Don’t Hurry To Consider Your AVC/H.264 Stream as HRD non-compatible if a HRD Analyzer Reports on Overflow with Excess 1 Bit
One of subtle drawbacks of AVC/H.264 HRD is that division operations are specified as abstract mathematical divisions, denoted by the symbol ÷ . The AVC/H.264 spec. specifies this symbol as follows:
÷ Used to denote division in mathematical equations where no truncation or rounding is intended
For example, the formula C-4 uses this abstract mathematical division:
tai,earliest( n ) = tr,n( n ) − ( initial_cpb_removal_delay[ SchedSelIdx ] + initial_cpb_removal_delay_offset[ SchedSelIdx ] ) ÷ 90000
Due to abstractness of the division ÷ in various implementations of HRD Analyzer slightly different magnitudes of CPB fullness might be calculated. Consequently, the following situation might occur: one HRD Analyzer with the division implemented in 32-bits floating point reports on a CPB overflow with excess of 1 bit while another HRD Analyzer with 64-bits floating point does not sense any violation.
23+ years’ programming and theoretical experience in the computer science fields such as video compression, media streaming and artificial intelligence (co-author of several papers and patents).
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