[whatwg] Background audio channels

[Paul Bakaus]

I support this proposal ­ makes total sense to me. We (Zynga) promise
we'll not misuse the priority channels :)

On 15.03.13 18:57, "Wesley Johnston" <wjohnston at mozilla.com> wrote:

>In most situations, when the user puts a webpage in the background, any
>media being played by the page should be paused. Any attempts to play
>audio by a background page should also be prevented. However, for some
>sites (music or radio apps) the user would like to continue to hear the
>app while they do something else. These pages should be able to designate
>their audio as a type that should keep playing while in the background.
>The useragent should also attempt to avoid having the stream killed by
>the operating system if possible. This is especially true on mobile
>devices, but the problem is also already prevalent on desktop.
>
>I think semantically we need a way to describe to the useragent how to
>play a particular track. I'd suggest we add an optional attribute to
>media elements, "audiochannel", designating the output and priority of
>this audio. The channel attribute can potentially take on three different
>values. "normal", "background", and "telephony".
>
>"normal" channels are the default for all media elements. Using them
>doesn't require any special permissions. Audio playing with these
>channels is paused when the web page moves into the background. In
>addition, calling play on an media element with this channel while in the
>background will put the element into the paused for user interaction
>state (i.e. playback won't start until the webapp is brought to the
>foreground)?
>
>"background" channels will continue to play when the page is put into the
>background. Trying to play a background channel while in the background
>should also work. The ability to play audio on this channel may require
>requesting permission from the UA first (i.e. possibly a prompt when the
>audio is first played or when moving to the background). If the user
>doesn't grant permission, these should throw a MediaError
>(MEDIA_ERR_CHANNEL_PERMISSION_NOT_GRANTED?) so that the page can know
>what has happened and do something appropriate.
>
>"telephony" channels are similar to "background" channels and can play
>even if the page is in the background. Playing audio on a telephony
>channel may cause any audio playing on "normal" or "background" channels
>to be paused or have their volume severely decreased. They also, on
>devices where its supported, will likely play over handset speakers
>rather than normal speakers. Similar to "background", these may require
>permission from the UA.
>
>Note: This is all based rather loosely on the AudioChannels
>implementation written for B2G recently [1]. It includes a few other
>use-cases on its wiki page, along with definitions of additional channels
>to accomadate them. I've been trying to simplify it down to handle the
>most common use cases. Finding the correct terminology here is difficult
>though. For instance, it seems likely that games will see the background
>channel and think its an appropriate place to play game background music,
>the exact type of audio you'd like to have paused when you leave the
>game. Ideas for better ways to describe it are welcome.
>
>[1] https://wiki.mozilla.org/WebAPI/AudioChannels