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• ffmpeg stream offset command (-itsoffset) not working

  12 juillet 2013, par jen

  I would really appreciate if someone could give some pointers regarding the use of itsoffset with ffmpeg. I have read a number of posts on this subject, some of them explain very clearly how to re-synchronize audio and video with -itsoffset, but I haven't been able to make it work.
  My avi file is encoded with ffmpeg, in two passes, using the following command for the second pass :

  ffmpeg -i whole-vts_01.avs -pass 2 -y -vcodec libxvid -vtag XVID -b:v 1300K -g 240 -trellis 2 -mbd rd -flags +mv4+aic -acodec ac3 -ac 2 -ar 48000 -b:a 128k output.avi

  For whatever reason, I end up with a 1 sec delay in the video (or the audio is 1 sec early). It doesn't happen too often but I see it from time to time.
  Among other attempts, I have tried the following :

  (1) ffmpeg -i output.avi -itsoffset 00:00:01.0 -i output.avi -vcodec copy -acodec copy -map 0:0 -map 1:1 output-resynched.avi
  
  (2) ffmpeg -i output.avi -itsoffset 00:00:01.0 -i output.ac3 -vcodec copy -acodec copy -map 0:0 -map 1:0 output-resynched2.avi
  
  (3) ffmpeg -itsoffset -00:00:01.00 -i output.avi output-resynched8.avi
  
  (4) ffmpeg -i output.avi -itsoffset -1.0 -i output.avi -vcodec copy -acodec copy -map 0:1 -map 1:0 output-resynched13.avi

  Here are the results :

  1. Audio garbled and only 5m 35 s long vs. 1h 41m.
  2. (Output.ac3 is audio component of output.avi) Video and audio
     identical to original, offset didn't work
  3. Audio did get shifted, but original encoding parameters replaced with default ones (as expected).
  4. Audio garbled and only 9m 56s long vs. 1h 41m.

  I see that many people explain, and apparently use the process described above, but it doesn't seem to be working for me. Am I missing something obvious ? I would very much like to be able to use -itsoffset as it is cleaner than my workaround solution.

  FWIW, here is a different, and longer way of obtaining the desired result :

  First create a shifted video only file using -ss :

  ffmpeg -i output.avi -ss 1.0 -vcodec copy -an oupput_videoshifted.avi

  Then extract the audio :

  ffmpeg -i output.avi -vn -acodec copy outputaudioonly.ac3

  And finally remux both components :

  ffmpeg -i output_videoshifted.avi -i output_audioonly.ac3 -vcodec copy -acodec copy -map 0:0 -map 1:0 output-resynched14.avi

  The process works, is fast enough, but I would really prefer to use the one pass -itsoffset solution.

• OpenCv and ffmpeg working toghether on iOS

  1er avril 2014, par jjca

  I'm developing an iOS app which captures frames from camera with openCV, following this tutorial, and encodes those frames into a video using ffmpeg.

  The capture works fine, the problem comes with the ffmpeg part. I'm getting the following linker error when i try to use anything of ffmpeg :

  Undefined symbols for architecture armv7 :
  "avcodec_find_encoder(AVCodecID)", referenced from :
  -[ViewController processImage :] in ViewController.o
  ld : symbol(s) not found for architecture armv7
  clang : error : linker command failed with exit code 1 (use -v to see invocation)

  It only happens when the class file is named *.mm but not using ffmpeg in pure objective-c code.

  I'm using the binaries provided by openCV and compiling the ffmpeg ones by myself.

  Would compile them together fix the problem ? is possible to this ?

• android ffmpeg command not working on HTC One M8 5.0.1

  10 juillet 2015, par mark mosleh

  I have been creating an application that records video with audio through the ffmpeg library.
  I also added ffmpeg.exe to raw files and am installing the binary inside project to run ffmpeg commands.

  I have tested many commands that works on most of the devices but on HTC one M8 it is not giving any output nor error and i have no clue why.

  The command is intended to take an input video.mp4 and create a slow-motion video output.mp4

  The command is the following :

  /data/data/com.vidcutter/cache/ffmpeg -i /storage/emulated/0/DCIM/markapp/TEMP_1436532617119/0.mp4 -filter:v setpts=3.0*PTS -q 0 -an /storage/emulated/0/DCIM/markapp/TEMP_1436532617119/1000.mp4

  It runs smoothly on all devices ive tested on except the M8

  Any help will be much appreciated !

  PS : It works ironically smoothly on HTC One M7 lol