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• How to convert mp4 to flv a bunch of files ?

  21 avril 2013, par jerdiggity

  Assuming I had a bunch of videos sitting inside the directory /home/user/videos/awaiting_conversion how would I go about using cron to run a script similar to this one to batch convert each video into a different format ?

  /bin/sh -c $'nice /usr/bin/ffmpeg -i \044'\'$'/home/user/videos/awaiting_conversion/video_file_1.mp4'\'$' -s \044'\'$'480x320'\'$' -vcodec libx264 -acodec libmp3lame -ab \044'\'$'64k'\'$' -vpre fast -crf \044'\'$'30'\'$' -ar \044'\'$'22050'\'$' -f flv -y \044'\'$'/home/user/videos/converted/video_file_1.flv'\'$''

  The above script works fine for a single conversion, but :

  1. It assumes that the name of the video is static/known (which will not be the case when batch converting).
  2. It assumes that there is only one video to convert (which may or may not be the case), i.e. there's no "loop".
  3. It leaves the original file in place instead of deleting it (which is what I would want to happen to prevent duplicate conversions).

  The ultimate question would be how do I run that script for each video that exists inside /home/user/videos/awaiting_conversion, passing the file name as a variable ?

• Using OpenCV 2.4.4 with FFmpeg in Windows

  22 décembre 2015, par aardvarkk

  I know there are other questions dealing with FFmpeg usage in OpenCV, but most of them appear to be outdated.

  By opening up the makefiles in CMake, I can verify that I’ve got the WITH_FFMPEG flag on. My output folder for the OpenCV build contains a bin folder, within which are Debug and Release folders, each containing a copy of a .dll file entitled opencv_ffmpeg244.dll. I can step into the source code of OpenCV when I create a VideoWriter and verify that the function pointers to the .dll get filled correctly. That much appears to be working.

  If I use the FOURCC code of CV_FOURCC_PROMPT, the following codecs work properly :

  • Microsoft Video 1
  • Intel IYUV codec
  • Logitech Video (I420)
  • Cinepak Codec by Radius
  • Full Frames (Uncompressed)

  The following codecs do not work properly (ie. produce a 0kb video file) :

  • Microsoft RLE

  If my understanding is correct, using FFMPEG should allow for encoding video using a whole bunch of new codecs (x264, DIVX, XVID, and so on). However, none of these appear in the prompt. Manually setting them by their FOURCC codes using the macro CV_FOURCC(...) also doesn’t work. For instance, using this : CV_FOURCC('X','2','6','4') produces the message :

  Could not find encoder for codec id 28: Encoder not found

  and makes a video file of size 0kb.

  Using this : CV_FOURCC('X','V','I','D') produces no error message, and makes a video file of 6kb that will not play in Windows Media Player or VLC.

  I tried manually downloaded the Xvid codec from Xvid.org. Once that was installed, it appeared under the VFW selection in the prompt, and the encoding worked properly. So it’s close to a solution, but if I try to set the FOURCC code directly, it still fails as above ! I have to pick it from the prompt every time. Isn’t FFmpeg supposed to include a whole bunch of codecs ? If so, why am I manually downloading the codec instead of using the one built into FFmpeg ?

  What am I missing here ? Is there a way to check that FFMPEG is "enabled" ? It seems like the only codecs available in the prompt are VFW codecs, not the FFMPEG ones. The .dll has been built and is sitting in the same folder as the executable, but it appears it’s not being used in any way.

  Lots of related questions here. Hoping to find somebody knowledgeable about the FFmpeg implementation in OpenCV and with some knowledge of how all of these pieces fit together.

• How do I run a shell script through a "for" or "foreach" loop in order to batch convert ?

  28 mars 2013, par jerdiggity

  Assuming I had a bunch of videos sitting inside the directory /home/user/videos/awaiting_conversion how would I go about using cron to run a script similar to this one to batch convert each video into a different format ?

  /bin/sh -c $'nice /usr/bin/ffmpeg -i \044'\'$'/home/user/videos/awaiting_conversion/video_file_1.mp4'\'$' -s \044'\'$'480x320'\'$' -vcodec libx264 -acodec libmp3lame -ab \044'\'$'64k'\'$' -vpre fast -crf \044'\'$'30'\'$' -ar \044'\'$'22050'\'$' -f flv -y \044'\'$'/home/user/videos/converted/video_file_1.flv'\'$''

  The above script works fine for a single conversion, but :

  1. It assumes that the name of the video is static/known (which will not be the case when batch converting).
  2. It assumes that there is only one video to convert (which may or may not be the case), i.e. there's no "loop".
  3. It leaves the original file in place instead of deleting it (which is what I would want to happen to prevent duplicate conversions).

  The ultimate question would be how do I run that script for each video that exists inside /home/user/videos/awaiting_conversion, passing the file name as a variable ?