Clarify how grouped streams are not "Ogg Opus files".

We mean to make .opus only for degenerate--not concurrently
multiplexed or grouped--but optionally sequentially multiplexed
or chained physical Ogg streams.

However, we don't mean to say you can't use this draft with
such streams.

Also, replace the reference to RFC3534 with RFC5334, which
obsoletes the previous reference by defining video/ogg and
audio/ogg.

doc/draft-ietf-codec-oggopus.xml

@@ -2,9 +2,9 @@
 <!DOCTYPE rfc SYSTEM 'rfc2629.dtd' [
 <!ENTITY rfc2119 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.2119.xml'>
 <!ENTITY rfc3533 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.3533.xml'>
-<!ENTITY rfc3534 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.3534.xml'>
 <!ENTITY rfc3629 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.3629.xml'>
 <!ENTITY rfc4732 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.4732.xml'>
+<!ENTITY rfc5334 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.5334.xml'>
 <!ENTITY rfc6381 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.6381.xml'>
 <!ENTITY rfc6716 PUBLIC '' 'https://xml2rfc.tools.ietf.org/tools/xml2rfc/public/rfc/bibxml/reference.RFC.6716.xml'>
 ]>
@@ -1142,9 +1142,6 @@ Elements such as the Ogg page capture pattern and the magic signatures in the
 An "Ogg Opus file" consists of one or more sequentially multiplexed segments,
  each containing exactly one Ogg Opus stream.
 The RECOMMENDED mime-type for Ogg Opus files is "audio/ogg".
-When Opus is concurrently multiplexed with other streams in an Ogg container,
- one SHOULD use one of the "audio/ogg", "video/ogg", or "application/ogg"
- mime-types, as defined in <xref target="RFC3534"/>.
 </t>
 
 <t>
@@ -1162,6 +1159,15 @@ audio/ogg; codecs=opus
 The RECOMMENDED filename extension for Ogg Opus files is '.opus'.
 </t>
 
+<t>
+When Opus is concurrently multiplexed with other streams in an Ogg container,
+ one SHOULD use one of the "audio/ogg", "video/ogg", or "application/ogg"
+ mime-types, as defined in <xref target="RFC5334"/>.
+Such streams are not strictly "Ogg Opus files" as described above,
+ since they contain more than a single Opus stream per sequentially
+ multiplexed segment, e.g. video or multiple audio tracks.
+In such cases the the '.opus' filename extension is NOT RECOMMENDED.
+</t>
 </section>
 
 <section title="IANA Considerations">
@@ -1194,8 +1200,8 @@ The authors agree to grant third parties the irrevocable right to copy, use,
 <references title="Normative References">
  &rfc2119;
  &rfc3533;
- &rfc3534;
  &rfc3629;
+ &rfc5334;
  &rfc6381;
  &rfc6716;