Re: WebVTT Spec Question

On Fri, Mar 8, 2013 at 3:10 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com>wrote:

> No, there is no conflict. The first one is the current spec, the second is
> the requirement on how to parse it so that the current spec can be extended
> in the future.
>

Just to clarify (at least to my understanding): The first is the file
format, and the second is the parser.  Both are part of the spec.  The file
format tells you what's valid--what authors should be writing.  The parser
tells you how to deal with every possible input, which includes error
handling (inputs that don't follow the file format) and--as you
said--forwards-compatibility.

I've seen a couple people confused by this, leading to people trying to
write implementations by looking at the file format, which is bad.  Browser
vendors understand it, since that's how the HTML spec works, but since
non-browser people without experience with that spec may be implementing
this (more than most other parts of the web), maybe there should be a brief
note at the top of the file format section explaining this.  ("If you're
implementing WebVTT, you're in the wrong place!")

We indeed have made use of header metadata lines in this spec:
> https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/608toVTT.html
>

This format doesn't seem to handle some important points we talked about
before, like blank lines and the "-->" issue.  I'll do some digging to see
what discussion there has been since then that I might have missed, review
the old thread to recall what the various concerns were and start a
separate thread with a summary so we can make sure we're not missing
anything.

On Fri, Mar 8, 2013 at 3:23 PM, David Ronca <dronca@netflix.com> wrote:
> Is implementation-specific metadata permissible (defined outside of any
public spec)? If so, any parser that did not recognize the metadata should
just ignore?

No, implementations should not be inserting custom metadata.  The spec
allows for metadata in order to leave room to add standard metadata in the
future without breaking existing parsers, because the old parsers--as long
as they follow the spec--understand how to skip past the headers, even
though it doesn't know what they mean.

If people start using this for their own purposes, it'll break things later
and subvert the forward planning built into the parser.

On Fri, Mar 8, 2013 at 5:18 PM, Ralph Giles <giles@mozilla.com> wrote:

> If you do want to do something application-specific here, at least try
> to follow the syntax rules implied by Silvia's draft. Then when you have
> some implementation experience, we should try to spec what those rules
> actually are.
>

Please don't do that, either.  Don't put anything in there at all until
we're sure of what the format should be.

-- 
Glenn Maynard