[FFmpeg-user] Framerate automatically increased while cropping

[Ulf Zibis]

Hi,

why is the framerate automatically changed here from 29.98 fps to 120 fps, and how can I prevent from this ?

$ ffmpeg -i Demo\ 31.10.2020\ Köln\ Vorspiel+Zugriff.mp4 -vf crop=640:320:640:176 Demo\ 31.10.2020\ Köln\ Vorspiel+Zugriff\ Ausschnitt.mp4
ffmpeg version 4.4-static https://johnvansickle.com/ffmpeg/ Copyright (c) 2000-2021 the FFmpeg developers
   built with gcc 8 (Debian 8.3.0-6)
   configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gmp --enable-libgme --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libdav1d --enable-libxvid --enable-libzvbi --enable-libzimg
   libavutil      56. 70.100 / 56. 70.100
   libavcodec     58.134.100 / 58.134.100
   libavformat    58. 76.100 / 58. 76.100
   libavdevice    58. 13.100 / 58. 13.100
   libavfilter     7.110.100 /  7.110.100
   libswscale      5.  9.100 /  5.  9.100
   libswresample   3.  9.100 /  3.  9.100
   libpostproc    55.  9.100 / 55.  9.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Demo 31.10.2020 Köln Vorspiel+Zugriff.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 512
     compatible_brands: isomiso2avc1mp41
     encoder         : Lavf58.76.100
   Duration: 00:07:30.03, start: 0.000000, bitrate: 2580 kb/s
   Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 2508 kb/s, 29.98 fps, 120 tbr, 90k tbn, 2k tbc (default)
     Metadata:
       handler_name    : VideoHandler
       vendor_id       : [0][0][0][0]
   Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 63 kb/s (default)
     Metadata:
       handler_name    : VideoHandler
       vendor_id       : [0][0][0][0]
Stream mapping:
   Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
   Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x65debc0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.1 Cache64
[libx264 @ 0x65debc0] profile High, level 3.1, 4:2:0, 8-bit
[libx264 @ 0x65debc0] 264 - core 161 r3048 b86ae3c - H.264/MPEG-4 AVC codec - Copyleft 2003-2021 - 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=3 lookahead_threads=1 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
Output #0, mp4, to 'Demo 31.10.2020 Köln Vorspiel+Zugriff Ausschnitt.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 512
     compatible_brands: isomiso2avc1mp41
     encoder         : Lavf58.76.100
   Stream #0:0(und): Video: h264 (avc1 / 0x31637661), yuv420p(progressive), 640x320, q=2-31, 120 fps, 15360 tbn (default)
     Metadata:
       handler_name    : VideoHandler
       vendor_id       : [0][0][0][0]
       encoder         : Lavc58.134.100 libx264
     Side data:
       cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
   Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, mono, fltp, 69 kb/s (default)
     Metadata:
       handler_name    : VideoHandler
       vendor_id       : [0][0][0][0]
       encoder         : Lavc58.134.100 aac
frame=    1 fps=0.0 q=0.0 size=       0kB time=00:00:00.00 bitrate= 920.9kbits/sframe=   61 fps=0.0 q=33.0 size=       0kB time=00:00:00.51 bitrate=   0.7kbits/frame=   81 fps= 54 q=33.0 size=       0kB time=00:00:00.68 bitrate=   0.6kbits/frame=  125 fps= 62 q=33.0 size=       0kB time=00:00:01.04 bitrate= 0.4kbits/frame=  165 fps= 65 q=33.0 size=       0kB time=00:00:01.38 bitrate=   0.3kbits/frame=  193 fps= 62 q=33.0 size=       0kB time=00:00:01.62 bitrate=   0.2kbits/frame=  229 fps= 62 q=33.0 size=       0kB time=00:00:01.92 bitrate= 0.2kbits/frame=  265 fps= 63 q=33.0 size=     256kB time=00:00:02.21 bitrate= 945.1kbits/frame=  301 fps= 61 q=33.0 size=     256kB time=00:00:02.51 bitrate= 832.9kbits/frame=  329 fps= 61 q=33.0 size=     256kB time=00:00:02.73 bitrate= 768.0kbits/frame=  361 fps= 60 q=33.0 size=     256kB time=00:00:03.03 bitrate= 692.3kbits/frame=  389 fps= 59 q=33.0 size=     256kB time=00:00:03.26 bitrate= 642.5kbits/

-Ulf