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• FFmpeg - Crossfading inputs with a duration 1s creates an empty output

  27 août 2021, par Sonia Seddiki

  I am trying to crossfade a silent input with a music to delay the moment when the music starts to play.

  


  I built the command using fluent-ffmpeg so I could choose the duration of the silent input through my program. The duration of the crossfade is calculated according to the duration of the 2 inputs, and equals 0 if one of them is too short.

  


  Below is an example of the resulting command :

  


  ffmpeg -f lavfi -i anullsrc=r=44100 -i music.mp3 -y -filter_complex [0]atrim=duration=0.28[atrim_0];[atrim_0][1]acrossfade=d=0:c1=tri:c2=tri[final] -map [final] output.mp3


  


  However, this command creates an empty output file when the duration of the silent input is inferior to 1 second, regardless of which music input is next. Using the same command with a trim duration > 1 second creates a valid output with the silence and the music.

  


  I have tried to look through the FFmpeg debug report but couldn't really see what was wrong.

  


  Below is an excerpt of the debug log report :

  


  Input file #0 (anullsrc=r=44100):
  Input stream #0:0 (audio): 14 packets read (28672 bytes); 14 frames decoded (14336 samples);
  Total: 14 packets (28672 bytes) demuxed
Input file #1 (music.mp3):
  Input stream #1:0 (audio): 504 packets read (210651 bytes); 504 frames decoded (578372 samples);
  Total: 504 packets (210651 bytes) demuxed
Output file #0 (output.mp3):
  Output stream #0:0 (audio): 0 frames encoded (0 samples); 0 packets muxed (0 bytes);
  Total: 0 packets (0 bytes) muxed


  


  Any idea what could cause this ?

  


  PS : I am using FFmpeg 4.4, and the same command with FFmpeg 4.2 lead to a segmentation fault. Don't know if this can be of any help

  


• FFMPEG combining many files and filters at once

  7 août 2018, par Vadim

  I need to make 1 video from 5 different pieces (mp4,mp3,png) :

  [0] input.mp4 (120fps 4 sec)

  1 sequence of .png (2 sec and its looped)

  [2] sound.mp3 (3 minutes, but i only need the same time as input.mp4)

  [3] Title1.mp4 (30fps its sets in begining)

  [4] Title2.mp4 (30 fps its sets in the end)

  ---

  I tried to explain in picture below :
  

  Its too hard for me to understand the filtergraph syntex as i thinks my steps must be like this :

  ---

  1. I need slow Input.mp4 to 30 frames "setpts=PTS*10,fps=30"and " boxblur=luma_radius=2:luma_power=1 boxblur=2:1" ill get outMain.mp4 [outMain]
  2. Then i overlay .png and .mp3 there is i have a problem, maybe "overlay=shorters=1" and "-loop 1"
     ill get outMain2.mp4[outMain2]
  3. And the final ill need to Concat it all in order "[3][outMain2][4]concat=n=3 out output.mp4"

  How to make it in one action and add a -ultrafast preset, speed is important for me ?
  Thanks

  I understood how to use filtegraph a bit :
  But it appears another question in comments with looping overlay after slowing video in one action...

  In first i slow video :

  ffmpeg -i input.mp4  -r 24 -vf "setpts=(10/1)*PTS" -c:v libx264 -preset ultrafast -crf 26 -c:a copy output.mp4

  Then Overlay png and add .mp3 :

  ffmpeg -i input.mp4 -i alpha.png -i dorn.mp3 -filter_complex "[0:v][1:v]overlay" -c:v libx264 -preset ultrafast -crf 26 -c:a copy -y -map 2:a -shortest out.mp4

  Add begin title and final title :

  ffmpeg -i input.mp4 -i preroll.mp4 -filter_complex "[1][0][1]concat=n=3" -preset ultrafast -crf 26 -c:a copy output.mp4

  But it freezes with "Buffer queue overflow, dropping" Will try to resolve problem.
  The key to the freeze was simple. If i want to paste [0] video in the begining and in the end i must specify one more "-i" for example :

  ffmpeg -i 0.mp4 -i 1.mp4 -i 0.mp4 -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0][2:v:0][2:a:0] concat=n=3:v=1:a=1 [v][a]" -map "[v]" -map "[a]" -c:v libx264 -preset ultrafast -crf 26 output_video.mp4

• FFMPEG : how to change framerate KEEPING the same duration ?

  19 mars 2016, par Camillo Gatto

  please consider C0003.MXF have a framerate different from 25fps

  I have try this :

  ffmpeg.exe -r 25 -i C0003.MXF -vcodec mpeg2video -g 0 -intra -pix_fmt yuv422p -q:v 0 -flags +ildct+ilme -an output25fps.mkv

  I need to change the framerate so that the final framerate is fixed to 25fps but also keep the same duration of the original C0003.MXF file, and the maximum video quality (using frame interpolation ?) plase how can I do ? thanks