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• Best solution to automatically enrich a video stream with dynamic overlay (text, images, ...)

  17 novembre 2016, par hg.m

  In my company, we are currently looking for a solution to enrich a given video stream (which is being broadcasted via RTMP) from a remote webcam with dynamic information, such as current date/time, special measure values which are available on a server or the most recent entries in a database. Basically we want to achieve a simple, dynamic on-screen display as, for example, TV stations are using. The modified stream should then be restreamed, for example to be viewed in VLC Player or on YouTube.

  So far, I came up with the following ideas :

  • Using OBS with some own scripts and plugins - that’s disadvantageous because we would like to run the solution on a high-network performance server 24/7 without a GUI. Basically I’d need a fully command-line based version of OBS.

  • Using ffmpeg : I know that there are text filters available, but they are mainly static (or periodically polling a file with text) and don’t allow for any design adjustments other than font, font size and color. It would be great if there was some way of overlaying a Webkit browser view onto the stream, because this would allow us to design the overlays in HTML5 and CSS and using WebSocket technology for updating the data.

    • The overlay could be captured with PhantomJS, but how should we unify it with the stream and would it be fast enough to render 30 FPS ?

  Are there additional (preferably open source) tools we could use ? What would be the best strategy to implement this without buying expensive TV broadcasting software ?

• Cleaning up after av_frame_get_buffer

  4 novembre 2016, par Jason C

  There are two aspects of my question. I’m using libav, ffmpeg, 3.1.

  ---

  First, how do you appropriately dispose of a frame whose buffer has been allocated with av_frame_get_buffer ? E.g. :

  AVFrame *frame = av_frame_alloc();
  
  frame->width = ...;
  
  frame->height = ...;
  
  frame->format = ...;
  
  av_frame_get_buffer(frame, ...);

  Do any buffers have to be freed manually, beyond the call to av_frame_free(frame) ? The documentation doesn’t mention anything special, but in my experience the ffmpeg documentation often leaves out important details, or at least hides them in places far away from the obvious spots. I took a look at the code for av_frame_free and av_frame_unref but it branched out quite a bit and I couldn’t quite determine if it covered everything.

  ---

  Second, if something beyond av_frame_free needs to be done, then is there any catch-all way to clean up a frame if you don’t know how its data has been allocated ? For example, assuming someBuffer is already allocated with the appropriate size :

  AVFrame *frame2 = av_frame_alloc();
  
  frame2->width = ...;
  
  frame2->height = ...;
  
  frame2->format = ...;
  
  av_image_fill_arrays(frame2->data, frame2->linesize, someBuffer, 
  
                       frame2->format, frame2->width, frame2->height, 1);

  Is there a way to free both frame and frame2 in the above examples using the exact same code ? That is frame and its data should be freed, and frame2 should be freed, but not someBuffer, since libav did not allocate it.

• How to compress video applying even blur effect

  17 octobre 2016, par Kukuster

  How to compress video applying well-looking apportioned blur effect, like in JPG image ?

  I tried some ffmpeg postprocesing libraries, they are fspp, spp, uspp (takes really long time to render), etc. I almost reached the goal using fspp with parameters 5:60:15 . But blur was stronger than needed, and it’s leave bad artifacts when i try to use less compression. Also uspp is does beautiful and compresses enough, but it’s leave about 50% of video unblured. I also haven’t much time to try all uspp features. Is there resolution special for this purpose ?

  The point is to implement video compression with the only side effect of compression approaches jpeg-compression-like blur or blur-mask-like. Also it would be very good if there is a simple option to choose between :
  1) more compress, less pretty blur / more strong blur ; and 2) less compress, prettier blur / less strong blur.

  I am used to use ffmpeg and i’m running linux, so it would be so nice if there is a way to solve this with ffmpeg.
  Here is my ffmpeg input data about the video streams :

    Duration : 00:01:03.02, start : 0.000000, bitrate : 4010 kb/s
      Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 3870 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
      Metadata :
        handler_name : VideoHandler
      Stream #0:1(eng) : Audio : aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 133 kb/s (default)
      Metadata :
        handler_name : SoundHandler
  

  Edit : attaching jpeg pictured as example of desired output :