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• ffmpeg : setting framerate changes also length

  21 février 2020, par planetmaker

  I’m creating videos from images sequences and I’d like to set the desired framerate of the resulting video file by the -r FPS flag with commands like

  ffmpeg -i %05d.bmp -r 30 -c:v h264 -vframes 780 -qscale:v 0 output.mp4

  However it seems that it does make a difference whether I set -r 30 or -r 60 in as much that the video ends earlier (thus less than specified 780 input images are used) the higher I set the framerate.

  The folder contains thousands of sequential images which follow the specified scheme %05d.bmp and I only need the first fixed-length part of this sequence - but at a higher frame rate than the default rate of 30fps.

  What part do I miss when trying to use the frame rate ? How do I set the FPS to a higher value but retaining the input length ?

• how to determine the average biterate and peak bitrate of a video using ffmpeg ?

  14 février 2018, par loki

  I don’t understand, when in ffmpeg i do ffmpeg -i <input /> i have :

  Video : hevc (Main) (hev1 / 0x31766568), yuv420p(tv), 1920x1080, 4997 kb/s, 30 fps, 30 tbr, 998795.00 tbn, 30 tbc (default)

  it’s show bitrate : 4997 kb/s BUT the size of the file is 114915563 bytes for a duration of 179 secondes. when i do math i have 114915563 / 179 = 641986 bytes/s = 642 kb/s :(

  What did i miss ? how to retrieve the average bitrate of a movie and the peak bitrate of a movie ?

• FFmpeg capture, mkvtimestamp_v2 and timecode don't play nice

  24 mai 2021, par Bouke

  Trying to capture and modify the TC in-file afterwards.
I've found a nice way to store the timestamps from the capture.
Gyan's brillant filterchain

  


  This works fine using this line :

  


  ffmpeg -hide_banner -f "decklink" -queue_size "1073741824" -raw_format "auto" -format_code "Hi50" -video_input "sdi" -i "bm mini One" -filter_complex "settb=1/1000,setpts=RTCTIME/1000-1500000000000,mpdecimate,split[out][ts];[out]setpts=N/25/TB[out]" -map "[out]" -c:a "copy" -c:v "prores" -profile:v "1" -vendor "ap10" -pix_fmt "yuv422p10le" "/Volumes/Data/tst1.mov" -map "[ts]" -f mkvtimestamp_v2 "/Volumes/Data/time.txt" -vsync 0


  


  But, when I add -timecode "00:00:00:00" (to force a TC atom in the output), horrible things happen.

  


  ffmpeg -f "decklink" -queue_size "1073741824" -raw_format "auto" -format_code "Hi50" -video_input "sdi" -i "bm mini One" -filter_complex "settb=1/1000,setpts=RTCTIME/1000-1500000000000,mpdecimate,split[out][ts];[out]setpts=N/25/TB[out]" -map "[out]" -timecode "00:01:00:00" -c:a "copy" -c:v "prores" -profile:v "1" -vendor "ap10" -pix_fmt "yuv422p10le" "/Volumes/Data/tst1.mov" -map "[ts]" -f mkvtimestamp_v2 "/Volumes/Data/time.txt" -vsync 0


  


  The timecode does not run at the video speed, skips a frame or two here and there, and the image freezes after a random amount of time (between 10 seconds and a minute or so).

  


  How come the timecode can mess up stuff that much ? From what I understand it's just a couple of atoms in the moov atom, and a reference where the actual TC value (as frames) is stored in the mdat.

  


  I highly suspect the -vsync 0 to also work on the video, and I've had issues with that before. If I omit that, the video is fine, the TC is fine, but there is no metadata output, just the # timecode format v2