[x264-devel] What is the problem of x264? Is it a bug?

[kevin bai]

Hi all,

When use x264 for 2 pass encoding, I find there is a big VQ gap at I frame.
I captured some logs as below:
The avg QP of index 6299  I frame jumps to 54.79, which make the total
frame is blur.
The content of the source steam is courseware, the most frames are still
only with some characters change.


1st pass
in:6290 out:6292 type:b dur:2 cpbdur:2 q:24.17 aq:26.93 tex:84 mv:10
misc:154 imb:0 pmb:3 smb:877 d:s ref:0 ;
in:6292 out:6293 type:b dur:2 cpbdur:2 q:24.17 aq:16.00 tex:0 mv:0 misc:128
imb:0 pmb:0 smb:880 d:- ref:0 ;
in:6296 out:6294 type:P dur:2 cpbdur:2 q:25.19 aq:21.69 tex:139165 mv:3188
misc:559 imb:212 pmb:222 smb:446 d:s ref:0 ;
in:6295 out:6295 type:B dur:2 cpbdur:2 q:26.24 aq:25.08 tex:104779 mv:4030
misc:495 imb:92 pmb:324 smb:464 d:s ref:0 ;
in:6294 out:6296 type:b dur:2 cpbdur:2 q:26.60 aq:27.30 tex:95845 mv:3841
misc:514 imb:84 pmb:306 smb:490 d:s ref:0 ;
in:6298 out:6297 type:P dur:2 cpbdur:2 q:28.68 aq:19.39 tex:144086 mv:3561
misc:449 imb:301 pmb:177 smb:402 d:s ref:0 ;
in:6297 out:6298 type:b dur:2 cpbdur:2 q:28.76 aq:29.67 tex:90747 mv:3950
misc:463 imb:102 pmb:330 smb:448 d:s ref:0 ;
in:6299 out:6299 type:I dur:2 cpbdur:2 q:31.59 aq:18.22 tex:308469 mv:24386
misc:441 imb:880 pmb:0 smb:0 d:s ref:;
in:6303 out:6300 type:P dur:2 cpbdur:2 q:31.97 aq:19.20 tex:12110 mv:496
misc:754 imb:26 pmb:172 smb:682 d:s ref:0 ;
in:6301 out:6301 type:B dur:2 cpbdur:2 q:32.40 aq:14.00 tex:8 mv:17
misc:151 imb:0 pmb:3 smb:877 d:s ref:0 ;
in:6300 out:6302 type:b dur:2 cpbdur:2 q:32.40 aq:17.00 tex:11 mv:3
misc:138 imb:0 pmb:1 smb:879 d:s ref:0 ;
in:6302 out:6303 type:b dur:2 cpbdur:2 q:32.40 aq:17.00 tex:11 mv:3
misc:138 imb:0 pmb:1 smb:879 d:- ref:0 ;
in:6307 out:6304 type:P dur:2 cpbdur:2 q:31.26 aq:16.81 tex:13638 mv:453
misc:725 imb:22 pmb:182 smb:676 d:s ref:0 ;

2nd pass
in:6292 out:6293 type:b dur:2 cpbdur:2 q:6.03 aq:3.00 tex:113 mv:267
misc:468 imb:0 pmb:532 smb:348 d:- ref:2048 0 0 0 ;
in:6296 out:6294 type:P dur:2 cpbdur:2 q:15.83 aq:14.33 tex:165460 mv:18106
misc:498 imb:122 pmb:312 smb:446 d:s ref:752 209 210 53 23 1 ;
in:6295 out:6295 type:B dur:2 cpbdur:2 q:15.68 aq:14.62 tex:123695 mv:11211
misc:502 imb:38 pmb:280 smb:432 d:s ref:626 63 19 1 0 ;
in:6294 out:6296 type:b dur:2 cpbdur:2 q:43.20 aq:12.03 tex:37729 mv:4327
misc:352 imb:17 pmb:165 smb:669 d:s ref:288 17 1 4 ;
in:6298 out:6297 type:P dur:2 cpbdur:2 q:39.84 aq:31.40 tex:20417 mv:8994
misc:573 imb:125 pmb:367 smb:388 d:s ref:464 46 477 344 96 29 12 ;
in:6297 out:6298 type:b dur:2 cpbdur:2 q:39.49 aq:44.37 tex:7298 mv:3565
misc:625 imb:12 pmb:335 smb:521 d:s ref:370 65 164 8 ;
in:6299 out:6299 type:I dur:2 cpbdur:2 q:54.79 aq:45.91 tex:22558 mv:7107
misc:439 imb:880 pmb:0 smb:0 d:s ref:;
in:6303 out:6300 type:P dur:2 cpbdur:2 q:35.56 aq:24.53 tex:159533 mv:19446
misc:221 imb:477 pmb:393 smb:10 d:s ref:1572 ;
in:6301 out:6301 type:B dur:2 cpbdur:2 q:56.92 aq:3.00 tex:0 mv:0 misc:136
imb:0 pmb:0 smb:880 d:s ref:0 ;
in:6300 out:6302 type:b dur:2 cpbdur:2 q:55.51 aq:3.00 tex:0 mv:0 misc:136
imb:0 pmb:0 smb:880 d:s ref:0 ;
in:6302 out:6303 type:b dur:2 cpbdur:2 q:55.33 aq:3.00 tex:0 mv:0 misc:136
imb:0 pmb:0 smb:880 d:- ref:0 0 ;
in:6307 out:6304 type:P dur:2 cpbdur:2 q:22.31 aq:12.04 tex:224603 mv:10127
misc:478 imb:98 pmb:712 smb:70 d:s ref:2202 580 58 8 ;


What's the problem? Is it a bug of x264?

Thanks,
Kevin
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