[ttml2] Audio related feature changes

nigelmegitt has just created a new issue for https://github.com/w3c/ttml2:

== Audio related feature changes ==
Having reviewed the BBC's ability to provide presentation implementations for the audio features, I would like to propose the following changes to at-risk features:

* remove the [`#embedded-audio`](https://www.w3.org/TR/ttml2/#feature-embedded-audio) feature designator, because it requires playback of audio resources embedded in the TTML2 file which BBC does not expect to be able to demonstrate. I would not like to remove the syntactical possibility of embedded audio resources directly, but arguably we may need to do that also. If I can find a way for BBC to implement this in the next day or so then I will propose "un-removing" `#embedded-audio` - I'm merely taking a conservative line here given the limited amount of remaining time.
* change `#embedded-audio` to `#audio` in [`#audio-description`](https://www.w3.org/TR/ttml2/#feature-audio-description) to match the previous change.
* Remove `#embedded-audio`, `#gain` and `#pan` from [`#audio-speech`](https://www.w3.org/TR/ttml2/#feature-audio-speech) because I do not think we can implement them all together straightforwardly, at least not so they are all applied at once to the same text using a combination of Web Audio API and Web Speech API, as they are in their current states; other implementation techniques could be made to work, such as making external asynchronous calls to a suitable text to speech service and playing back the resulting audio resource, but that requires a further degree of complexity.
* Remove `#speech` because it is not clear what it means for an implementation to "support" a speech synthesis processor, for example must the implementation include one or merely access one remotely? If the implementation can successfully implement `#speak` and `#pitch` then it has adequate support; further support is not required, in my view.

Please view or discuss this issue at https://github.com/w3c/ttml2/issues/990 using your GitHub account

Received on Monday, 10 September 2018 08:32:18 UTC