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• Reliable video decode-(heavy edit)-encode with Mediacodec

  27 mai 2017, par Jason M

  I am building a Android app that does heavy video processing. I have read some background and examples from bigflake as well as the official docs but did not get a final answer. Here is what I would like to do in my app :

  1. Decode a mp4 video into raw yuv frames ;
  2. Edit each frame with a lot of computation, including flipping and cropping, preferably with my existing native C++ ;
  3. Encode the raw frames into another video.

  I am using API22 for robustness since "All video codecs support flexible YUV 4:2:0 buffers since LOLLIPOP_MR1." Unfortunately, when I call

  encoder.getInputImage();

  instead of

  encoder.getInputBuffer();

  I get a null, similar to This post with no answer. Is this a common issue ? Do I have other options to decode-edit-encode a video without either rendering to a Surface or using FFMPEG, which is a headache to build and debug ?

• Fetching movies' frames via ffmpeg and feed it to vlfeat's sift

  16 novembre 2012, par Karl

  I am going to develop a program that uses ffmpeg and vlfeat on a linux server.

  My task is simply : get some frames from a movie file and feed these frames to vlfeat's sift.

  I am reading through some documents regarding using ffmpeg in c development, mainly here and here. As stated in the site, "There is not much "web based" official documentation for using these libraries." And some tutorials there might be a little outdated. I also read around that the API might differ from version to version. So I would like to ask for the following :

  1. Is it safe to follow this tutorial for the current implementation ?

     • If so, given the impression from above, what are some of the things that should be change for the current implementation ? (currently I got ffmpeg-git-c995644)
     • If not, what are the functions to acquire the frames of the movie file in any format ?

  2. For vlfeat side, if I am to feed a movie's image frame from ffmpeg, what kind of conversion is required so that vlfeat's sift implementation can "digest" the movie's image frame ?

• Gstreamer video increases latency with decresed FPS

  19 novembre 2024, par Ri Di

  I am using RPI 5 to stream the video :

  


  rpicam-vid -t 0 --camera 0 --nopreview --mode 2304:1296:10:P --codec yuv420 --width 640 --height 360 --framerate 10 --rotation 0 --autofocus-mode manual --inline --listen -o - | ffmpeg -f rawvideo -pix_fmt yuv420p -s:v 640x360 -r 10 -i /dev/stdin -c:v libx264 -preset ultrafast -tune zerolatency -maxrate 300k -bufsize 50k -g 30000 -f mpegts tcp://192.168.0.147:1234


  


  View it with :

  


  gst-launch-1.0 -v tcpserversrc host=0.0.0.0 port=1234 ! queue ! tsdemux ! h264parse ! avdec_h264 ! videorate ! video/x-raw,framerate=10/1 ! videoconvert ! autovideosink sync=false


  


  Problem is that with 10 FPS I get around 2s of latency ! While 56 or 120 FPS results in below 300ms latency.

  


  Is the problem in sender or reader side ? Or both ?

  


  I am not planning to use the 10 FPS, its only for demonstration of problem. But I would like to get lower latency at 56 FPS - just like at 120 FPS (around 80-100 ms difference) or maybe even better, as it seems to get lower with higher FPS.

  


  Maybe there is some kind of buffering parameter which holds frames ?

  


  (of course, when testing with higher FPS I change both numbers in sender and the one in reader command. The camera is v3 RPI official)

  


  Also I'd like to mention that same thing happens with ffplay :

  


  ffplay -i -probesize 3000 tcp://0.0.0.0:1234/?listen