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• Use ffmpeg to match an image to source frames in video [closed]

  25 mai 2024, par user22335954

  I'm trying to write an application to split a single video into multiple pieces based on the appearance of a specific image. (Think title cards). I have video files that may have more than one episode or content inside of a single file and I want them split anywhere I find that title card or image.

  


  My application works by the user providing a timestamp in the format of 00:00:00 to specify the title card image which is then used like this :

  


  ffmpeg -i FILE -qmin 1 -qscale:v 1 -vframes 00:00:00 -f image2 img.png


  


  Now I want to compare that image (img.png) to the source video file using the following example command I've found :

  


  ffmpeg -i FILE -loop 1 -i img.png -an -filter_complex "blend=difference:shortest=1,blackframe=90:20" -f null


  


  I've had to play around with the blackframe=90:20 values to get what I think are correct matches, but I don't understand what these values and/or the blackframe filter is actually controlling. The blend documentation : https://ffmpeg.org/ffmpeg-filters.html#Examples-46 doesn't seem to go into much detail about what is actually happening. I do understand the difference blend means I'm essentially looking for the smallest difference, indicating a frame match to my img, but beyond that I'm sort of just guessing.

  


  Additionally, the output shows a bunch of :

  


  [Parsed_blackframe_1 @ 0x5c1183081880] frame:195 pblack:99 pts:6506 t:6.506000 type:B last_keyframe:135


  


  Based on the frames I can parse those out to find the non-sequential frames and find how how many segments I expect in the video, but when I go to split them, I don't know how to translate the frame or the t value into a timestamp format of 00:00:00. Even for matches that I'm 100% sure of, the frame values don't seem to line up with what I expect. For example, from watching the video, I know that a perfect match occurs at exactly 00:01:45, but the blackframe data says the match occurs at frame 1471 or t:49.08 (the video has a framerate of 29.97). 1471 / 29.97 is indeed 49.08, but that does not correlate to the actual time of 1:45 (105 seconds). How can I convert these values into timestamps (or just show the timestamps of the frames) ?

  


• How to capture device input with ffmpeg in C ?

  24 mai 2019, par Yi Lin Liu

  I am trying to use ffmpeg in my C code to capture device input, like screen and audio record. I have looked through their official documentation and wiki, but the API documentation is not really well explained compare to the command line usage.

  According to the documentation, if I want to record audio with alsa on linux I could, for example

  ffmpeg -f alsa -i hw:&lt;#card>,&lt;#device> -t <seconds> out.wav
  
  </seconds>

  I want to use the C API to do the same thing, any idea ?

• x264vfw - H.264/MPEG-4 AVC codec is advisable to use ?

  25 avril 2012, par Dhaval Kariya

  I have generated graph using GraphEdit utility of Directshow.

  My Graph is as follow

  osprey card -> x264vfw - H.264/MPEG-4 AVC codec -> GDCL Multiplexer -> File writer (.mp4

  file)

  I use "x264vfw - H.264/MPEG-4 AVC codec" downloaded from

  http://sourceforge.net/projects/x264vfw/. I want to know is this advisable to use this

  coded to encode the live video stream ? And what about the support and

  licensing for the same ?

  Thank You.