JVET HEVC: Ticket #544: Non-normative aspects in scaling process (8.6.3) should be removed
https://hevc.hhi.fraunhofer.de/trac/hevc/ticket/544
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Equations (8-262), (8-264), and (8-270) should be removed as they relate to a specific implementation to avoid 32-bit overflow in some corner cases. Removing these equations has no normative impact.
levelLimit defined in equations (8-262) and (8-264) takes value 15 most of the time, and value 14 for a combination of log2TrSize=2 and large qP values such that BitDepth - qP/6 = 0.
The case where levelLimit is 15 is not relevant anymore following adoption of I0254.
In the case where levelLimit is 14, the clipping to the -16384..16383 range defined in (8-270) has no effect on the value computed in (8-271) since (8-271) scales the output of (8-270) by a factor of at least 40 and defines another clipping operation to the -32768..32767 range. The clipping operation of (8-270) should thus be removed from the specification as it has no normative effect.
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For simplicity, it may also be preferable to define the scaling process using a single equation (without changing the normative behavior):
d_ij = Clip3( −32768, 32767,( ( c_ij * M[i][j] * levelScale[ qP%6 ] << ( qP/6 ) ) + ( 1 << ( shift + 3 ) ) ) >> (shift + 4) )
where M[i][j] = 16 if scaling_list_present_flag is equal to 0
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<p>
It may be appropriate to add a note to clarify than for c_ij = -32768, M[i][j] = 255, qP = 51, and shift = 1, the correct value of d_ij is -32768 (and not 32767, which is the value one might get if not correctly implementing corner cases).
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en-usTrac 1.0.18DefaultCC PluginThu, 24 May 2012 18:27:30 GMTcc set
https://hevc.hhi.fraunhofer.de/trac/hevc/ticket/544#comment:1
https://hevc.hhi.fraunhofer.de/trac/hevc/ticket/544#comment:1
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<li><strong>cc</strong>
<em>bbross</em> <em>wjhan</em> <em>jct-vc@…</em> added
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TicketbbrossFri, 01 Jun 2012 20:35:11 GMTstatus changed; resolution set
https://hevc.hhi.fraunhofer.de/trac/hevc/ticket/544#comment:2
https://hevc.hhi.fraunhofer.de/trac/hevc/ticket/544#comment:2
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<li><strong>status</strong>
changed from <em>new</em> to <em>closed</em>
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<li><strong>resolution</strong>
set to <em>fixed</em>
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</ul>
<p>
Fixed in D7 (I1003) d2
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