This Section defines a number of baseline media formats that the members of
the W3C SYMM Working Group believe will be widely supported by SMIL players.
Authors are encouraged to encode media objects in these formats to ensure that
their SMIL documents can be played back by a wide range of SMIL
implementations. Often, for audio and video formats, the baseline formats will
be used as fallbacks when a player cannot render a more efficient, but less
widely supported format. This can be achieved by using a
element as shown in the following example:
<switch> <audio src="non-baseline-format-file" /> <audio src="baseline-format-file" /> </switch>
Note that this Section is non-normative, and that thus implementation of the baseline formats is not a precondition for conformance to this specification.
For selecting the baseline formats, the following criteria were used:
@@ defined as follows: The content of the "audio/basic" subtype is single channel audio encoded using 8bit ISDN mu-law [PCM] at a sample rate of 8000 Hz. Note that this is probably a subset only of .au - need a spec for .au.
Bandwidth: 64 Kbit/s
Editor's note: The Working Group encourages information on other audio formats that have lower bandwidth requirements than audio/basic and also do not require a license fee.
@@@ all the following "support" lists will not go in the final version
@@ efforts to come up with license-free audio codecs
@@ are there licensing requirements for MPEG-1 ? The availability of Linux code would tend to suggest there aren't.
@@ should restrict to one track and one codec, e.g motion JPEG or Cinepak
Editor's note: The Working Group encourages information on other video formats that have lower bandwidth requirements that do not require a license fee.
For profiles supporting SMIL layout, players must choose a font size so
that the constraints expressed by the
fit attribute of the
region element associated with the media object are
fulfilled. If there is no associated
region element, @@@ all
bets are off, since text has no intrinsic size.
@@ need to provide interpretation for "fit" attribute for objects
without intrinsic size
@@ suggestion to use CSS proposal for "copyfitting" (@@ pointer ?)
@@ suggestion to use generic CSS font names, see http://www.w3.org/TR/REC-CSS2/fonts.html#generic-font-families
@@ suggestion to require CSS support for text/plain
XHTML profile consisting only of the
basic modules [XMOD] "Structure" (contains e.g.
body element), "Basic Text" (contains e.g.
h1 element), "Hyptertext" (contains
element) and "List" (contains e.g.
elements). The elements in this profile should be formatted using
formatting described in CSS2 (@@ this means that the formatting is
mostly fixed, and that there is no need to support CSS).
@@ Auxiliary links