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• Combining All MP4s in Directory with ffmpeg

  13 octobre 2015, par Eric Marcinowski

  I’ve been wrestling trying to get the syntax right on this batch file and I can’t for the LIFE of me figure out why some things aren’t working.

  1) The variable ’i’ is not getting incremented.
  and
  2) Concatenation on strc doesn’t seem to want to...well, concatenate.

  set i=0
  
  set "strc=concat:"
  
  
  
  for %%f in (*.mp4) do (
  
      set /a i+=1
  
      set "str=intermediate%i%.ts"
  
  
  
      set strc="%strc% %str%|"
  
  
  
      ffmpeg -i "%%f" -c copy -bsf:v h264_mp4toannexb -f mpegts "%str%"
  
  )
  
  
  
  set strc="%strc:-1%"
  
  ffmpeg -i "%strc%" -c copy -bsf:a aac_adtstoasc Output.mp4

• x86 : simple_idct10_template : fix overflow in pass

  12 octobre 2015, par Christophe Gisquet

  x86 : simple_idct10_template : fix overflow in pass
  When the input of a pass has 15 or 16 bits of precision (in particular
  
  the column pass), the addition of a bias to W4 may lead to overflows
  
  in the input to pmaddwd.
  This requires postponing the adding of the bias to after the first
  
  butterfly. To do so, the fact that m15, unused although zeroed, is
  
  exploited. In case the pass is safe, an address can be directly used,
  
  and the number of xmm regs can be decreased. Otherwise, the 32bits bias
  
  is loaded into it.
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/x86/proresdsp.asm
  • [DH] libavcodec/x86/simple_idct10_template.asm

• Join mp4 files in linux [migrated]

  18 décembre 2012, par Jose Armando

  I want to join two mp4 files to create a single one. The video streams are encoded in h264 and the audio in aac. I can not re-encode the videos to another format due to computational reasons. Also, I cannot use any gui programs, all processing must be performed with linux command line utilities. FFmpeg cannot do this for mpeg4 files so instead I used MP4Box

  e.g. MP4Box -add video1.mp4 -cat video2.mp4 newvideo.mp4

  unfortunately the audio gets all mixed up. I thought that the problem was that the audio was in aac so I transcoded it in mp3 and used again MP4Box. In this case the audio is fine for the first half of newvideo.mp4 (corresponding to video1.mp4) but then their is no audio and I cannot navigate in the video also. My next thought was that the audio and video streams had some small discrepancies in their lengths that I should fix. So for each input video I splitted the video and audio streams and then joined them with the -shortest option in ffmpeg.

  thus for the first video I ran

   avconv -y -i video1.mp4 -c copy -map 0:0 videostream1.mp4
  
  
  
   avconv -y -i video1.mp4 -c copy -map 0:1 audiostream1.m4a
  
  
  
   avconv -y -i videostream1.mp4 -i audiostream1.m4a  -c copy -shortest  video1_aligned.mp4

  similarly for the second video and then used MP4Box as previously. Unfortunately this didn't work either. The only success I had was when I joined the video streams separetely (i.e. videostream1.mp4 and videostream2.mp4) and the audio streams (i.e. audiostream1.m4a and audiostream2.m4a) and then joined the video and audio in a final file. However, the synchronization is lost for the second half of the video. Concretelly, there is a 1 sec delay of audio and video. Any suggestions are really welcome.