Still severe bitrate loss with aq-mode 2

[asarian]

Okay, I'm still experiencing severe bitrate loss with aq-mode 2.

Yesterday I re-encoded Blade Runner -- The Final Cut again (not having made the same mistake of throwing away the old encode first).

Old Encode: CRF 16, aq=1 = 16.2G
New Encode: CRF 14, aq=2 = 11.5G

As you can tell from the MediaInfo below, for the New Encode I lowered CRF by 2 (which ought to add ~25% filesize/bitrate). And still, the bitrate under aq=2 drops drastically below that of the Old Encode (by ca. 30%).

So, simple question, what's causing this? Is the newer x264 that much more efficient? I just can't explain this huge bitrate loss (overall nearly 6 Mbps).

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Old Encode:

Video
Bit rate                         : 19.7 Mbps
Maximum bit rate                 : 35.0 Mbps
Stream size                      : 16.2 GiB (71%)
Writing library                  : x264 core 66 r1093M 1df50b9
Encoding settings                : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x133 / me=tesa / subme=9 / psy_rd=1.0:0.0 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=-2 / threads=3 / nr=0 / decimate=1 / mbaff=0 / bframes=3 / b_pyramid=1 / b_adapt=2 / b_bias=0 / direct=3 / wpredb=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=crf / crf=16.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / vbv_maxrate=35000 / vbv_bufsize=35000 / ip_ratio=1.40 / pb_ratio=1.30 / aq=1:1.00

New Encode:

Video
Bit rate                         : 14.0 Mbps
Maximum bit rate                 : 40.0 Mbps
Stream size                      : 11.5 GiB (64%)
Writing library                  : x264 core 98 r1649 c54c47d
Encoding settings                : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x3:0x133 / me=tesa / subme=10 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=32 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-2 / threads=6 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=8 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=crf / mbtree=1 / crf=14.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / vbv_maxrate=60000 / vbv_bufsize=70000 / crf_max=0.0 / ip_ratio=1.40 / aq=2:1.00 / nal_hrd=non