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• record long videos from multiple webcams with FFmpeg

  4 août 2020, par Nagamoto

  I am using

  


  ffmpeg -f dshow -vcodec mjpeg -t 6000 -rtbufsize 2.14748e+09  -video_size 1920x1080 -framerate 60 -i video=camID-0 -f dshow -vcodec mjpeg -t 6000 -rtbufsize 2.14748e+09  -video_size 1920x1080 -framerate 60 -i video=camID-1 -map 0  -c:v libx264 -preset ultrafast -y -r 30 fileName_0.mp4 -map 1  -c:v libx264 -preset ultrafast -y -r 30 fileName_1.mp4

  


  to record video from two webcams. Since the output will be compressed further down the line I am mostly concerned with quality and not losing frames. But after about 2min the real-time buffer is full :

  


  [dshow @ 00000221716edf80] real-time buffer [@device_pnp_\\?\usb#vid_15aa&pid_1555&mi_00#6&b8e4142&0&0000#{65e8773d-8f56-11d0-a3b9-00a0c9223196}\global] [video input] too full or near too full (75% of size: 2147480000 [rtbufsize parameter])! frame dropped!


  


  On the other hand capturing uncompressed video results in huge filesizes (1.3 TB for an hour) but encoding with the settings above the computer can't keep up.
Currently the webcams capture 60fps- which is not a must but I can't set them to anything lower.

  


  How can I record long video (max 1.5h) with good quality while keeping file-sizes manageable ?

  


  ffmpeg -f dshow -list_options true -i video="3.0 USB Camera"



ffmpeg version 4.3 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200621
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libgsm --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
[dshow @ 000001f32953c380] DirectShow video device options (from video devices)
[dshow @ 000001f32953c380]  Pin "Capture" (alternative pin name "0")
[dshow @ 000001f32953c380]   vcodec=mjpeg  min s=1920x1080 fps=60.0002 max s=1920x1080 fps=60.0002
[dshow @ 000001f32953c380]   vcodec=mjpeg  min s=1920x1080 fps=60.0002 max s=1920x1080 fps=60.0002
[dshow @ 000001f32953c380]   vcodec=mjpeg  min s=1280x720 fps=60.0002 max s=1280x720 fps=60.0002
[dshow @ 000001f32953c380]   vcodec=mjpeg  min s=1280x720 fps=60.0002 max s=1280x720 fps=60.0002
[dshow @ 000001f32953c380]   vcodec=mjpeg  min s=640x480 fps=60.0002 max s=640x480 fps=60.0002
[dshow @ 000001f32953c380]   vcodec=mjpeg  min s=640x480 fps=60.0002 max s=640x480 fps=60.0002
[dshow @ 000001f32953c380]   pixel_format=yuyv422  min s=1920x1080 fps=60.0002 max s=1920x1080 fps=60.0002
[dshow @ 000001f32953c380]   pixel_format=yuyv422  min s=1920x1080 fps=60.0002 max s=1920x1080 fps=60.0002
[dshow @ 000001f32953c380]   pixel_format=yuyv422  min s=1280x720 fps=60.0002 max s=1280x720 fps=60.0002
[dshow @ 000001f32953c380]   pixel_format=yuyv422  min s=1280x720 fps=60.0002 max s=1280x720 fps=60.0002
[dshow @ 000001f32953c380]   pixel_format=yuyv422  min s=640x480 fps=60.0002 max s=640x480 fps=60.0002
[dshow @ 000001f32953c380]   pixel_format=yuyv422  min s=640x480 fps=60.0002 max s=640x480 fps=60.0002
video=3.0 USB Camera: Immediate exit requested


  


• FFMPEG : cut clips from a long video with "fast seek" while maintaining accuracy

  15 août 2020, par japseow

  I have this 3 hour long video which consists of <1-5 seconds of black frames> — < clip > — <1-5 seconds of black frames> — < clip > — ...

  &#xA;

  I could successfully get the clip without the black frames with the slow seek, but it takes over 4 minutes just for seeking.

  &#xA;

  ffmpeg -y -i "C:\Users\user\Videos\obs\part1.mp4" -ss 4370.48 -to 4384.95 -c:a copy -c:v hevc_nvenc -rc vbr_hq -cq 19 -b:v 10000k -maxrate:v 12500k "C:\Users\user\Videos\obs\____delete1.mp4"

  &#xA;

  I tried using the fast seek which takes only 4 sec, but it includes a 4 sec blackframe chunk at the end of the video. The output that should've been 14 sec long became 18 sec.

  &#xA;

  ffmpeg -y -ss 4370.48 -i "C:\Users\user\Videos\obs\part1.mp4" -to 14.47 -c:a copy -c:v hevc_nvenc -rc vbr_hq -cq 19 -b:v 10000k -maxrate:v 12500k "C:\Users\user\Videos\obs\____delete2.mp4"

  &#xA;

  My video has around 640 clips so it's impractical to wait that long just for seeking, and it'll only get worse when I'll be seeking at around the 2+ hour mark.

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• Using moviepy, how can I splice up long videos into 8-second bits ?

  18 septembre 2020, par ekinugurel

  relatively new python user here. I'm trying to use moviepy to splice up 5 min long videos into 8-second bits. I used the code in this thread to extract subclips and it works. I did the following to make it a loop that covers the whole video, but I only get one 8-sec video as an output :

  &#xA;

  from moviepy.video.io.ffmpeg_tools import ffmpeg_extract_subclip
videopath = '../img/videos/Mopac+Cesarchavez-1.m4v'

for sec in videopath:
    sec = 0
    ffmpeg_extract_subclip(videopath, sec, sec+8.00, "../img/videos/subclips/testclip.mp4")
    if sec == 327:
        break


  &#xA;

  Do I need to specify a naming convention so that my output isn't just one video ? How would I do that ?

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