[FFmpeg-user] null video sink

Roger Pack rogerdpack2 at gmail.com
Tue Dec 29 23:56:25 CET 2015


Hello.
I noticed the docs for the "null" video filter say:
https://ffmpeg.org/ffmpeg-filters.html#nullsink
Null video sink: do absolutely nothing with the input video. It is
mainly useful as a template and for use in analysis / debugging tools.

Could anyone be kind enough to show me how to use this in a filtergraph?
When I try to, it seems to still output and encode:

$ ffmpeg -i screencast.mp4   -filter_complex
"[0]scale=640:360[output],[output]nullsink" out.mp4
ffmpeg version 2.8.1 Copyright (c) 2000-2015 the FFmpeg developers
  built with Apple LLVM version 7.0.0 (clang-700.0.72)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/2.8.1_1
--enable-shared --enable-pthreads --enable-gpl --enable-version3
--enable-hardcoded-tables --enable-avresample --cc=clang
--host-cflags= --host-ldflags= --enable-opencl --enable-libx264
--enable-libmp3lame --enable-libvo-aacenc --enable-libxvid
--enable-ffplay --enable-vda
  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
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'screencast.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.40.100
  Duration: 00:08:45.00, start: 0.000000, bitrate: 856 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p,
640x480, 599 kb/s, 15 fps, 15 tbr, 90k tbn, 30 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz,
stereo, fltp, 253 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
[libx264 @ 0x7ffbab821a00] using cpu capabilities: MMX2 SSE2Fast SSSE3
SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0x7ffbab821a00] profile High, level 2.2
[libx264 @ 0x7ffbab821a00] 264 - core 148 r2601 a0cd7d3 - 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=15 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 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.40.101
    Stream #0:0(und): Video: h264 (libx264) ([33][0][0][0] / 0x0021),
yuv420p, 640x480, q=-1--1, 15 fps, 15360 tbn, 15 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc56.60.100 libx264
    Stream #0:1(und): Audio: aac (libvo_aacenc) ([64][0][0][0] /
0x0040), 44100 Hz, stereo, s16, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      encoder         : Lavc56.60.100 libvo_aacenc
Stream mapping:
  Stream #0:0 (h264) -> scale (graph 0)
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (aac (native) -> aac (libvo_aacenc))
Press [q] to stop, [?] for help
frame=  552 fps=460 q=-1.0 Lsize=    1107kB time=00:00:37.27 bitrate=
243.2kbits/s

Thank you.
-roger-


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