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• lavc/opusdsp : simplify R-V V postfilter

  16 décembre 2023, par Rémi Denis-Courmont

  lavc/opusdsp : simplify R-V V postfilter
  This skips the round-trip to scalar register for the sliding 'x'
  
  coefficients, improving performance by about 5%. The trick here is that
  
  the vector slide-up instruction preserves elements in destination vector
  
  until the slide offset.
  The switch from vfslide1up.vf to vslideup.vi also allows the elimination
  
  of data dependencies on consecutive slides. Since the specifications
  
  recommend sticking to power of two offsets, we could slide as follows :
          vslideup.vi v8, v0, 2
  
          vslideup.vi v4, v0, 1
  
          vslideup.vi v12, v8, 1
  
          vslideup.vi v16, v8, 2
  However in the device under test, this seems to make performance slightly
  
  worse, so this is left for (in)validation with future better hardware.
  

  • [DH] libavcodec/riscv/opusdsp_rvv.S

• Converting a H.264-Stream with node.js using fluent-ffmpeg

  10 novembre 2014, par Andreas Lackner

  I want to convert a H.264 stream (provided by a foscam via RTSP) into a ogg-stream (via HTTP) using node.js and ffmpeg.
  So far I tried it with VLC, wich works fine. But VLC needs too much CPU power.

  I’ve tried the following :

  var ffmpeg = require('fluent-ffmpeg');
  
  var http = require('http');
  
  
  
  http.createServer(function (req, res) {
  
      var command = ffmpeg();
  
      command.input('rtsp://user:password@foscam.example.com:88/videoMain');
  
      command.inputFormat('rtsp');
  
      command.videoCodec('libtheora');
  
      command.audioCodec('libvorbis');
  
      command.toFormat('ogg');
  
  
  
      console.log('New Request');
  
      res.writeHead('200', {
  
          'Content-Type' : 'video/ogg',
  
          'Connection' : 'keep-alive',
  
          "Accept-Ranges" : "bytes"
  
      });
  
      command.on('error', function(err, stdout, stderr) {
  
            console.log("error:"+err);
  
            console.log('ffmpeg stdout: ' + stdout);
  
            console.log('ffmpeg stderr: ' + stderr);
  
          });
  
      command.output(res);
  
  }).listen(8080, 'localhost');

  If I try to open the stream with VLC, I don’t get any response.
  Does anybody know what’s wrong ?

• Thread count option in FFmpeg for FASTEST conversion to h264 ?

  9 février, par S B

  I need to maximize speed while converting videos using FFmpeg to h264

  



  

  • Any input format of source videos

  


  • User's machine can have any number of cores

  


  • Power and memory consumption are non-issues

  


  



  Of course, there are a whole bunch of options that can be tweaked but this question is particularly about choosing the best -thread <count></count> option. I am trying to find an ideal thread count as a function of

  



  

  • no. of cores

  


  • input video format

  


  • h264-friendly values maybe ?

  


  • anything else missed above ?

  


  



  I am aware the default -thread 0 follows one-thread-per-core approach which is supposed to be optimal. But I am not sure if this is time or space-optimized. Also, on certain testcases, I've seen more threads (say 4 threads on my dual core test machine) finishes quicker than the default.

  



  Any other direction, say configure options w.r.t. threads, worth pursuing ?