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• FFMPEG - Get the exact calculated audio filesize after encode

  14 janvier 2016, par Youssef El Gharbaoui

  Im trying to guess an audio (mp3) filesize before encode with ffmpeg, afterward, need to have the exact calculated filesize.

  Here is the formula im using to predict and calculate the filesize (hope im not wrong) :

  ( Bitrates x Duration ) / 8) x 1000 = Filesize in Bytes.

  Im going to give a real example so that everyone can understand the use case.

  Example :

  Having an m4a file with the following data :

  • Name : Assuming xxx.m4a
  • Filesize : 8 304 014 bytes (8,3 Mo)
  • Bitrates : 256k
  • Duration : 260 seconds

  Expected filesize : ( (256 x 260) / 8 ) x 1000 = 8 320 000 bytes

  Then im running the following ffmpeg command :

  ffmpeg -i xxx.m4a -f mp3 -y -minrate 256k -maxrate 256k -bufsize 256k -b:a 256k -fs 8320000 output.mp3

  Console output :

  ffmpeg version 2.7.2 Copyright (c) 2000-2015 the FFmpeg developers
  
    built with Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.7.2_1 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang     --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-vda
  
    libavutil      54. 27.100 / 54. 27.100
  
    libavcodec     56. 41.100 / 56. 41.100
  
    libavformat    56. 36.100 / 56. 36.100
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 16.101 /  5. 16.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.100 /  1.  2.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'xxx.m4a':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2mp41
  
      encoder         : Lavf56.36.100
  
    Duration: 00:04:20.53, start: 0.000000, bitrate: 254 kb/s
  
      Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 253 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  Output #0, mp3, to 'output.mp3':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2mp41
  
      TSSE            : Lavf56.36.100
  
      Stream #0:0(und): Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp, 256 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
        encoder         : Lavc56.41.100 libmp3lame
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (aac (native) -> mp3 (libmp3lame))
  
  Press [q] to stop, [?] for help
  
  size=    8127kB time=00:04:20.02 bitrate= 256.1kbits/s    
  
  video:0kB audio:8127kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.011765%    

  Problem and Questions :

  • Can you tell me why im I getting an output with 8 322 546 bytes and
    not 8 320 000 as expected ?
  • Is there something wrong in my formula or the ffmpeg command ?
  • What solution can you suggest to get the exact predicted filesize ?

  Thank you in advance.

• passing script variable of filename with spaces in bash to external program (ffmpeg) fails

  13 janvier 2016, par BostonScott

  Short story : I’m trying to write a script that will use FFmpeg to convert the many files stored in one directory to a "standard" mp4 format and save the converted files in another directory. It’s been a learning experience (a fun one !) since I haven’t done any real coding since using Pascal and FORTRAN on an IBM 370 mainframe was in vogue.

  Essentially the script takes the filename, strips the path and extension off it, reassembles the filename with the path and an mp4 extension and calls FFmpeg with some set parameters to do the conversion. If the directory contains only video files with without spaces in the names, then everything works fine. If the filenames contain spaces, then FFmpeg is not able to process the file and moves on to the next one. The error indicates that FFMpeg is only seeing the filename up to the first space. I’ve included both the script and output below.

  Thanks for any help and suggestions you may have. If you think I should be doing this in another way, please by all means, give me your suggestions. As I said, it’s been a long time since I did anything like this. I’m enjoying it though.

  I’ve include the code first followed by example output.

  for file in ./TBC/*.mp4
  
      do
  
  
  
      echo "Start of iteration"
  
      echo "Full text of file name:" $file
  
  
  
      #Remove everything up to  "C/" (filename without path)
  
      fn_orig=${file#*C/}
  
      echo "Original file name:" $fn_orig
  
  
  
      #Length of file name
  
      fn_len=${#fn_orig}
  
      echo "Filename Length:" $fn_len
  
  
  
      #file name without path or extension
  
      fn_base=${fn_orig:0:$fn_len-4}
  
      echo "Base file name:" $fn_base
  
  
  
      #new filename suffix
  
      newsuffix=".conv.mp4"
  
  
  
      fn_out=./CONV/$fn_base$newsuffix
  
      echo "Converted file name:" $fn_out
  
  
  
      ffmpeg -i $file -metadata title="$fn_orig" -c:v libx264 -c:a libfdk_aac -b:a 128k $fn_out
  
  
  
      echo "End of iteration"
  
      echo
  
      done
  
  echo "Script completed"

  With the ffmpeg line commented out, and two files in the ./TBC directory, this is the output that I get

      Start of iteration
  
      Full text of file name: ./TBC/Test file with spaces.mp4
  
      Original filename: Test file with spaces.mp4
  
      Filename Length: 25
  
      Base filename: Test file with spaces
  
      Converted file name: ./CONV/Test file with spaces.conv.mp4
  
      End of iteration
  
  
  
      Start of iteration
  
      Full text of file name: ./TBC/Test_file_with_NO_spaces.mp4
  
      Original file name: Test_file_with_NO_spaces.mp4
  
      Filename Length: 28
  
      Base file name: Test_file_with_NO_spaces
  
      Converted file name: ./CONV/Test_file_with_NO_spaces.conv.mp4
  
      End of iteration
  
  
  
      Script completed

  I won’t bother to post the results when ffmpeg is uncommented, other than to state that it fails with the error :
  ./TBC/Test : No such file or directory

  The script then continues to the next file which completes successfully because it has no spaces in its name. The actual filename is "Test file with spaces.mp4" so you can see that ffmpeg stops after the word "Test" when it encounters a space.

  I hope this has been clear and concise and hopefully someone will be able to point me in the right direction. There is a lot more that I want to do with this script such as parsing subdirectories and ignoring non-video files, etc.

  I look forward to any insight you can give !

• How do you create a crossfade transition between multiple videos in FFMPEG ?

  5 janvier 2016, par Katie Yamato

  I am currently looping MP4 videos with audio through FFMPEG. Here is the code

  del intermediate1.ts
  
  del f.txt
  
  echo file intermediate1.ts>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  echo file intermediate1.ts>>f.txt
  
  
  
  ffmpeg -i "SHORT MUSIC.mp4" -c copy -bsf:v h264_mp4toannexb -f mpegts intermediate1.ts -nostdin
  
  ffmpeg -f concat -i f.txt -c copy -bsf:a aac_adtstoasc "LONG MUSIC.mp4" -nostdin

  However, the transition between each instance of the videos is not smooth. It cuts off as the next instance is shown. Would there be a way create a blend/crossfade transition for the videos ?

  I have come across this method however, it is only for 2 videos
  http://superuser.com/questions/778762/crossfade-between-2-videos-using-ffmpeg

  Hope someone can help me !
  Thank you very much !!