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• Variable is not being assingned value from the stdout of a command

  29 juillet 2021, par Jesse Hix

  When I try to run the entire program I get an error concerning the assignment of the y variable leading to the entire thing crashing. I have tried a few different ways of formatting but none of them have worked

  


  echo -e "Enter the name of the carrier video (include .mp4, .mp3, etc):"
read -r carrier_video
echo -e "Enter starting point x: "
read -r x
command rmdir frames
command mkdir frames

var=$(ffprobe -v error -select_streams v:0 -count_packets -show_entries stream=nb_read_packets -of csv=p=0 "$carrier__video")
command $(ffmpeg -i $carrier_video -vf select="between(n\,'$x'\,'$var')" -vsync 0 frames/frames%d.jpeg)


  


  Error :

  


   libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'original.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomavc1
    creation_time   : 2018-09-11T11:07:38.000000Z
  Duration: 00:00:21.12, start: 0.000000, bitrate: 21519 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 3840x2160, 21514 kb/s, 25 fps, 25 tbr, 25 tbn, 50 tbc (default)
    Metadata:
      creation_time   : 2018-09-11T11:07:38.000000Z
      handler_name    : L-SMASH Video Handler
      encoder         : AVC Coding
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
Press [q] to stop, [?] for help

[Parsed_select_0 @ 0x5582453fdec0] [Eval @ 0x7ffedaf0ddb0] Undefined constant or missing '(' in ')'
[Parsed_select_0 @ 0x5582453fdec0] Error while parsing expression 'between(n,500,)'
[AVFilterGraph @ 0x5582453fd100] Error initializing filter 'select' with args 'between(n,500,)'
Error reinitializing filters!
Failed to inject frame into filter network: Invalid argument
Error while processing the decoded data for stream #0:0
Conversion failed!



  


• MP4 moof fragment headers

  23 juillet 2019, par Ariana

  I have a MP4 parser software that get’s a fragmented .mp4 video, parses the MOOV and fragment headers and streams it. I have generated a .mp4 file myself using FFMPEG and MP4Box/bento4, but the software has problems processing it.

  ffmpeg -i input.mp4 -g 25 -c:v libx264 -c:a copy out1.mp4
  
  
  
  mp4fragment out1.mp4 --fragment-duration 1000 --track 'video' output.mp4

  Using the MP4 Explorer software, I noticed in my generated .mp4 file, for all moof.traf.trun, sample duration is set to 0, but in the Track Fragment Header box, it sets the default_sample_duration to 512. While in the another .mp4 file which works fine, there is no default_sample_duration field, but each individual sample has a duration of size 512. Looks like this might cause the problem. The right figure shows the working mp4, and the left one is my generated mp4.

  Is this an update in the newer versions of FFMPEG (or MP4Box or bento4) ? Is there any ways to force setting the sample duration in samples ?

  My .mp4 file

  The working .mp4 file

  

• Merge/Blend/Composite transparent webm files with a jpg/png using ffmpeg

  13 avril 2021, par Lokanath

  I previously had generated color.webm and alpha.webm files withffmpeg using png images.
However, when I play the generated videos in my application it consumes quite some resources so I have decided to create a standard video(No alpha needed), I cannot re-record the videos as there are a lot of them at this point.

  


  I am generating the alpha and color video using the following command ffmpeg -framerate 30 -i img%d.png -filter_complex "alphaextract[a]" -map 0:v -c:v libvpx-vp9 -pix_fmt yuv420p -auto-alt-ref 0 -crf 15 -b:v 0 color.webm -map "[a]" -c:v libvpx-vp9 -pix_fmt yuv420p -auto-alt-ref 0 -crf 15 -b:v 0 alpha.webm

  


  I am looking to get a final video output where in alpha values are replaced with the png/jpg image, it's more like replacing the green screen with a background however in my case greenscreen is the alpha channel.

  


  Could any one let me know how to combine alpha.webm, color.webm with a jpg/png image without minimal or no quality loss ?
.