[shon3i]

Seems that BDQuest not follow BD-Specs, because clearly stay that 720p can use max 6 reference frames, and here is parametar limits for AVC

Parameter limits
Following constraints are applied for all HDMV MPEG-4 AVC video streams.
• Minimum size per one slice is 1 macroblock row (macroblock row or macroblock pair row). A slice
shall be composed of one or more macroblock rows. A macroblock row indicates all the
macroblocks in a horizontal row of macroblocks.
• Maximum number of frames or complementary field pairs which are stored in DPB is restricted in
addition to ITU-T H.264 | ISO/IEC 14496-10.
�� In case of level 4.1 and 4
�� For 1920x1080: 4 (as defined in ITU-T H.264 | ISO/IEC 14496-10[11].)
�� For 1440x1080: 4
�� For 1280x720: 6
�� For 720x480 or 720x576: 6
�� In case of level 3.2 and 3.1
�� For 720x480 or 720x576: 6
�� In case of level 3
�� For 720x480:6
�� For 720x576: 5
• In case of level 4 and level 4.1, the size of CPB shall be less than or equal to 30000 [1000bits].
• Minimum compression ratio (MinCR) (Note) for Main profile and the equivalent constraint for High
profile shall be restricted as follows;
�� For Main profile level 4.1, MinCR=4 for movie stream, MinCR=2 for still picture
�� For High profile level 4.1, the same semantic constraint as described above shall be applied.
�� For other levels of High profile, the same semantic constraint on MinCR for Main profile shall
be applied.
(Note): The semantic constraint on MinCR for Main profile is described in Annex A of the ISO/IEC
14496-10[11].
• If level_idc in SPS indicates level 4.1, each picture shall be encoded as multi-slice picture with 4 or
more slices per picture. The number of macroblocks in any slice shall not exceed 1/2 of the total
number of macroblocks. The number of macroblock rows in every slice in the picture should be as
equal as possible for the current picture height and interlace coding mode.
�� In case of 1920x1080 video format with frame_mbs_only_flag=1, it is recommended that
each slice has 17 macroblock rows (17/17/17/17 configuration).
�� In case of 1920x1080 video format with frame_mbs_only_flag=0 and
mb_adaptive_frame_field_flag=0, it is recommended that in each field, odd numbered slices
have 8 macroblock rows each and even numbered slices have 9 macroblock rows each
(8/9/8/9 configuration) or some similar configuration.
�� In case of 1920x1080 video format with frame_mbs_only_flag=0 and
mb_adaptive_frame_field_flag=1, it is recommended that odd numbered slices have 16
macroblock rows each and even numbered slices have 18 macroblock rows each
(16/18/16/18 configuration) or some similar configuration.
�� In case of 1280x720 video format, it is recommended that four slices have 11/11/11/12 or
some similar configuration.