known.
</div>
<div class="note">
The algorithm to select the <a>remote playback source</a> for a
selected device depends on the user agent and supported <a>remote
playback device</a> types. For example, in case of <a>media
mirroring</a> the user agent can simply follow the
{{HTMLMediaElement}}'s <a data-cite="HTML#concept-media-load-algorithm">
resource selection algorithm</a>.
However, if <a>media remoting</a> or <a>media flinging</a> is used,
the best media source can depend on the selected <a>remote playback
device</a> fetch and playback capabilities.
</div>
</section>
<section data-link-for="RemotePlayback">
<h4>
Expand Down Expand Up @@ -1131,25 +1137,24 @@ <h4>
"RemotePlaybackState">connected</a> through an icon or other means.
</p>
<div class="note">
The mechanism that is used to connect the user agent with the
<a>remote playback device</a> and play the <a>remote playback
source</a> is an implementation choice of the user agent. The
connection will likely have to provide a two-way messaging
abstraction capable of carrying media commands to the remote
playback device and receiving media playback state in order to keep
the <a>media element state</a> and <a>remote playback state</a> in
sync (unless <a>media mirroring</a> is used).
The mechanisms that are used to connect the user agent with the
<a>remote playback device</a>, select the <a>remote playback
source</a>, and initiate playback are all implementation choices of
the user agent. The connection will likely have to provide a two-way
messaging abstraction capable of carrying media commands to the
remote playback device and receiving media playback state in order
to keep the <a>media element state</a> and <a>remote playback
state</a> in sync (unless <a>media mirroring</a> is used).
</div>
<div class="note">
The user agent is encouraged to pass locale and text direction
information to the <a>remote playback device</a> when possible, so
that the <a>remote playback device</a> can adjust its user
interface and operational functions to locale-specific attributes
that reflect the user's preferences. For example, the <a>remote
playback device</a> can use that information to choose the same
default text track as the user agent, as well as to set the HTTP
`Accept-Language` header it sends to fetch media
resources.
that the <a>remote playback device</a> can adjust its user interface
and operational functions to locale-specific attributes that reflect
the user's preferences. For example, the <a>remote playback
device</a> can use that information to choose the same default text
track as the user agent, as well as to set the HTTP
`Accept-Language` header it sends to fetch media resources.
</div>
<div class="note">
The user agent should not render output from the media element while
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