Create an FFmpeg preset file from x264 options

Question

I want to create an FFmpeg preset file. If I run a sample command it shows the currently used presets

$ ffmpeg -i infile.mp4 outfile.mp4
[libx264 @ 0000000002a9a5c0] 264 - core 140 r2377 1ca7bb9 - H.264/MPEG-4 AVC codec
- Copyleft 2003-2013 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 
deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 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=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1
interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 
b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 
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

Now I take those values and create a preset file as specified in the documentation.

§ Preset files

However if I try to use that file it errors out

$ ffmpeg -i infile.mp4 -fpre settings.txt outfile.mp4
settings.txt: Invalid option or argument: 'cabac=1
', parsed as 'cabac' = '1'

Solution

When you specify options in preset files, those map to actual ffmpeg options, not the encoder options it prints when you look at the debug output.

For example, fast_pskip in x264 is called -fast-pskip in ffmpeg. Same for rc_lookahead which is called rc-lookahead. Have a look at ffmpeg -h full, section libx264 AVOptions for all possible options you can map directly.

For all others you want to use the -x264opts option and pass a list of key=value:key=value, for example:

ffmpeg -i input.mp4 -c:v libx264 -x264-params rc_lookahead=30:keyint=500 output.mp4

Note that there's rarely a point in manually configuring these options. Use the -preset option and choose one of the x264 presets if you want to keep it simple.

Comments

[Elisa Cha Cha]

Looks like the default preset medium was likely used. Why do you want to try to copy these? Why not just use the standard presets (and maybe the -tune option)?

[Rajib]

To pass x264 options directly you need to use -x264opts. I don't know the documentation you refer to but it could be you are using x264 options.

[Zombo]

I checked ffmpeg -h full, however for example I saw no bluray_compat. Is some table available to link these two disparate naming systems?

[slhck]

There is one here: sites.google.com/site/linuxencoding/x264-ffmpeg-mapping – but I'm pretty sure it's a bit outdated.