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• Integrating CUDA-based video decoder into libavcodec/ffmpeg

  1er février 2019, par tmlen

  I have a CUDA-based decoder of a video format running on the GPU. I am trying to add a "codec" into libavcodec that uses it as external decoder

  Currenty, I have it working such that I can play a sequence of pictures using ffplay, which
  get decoded on the GPU with the external decoder.

  But with the current implementation, the codec module copies its output (in a RGB24 pixel format) from GPU memory to host memory after each frame, and gives this to libavcodec in its AVFrame. So with this when using ffplay, it will copy the output images back and forth between GPU and host two times (as ffplay has to copy the data to GPU for display).

  My goal is to leave the uncompressed data on GPU using on a CUDA device buffer, and have ffmpeg use it.

  ffmpeg seems to have support for this using AVHWAccel.

  • Is there any example implementation that uses this with a CUDA based decoder (not using the dedicated hardware decoders through NVDEC, CUVID, etc.) ?

  • Does ffmpeg need the output in a pixel format in a CUDA buffer, or can it also be in texture memory, in a CUDA array ?

  • Is it possible to have the hardware decoder as primary decoder of the AVCodec. It seems that hardware-acceleration is foreseen as an add-on, with the software decoder implemented by AVCodec available as fallback ?

  • It seems that ffmpeg will allocate a pool of CUDA buffers to receive its output. Is it also possible to allocate the output buffers oneself in the module’s implementation, and control how many buffers there will be.

  • Is it possible to control with how many CPU threads the decoder will be called ? With the external decoder’s interface, ideal would be one writer thread that pushes compressed codestreams, and one reader thread that pulls the uncompressed output to a CUDA buffer.

• random_seed : Rewrite the generic clock() based seed code

  11 juin 2012, par Michael Niedermayer

  random_seed : Rewrite the generic clock() based seed code
  The new code is faster and reuses the previous state in case of
  
  multiple calls.
  The previous code could easily end up in near-infinite loops,
  
  if the difference between two clock() calls never was larger than
  
  1.
  This makes fate-parseutils finish in finite time when run in wine,
  
  if CryptGenRandom isn’t available (which e.g. isn’t available if
  
  targeting Windows RT/metro).
  Patch originally by Michael Niedermayer but with some modifications
  
  by Martin Storsjö.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/random_seed.c

• How to combine/concatenate videos stored in AWS S3 bucket based on title of the file name

  9 juin 2020, par orangecube

  I am using a service that allows me to record videos that get automatically pushed to a folder (submissions) in an S3 bucket. There are multiple videos however they need to be grouped together and concatenated so the output is one video per group.

  



  So, basically, any tips on how I can take videos based on the title and stitch them together ?

  



  Example :

  



  Submissions folder will have :

  



  a-100-2.mp4
a-200-6.mp4
b-123-5.mp4


  



  Expected output in processed folder :

  



  a.mp4     - (both 'a' videos get stitched together)
b.mp4     - (only 'b' gets sent over since there is only one video.)


  



  Thanks in advance !

  



  Edit : Some additional and detailed information below if it helps.

  



  The files will be labeled with :
name-location-video_token-stream_token.mp4

  



  Need help creating a script or process that will concatenate the videos using the procedure outlined below :

  



  Processing rules (back end) :

  



  


  1. Check if videos have same video_token in ‘submissions folder’. If so, keep the newest one and delete old ones.

  


  2. Take all videos in ‘submissions folder’ with same name and location in title and concatenate the videos. Save output video to a new folder in the bucket labeled as the location for the folder name. 
Output file name : 
name-location-year.mp4.

  


  



  EXAMPLE :

  



  Submissions folder :
joey-toronto-001-354.mp4

  



  joey-toronto-001-241.mp4 - this will be deleted

  



  joey-toronto-103-452.mp4

  



  alex-montreal-352-232.mp4

  



  alex-montreal-452-223.mp4

  



  Resulting output :

  



  Toronto folder :

  



  Joey-toronto-2020.mp4

  



  Montreal folder :

  



  Alex-montreal-2020.mp4