Opened 11 years ago

Closed 11 years ago

#448 closed defect (fixed)

libx264 preset's rc_lookahead value is overwritten

Reported by: Andrew Wason Owned by:
Priority: normal Component: avcodec
Version: git-master Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

Specifying -preset slow with libx264 should result in rc_lookahead of 50, instead it is 40.

In X264_init() x4->params.rc.i_lookahead is initialized to 50 by x264_param_default_preset() for the "slow" preset. But then later it is overwritten by avctx->rc_lookahead which is 40

This problem was introduced in commit d4b967131842e7c225e5f83cb82337d4474a0bb7 which added the rc_lookahead private option.

From a gdb session:

257         if (x4->preset || x4->tune)
(gdb) 
258             if (x264_param_default_preset(&x4->params, x4->preset, x4->tune) < 0) {
(gdb) p x4->preset
$7 = 0x14790c0 "slow"
(gdb) n
263         if (avctx->level > 0)
(gdb) p x4->params.rc.i_lookahead
$8 = 50
[...]
335         if (avctx->rc_lookahead >= 0)
(gdb) 
336             x4->params.rc.i_lookahead             = avctx->rc_lookahead;
(gdb) 
337         if (avctx->weighted_p_pred >= 0)
(gdb) p x4->params.rc.i_lookahead
$9 = 40

Full ffmpeg output:

ffmpeg -i /tmp/apollo11.mov -an -codec:v libx264 -preset:v slow -y /tmp/foo.mp4

ffmpeg version N-32420-g88fddd0, Copyright (c) 2000-2011 the FFmpeg developers
  built on Sep  9 2011 20:33:39 with gcc 4.4.3
  configuration: --extra-cflags=-I/opt/motionbox/foundation/6.4.0/include --extra-ldflags=-L/opt/motionbox/foundation/6.4.0/lib --enable-libx264 --enable-gpl --enable-debug=gdb3 --disable-optimizations
  libavutil    51. 16. 0 / 51. 16. 0
  libavcodec   53. 13. 0 / 53. 13. 0
  libavformat  53. 12. 0 / 53. 12. 0
  libavdevice  53.  3. 0 / 53.  3. 0
  libavfilter   2. 39. 0 /  2. 39. 0
  libswscale    2.  1. 0 /  2.  1. 0
  libpostproc  51.  2. 0 / 51.  2. 0
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x25d6780] max_analyze_duration 5000000 reached at 5000000

Seems stream 0 codec frame rate differs from container frame rate: 600.00 (600/1) -> 3.00 (3/1)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/tmp/apollo11.mov':
  Metadata:
    creation_time   : 1998-01-05 21:59:31
  Duration: 00:00:06.66, start: 0.000000, bitrate: 22 kb/s
    Stream #0.0(eng): Video: svq1 (SVQ1 / 0x31515653), yuv410p, 80x60, 13 kb/s, SAR 1:1 DAR 4:3, 3 fps, 3 tbr, 600 tbn, 600 tbc
    Metadata:
      creation_time   : 1998-01-05 21:59:31
    Stream #0.1(eng): Audio: qcelp (Qclp / 0x706C6351), 8000 Hz, 1 channels, flt
    Metadata:
      creation_time   : 1998-01-05 21:59:31
Incompatible pixel format 'yuv410p' for codec 'libx264', auto-selecting format 'yuv420p'
[buffer @ 0x25d1200] w:80 h:60 pixfmt:yuv410p tb:1/1000000 sar:1/1 sws_param:
[buffersink @ 0x25d7ec0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'src' and the filter 'out'
[scale @ 0x25d8520] w:80 h:60 fmt:yuv410p -> w:80 h:60 fmt:yuv420p flags:0x4
[libx264 @ 0x25de5c0] using SAR=1/1
[libx264 @ 0x25de5c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.2
[libx264 @ 0x25de5c0] profile Main, level 1.0
[libx264 @ 0x25de5c0] 264 - core 116 mbox/4.3.1 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - http://www.videolan.org/x264.html - options: cabac=1 ref=5 deblock=1:0:0 analyse=0x1:0x111 me=umh subme=8 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=0 b_adapt=2 b_bias=0 direct=3 weightb=0 open_gop=0 weightp=2 keyint=250 keyint_min=3 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to '/tmp/foo.mp4':
  Metadata:
    creation_time   : 1998-01-05 21:59:31
    encoder         : Lavf53.12.0
    Stream #0.0(eng): Video: h264 (![0][0][0] / 0x0021), yuv420p, 80x60 [SAR 1:1 DAR 4:3], q=-1--1, 3 tbn, 3 tbc
    Metadata:
      creation_time   : 1998-01-05 21:59:31
Stream mapping:
  Stream #0.0 -> #0.0 (svq1 -> libx264)
Press [q] to stop, [?] for help
frame=   20 fps=  0 q=21.0 Lsize=      16kB time=00:00:06.33 bitrate=  20.8kbits/s    
video:15kB audio:0kB global headers:0kB muxing overhead 7.083741%
frame I:1     Avg QP:20.35  size:   867
[libx264 @ 0x25de5c0] frame P:9     Avg QP:22.59  size:   852
[libx264 @ 0x25de5c0] frame B:10    Avg QP:23.73  size:   611
[libx264 @ 0x25de5c0] consecutive B-frames: 15.0% 50.0% 15.0% 20.0%
[libx264 @ 0x25de5c0] mb I  I16..4: 15.0%  0.0% 85.0%
[libx264 @ 0x25de5c0] mb P  I16..4:  4.4%  0.0% 57.8%  P16..4: 10.6% 11.7% 15.6%  0.0%  0.0%    skip: 0.0%
[libx264 @ 0x25de5c0] mb B  I16..4:  0.0%  0.0% 37.5%  B16..8: 18.0% 18.0% 19.6%  direct: 6.5%  skip: 0.5%  L0:49.4% L1:27.2% BI:23.4%
[libx264 @ 0x25de5c0] direct mvs  spatial:0.0% temporal:100.0%
[libx264 @ 0x25de5c0] coded y,uvDC,uvAC intra: 96.1% 94.7% 63.3% inter: 75.4% 92.2% 28.5%
[libx264 @ 0x25de5c0] i16 v,h,dc,p:  0% 64% 18% 18%
[libx264 @ 0x25de5c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 13% 11%  5%  6%  9%  6%  8% 10%
[libx264 @ 0x25de5c0] i8c dc,h,v,p: 35% 18% 29% 17%
[libx264 @ 0x25de5c0] Weighted P-Frames: Y:33.3% UV:22.2%
[libx264 @ 0x25de5c0] ref P L0: 76.5%  8.8%  5.9%  5.9%  1.5%  1.5%
[libx264 @ 0x25de5c0] ref B L0: 96.8%  2.4%  0.9%
[libx264 @ 0x25de5c0] kb/s:17.57

Change History (2)

comment:1 by Andrew Wason, 11 years ago

It looks like other x264 preset options have the same issue, these options have their "slow" preset defaults changed due to the default value of avctx->flags2:

param preset value value used
x4->params.i_bframe_pyramid X264_B_PYRAMID_NORMAL X264_B_PYRAMID_NONE
x4->params.analyse.b_transform_8x8 1 0
x4->params.analyse.b_weighted_bipred 1 0
x4->params.analyse.b_mixed_references 1 0

comment:2 by Carl Eugen Hoyos, 11 years ago

Resolution: fixed
Status: newclosed

I suspect this has just been fixed (by you), please reopen if I am wrong.

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