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• avdevice/decklink_dec : add option to align capture start time

  28 septembre 2018, par Karthick Jeyapal

  avdevice/decklink_dec : add option to align capture start time
  This option is useful for maintaining input synchronization across N
  
  different hardware devices deployed for 'N-way' redundancy.
  
  The system time of different hardware devices should be synchronized
  
  with protocols such as NTP or PTP, before using this option.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] doc/indevs.texi
  • [DH] libavdevice/decklink_common_c.h
  • [DH] libavdevice/decklink_dec.cpp
  • [DH] libavdevice/decklink_dec_c.c
  • [DH] libavdevice/version.h

• How to ask FFMPEG to trim a video from start up to the end where there are no changes in frames ? [closed]

  27 août 2023, par jtrner

  I got a copy of our training module videos but these are desktop screen recorded. There are some videos where it supposed to end up to the length of the video, say 00:45:00, but because the "screen recorder" was not stopped (probably the person recording it left the computer) so there are added static frames towards the end (like 5 to 30 mins) and making the videos longer and file sizes bigger than it should be. So instead to end at 00:45:00, the video end timestap would be like say, 00:59:00.

  


  So how would I ask ffmpeg to "trim" the videos up to the part where the frames stopped and no changes at all ? And I also like to have a buffer of like 10 seconds after the supposedly end of the video, just to make sure that ffmpeg correctly detects the segments where the frames stopped.

  


  I'm only familiar with the video timming but don't have any idea on what filter to use to detect frame changes on videos using ffmpeg.

  


• FFmpeg start slowly with multiple instance on nvidia T4 GPU

  3 août 2020, par wyWang

  


  environment：

  


  

  1. OS:Centos7

  


  2. FFMPEG version : 4.2

  


  3. GPU : NVIDIA Tesla T4

  


  


  


  I have a requirement to work with multiple FFMPEG instance,command like this :

  


  ffmpeg -y -loglevel info -hwaccel cuvid -hwaccel_output_format cuda -c:v h264_cuvid \
    -i http://xx/xxxx.mp4 \
    -c:v  h264_nvenc  -ss 0 -t 600 out.mp4


  


  and the output like this :

  


  ffmpeg version 4.2.git Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-39)
  configuration: --enable-cuda-nvcc --enable-cuda --enable-cuvid --enable-nvenc --enable-libnpp --prefix=/snbeauty//platform/centos --pkg-config-flags=--static --extra-cflags='-I/snbeauty//platform/centos/include -I/usr/local/cuda/include/ -Werror=implicit-function-declaration -std=gnu99' --extra-ldflags='-L/snbeauty//platform/centos/lib64 -L/snbeauty//platform/centos/lib -L/usr/local/lib64 -L/usr/lib64 -L/usr/local/cuda/lib64 -L/lib64' --extra-libs='-lpthread -lm -lEGL -lGL -lpng -lYNEffect -ltracker -lcuda -lcudart' --bindir=/snbeauty//platform/centos/bin --enable-static --enable-nonfree --enable-libfreetype --enable-libfribidi --enable-libfontconfig --enable-filters --enable-version3 --enable-gpl --enable-libass --enable-libfdk_aac --enable-encoder=libfdk_aac --enable-opengl --enable-filter=xiu --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libtheora --enable-libwebp --enable-frei0r --enable-openssl --enable-gray --enable-libxml2 --enable-libxvid
  libavutil      56. 42.100 / 56. 42.100
  libavcodec     58. 73.102 / 58. 73.102
  libavformat    58. 39.101 / 58. 39.101
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 77.100 /  7. 77.100
  libswscale      5.  6.100 /  5.  6.100
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'http://xxx/xxxx.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.29.100
  Duration: 00:38:52.05, start: 0.000000, bitrate: 5370 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1920x1080, 5245 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 119 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (h264_cuvid) -> h264 (h264_nvenc))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
Output #0, mp4, to 'out.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.39.101
    Stream #0:0(und): Video: h264 (h264_nvenc) (Main) (avc1 / 0x31637661), cuda, 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 2000 kb/s, 25 fps, 12800 tbn, 25 tbc (default)
    Metadata:
      handler_name    : VideoHandler
      encoder         : Lavc58.73.102 h264_nvenc
    Side data:
      cpb: bitrate max/min/avg: 0/0/2000000 buffer size: 4000000 vbv_delay: N/A
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      encoder         : Lavc58.73.102 aac
frame=15000 fps=336 q=26.0 Lsize=  152462kB time=00:10:00.00 bitrate=2081.6kbits/s speed=13.4x    
video:142668kB audio:9418kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.247139%
[aac @ 0x32437c0] Qavg: 168.657

real    0m45.568s
user    0m29.034s
sys 0m2.961s


  


  is very fast

  


  But when I try concurrent 10 processes to run this command with different input url,ffmpeg start is very slowly. Then I found FFmpeg is slowly in this step :

  


  Stream mapping:
  Stream #0:0 -> #0:0 (h264 (h264_cuvid) -> h264 (h264_nvenc))
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))


  


  When the video is very short(like 0.5s or 1s), FFmpeg takes a long time to start.The actual codec takes less time than the boot time.

  


  I would like to ask what causes this problem ? (Nvidia GPU limit or FFmpeg) .And any way to solve it.

  


  Thanks !