[HarfBuzz] Any comments on ISO OFFS (ISO 14496-22 & ISO 9541-4)
lars at trolltech.com
Wed Jun 28 02:08:31 PDT 2006
On Wednesday 28 June 2006 07:07, mpsuzuki at hiroshima-u.ac.jp wrote:
> Recently, ISO MPEG-4 committie is going to replace their
> "standard" font format by OpenType, because existing PFR
> (by Bitstream) is not easy to produce a digital contents
> including internationalized text in non-Latin script.
> I heard that OpenType specification v1.4 is approved as
> ISO 14496-22, as it is.
> Although the new standard ISO 14496-22 is only for
> coding of multimedia data around moving pictures,
> the committie for ISO 9541 will approve same standard as
> new standard font format ISO 9541-4 (I remember, at
> present, ISO standard font format is only PS Type1 -
> in ISO 9541-1). So, I think, ISO 9541-4 will be the
> first standardization of TrueType graphic language :-).
> Do HarfBuzz developers have any comment on the standardization?
Moving to OpenType as the standard font format is a good move. It's currently
the only font format that is supported natively on all major operating
systems. At the same time the standard is open and available to everyone.
There is one thing I would like to point out: A small part of the standard has
some patent restrictions on it (see http://www.freetype.org/patents.html). It
would be nice to finally get a clarification from Apple on the issue, as I
don't think as standard such as OpenType (especially if it's going to be part
of ISO) should have patent restrictions on it. Maybe a standards body as the
MPEG-4 committee can achieve something here.
> I think, from the viewpoint of "standard", OpenType
> specification itself is insufficient to layout Unicode text.
> For example, the detailed procedure (which layout feature
> should be applied 1st, which is 2nd, ...) to layout Devanagari
> script is not described in OpenType font format. It is
> described in Microsoft's "Script-specific Development"
> document, but it is dependent with Uniscribe, and revised
> by Microsoft's VOLT community.
You are correct here. OpenType is just a font format. The script specific
documents describe how to do the layouting for a particular writing system.
> So, I'm afraid, the approving OpenType font format v1.4
> itself does not support to implement portable OpenType
> renderer. More detailed specification is required, even
> if it's just another approval of Microsoft implementation.
> (there can be a nightmare: a MPEG-4 video player including
> Uniscribe can show closed caption correctly, but others
> cannot. Oops)
Uniscribe is not the only implementation that implements the script specific
rules. Qt and Pango both implement the same rules for their text layouting
engines, as far as I know ICU also has some support for them.
So you are not limited to Microsofts Uniscribe library to achieve correct
layout of complex writing systems.
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