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• Should I use the MP3 or AAC codec for a .mp4 file?

  8 November 2014, by Justin Jenkins

  We have an encoding process in place using ffmpeg on Mac OS X. This process will take a source video and a couple files from that: .m3u8 video, .mp4 video and .mp3 audio file.

  By default we’ve used the video from our m3u8 process which is a h264 (via libx264) video with AAC (via libfaac) audio.

  We are mostly using these videos on mobile devices (hence the m3u8 files) but we also use the .mp4 files for Android, Windows Phone, etc. More and more we also need to offer these same videos on the web via either a flash player or HTML5 player.

  Therefore, we’d like to have the best audio/video codec combo for all these uses ... where I’m confused is to what is "standard" for a .mp4 file?

  If the .mp4 uses the mp3 codec then it plays just fine everywhere but QuickTime, in QuickTime the video plays but there is not audio (works just fine in VLC player tho.)

  I’ve been told it’s due to how QuickTime uses file extensions to assume information about the video instead of trying to actually get the codec data from the file? This does make some sense, if we encode the same file but use AAC for the audio codec then it works just fine in QuickTime.

  So --- what’s the "correct" or "ideal" audio/video codec combo --- is it best and safe to use AAC (i.e. will it work on a broad range of devices) even though it’s not a "free" codec?

• Start/Stop Ffmpeg video capture

  2 November 2011, by Dasas

  I'm currently using ffmpeg for recording video from a webcam source.

  At the moment i use java to call for ffmpeg to execute.

  The code is pretty straightforward

  ffmpeg -f dshow -i video="Dualpix HD720p for Notebooks" -s cif -r 20 -f flv TEST.FLV
  
  Runtime.getRuntime().exec("rundll32 SHELL32.DLL,ShellExec_RunDLL " + cmd);

  and it works fine.

  The only real issue occour when when i need to stop the recording process.

  I know that i can press q or even ctrl+c in the CMD but i need to stop the process without keyboard input.

  That would be pretty easy to achive by killing the process but in this case ffmpeg do not finalize the video leaving me with a corrupt, need to fix, output.

  Is there any way to trigger the finalizing process "remotely".

  Thx,
  D.

  *******EDIT**********

  Thx for the prompt answer, i think you're referring to

  Process.getOutputStream()

  As for this case i have tried with this code:

  public Process doCommand(String cmd) throws Exception {
  
  
  
      rt = Runtime.getRuntime();
  
      Process proc = rt.exec(cmd);
  
      recOS= proc.getOutputStream();
  
      regcIS= proc.getInputStream();
  
  
  
      return proc;
  
  
  
  }
  
  
  
     receOS.write(("q/n".getBytes()));
  
     recOS.flush();

  I'm still getting an error, to be more specific, java.io.ioexception The pipe is being closed ...

• Naive Sorenson Video 1 Encoder

  12 September 2010, by Multimedia Mike — General

  (Yes, the word is “naive” — or rather, “naïve” — not “native”. People always try to correct me when I use the word. Indeed, it should actually be written with 2 dots over the ‘i’ but who has a keyboard that can easily do that?)

  At the most primitive level, programming a video encoder is about writing out a sequence of bits that the corresponding video decoder will understand. It’s sort of like creating a program — represented as a stream of opcodes — that will run on a given microprocessor or virtual machine. In fact, reading a video codec bitstream specification will reveal a lot of terminology along the lines of “transmitting information to the decoder” or “signaling the decoder to do xyz.”

  Creating a good encoder that will deliver decent quality at a reasonable bitrate is difficult. Creating a naive encoder that produces a technically compliant bitstream, not so much.

  
  
  

  When I wrote an FFmpeg encoder for Sorenson Video 1 (SVQ1), the first step was to just create a minimally compliant bitstream. The coarsest encoding mode that SVQ1 allows is to encode the average (mean) of each 16×16 block of samples. So I created an encoder that just encoded the mean of each block. Apple’s QuickTime Player was able to play the resulting video in all of its blocky glory. The result rather reminds me of the Super Nintendo’s mosaic effect.

  Level 5 blocks (mean-only 16×16 encoding):
  

  
  
  

  Level 3 blocks (mean-only 8×8 encoding):
  

  
  
  

  It’s one thing for your own decoder (in this case, FFmpeg’s own decoder) to be able to decode the data. The big test is whether the official decoder (in this case, Apple QuickTime Player) can decode the file.

  
  
  

  Now that’s a good feeling. After establishing that sort of baseline, it’s possible to adapt more and more features of the codec.