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• vp9 : invert order in l[] intra prediction array.

  9 février 2014, par Ronald S. Bultje

  vp9 : invert order in l[] intra prediction array.
  The directional intra predictors either don’t care about order (dc, h,
  
  dc_left, tm), or they prefer inverted order (vr, dr, hd). This allows
  
  more efficient SIMD implementations.
  

  • [DH] libavcodec/vp9.c
  • [DH] libavcodec/vp9dsp.c

• Extract RTP-packages from video

  5 août 2019, par Gregor A. Lamche

  I have a proprietary REST server that acts as a sort of RTSP server and establishes a UDP stream to another program for video streaming (no audio). It works fine and I can already stream videos. The only issue is that it can only stream one (proprietary) file (container) format at the moment as I’m limited by my media source code.

  I need a code/library which I can give any video file of a common video format/encoding (MPEG-4/MJPEG/H264) and it returns me the RTP-packages that I can then stream (or how to extract the content myself). Alternatively I already got a video player which gives me YUV frames of any video I give it, which in turn I could convert into RTP-packages provided I know how.

  Rendering is done on client side, and something I don’t care about. Though, I will have to set the encoding flags correctly.

  I know roughly about the RTP-header, but have no idea what bytes to write into its content. I heard of FFmpeg and Live555, but for neither could I find example code to extract those packages from a file (let alone a c# wrapper).

• How to create an encoding ladder for any aspect ratio ?

  18 avril 2024, par volume one

  For a given video uploaded by a user, I need to create three versions of it to cover standard definition (SD), high definition (HD), full high definition (FHD), and ultra high definition (UHD e.g. 4K). "resolution/encoding ladders" for standard aspect ratios like 16:9 and 4:3.

  


  For 4:3 we might have :

  


  640 x 480
960 x 720
1440 x 1080
2880 x 2160


  


  For 16:9 we might have :

  


  854 x 480
1280 x 720
1920 x 1080
3840 x 2160


  


  If a user uploads a file in either of those aspect ratios, we can create the four different versions because the resolution standards are known.

  


  However if a user uploads a video with an unforseen aspect ratio, say 23:19, then how would you go about formatting that video into SD, HD, FHD, and UHD versions ?

  


  If a 23:19 video is indeed uploaded then I am not looking to resize it to fit a different 'standard' aspect ratio. It must remain the same aspect ratio, but have four quality versions. The problem is what height and width sizes to create for non-standard resolutions ?

  


  I have already come accross many aspect ratios like 16:10, 21:9, 1.85:1, 2.39:1. How could I take care of making quality variations of those ?

  


  I am using Node.js and FFMpeg for video processing.