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• Making Sound To High To Hear Or Undetecable with Sox/FFMPEG

  28 octobre 2016, par Devin Dixon

  I want to make a sound that is too high to be detected by the human ear. From my understanding, humans can hear sounds between 20hz and 44000hz.

  With sox, I am making a sound that is 50000hz. The problem is I can still hear it. The command I am using is this :

  sox -n -r 50000 output.wav rate -L -s 50050 synth 3 sine 

  Either I have super good hearing or I am doing something wrong. How can I make this sound undetectable with SOX of FFMPEG ?

• make/cmake error : relocation R_X86_64_32 against `ff_a64_muxer' can not be used when making a shared object

  21 juin 2017, par NotCras

  Here’s what’s going on. I’m trying to set up OpenSceneGraph, however I run into the following error during the make process (spaces added for easier reading) :

  /usr/bin/ld: /usr/local/lib/libavformat.a(allformats.o): relocation R_X86_64_32 against `ff_a64_muxer' can not be used when making a shared object; recompile with -fPIC
  
  
  
  /usr/local/lib/libavformat.a: error adding symbols: Bad value
  
  
  
  collect2: error: ld returned 1 exit status
  
  
  
  src/osgPlugins/ffmpeg/CMakeFiles/osgdb_ffmpeg.dir/build.make:291: recipe for target 'lib/osgPlugins-3.4.0/osgdb_ffmpeg.so' failed
  
  
  
  make[2]: *** [lib/osgPlugins-3.4.0/osgdb_ffmpeg.so] Error 1
  
  
  
  CMakeFiles/Makefile2:6663: recipe for target 
  
  
  
  'src/osgPlugins/ffmpeg/CMakeFiles/osgdb_ffmpeg.dir/all' failed
  
  
  
  make[1]: *** [src/osgPlugins/ffmpeg/CMakeFiles/osgdb_ffmpeg.dir/all] Error 2
  
  
  
  make[1]: *** Waiting for unfinished jobs....

  This error does not stop the cmake process. A little later (error above occurs at 39%, process fails at 46%), I get this error :

  Makefile:127: recipe for target 'all' failed
  
  
  
  make: *** [all] Error 2

  Then the process stops.

  I’ve looked at some other solutions, but they didn’t have what I needed (here and here). I’ve run cmake with the -fPIC flag and that didn’t solve anything.

  I found a potential solution here but I don’t know how to implement "recompile your FFmpeg/libavcodec/libavformat with pic enabled". Can anyone talk me through it or give me a good resource ? I’ve never done it before and I don’t want to mess up my computer.

  Any help would be much appreciated. Thanks in advance !

• Non-Monotonous DTS error in current ffmpeg builds causing frame drops, but not on ffmpeg 1.2

  11 avril 2021, par pentinex

  I'm sorry to ask about such a frequently mentioned subject, but I looked through so many threads and I could never figure out what exactly is wrong, so I'm at the end of my wits. Basically, I want to concat a bunch of .ts files using ffmpeg. I use this command line :

  


  ffmpeg -allowed_extensions ALL -fflags +igndts -i chunklist.m3u8 -c copy "output.mkv"

  


  The .m3u8 file contains all the .ts parts. When I do this and it throws Non-Monotonous DTS errors, the result ends up having dropped frames where the DTS errors occur. I have tried multiple approaches :

  


  

  1. As you see above, I added "-fflags +igndts" at one point, though it doesn't help.

  


  2. I experimented with "-fflags +genpts" just out of desperation. Predictably, this made it worse.

  


  3. I tried muxing video and audio separately, to no avail.

  


  


  But weirdly enough, there is one "solution" : when I use ffmpeg 1.2, the resulting video plays smoothly. It doesn't come without issues. The resulting video always reports a frame rate of half of what it should be (14.98 when it should be 29.97). But it plays just like it should. Ideally though, I wouldn't want to use such an old version of ffmpeg, since I'm sure there are things in the background that may go wrong and I'm not even noticing those, so I'd hope I could get these kinds of results on current builds of ffmpeg.

  


  Does anybody have an idea ? I'm kind of losing my mind with this one.