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• How to concatenate two AAC files smoothly ?

  15 août 2013, par James Deng

  To save time, I want to segment and transcode a large video file on multiple computers.

  I use ffmpeg to transcode the segments of the large video file with :

  ffmpeg -i large_movie.mp4 -ss 00:00:00 -t 00:01:00 -acodec libfaac seg0.flv
  
  ffmpeg -i large_movie.mp4 -ss 00:01:00 -t 00:01:00 -acodec libfaac seg1.flv
  
  ...

  And concatenate the segments with :

   ffmpeg -i concat.conf -vcodec copy -acodec copy result.flv

  The content of the concat.conf :

  ffsconcat version 1.0
  
  file seg0.flv
  
  file seg1.flv
  
  ...

  Now we get a result FLV file result.flv content all the segments. But when I play this file, I found the segment boundary audio may be momentarily interrupted ! I'm sure those segments is closely associated, and the timestamp is right.

  When I decode the AAC sample in segment file to a wave format, and open the wave with CoolEdit, I found at the front and the end of the file, the value of audio sample is very small (mute ?) ! At the front of the file, there is about 21ms 'mute' sample. And at the end of the file, there is about 3ms 'mute' sample.

  Is the mute samples result the momentarily interrupt ? How to concatenate media file containing AAC smoothly ?

  ---

  After further testing, I found if you split a wave file to small wave files, then encode this small wave files to small aac file use faac :

  faac -P -R 48000 -B 16 -C 2 -X -o 1.aac 1.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 2.aac 2.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 3.aac 3.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 4.aac 4.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 5.aac 5.wav

  The console output like this :

  [hugeice@fedora19 trans]$ faac -P -R 48000 -B 16 -C 2 -X -o 5.aac 5.wav
  
  Freeware Advanced Audio Coder
  
  FAAC 1.28
  
  
  
  Quantization quality: 100
  
  Bandwidth: 16000 Hz
  
  Object type: Low Complexity(MPEG-2) + M/S
  
  Container format: Transport Stream (ADTS)
  
  Encoding 5.wav to 5.aac
  
     frame          | bitrate | elapsed/estim | play/CPU | ETA

  And concatenate this small aac files to a big aac files use :

  cat 1.aac 2.aac 3.aac 4.aac 5.aac > big.aac

  Now, if you play the big.aac, there is a momeniary interrupt at the segment boundary !

  The question becomes how segment coding and concatenate aac files smoothly ?

• FFMPEG - How to do PIP with mp4 and png

  4 avril 2017, par user3599518

  I would like to display the MP4 file, where is the black box in PNG

  

  

  ffmpeg -y  -i d.mp4  -vf "movie=trans.png [small]; [in] scale=320:180 [in]; [small][in] overlay=130:2  [out]" -s 640x360 /var/www/PIP.flv

  I tried, but I failed to do.

• Remux programatically using FFmpeg

  2 juillet 2015, par user1861447

  I am new to FFmpeg.
  But I am really excited to learn more about it.

  I tried remuxing example as a first step.

  I have taken remux example available at ffmpeg.org.

  I compiled andlinked to ffmpeg .so files.
  Everything went fine.

  Now I downloaded a webm file (small.webm).
  It contains vp8 and vorbis frames.

  I did remux it and output file is remuxed.webm

  I can play the remuxed webm file.

  So far so good.

  ---

  Now I wanted to remux a webm file that contains vp8 and opus frames.
  I could not get such file in internet.

  So I converted small.webm file to another file say output.webm that contains vp8 and opus frames using below command.

  ./ffmpeg -i small.webm -c:v libvpx -c:a libopus -qmin 0 -qmax 20 output.webm

  I opened output.webm in a mozilla browser and I am able to play it. Looks everything fine here.

  Then I did remux of output.webm and say resultant file is remuxed.webm.

  If I try to pay remuxed.webm in mozilla browser, it does not play.
  It gives an error Video can't be played because the file is corrupt

  Can somebody help me to understand when I remux vp8/vorbis file it works, and when I remux vp8/opus file it does not work using the example at ffmpeg.org.

  I am using ffmpeg 2.7.1 version.