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<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Hi – I am new to this list, having just heard about
the chapter tags work. I am a researcher at Yahoo Berkeley, working on
annotation of time based media, and so we are naturally interested in the work
going on with Chapter tagging of MP3 content.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>My colleagues and I went through the docs today, and our
first impression is that we like much of what we see. We have a couple of
clarifying questions, and some suggestions. I am no expert on MP3 “syntax”
and header constraints, so forgive me if I make some silly suggestions that are
not in the spirit of MP3.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>My background is with XML formats, and especially SMIL [*].
As such, I was translating in my head from the descriptions I read to how I
think about descriptions for timing. I hope this is useful both from the
perspective of clarifying the semantics as expressed in your docs, and as an
introduction to producing a description of an XML schema that would parallel
your work (e.g., as an interchange language for tools producing ID3 Chapter frames).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>In SMIL timing [**], there are two common time containers: “par”
(for parallel) and “seq” (for sequence or sequential). Children of
par elements have timing relative to the par, but can overlap one another with
few constraints. Children of a seq are defined to be a sequence, and are
constrained to play one after another, possibly with delays between any two
items. While SMIL is defined for synchronization, the basic concepts can be
applied to this case as a description of the relationship of the chapters in a
CTOC element. It looks to me like CTOC plus the “Ordered bit”
in the flags is more or less equivalent to this – am I right? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>In the spec, the Chapter start time and end time are defined
as being relative to the beginning of the file, and yet the CTOC structure
implies that there is a hierarchy of chapter elements. I would think that it
makes more sense to have the timing reflect the TOC structure. Thus if I have
defined a major section of the file as a chapter, I can describe pieces within
that section relative to the section begin, rather than from the beginning of
the file. This means that start times and byte offsets must be added together
to find an absolute offset into the file, but it also means that excerpting a
section of the whole file is more straightforward (only the top-level offsets
change).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>This would of course require that the CTOC elements also
have timing information – does that conflict very much with your current thinking?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>We’ve been playing with some syntax to describe temporal
extents in media as part of an annotation framework. We are developing the XML
syntax for this now, but I can say that it borrows from SMIL timing syntax
(although a good deal more constrained (simpler) than the expressivity of SMIL
2.0 Timing. We are hoping that this would meld well with the ID3 chapter tags
work, allowing us a means of encapsulating our semantics in an MP3 file. Have
you done anything yet in the area of an XML syntax for the ID3 chapter tags? We’d
be happy to contribute to such an effort.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Thanks - Patrick<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>[*] SMIL 2.0 at W3C: <a
href="http://www.w3.org/TR/2005/REC-SMIL2-20050107/">http://www.w3.org/TR/2005/REC-SMIL2-20050107/</a>
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>[**] SMIL 2.0 time containers: <a
href="http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-timing.html#Timing-TimeContainerSyntax">http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-timing.html#Timing-TimeContainerSyntax</a>
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
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