[FFmpeg-user] Unexpected additional frames while stream copy

Ferdi Scholten ferdi at sttc-nlp.nl
Mon Oct 2 00:25:22 EEST 2023 


On 01-10-2023 19:28, Ulf Zibis wrote:
> Hi,
>
> I have a video, grabbed from screen with "-c:v libx264rgb -crf 0 
> -preset ultrafast".
>
> When I re-encode a small scene out of it, it counts 576 frames. (Same 
> number of images, when I extract all frames as JPEG.)
>
> But when I just do a stream copy, I get 761 frames, even when I use 
> "-fps_mode:v passthrough", which should be superfluous.
>
> Can one explain this miracle?
Stream copying can only cut on key-frames as far as I know. That might 
be your difference?
>
>
> $ ffmpeg -ss 1:24:43 -t 50 -i roh_de.mkv -fps_mode:v passthrough -c:v 
> libx264rgb -crf 0 -preset veryslow -c:a copy roh_de_slow.mkv
> ffmpeg version 5.1.1-1ubuntu2.1 Copyright (c) 2000-2022 the FFmpeg 
> developers
>   built with gcc 12 (Ubuntu 12.2.0-3ubuntu1)
>   configuration: --prefix=/usr --extra-version=1ubuntu2.1 
> --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu 
> --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl 
> --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom 
> --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca 
> --enable-libcdio --enable-libcodec2 --enable-libdav1d 
> --enable-libflite --enable-libfontconfig --enable-libfreetype 
> --enable-libfribidi --enable-libglslang --enable-libgme 
> --enable-libgsm --enable-libjack --enable-libmp3lame 
> --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt 
> --enable-libopus --enable-libpulse --enable-librabbitmq 
> --enable-librist --enable-librubberband --enable-libshine 
> --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt 
> --enable-libssh --enable-libsvtav1 --enable-libtheora 
> --enable-libtwolame --enable-libvidstab --enable-libvorbis 
> --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 
> --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi 
> --enable-lv2 --enable-omx --enable-openal --enable-opencl 
> --enable-opengl --enable-sdl2 --disable-sndio --enable-pocketsphinx 
> --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm 
> --enable-libiec61883 --enable-chromaprint --enable-frei0r 
> --enable-libx264 --enable-libplacebo --enable-shared
>   libavutil      57. 28.100 / 57. 28.100
>   libavcodec     59. 37.100 / 59. 37.100
>   libavformat    59. 27.100 / 59. 27.100
>   libavdevice    59.  7.100 / 59.  7.100
>   libavfilter     8. 44.100 /  8. 44.100
>   libswscale      6.  7.100 /  6.  7.100
>   libswresample   4.  7.100 /  4.  7.100
>   libpostproc    56.  6.100 / 56.  6.100
> Input #0, matroska,webm, from 'roh_de.mkv':
>   Metadata:
>     ENCODER         : Lavf59.27.100
>   Duration: 02:34:59.82, start: 0.000000, bitrate: 80644 kb/s
>   Stream #0:0: Video: h264 (High 4:4:4 Predictive), gbrp(pc, 
> gbr/unknown/unknown, progressive), 1680x888 [SAR 1:1 DAR 70:37], 25 
> fps, 25 tbr, 1k tbn
>     Metadata:
>       DURATION        : 02:34:59,760000000
>   Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp
>     Metadata:
>       DURATION        : 02:34:59,818000000
> Stream mapping:
>   Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264rgb))
>   Stream #0:1 -> #0:1 (copy)
> Press [q] to stop, [?] for help
> [libx264rgb @ 0x558efa1dde80] using SAR=1/1
> [libx264rgb @ 0x558efa1dde80] using cpu capabilities: MMX2 SSE2Fast 
> SSSE3 SSE4.1 Cache64
> [libx264rgb @ 0x558efa1dde80] profile High 4:4:4 Predictive, level 
> 5.0, 4:4:4, 8-bit
> [libx264rgb @ 0x558efa1dde80] 264 - core 164 r3095 baee400 - 
> H.264/MPEG-4 AVC codec - Copyleft 2003-2022 - 
> http://www.videolan.org/x264.html - options: cabac=1 ref=16 
> deblock=1:0:0 analyse=0x3:0x133 me=umh subme=9 psy=0 mixed_ref=1 
> me_range=24 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 
> fast_pskip=0 chroma_qp_offset=0 threads=3 lookahead_threads=1 
> sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 
> constrained_intra=0 bframes=0 weightp=2 keyint=250 keyint_min=25 
> scenecut=40 intra_refresh=0 rc=cqp mbtree=0 qp=0
> Output #0, matroska, to 'roh_de_slow.mkv':
>   Metadata:
>     encoder         : Lavf59.27.100
>   Stream #0:0: Video: h264 (H264 / 0x34363248), rgb24(pc, 
> gbr/unknown/unknown, progressive), 1680x888 [SAR 1:1 DAR 70:37], 
> q=2-31, 25 fps, 1k tbn
>     Metadata:
>       DURATION        : 02:34:59,760000000
>       encoder         : Lavc59.37.100 libx264rgb
>     Side data:
>       cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
>   Stream #0:1: Audio: aac (LC) ([255][0][0][0] / 0x00FF), 48000 Hz, 
> stereo, fltp
>     Metadata:
