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• Latch-Based Performance Optimization for Field-Programmable Gate Arrays [on hold]

  22 mars 2014, par user3448912

  how can i replace the flip-flops in fpga by pulsed latches ?i tried that with howard algorithm by writing the verilog code for that.i have to take the area and power analysis.which synopsis tool is useful ?i am getting the timing report from xilinx.

• ffmpeg extract segment from video on-the-fly

  29 novembre 2022, par brunoais

  Context

  


  I want to make a service that hosts mp4 files but also provides video streaming.

  


  The server side is made of 2 "small" edge servers with capacity to cache about 0.1% of the content and one main server with a fraction of the bandwidth of the edge servers but much more robust storage.

  


  Recent status

  


  With the help of the ffmpeg manual,
  
Recently, when a segment is requested by an edge server, I run this command in ffmpeg

  


  ffmpeg -i in.mp4 -f hls -hls_list_size 0 -hls_playlist 1 -hls_time 60 -strftime 1  -hls_flags independent_segments+second_level_segment_index+second_level_segment_duration -hls_base_url '/path/to/file/' -hls_segment_filename 'name_%%03d.ts'  -c copy -copyts -hls_segment_type fmp4 out.m3u8


  


  Then obtain the requested segment (plus 3 subsequent ones) then delete everything.

  


  Current status

  


  Currently, I tried to get some level of optimization using -to :

  


  ffmpeg -i in.mp4 -to  -f hls -hls_list_size 0 -hls_playlist 1 -hls_time 60 -strftime 1  -hls_flags independent_segments+second_level_segment_index+second_level_segment_duration -hls_base_url '/path/to/file/' -hls_segment_filename 'name_%%03d.ts'  -c copy -copyts -hls_segment_type fmp4 out.m3u8


  


  Then sending the requested segments to the edge that requested them, then delete the result.
Do note that /path/to/file/ is a tmpfs with quite modest capacity (files can't stay there for too long).

  


  The current setback

  


  The main issue I get with the current process is that it takes a long time to obtain the last segments (2-4s).
That creates a bottleneck in how long segments take to be served. I can increase the buffer from 3 videos to 5 (or even more) but that doesn't solve the actual problem and, instead, will bring more strain on other areas.

  


  Cutting is not reliable

  


  There doesn't seem to exist an option to select what segments to generate using ffmpeg.

  


  Using cutting argument for start time (-ss) has shown to usually work but regularely causes the first keyframe used to be wrong. However, I believe I have all segment files in variable length and cut at the keyframe of the original file.

  


  Help needed

  


  How to extract an arbitrary segment of an mp4, described in the m3u8 file (which was done in a previous extraction) ?

  


  I have full control over ffmpeg and I can automate edits to the m3u8 file after generating them, as required. However, I need to understand and see how can this be solved.

  


• lavd/x11grab : fix vertical repositioning

  28 mars 2019, par Octavio Alvarez

  lavd/x11grab : fix vertical repositioning
  There is a calculation error in xcbgrab_reposition() that breaks
  
  vertical repositioning on follow_mouse. It made the bottom
  
  reposition occur when moving the mouse lower than N pixels after
  
  the capture bottom edge, instead of before.
  This commit fixes the calculation to match the documentation.
  follow_mouse : centered or number of pixels. The documentation says :
  When it is specified with "centered", the grabbing region follows
  
  the mouse pointer and keeps the pointer at the center of region ;
  
  otherwise, the region follows only when the mouse pointer reaches
  
  within PIXELS (greater than zero) to the edge of region.
  

  • [DH] libavdevice/xcbgrab.c