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• ffmpeg encoding plays very fast. Audio.mp4 and Video.mp4 work, but both together don't

  25 février 2013, par Peter.O

  In both steps 3 and 4 below, the .mp4 plays normally. However, although I've used what seems to be the same settings in the last step (audio + video), that step does not work. The video plays more than 10 times too fast... also the audio does not play.

  The ffmpeg messages for step 5 show that it has included audio.

  Output #0, mp3, to '/tmp/test.mp4':
  
      Stream #0.0: Video: libx264, yuv420p, 720x480, q=2-31, 90k tbn, 23.98 tbc
  
      Stream #0.1: Audio: libmp3lame, 48000 Hz, stereo, s16, 128 kb/s

  Subsequently running ffmpeg -i shows no trace of the audio, but it does report on the video... What have I missed, to get it muxed properly ?...

  #!/bin/bash
  
  
  
  # 1. create Audio 
  
  wine avs2pipe.exe audio "$src_avs" >"$temp_pcm"
  
  
  
  # 2. create Video 
  
  wine avs2yuv.exe "$src_avs" - |
  
    x264 --stdin y4m --output "$temp_h264" - 2>/dev/null
  
  
  
  # 3. This works.  (audio only)
  
  # encode `audio.mp4 
  
  ffmpeg -acodec pcm_s16le -f u16le -ac 2 -ar 48000 -i "$temp_pcm" \
  
         -acodec libmp3lame -f mp3 -ar 48000 -ab 128k  -y "$audio_mp4"
  
  
  
  # 4. This works.  (video only)
  
  # encode `video.mp4 
  
  ffmpeg -i "$temp_h264" \
  
         -vcodec copy -y "$video_mp4"
  
  
  
  # 5. This DOES NOT work!  It plays very fast.
  
  # encode `final.mp4' 
  
  ffmpeg -acodec pcm_s16le  -f u16le  -ac 2 -ar 48000  -i "$temp_pcm" \
  
         -i "$temp_h264" \
  
         -acodec libmp3lame -f mp3 -ar 48000 -ab 128k \
  
         -vcodec copy \
  
         -y "$final_mp4"

• Using FFMPEG in Java (developing on Mac)

  1er mai 2012, par Luuk D. Jansen

  I am trying to evoke FFMPEG directly in my Java code (running under the Playframework !).
  The final product will run on a Linux/Debian distro, but I first need to test on my Mac (I don't know if it works on Debian yet).

  I try to execute the simple code :

  Process pr = Runtime.getRuntime().exec(new String[]{"bash","-c", "ffmpeg"});

  or simpler :

  Process pr = Runtime.getRuntime().exec("ffmpeg")

  or using ProcessBuilder :

  Process pr = new ProcessBuilder("/opt/local/bin/ffmpeg").start();

  What I get is an error code 133, but I cannot find what this means.
  In the terminal the command gives the normal output. I can also replace 'ffmpeg' with e.g. 'ls -la' and get the directory listing. But I don't know what the problem is that ffmpeg does not work.

  Anybody any clues ?
  Thanks !

  UPDATE :
  I looked at the error stream. These are the errors I get. How is it that it works in the terminal, but not in using Java ?

  14:43:19,619 DEBUG ~ FFMPEG: dyld: Library not loaded: /opt/local/lib/libogg.0.dylib
  
  14:43:19,619 DEBUG ~ FFMPEG:   Referenced from: /opt/local/bin/ffmpeg
  
  14:43:19,619 DEBUG ~ FFMPEG:   Reason: Incompatible library version: ffmpeg requires version 9.0.0 or later, but libogg.0.dylib provides version 6.0.0

• FFmpeg screencast recording : which codecs to use ?

  24 avril 2013, par mkaito

  I've been experimenting with recording screencasts using FFmpeg's X11grab module, which has worked more or less fine so far. I understand that a/v encoding is a complex process with many fine details, but I'm doing my best to learn.

  I'd like to do "lightweight" recording of a video stream, that puts as little strain as possible on the system while the stream is being recorded. I record two audio streams separately with pacat and sox. Later, the whole thing is filtered, normalized, encoded, and combined into a Matroska container.

  Right now, I'm having ffmpeg record a rawvideo stream to be fed to x264's yuv4 demuxer. I experimented with ffv1 and straight x264 recording before. My system can't handle real time encoding with x264 on the settings I want for the final stream, so I have to recompress separately once the recording is done. I've found that ffv1 gives me terrible frame dropping, and yuv4 too, but less so. I suspect this is due to hard drive speed, even if I'm sitting in a SATA3 Caviar Black that's being used exclusively to hold the recorded data.

  The question is, which combination of video codecs should I look at ? Record straight in x264 and recompress to "better" x264 later ? Raw video, then compress ? How would I go about pinpointing issues such as the frame drops I've been experiencing ?

  EDIT : This is the ffmpeg line I currently use.

  ffmpeg -v warning -f x11grab -s 1920x1080 -r 30000/1001 -i :0.0\
  
  -vcodec rawvideo -pix_fmt yuv420p -s 1280x720\
  
  -threads 0\
  
  recvideo.y4m