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• Decode h264 video with csharp

  28 août 2011, par john bowring

  I am looking for a way to decode h264 (or indeed any video format) using c#. The ultimate goal is to be able to decode the images and very strictly control the playback in real time. The project I am working on is a non-linear video art piece where the HD footage is required to loop and edit itself on the fly, playing back certain frame ranges and then jumping to the next randomly selected frame range seamlessly.

  I have created an app which reads image files (jpegs) in from the disk and plays them on screen in order, I have total control over which frame is laoded and when it is displayed but at full HD res it takes slightly longer than I want to load the images from hard drive (which are about 500k each), I am thinking that using a compressed video format would be smaller and therefore faster to read and decode into a particular frame however I cannot find any readily avaiable way to do this.

  Are there any libraries which can do this ? i.e. extract an arbitrary frame from a video file and serve it to my app in less time than it takes to show the frame (running at 25fps), I have looked into the vlc libraries and wrappers for ffmpeg but I don't know which would be better or if there would be another even better option. Also I dont know which codec would be the best choice as some are keyframe based making arbitrary frame extraction probably very difficult.

  Any advice welcome, thanks

• ffmpeg on the fly switch video from rtsp stream

  31 juillet 2021, par John Williamson

  I have a nest doorbell which provides a video stream via rtsp but for security the url is valid for just 4 minutes at which point a new url is provided i.e.

  


  15:25 - rtsps://stream-eu1-delta.dropcam.com:443/sdm_live_stream/CiQA2.....
15:29 - rtsps://stream-eu1-delta.dropcam.com:443/sdm_live_stream/vY8pB.....


  


  I'm able to play the individual streams to a rtsp-simple-server using

  


  ffmpeg -nostdin  -i  rtsps://stream-eu1-delta.dropcam.com:443/sdm_live_stream/CiQA2.... -q:v 1 -f rtsp rtsp://localhost:8554/live


  


  But is there any way to switch to the latest url on the fly ? I've looked at ffmpeg concate but this requires files. I don't really care about freezing or black between the switching, only that the output stream should remain open.

  


  ffmpeg version 4.2.4-1ubuntu0.1 running on Ubuntu 20.04.2 LTS

  


• speeding up x264 encoding (C++ code with libavcodec)

  20 décembre 2012, par Hrishikesh_Pardeshi

  I am trying to capture windows screen (continuous screen shots) and encode them into x264. For that I am using avcodec_encode_video2 function available with libavcodec. However, it takes a huge amount of time. The time fluctuates between 25 – 1800 milliseconds for encoding individual frames.

  I tried tried both 1080p and 720p with video recording on screen.

  These are the settings I am using. This was tested on Windows 7, win32 release build with 4 GB of RAM.

  bit_rate = 2000, width = 1920, height = 1080
  qmin = 0, qmax = 0, max_b_frames = 0, frame_rate = 25, pixel_format = YUV 4:4:4.
  The remaining settings are default which are fetched using avcodec_get_context_defaults3().

  Sample data(in milliseconds) for 20 frames (consecutive and chosen randomly) in a set of 250 frames.
  121, 106, 289, 126, 211, 30, 181, 58, 213, 34, 245, 50, 56, 364, 247, 171, 254, 83, 82, 229

  For the application it is a must that it captures at least at 15 fps. Can someone help out to tell whether any options can be used to improve the frame rate. I need to encode lossless, but I am open to some file size increase.

  Thanks in advance.