Opened 8 years ago

Closed 7 years ago

#1229 closed defect (wontfix)

PSNR computation for Bit_Depths > 8

Reported by: gosk_balem Owned by:
Priority: minor Milestone:
Component: HM Version: HM-12.1
Keywords: PSNR Cc: fbossen, ksuehring, davidf, jct-vc@…

Description

During the PSNR computations, the maxvalY and maxvalC are computed as follows -

Int maxvalY = 255 << (g_bitDepthY-8);
Int maxvalC = 255 << (g_bitDepthC-8);

My contention is that they are incorrect and should be computed as

Int maxvalY = (1 << g_bitDepthY) - 1;
Int maxvalC = (1 << g_bitDepthC) - 1;

Change History (5)

comment:1 Changed 8 years ago by DefaultCC Plugin

  • Cc fbossen ksuehring davidf jct-vc@… added

comment:2 Changed 8 years ago by pandrivon

You are right. Besides, HM and JM PSNR computation do not match. This was already discussed with JCTVC-I0108. Chairs note were:
"The contributor noted a (very) small difference between the PSNR calculations in HM and JM. This difference not seem significant."
This was recalled some meetings after but no action were taken.

comment:3 Changed 8 years ago by dthoang

In the meeting notes of the January 2011 meeting in Daegu, there is this decision.

Decision: It was agreed that, when IBDI is turned on, the output of the decoding process is, in principle,
extended bit depth video, and the PSNR should be calculated without rounding the output first, with
PSNR calculated as PSNR = 10 * log10( (255*2^(N-8))^2 / MSE ).

This is the reason why the PSNR computation is what it is today. Although the reason may no longer apply since IBDI is no longer supported, any change in PSNR computation should be proposed and discussed at the next meeting.

comment:4 Changed 8 years ago by ksuehring

  • Milestone HM-13.0 deleted

comment:5 Changed 7 years ago by ksuehring

  • Resolution set to wontfix
  • Status changed from new to closed

I did not see this discussion being brought up during a JCT-VC meeting. I will close the software ticket here, because there is nothing to do in the software unless we decide to change the calculation at a meeting.

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