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• FFMPEG resulting audio file is longer than input file

  26 septembre 2015, par D3_JMultiply

  A Foreword : I have looked at the topics on stackoverflow related to this topic. None of them answer the question or have anything to do with the issue.

  I make LP videos on YouTube. I recently started using .TS (Transport Stream) files to record with through the answer here. When extracting the second audio stream from the file through ffmpeg I end up with an audio file 7 seconds longer than the video file I used as input. The file used as input is 12:50 and the audio file is 12:57.

  I believe this is due to the fact that ffmpeg is changing the bitrate of the file. The source bitrate is 167 kb/s and according to the console output ffmpeg is saving it as 164.7 kb/s.

  I know I can manually define the bitrate to save as via -b:a:0 167k but I want this batch file to work with any file I give it, and the bitrate of the stream in question varies, as it’s the mic/aux stream. I am writing a utility in Batch so I can just drag and drop the file to extract the second audio stream, so I’d love to avoid reading the bitrate unless there’s an ffmpeg command that returns the bitrate for a specific stream in the input file that is easy to parse.

  For the codec you can use -c:a:0 copy, why can’t you use copy on the bitrate ? To me it makes no sense.

  The command I’m using to extract the audio :

  ffmpeg -i "%~1" -map 0:2 -c:a:0 copy "%~n1.aac"

  The entire batch file :

  @echo off
  
  
  
  REM This code checks to ensure the command-line variables have been properly set.
  
  
  
  if [%1]==[] goto ALERT
  
  if [%2]==[] (
  
      SET outpt="%~n1.aac"
  
      goto END_COMMENT
  
  )
  
  SET outpt="%~2"
  
  
  
  GOTO END_COMMENT
  
  
  
  ------------------------------------------
  
  
  
  The code below actually runs the extraction of the audio stream with the configured values
  
  
  
  ffmpeg -i  -map 0:2 -c:a:0 copy 
  
  
  
  ffmpeg -i  -map
  
      The base command, map tells ffmpeg that we wish to define the order of streams
  
      we with to operate on
  
  
  
  0:2
  
      Defines the stream to work on, 0 is the input, so input 0 (the file) and 2 is the stream (0=video,1+=audio, last stream may be metadata)
  
  
  
  -c:a:0 copy
  
      Codec of audio stream 0 for output should be an exact copy of all applicable settings from input stream
  
  
  
  
  
      The name of the file to output. The extension should match the codec. For most intents this will be .aac
  
  
  
  ------------------------------------------
  
  
  
  :END_COMMENT
  
  
  
  echo %outpt%
  
  
  
  ffmpeg -i "%~1" -map 0:2 -c:a:0 copy %outpt%
  
  goto END
  
  
  
  :ALERT
  
  @echo Incorrect usage: At least 1 param is required
  
  @echo     ^ = Required
  
  @echo     [param] = Optional
  
  @echo(
  
  @echo     extract.bat ^ [output_file]
  
  
  
  :END
  
  pause

  At request the following file is the full output of -v 9 -loglevel 99 (I don’t see how 8 MB worth of [mpegts @ Address] is useful, but here you go : https://www.dropbox.com/s/0ous9hc6e2kbyvp/log.txt?dl=0

• Using ffmpeg with chunks of file

  27 juin 2020, par Yashik

  I am trying to download a file as 100mb chunks and I need to convert this using ffmpeg and upload this file to dropbox.
The code I tried :

  


  import os
import requests

#---snip---#

for chunk in r.iter_content(chunksize=chunksize):
  #chunksize is 100mb
  fp = open("a.mp4","wb")
  fp.write(chunk)
  fp.close()
  os.system("ffmpeg -i a.mp4 a.mkv")
  
  #code for uploading


  


  The error is moov atom is not found

  


  1.How can I convert file chunks with ffmpeg ?

  


  2.Can I convert without ever needing to save to a.mp4, like giving chunk directly to ffmpeg ?

  


  Ps : The problem occurs with file size greater than 100mb

  


  Edit :

  


  After converting the file is appended to file in dropbox

  


  What I want :

  


  

  • Sample.mp4 - 200mb

  


  • Downloads file as chunks 100mb

  


  • Converts the chunk

  


  • Upload to drive (multipart)

  


  


• Finding file extension for media file using ffprobe

  12 septembre 2013, par luddet

  I'm writing a media handling tool, using ffmpeg and ffprobe.

  Part of the workflow consists of the application retreiving media files with nondescript extensionless file names.
  Now I could get the extension from the media source but that would not fit as neatly into the program code flow, so I'm using ffprobe to extract the format information.

  The problem i have encountered is the format "QuickTime / MOV" where ffprobe gives me

   format_name="mov,mp4,m4a,3gp,3g2,mj2" 

  Is there a way to know which of the extensions is most appropriate ?

  I guess the simplest solution is to pick the first,mov, since that should work for all of them. But I would prefer to be more specific.

  Any way to accomplish this ?