0000366: Error in deblocking process of mbaff frames

ID	Project	Category	View Status	Date Submitted	Last Update

0000366	JVT JM H.264/AVC reference software	decoder	public	2020-04-07 21:40	2020-11-25 16:28

Reporter	Dev	Assigned To
Priority	normal	Severity	major	Reproducibility	always
Status	resolved	Resolution	open

Summary	0000366: Error in deblocking process of mbaff frames
Description	Hi, It seems that there is a error in JM H.264 decoder in deblocking process of MbAff frames for luma field macroblocks. The following is for JM 11.0 but the same problem also exists in newer versions. The error is in calculating pixQ.pos_y in loopfilter.c. In EdgeLoop() you use getNeighbour() for it. Pos_y calculated in get_mb_pos(), get_mb_block_pos() as y = (((mb_addr / 2) / PicWidthInMbs) * 2 + (mb_addr % 2)) * 16; i.e. y = ((mb_addr / 2) / PicWidthInMbs) * 32 + ((mb_addr % 2) * 16) It is a position of the upper-left luma sample of the macroblock CurrMbAddr and it is determined in standart (subclause 8.7.1) as inverse macroblock scanning process (6.4.1) and assigned to yI: y = ((mb_addr / 2) / (PicWidthInSamples / 16)) * 32 + (mb_addr % 2); i.e. y = ((mb_addr /2) / PicWidthInMbs) * 32 + (mb_addr % 2) So for odd values of mb_addr the result in JM is wrong.
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Date Modified	Username	Field	Change
2020-04-07 21:40	Dev	New Issue
2020-11-25 16:27	Dev	Note Added: 0000645
2020-11-25 16:28	Dev	Status	new => resolved

Dev 2020-11-25 16:27 reporter ~0000645	At the end I figured it out. It is not a bug, it is just a method to store data. Everything is in full compliance with the standard.