Supporting SMPTE-TT

[alexandercerutti]

With the integration of the TTML adapter, we are evaluating if we should support SMPTE ttp:timeBase.

There's also an extension of TTML which supports some features.
The article on Speechpad (linked below) describes them nicely.

Notes on adapters

Should we support SMPTE-TT inside TTML Adapter or in a different adapter?

If choosing a different adapter, we put ourselves in front of a choice: should we duplicate the adapter code or make adapters extendable?

When choosing the extendability, we are talking about changing the architecture to let adapters be hookable or something like that. Extenders should be able to intercept the parsing phase. Intercepting points must be defined.

Notes on captions-renderer

Of course, this change will go to impact also the captions-renderer. This is due to the support of bitmap images by SMPTE-TT, along with rendering style.

Useful resources

• https://ieeexplore.ieee.org/document/7290363
• https://www.speechpad.com/captions/smpte-tt