ffmpeg过滤图像处理

Question

ffmpeg is applying some filters to the images before constructing the video. Is there any way to know those filters?

I'm using this command (so every parameters are kept by default):

ffmpeg -framerate 12 -i frame%02d.jpg out.mp4

Example of one frame:

Image file:

From the video:

I'm working on image processing with c++ and I'm interested in the way ffmpeg filtering the images

EDIT

When I launch the command line, that what I get in the terminal:

ffmpeg -framerate 5 -i frame%02d.jpg output.mp4


ffmpeg version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
[mjpeg @ 0x23e8600] Changeing bps to 8
Input #0, image2, from 'frame%02d.jpg':
  Duration: 00:01:40.20, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 2576x1456 [SAR 1:1 DAR 23:13], 5 fps, 5 tbr, 5 tbn, 5 tbc
No pixel format specified, yuvj420p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
[libx264 @ 0x23ec680] using SAR=1/1
[libx264 @ 0x23ec680] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x23ec680] profile High, level 5.0
[libx264 @ 0x23ec680] 264 - core 148 r2643 5c65704 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - 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=5 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 'output.mp4':
  Metadata:
    encoder         : Lavf56.40.101
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuvj420p(pc), 2576x1456 [SAR 1:1 DAR 23:13], q=-1--1, 5 fps, 10240 tbn, 5 tbc
    Metadata:
      encoder         : Lavc56.60.100 libx264
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
Press [q] to stop, [?] for help
frame=  501 fps=3.8 q=-1.0 Lsize=  154288kB time=00:01:39.80 bitrate=12664.6kbits/s    
video:154284kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.002771%
[libx264 @ 0x23ec680] frame I:3     Avg QP:17.31  size:564506
[libx264 @ 0x23ec680] frame P:498   Avg QP:19.27  size:313841
[libx264 @ 0x23ec680] mb I  I16..4:  0.2% 97.1%  2.7%
[libx264 @ 0x23ec680] mb P  I16..4:  0.0% 46.3%  0.5%  P16..4: 12.5% 13.0%  7.7%  0.0%  0.0%    skip:20.1%
[libx264 @ 0x23ec680] 8x8 transform intra:98.9% inter:73.3%
[libx264 @ 0x23ec680] coded y,uvDC,uvAC intra: 99.0% 99.7% 96.0% inter: 52.0% 57.7% 37.0%
[libx264 @ 0x23ec680] i16 v,h,dc,p: 17% 16% 13% 54%
[libx264 @ 0x23ec680] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 10% 12% 33%  6%  7%  6%  8%  7% 10%
[libx264 @ 0x23ec680] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 12% 13% 14% 10% 13%  9% 11%  8% 10%
[libx264 @ 0x23ec680] i8c dc,h,v,p: 66% 14% 14%  5%
[libx264 @ 0x23ec680] Weighted P-Frames: Y:2.0% UV:1.2%
[libx264 @ 0x23ec680] ref P L0: 45.6% 16.0% 20.4% 17.6%  0.5%
[libx264 @ 0x23ec680] kb/s:12613.66

Answer 1

If the input's pixel format cannot be applied to the output, ffmpeg will auto insert a scaler to perform the conversion.

Running the command with loglevel 40 or above will show presence of these auto-inserted filters.

[graph 0 input from stream 0:0 @ 0000000002bffb40] w:320 h:240 pixfmt:rgb24 tb:1/25 fr:25/1 sar:1/1 sws_param:flags=2
[auto_scaler_0 @ 0000000002bb7f20] w:iw h:ih flags:'bicubic' interl:0
[format @ 0000000002bfe940] auto-inserting filter 'auto_scaler_0' between the filter 'Parsed_null_0' and the filter 'format'
[auto_scaler_0 @ 0000000002bb7f20] w:320 h:240 fmt:rgb24 sar:1/1 -> w:320 h:240 fmt:yuv444p sar:1/1 flags:0x4

Similar holds for audio eg auto-resampler may be added.

Answer 2

All filters are documented in the official FFmpeg documentation: http://ffmpeg.org/ffmpeg-filters.html

As far as I know, no filters are applied by default.

I also don't see any significant difference between the images you've posted.