0000056: SE decoding integer range overflow

ID	Project	Category	View Status	Date Submitted	Last Update

0000056	JVT JM H.264/AVC reference software	decoder	public	2007-06-07 13:31	2007-08-08 15:07

Reporter	Karsten Suehring	Assigned To
Priority	normal	Severity	minor	Reproducibility	always
Status	acknowledged	Resolution	open
Platform	any
Product Version	JM 12.2

Summary	0000056: SE decoding integer range overflow
Description	"zhang" reported: We have a problem about SE decoding in JM. While decoding delta_pic_order_cnt_bottom, the input bistream(removed emulation prevetion byte 0x03) is 000000000000000000000000000000011111111111111111111111111111110 (binary), it's value should be 0x7fff_ffff = 2^31 - 1, the max. value of delta_pic_order_cnt_bottom defined in spec. 7.4.3 but use JM decoder, it's decoded value = -1, In JM vlc.c void linfo_se(int len, int info, int value1, int dummy) { int n; assert (len/2<32); n = (1 << (len/2))+info-1; value1 = (n+1)/2; if((n & 0x01)==0) // lsb is signed bit value1 = -*value1; } n is 32 bit value will be overflow because n is a signed value. Another, in the case that SE value equal -2^31, n must be 33 bit(at least) unsigned value. Is this condition is my mis-understanding or there is a problem in JM ?
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Date Modified	Username	Field	Change
2007-06-07 13:31	Karsten Suehring	New Issue
2007-08-08 15:07	Karsten Suehring	Relationship added	related to 0000044
2007-08-08 15:07	Karsten Suehring	Status	new => acknowledged