>       DURATION        : 02:34:59,818000000
> frame=  576 fps=0.7 q=-1.0 Lsize=  620554kB time=00:00:50.01 
> bitrate=101645.2kbits/s speed=0.064x
> video:619584kB audio:944kB subtitle:0kB other streams:0kB global 
> headers:0kB muxing overhead: 0.004287%
> [libx264rgb @ 0x558efa1dde80] frame I:48    Avg QP: 0.00 size:899822
> [libx264rgb @ 0x558efa1dde80] frame P:528   Avg QP: 0.00 size:1119814
> [libx264rgb @ 0x558efa1dde80] mb I  I16..4..PCM: 46.5% 17.4% 36.1%  0.0%
> [libx264rgb @ 0x558efa1dde80] mb P  I16..4..PCM: 25.9% 10.3% 23.3%  
> 0.0%  P16..4:  7.4%  2.3% 10.1%  5.7%  8.7%    skip: 6.4%
> [libx264rgb @ 0x558efa1dde80] 8x8 transform intra:17.4% inter:16.2%
> [libx264rgb @ 0x558efa1dde80] coded y,u,v intra: 88.7% 84.4% 90.1% 
> inter: 80.2% 79.4% 80.7%
> [libx264rgb @ 0x558efa1dde80] i16 v,h,dc,p: 47% 53%  0%  0%
> [libx264rgb @ 0x558efa1dde80] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 49% 47%  
> 2%  0%  1%  0%  0%  0%  0%
> [libx264rgb @ 0x558efa1dde80] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 42% 44%  
> 1%  2%  3%  3%  3%  2%  1%
> [libx264rgb @ 0x558efa1dde80] Weighted P-Frames: Y:66.1% UV:64.6%
> [libx264rgb @ 0x558efa1dde80] ref P L0: 41.8%  5.3%  9.1% 14.8% 7.2%  
> 6.2%  3.8%  2.9%  1.8%  1.9%  1.3%  1.2%  0.6%  1.1%  0.5% 0.4%
> [libx264rgb @ 0x558efa1dde80] kb/s:101512.49
>
>
> $ ffmpeg -ss 1:24:43 -t 50 -i roh_de.mkv -c copy -fps_mode:v 
> passthrough roh_de_fast.mkv
> ffmpeg version 5.1.1-1ubuntu2.1 Copyright (c) 2000-2022 the FFmpeg 
> developers
>   built with gcc 12 (Ubuntu 12.2.0-3ubuntu1)
>   configuration: --prefix=/usr --extra-version=1ubuntu2.1 
> --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu 
> --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl 
> --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom 
> --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca 
> --enable-libcdio --enable-libcodec2 --enable-libdav1d 
> --enable-libflite --enable-libfontconfig --enable-libfreetype 
> --enable-libfribidi --enable-libglslang --enable-libgme 
> --enable-libgsm --enable-libjack --enable-libmp3lame 
> --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt 
> --enable-libopus --enable-libpulse --enable-librabbitmq 
> --enable-librist --enable-librubberband --enable-libshine 
> --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt 
> --enable-libssh --enable-libsvtav1 --enable-libtheora 
> --enable-libtwolame --enable-libvidstab --enable-libvorbis 
> --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 
> --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi 
> --enable-lv2 --enable-omx --enable-openal --enable-opencl 
> --enable-opengl --enable-sdl2 --disable-sndio --enable-pocketsphinx 
> --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm 
> --enable-libiec61883 --enable-chromaprint --enable-frei0r 
> --enable-libx264 --enable-libplacebo --enable-shared
>   libavutil      57. 28.100 / 57. 28.100
>   libavcodec     59. 37.100 / 59. 37.100
>   libavformat    59. 27.100 / 59. 27.100
>   libavdevice    59.  7.100 / 59.  7.100
>   libavfilter     8. 44.100 /  8. 44.100
>   libswscale      6.  7.100 /  6.  7.100
>   libswresample   4.  7.100 /  4.  7.100
>   libpostproc    56.  6.100 / 56.  6.100
> Input #0, matroska,webm, from 'roh_de.mkv':
>   Metadata:
>     ENCODER         : Lavf59.27.100
>   Duration: 02:34:59.82, start: 0.000000, bitrate: 80644 kb/s
>   Stream #0:0: Video: h264 (High 4:4:4 Predictive), gbrp(pc, 
> gbr/unknown/unknown, progressive), 1680x888 [SAR 1:1 DAR 70:37], 25 
> fps, 25 tbr, 1k tbn
>     Metadata:
>       DURATION        : 02:34:59,760000000
>   Stream #0:1: Audio: aac (LC), 48000 Hz, stereo, fltp
>     Metadata:
>       DURATION        : 02:34:59,818000000
> Output #0, matroska, to 'roh_de_fast.mkv':
>   Metadata:
>     encoder         : Lavf59.27.100
>   Stream #0:0: Video: h264 (High 4:4:4 Predictive) (H264 / 
> 0x34363248), gbrp(pc, gbr/unknown/unknown, progressive), 1680x888 [SAR 
> 1:1 DAR 70:37], q=2-31, 25 fps, 25 tbr, 1k tbn
>     Metadata:
>       DURATION        : 02:34:59,760000000
>   Stream #0:1: Audio: aac (LC) ([255][0][0][0] / 0x00FF), 48000 Hz, 
> stereo, fltp
>     Metadata:
>       DURATION        : 02:34:59,818000000
> Stream mapping:
>   Stream #0:0 -> #0:0 (copy)
>   Stream #0:1 -> #0:1 (copy)
> Press [q] to stop, [?] for help
> frame=  761 fps=9.6 q=-1.0 Lsize=  876100kB time=00:00:50.01 
> bitrate=143502.8kbits/s speed=0.633x
> video:875127kB audio:944kB subtitle:0kB other streams:0kB global 
> headers:0kB muxing overhead: 0.003238%
>
>
> -Ulf
>
>
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