[M4IF Technotes] Using fixed_vop_rate

[Gary Sullivan]

All syntax values should obviously still be correct
unless the standard says otherwise.  I believe
fixed_vop_rate=1 is just an indication that
specific behavior in the other fields is
ensured (and if the decoder sees something
else, then there is some kind of problem).
Just think of it as a redundant representation of
the information using an overcomplete set of basis
functions ;-)
Best Regards,
-Gary S.
+> -----Original Message-----
+> From: Ralph Neff [mailto:neff   packetvideo.com] 
+> Sent: Friday, March 22, 2024 6:01 PM
+> To: technotes   lists.m4if.org
+> Subject: [M4IF Technotes] Using fixed_vop_rate
+> 
+> 
+> 
+> Hi,
+> 
+> I have a question on the use of fixed_vop_rate in MPEG-4 
+> visual.  With fixed_vop_rate == 1, what happens to the
+> rest of the time fields (e.g. modulo_time_base and 
+> vop_time_increment)?  Specifically:
+> 
+>   1. If I author a stream and set fixed_vop_rate == 1, do I still
+>       have to maintain the fields normally used for variable
+>       display times?  Or can I set them to zero-or-random
+>       values?
+>   2. When decoding a file with fixed_vop_rate == 1, should a
+>       decoder ignore these other time fields?  Or can it use them,
+>       expecting them to match the fixed rate?
+> 
+> I'm curious because the usual time fields are present in the
+> syntax even when using fixed_vop_rate mode, so it's not clear
+> to me whether fixed_vop_rate is intended as a hint or as a
+> complete override.  Thanks for any help understanding this.
+> 
+> -Ralph
+> 
+> 
+> Ralph Neff   *   Packetvideo   *   www.pv.com
+> neff   pv.com   *  phone: 858-731-5408   *   fax: 858-731-5311
+> 
+> 
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