[M4IF Technotes] video packet length

[Gary Sullivan]

I believe there is no signal of video packet length in an MPEG-4 Visual
bitstream.  The decoder can (and shall) determine the length by
examining the values of the bits in the stream to see whether the
contents match macroblock data or bit-stuffing/resync/start-code.
Although you say you know it is specified, I'm not aware of any
specified maximum length (other than the rather absurd limit computed
from the VBV fullness and VBV buffer capacity or computed from the
remaining number of macroblocks in a picture).
Fixed-interval synchronization is also not specified.  It is something
an encoder can choose to do or not to do, as far as the video spec is
concerned.  What need is there to signal this to a decoder?
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: technotes-admin   lists.m4if.org 
+> [mailto:technotes-admin   lists.m4if.org] On Behalf Of 
+> ramakrishna_kakarala   agilent.com
+> Sent: Wednesday, June 18, 2023 10:03 AM
+> To: technotes   lists.m4if.org
+> Subject: [M4IF Technotes] video packet length
+> 
+> 
+> Hi,
+> 
+> How is video packet length signalled to the
+> decoder? I don't see a field for it in the 
+> video bitstream syntax.  I know the *maximum* length 
+> is specified (if data partitioning is used)
+> but I don't know how the actual value is
+> signalled.  Is it signalled in the systems
+> layer?
+> 
+> If the packet length is not signalled,
+> then how does fixed interval synchronization
+> work? 
+> 
+> thanks for your help
+> Ram
+> ---------------------------------
+> Ramakrishna Kakarala  
+> Agilent Technologies  
+> 5301 Stevens Creek Blvd, MS 51L-GX
+> Santa Clara, CA 95052-8059
+> ramakrishna_kakarala   agilent.com 
+> Tel (408) 553-2349
+> Fax (408) 553-3794> 
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