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• Seek in fragmented MP4

  15 novembre 2020, par Stefan Falk

  For my web-client I want the user to be able to play a track right away, without having to download the entire file. For this I am using a fragmented MP4 with the AAC audio coded (Mime-Type : audio/mp4; codecs="mp4a.40.2").

  


  This is the command that is being used in order to convert an input file to a fMP4 :

  


  ffmpeg -i /tmp/input.any \
  -f mp4 \
  -movflags faststart+separate_moof+empty_moov+default_base_moof \
  -acodec aac -b:a 256000 \
  -frag_duration 500K \
   /tmp/output.mp4


  


  If I look at this file on MP4Box.js, I see that the file is fragmented like this :

  


  ftyp
moov
moof
mdat
moof
mdat
..
moof
mdat
mfra


  


  This looks alright so far but the problem I am facing now is that it's not apparent to me how to start loading data from a specific timestamp without introducing an additional overhead. What I mean by this is that I need the exact byte offset of the first [moof][mdat] for a specific timestamp without the entire file being available.

  


  Let's say I have a file that looks like this :

  


  ftyp
moov
moof # 00:00
mdat 
moof # 00:01
mdat
moof # 00:02
mdat
moof # 00:03
mdat
mfra


  


  This file however, is not available on my server directly, it is being loaded from another service, but the client wants to request packets starting at 00:02.

  


  Is there a way to do this efficiently without me having to load the entire file from the other service to my server ?

  


  My guess would be to load [ftyp][moov] (or store at least this part on my own server) but as far as I know, the metadata stored in those boxes won't help me to find a byte-offset to the first [moof][mdat]-pair.

  


  Is this even possible or am I following the wrong approach here ?

  


• Compile ffmpeg for linux with mp3

  17 septembre 2011, par user916350

  I need compiled executable ffmpeg for my web-service on php. I downloaded source from author's site, and created executable file, but this file doesn't consist mp3 library (I need it). I read that I need download library from repository, but I think that I can't do that on hosting. Why can I create executable file with mp3 codec for easy copying ffmpeg on server ?

• passing a python variable into ffmpeg output filename [duplicate]

  10 octobre 2018, par user243

  This question already has an answer here :

  • How do I put a variable inside a String in Python ?
    
    6 answers
    

  I am using the code below to parse the variable "a" as the output filename in ffmpeg but not been able to work it out so far. How do I,

  1. parse this variable to output filename ?

  2. I am passing sys.argv[1] as input filename. How do I associate this to the output filename as well. I am looking for a filename something like below,

     sys.argv[1]_variable(a).ts

  which is inputfilename_variable(a).ts

  Below is the code i am using,

  # -*- coding: utf-8 -*-
  
  import subprocess, sys
  
  firstarg=sys.argv[1]
  
  output = subprocess.Popen (['ffprobe', '-loglevel', 'fatal', '-select_streams', 'p:program_id=p:1', '-show_entries', '-of', 'csv=%s' % ("p=0"), '-i', sys.argv[1]], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
  
  out = output.communicate() [0]
  
  result = out.split('\n')
  
  a = str(result [0])
  
  b = str(result [1])
  
  cmds = ['ffmpeg', '-i', sys.argv[1], '-c', 'copy', '-map', 'p:2', 'str(a).ts']
  
  subprocess.Popen(cmds)