[FFmpeg-trac] #261(avcodec:new): ffmpeg now sets libx264 open_gop=1 by default

[FFmpeg]

#261: ffmpeg now sets libx264 open_gop=1 by default
------------------------+-------------------------
 Reporter:  rectalogic  |        Type:  defect
   Status:  new         |    Priority:  normal
Component:  avcodec     |     Version:  git-master
 Keywords:              |  Blocked By:
 Blocking:              |  Reproduced:  0
 Analyzed:  0           |
------------------------+-------------------------
 x264 default is closed gop (open_gop=0), ffmpeg defaults to open gop
 unless -flags +cgop is specified.

 This commit
 [http://git.videolan.org/?p=ffmpeg.git;a=commit;h=e25c67108a77b2dbf13de1339b5314d07e3ffa02
 e25c67108a77b2dbf13de1339b5314d07e3ffa02] applies the ffmpeg setting to
 libx264, and changed all the libx264 ffpresets to specify +cgop so the
 x264 default remained the same.

 Now that ffpresets aren't used and the new -preset (libx264 internal
 presets) is used, open_gop=1 is set for libx264 by default unless -flags
 +cgop is passed explicitly to ffmpeg.

 {{{
 ffmpeg -i input.mov -acodec libfaac -ab 64k -ar 44100 -ac 1 -pass 2
 -threads 0 -vcodec libx264 -preset slow -wpredp 0 -r 1200/40 -g 8*1200/40
 -b 700k -bt 700k -f mp4 -y output.mp4
 [...]
 ffmpeg: [libx264 @ 0x150b5c0] profile High, level 3.0
 ffmpeg: [libx264 @ 0x150b5c0] 264 - core 115 d0d6ea718 - 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=0x3:0x113 me=umh subme=8 psy=1
 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1
 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=18
 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0
 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=2 b_bias=0 direct=3
 weightb=1 open_gop=1 weightp=0 keyint=250 keyint_min=25 scenecut=40
 intra_refresh=0 rc_lookahead=50 rc=2pass mbtree=1 bitrate=700 ratetol=1.0
 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 cplxblur=20.0 qblur=0.5 ip_ratio=1.40
 aq=1:1.00
 }}}

 I'm not sure if this is considered a bug, but it's a change in behavior
 and the intention of that commit was clearly to preserve the x264 default.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/261>
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