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• ffmpeg showwaves in combination with picture slideshow

  14 avril 2023, par Sascha

  i use ffmpeg to create a audio Visualization with a static background picture.
This works like it should. I can change the resolution, the picture and the color of the waveform.

  


  ffmpeg -i Audio.mp3 -loop 1 -framerate 25 -i img001.jpg -filter_complex "[0:a]aformat=channel_layouts=mono,showwaves=s=1280x720:mode=cline:r=25:colors=black[v];[1:v]scale=1280x720[bg];[bg][v]overlay=format=auto:x=(W-w)/2:y=(H-h)/2,format=yuv420p[outv]" -map "[outv]" -map 0:a -c:v libx264 -c:a copy -shortest Output.mp4

  


  Now i would like to have the possibility to have more than one picturs.
For that i use the following code.

  


  ffmpeg -framerate 1/5 -i img%%03d.jpg -i Audio.mp3 -r 25 -c:v libx264 -pix_fmt yuv420p Output.mp4

  


  or that one for a fading effect.

  


  ffmpeg -i Audio.mp3 -i img%%03d.jpg -vf zoompan=d=(%Framerate%+1)/1:s=%Resolution%:fps=1,framerate=25:interp_start=0:interp_end=255:scene=100 -c:v mpeg4 -q:v 2 Output.mp4

  


  I calculate the framerate with "audiolenght/numbers of picture" in my code before.
That also works like it should.

  


  But in combination, it will not work, maybe because of the framerate 1/5 of the slideshow and the framerate of the waveform.

  


  Can someone help me ?

  


  best regards
Sascha

  


• FFMpeg : 2 pass encoding, first with CRF and second with maxrate of first pass average bitrate ?

  28 septembre 2022, par Alireza Rinan

  I usually do conversions with ffmpeg 1 pass CRF 22 with maxrate 1400k for some movies to convert them to 720p and generate smallest size with best quality, the parameters I use is :

  


  c:v libx264 -vf format=yuv420p,scale=1280:-2 -crf 22 -maxrate 1400k -bufsize 7000k


  


  Doing this too much I found that apart from the black bars that reduces bitrate, the color theme, number of high movement scenes... etc affects the bitrate too much, CRF 22 makes sure you get constant quality at every scene, that makes bitrate reaches my maximum 1400k at some scenes while the reset of the scenes in some movies are barely 800k, this result the average bitrate for a same movie reaches for example about 1100k, for these movies I do the encoding again with lower maxrate
(Ex:1100k) and I get same quality with lower average rate 1000k.

  


  Now I'm wondering is there any automated method in 2 pass to get same result ?
For example doing the first pass in CRF 22 and the second pass at average bitrate of first pass to lower the quality of those bitrate rages in first pass ?

  


• How can I tell ffmpeg to start to write on file as soon as it detects some motion ?

  29 mai 2017, par krvl

  A little background. I am recording a stream from a camera (using rtsp protocol) and I’d like to save on the disk not the whole input stream but only some excerpts after a motion is detected.
  The "basic" command I’m using is something like :

  ffmpeg -i rtsp://{my_camera_address}/ -movflags +frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov -acodec aac -vcodec h264 output.mp4

  I recently add the -movflags option to achieve a sort of realtime, that is I can read the video file while is’t been written by ffmpeg.
  A user suggested in this question to add a filter to ffmpeg command in order to grab only the frames where a motion is detected, they used this option :

  -vf select=gt(scene\,0.05),setpts=N/(25*TB)

  But it has some incompatibility with the -vcodec copy option, although this is not a big issue.

  My question is : is it possibile to use the filter (or another option) just to trigger the file writing ? For example, I save a 5 minutes video after a motion-detection is triggered.