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• checkasm : use perf API on Linux ARM*

  1er septembre 2017, par Clément Bœsch

  checkasm : use perf API on Linux ARM*
  On ARM platforms, accessing the PMU registers requires special user
  
  access permissions. Since there is no other way to get accurate timers,
  
  the current implementation of timers in FFmpeg rely on these registers.
  
  Unfortunately, enabling user access to these registers on Linux is not
  
  trivial, and generally involve compiling a random and unreliable github
  
  kernel module, or patching somehow your kernel.
  Such module is very unlikely to reach the upstream anytime soon. Quoting
  
  Robin Murphin from ARM :
  > Say you do give userspace direct access to the PMU ; now run two or more
  
  > programs at once that believe they can use the counters for their own
  
  > "minimal-overhead" profiling. Have fun interpreting those results...
  
  >
  
  > And that's not even getting into the implications of scheduling across
  
  > different CPUs, CPUidle, etc. where the PMU state is completely beyond
  
  > userspace's control. In general, the plan to provide userspace with
  
  > something which might happen to just about work in a few corner cases,
  
  > but is meaningless, misleading or downright broken in all others, is to
  
  > never do so.
  As a result, the alternative is to use the Performance Monitoring Linux
  
  API which makes use of these registers internally (assuming the PMU of
  
  your ARM board is supported in the kernel, which is definitely not a
  
  given...).
  While the Linux API is obviously cross platform, it does have a
  
  significant overhead which needs to be taken into account. As a result,
  
  that mode is only weakly enabled on ARM platforms exclusively.
  Note on the non flexibility of the implementation : the timers (native
  
  FFmpeg vs Linux API) are selected at compilation time to prevent the
  
  need of function calls, which would result in a negative impact on the
  
  cycle counters.
  

  • [DH] configure
  • [DH] tests/checkasm/checkasm.c
  • [DH] tests/checkasm/checkasm.h

• passing additional values to s3 event notification for lambda consumption

  8 septembre 2017, par user1790300

  I have to write code in react-native that allows a user to upload videos to amazon s3 to be transcoded for consumption by various devices. For the processing after the upload occurs ; I am reviewing two approaches :

  1) I can use Lambda with ffmpeg to handle the transcoding immediately after the uploading occurs (my fear here would be the amount of time required to transcode the videos and the effect on pricing if it takes a considerable amount of time).

  2) I can have s3 pass an sns message to a rest api after the created event occurs and the rest api generate a rabbitmq message that will be processed by worker that will perform the transcoding using ffmpeg.

  Option 1) seems to be the preferable option based on a completion time perspective. How concerned should I be with using 1) considering how long video transcoding might take as opposed to option 2) ?

  Also, regardless, I need a way to pass additional parameters to lambda or along the sns messaging that would allow me to somehow associate the user who uploaded the video with their account. Is there a way to pass additional text-based values to s3 to pass along to lambda or along sns when the upload completes, as a caveat I plan to upload the video directly to s3 using the rest layer(found this answer here : http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPUT.html#RESTObjectPUT-responses-examples) ?

• make webbased ffmpeg-live transcoder on linux for multiple streams

  11 juillet 2017, par Dlniya Dlzar

  Hi I am planning to make webbased ffmpeg-live transcoder on linux for multiple streams .
  Using ffmpeg and ngnix-rtmp is the basic that i found and planning to do it
  my plan is (Web interface for adding and modifying streams (name ,input,output..)
  in database , database i mean (json file). and execute ffmpeg command depend on the JSON file (now one more thing i want to do , is to monitor streams based on
  nginx-rtmp-module/stat.xsl
  git https://github.com/arut/nginx-rtmp-module/blob/master/stat.xsl
  and restart streams if there is problem , like no audio or picture
  whats is best structure to do it ?? which language is good to do the proccess
  is there any missing knowledges ?? is there any other better way in your mind ??