[Mp4-tech][video] modulo time question

[Herbert Thoma]

Hi!
Sandip Parikh schrieb:
> Hello:
> 
> I recently came across a MPEG-4 (SP L1) stream that did not always have
> modulo_time_base set to non-zero when the vop_time_increment wrapped
> around:
> 
> vop_time_increment      modulo_time
> 340                                    0
> 407                                    0
> 474                                    0
> 541                                    0
> 0                                        0    // modulo_time_base
> remains 0
> 67                                    0
> 134                                    0
> 201                                    0
> 
> Is this valid ? If so, how should a decoder interpret the presentation
> times ?

I think the only case where this would be valid is when a GOV header is in the
bitstream directly before the VOP where the modulo_time_base remains 0. A GOV
header does "reset" the modulo_time_base.
Regards,
  Herbert.
> Thank you,
> 
> Regards,
> 
> Sandip
> 
> 
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-- 
Herbert Thoma
Group Manager Video
Multimedia Realtime Systems Department
Fraunhofer IIS
Am Wolfsmantel 33, 91058 Erlangen, Germany
Phone: +49-9131-776-323
Fax:   +49-9131-776-399
email: tma iis.fhg.de
www: http://www.iis.fhg.de/