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• More efficient way to assign multiple variables in a FOR loop ?

  9 juin 2020, par Tom

  I'm trying to capture the output of ffprobe to assign to two variables - currently I just run the loop twice to captue the encoder and codec_name tag. Is there a more effcient way to do this from within a single loop ?

  



  for /F "delims=" %%i in ('ffprobe -v error -show_entries format_tags^=encoder -of default^=nw^=1:nk^=1 %%a 2^>^&1') do set "encoder=%%i"
echo !encoder!

for /F "delims=" %%j in ('ffprobe -v error -show_entries stream^=codec_name -of default^=nw^=1:nk^=1 %%a 2^>^&1') do set "codec_name=%%j"
echo !codec_name!    


  



  Here's the full code for info - it's a batch reverse function in FFMPEG.

  



  @echo off
md "%cd%\_reversedFiles"

for %%a in (*.wav) do (
    SETLOCAL enabledelayedexpansion
    for /F "delims=" %%i in ('ffprobe -v error -show_entries format_tags^=encoder -of default^=nw^=1:nk^=1 %%a 2^>^&1') do set "encoder=%%i"
    echo !encoder!

    for /F "delims=" %%j in ('ffprobe -v error -show_entries stream^=codec_name -of default^=nw^=1:nk^=1 %%a 2^>^&1') do set "codec_name=%%j"
    echo !codec_name!

    ffmpeg -i %%a -af areverse -c:a !codec_name! "\_reversedFiles\%%~na.wav" 
    bwfmetaedit "\_reversedFiles\%%a" -a --ISFT="!encoder!"
)


  



  For ease of sharing it needs to be in a batch file.

  


• ffmpeg bitrate error when trying to capture frames at intervals from a video

  25 octobre 2011, par TheShaggyBeard

  Here is the error I get from running this script :

  [mjpeg @ 0x8559710]bitrate tolerance too small for bitrate
  Error while opening codec for output stream #0.0 - maybe incorrect parameters such as bit_rate, rate, width or height

  So here is what I am trying to do - I want to automate creating animated gif previews from a video file (in this case I know they will always be a specific format being mp4). Here is what I have :

  echo 'Save the file-name and make a folder named "filenamemp4"'
  
  fileName=$(find . -type f -name "*.mp4")
  
  folderName=$( cat $fileName | grep -o [[:alnum:]] | tr -d '\n' | cat)
  
  
  
  echo 'Grab the frame rate and total number of frames and put them into xaa and xab'
  
  qtinfo asa.mp4 | awk 'NR = 1 { print $2 }' | grep -o "^[0-9]*" | split -l 1
  
  
  
  echo 'Assign values to variable'
  
  frameRate=$(cat xaa)
  
  frameTotal=$(cat xab)
  
  videoLength=$(expr $frameTotal / $frameRate)
  
  
  
  echo 'Take a screenshot at 10% intervals - this is the part that gives me a bitrate error.  It says that the -r option has an invalid input being 1 / value of videoLength' 
  
  ffmpeg -i $fileName -y -ss $videoLength -an -sameq -f image2 -s 'qcif' -r $(expr 1/$videoLength) preview%02d.jpg
  
  
  
  echo 'Take the jpgs and mash them into an animated gif'
  
  convert -delay 50 -loop 10 preview*.jpg preview.gif
  
  
  
  echo 'Move the gif to the specified folder'
  
  mv preview.gif $folderName/preview.gif
  
  
  
  echo 'Clean Up'
  
  find . -type f -name "*.jpg" -exec rm -rf {} \;

  So perhaps there is a better way of doing this, or I am understanding how to use the -r option of ffmpeg wrong. In the tutorial I read on ffmpeg for a similar scenario, they used -r 1/5 to produce frames with a 5 second interval. My assumption is that for the desired interval you want, you just slap it in the denominator for the -r option.

• ffmpeg fails with a wall of red hex output but only when in a bash loop

  2 avril 2016, par jozxyqk

  Similar question here, but no solution : https://www.reddit.com/r/linuxquestions/comments/m00f0/hex_output_from_ffmpeg_when_run_in_a_loop/

  I’m trying to batch encode some video. I have a list of filenames in a text file and read each one in a bash loop. This is it :

  OUT=./out
  
  mkdir -p $OUT
  
  
  
  while read inputfile; do
  
  b=$(basename "$inputfile")
  
  outputfile="$OUT/$b"
  
  echo
  
  echo
  
  echo "$inputfile"
  
  echo "$outputfile"
  
  echo
  
  ffmpeg -i "$inputfile" "$outputfile" || exit
  
  done < files.txt

  When I run it, the ffmpeg command seems to start OK, then spits out a massive wall of red hex dump like text (as below). It does finish without error, but the file is only a few hundred frames long.

  [libx264 @ 0x1b68d60] frame= 537 QP=31.44 NAL=0 Slice:B Poc:70  I:2    P:239  SKIP:987  size=516 bytes
  
  stream #1:                                                                                                                                                
  
    keyframe=1                                                                                                                                              
  
    duration=0.024                                                                                                                                          
  
    dts=25.992  pts=25.992                                                                                                                                  
  
    size=336                                                                                                                                                
  
  00000000  ff fb 84 64 1a 0e d3 21 3f d4 93 18 6a e6 33 a4 ...d...!?...j.3.
  
  00000010  6a 63 25 22 4a 0c d1 1d 52 6c bd ab c0 bf 23 69 jc%"J...Rl....#i
  
  ... LOTS MORE

  The other really weird thing is that the next inputfile in the bash loop is broken and has only the last few characters, which does not happen if I simply comment out the ffmpeg line.

  What could ffmpeg be doing to interfere with the bash loop like this ?

  (ffmpeg 2.8.6, bash 4.3.42(1), fedora 23)