[webvtt] Wide Review Comment 2017: Timestamp syntax

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

== Wide Review Comment 2017: Timestamp syntax ==
Copy/paste from https://lists.w3.org/Archives/Public/public-tt/2017Sep/0080.html - raising as an issue for tracking/disposition purposes.

The syntax of WebVTT timestamps requires that all timestamps contain a full stop character followed by three digits. This is a likely source of errors in two ways: Firstly, if a conformant processor sees a timestamp with a different number of characters (even a greater number) after the full stop, rather than returning a valid alternative time, it returns an error. This is therefore not robust to authoring errors. Secondly, a non-conformant processor that does not return an error must make a decision about how to deal with the strange number of digits. Since it is clearly defined as a "number of milliseconds" most interpretations would/should treat a timestamp such as "00:00:01.2" as having 2 milliseconds, but this is contrary to the normal mathematical representation of a fractional value, which would consider it to be 200 milliseconds. I would propose that the parser should a) append '0's after the value4 string to pad it to 3 characters if it has fewer than 3 and b) truncate the value4 string to 3 characters if it has more than 3. (rounding seems pointlessly complex when the significance is +/- 0.5ms and the user agent probably doesn't meet that level of precision anyway)


Please view or discuss this issue at https://github.com/w3c/webvtt/issues/370 using your GitHub account

Received on Wednesday, 27 September 2017 11:02:49 UTC