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• Decryption of mp4 file by replacing first 32 bytes with another key file

  17 octobre 2016, par JanviM

  We receive an encrypted video file and a key.header file
  The video will decrypt and become playable after replacing the first 32 bytes of video data with 32 bytes of the key file.

  Few approaches thought of :

  1.As serving video through Nginx,is there any utility/plugin of Nginx which can decrypt the file on the go to manage the load on server.

  2.Using nginx-rtmp module, is there any ffmpeg command available to replace 32 bytes of video file with key file i.e. to make video playable after decrypting.

  Can anyone please suggest how to implement the above approach or any other utility available for making the video playable after decrypting on the go while serving the video through nginx ?

• Using ffprobe to get number of keyframes in raw AVI file *without* processing entire file ?

  26 juillet 2018, par aggieNick02

  This question and answer cover how to get the framecount and keyframe count from an AVI file, which is very useful. I’ve got a raw AVI file and want to count the number of keyframes (equivalent to non-dropped frames for raw AVI), but it takes a long time to process through a raw AVI file.

  There is some way to get this information without fully processing the file, as VirtualDub provides both framecount and key framecount in the file information, as well as total keyframe size, almost instantly for a 25-second raw 1920x1080 AVI. But ffprobe requires count_frames to populate nb_read_frames, which takes some good processing time.

  I can do some math with the file’s size and the frame’s width/height/format to get a fairly good estimate of the number of frames, but I’m worried the overhead of the container could be enough to throw the math off for very short clips. (For my 25 second clip, I get 1286.12 frames, when there are really 1286.)

  Any thoughts on if there is a way to get this information programatically with ffprobe or ffmpeg without processing the whole file ? Or with another API on windows ?

• Getting file info with ffmpeg, object file recognized as Audio ?

  27 octobre 2011, par cpl

  I'm testing a C++ program that should iterate in a directory and find all multimedia files. I used an iteration routine, and for every file I tried using the libav functions to open the file, such as av_find_stream_info in order to find stream info. It works fine for multimedia files, such as video and images, but the problem is that it recognizes some files as audio or video, for example it sees an audio stream inside a .o file ! I also tried to use av_read_frame and it worked fine, without errors ! I would like to avoid filtering by extension, is there any other solution to find "playable" files ?

  Thanks