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• Camera Rendering Buffers and Stutters When Processing Large Video Files with FFmpeg

  20 avril 2023, par TIANYU HU

  When rendering a real-time camera, I use ffmpeg to process a large video file(like 4G or even larger) at the same time. However, I noticed that the video frames are buffering and stuttering, indicated they are probably competing for limited system resources, like cpu, memory or I/O bandwidth etc.

  


  I‘ve tried a lot of experiments to figure out the root cause. Firstly I limit the cpu usage of ffmpeg to 25%, but sadly it’s not getting better.

  


  Then I suspect that ffmpeg would read the large video file from disk to page cache in memory as much as it can before processing, and the generated files are going to be written back from page cache to disk. The RAM of our computer is 8G, apparently it needs to swap in and swap out pages between memory and disk. This process is costly for the CPU, and other processes are likely to trigger an interrupt named “Page Fault” when they access pages that are not actually loaded into memory. If the time taken for “page fault” is too long, the program may lag.

  


  Lastly I configure the system parameters related to “write back dirty pages to disk”, such as vm.dirty_writeback_centisecs and vm.dirty_background_ratio, to try to write back the dirty (Disk I/O) more frequently or infrequently. But I’m not quite sure what would happen if I modify these parameters.

  


  Expection :
The requirement can be summarized as “real-time video rendering has higher priority, and the low rate of large file processing is accepted”, are there any possible solutions of this issue from your perspective ? Thanks in advance.

  


• Trying to produce a stream of OGG encoded audio originating from microphone yields a completely quiet file

  3 décembre 2019, par Dan

  Basically title. I want to produce a constant stream of audio data encoded in OGG coming from my microphone. This is my current setup :

  var mic = require('mic');
  
  var fs = require('fs');
  
  var { exec } = require('child_process')
  
  
  
  var micInstance = mic({
  
      rate: '44100',
  
      channels: '1',
  
      debug: true,
  
      exitOnSilence: 0,
  
      device: 'pulse',
  
  
  
  });
  
  
  
  var micInputStream = micInstance.getAudioStream(); 
  
  var outputFileStream = fs.createWriteStream('output.final.ogg');
  
  var transcode = exec('ffmpeg -loglevel panic -i pipe: -f ogg -')
  
  
  
  micInputStream.pipe(transcode.stdin)
  
  transcode.stdout.pipe(outputFileStream)

  When I pipe micInputStream directly to process.stdout then use a unix pipe to pipe the data to a output.wav file, I can play it back.

  When I pipe micInputStream directly to process.stdout then use a unix pipe to pipe the data to ffmpeg, then unix-pipe all that data into a output.ogg file, I can also play it back.

  But when I try my code, I get an OGG file, but when I play it back, it’s quiet.

  I’m at a loss, how do I just create a readableStream containing an endless stream of audio coming from the mic, encoded in OGG ?

• Streaming MP4 frames to HTML5, what am I doing wrong ?

  5 septembre 2014, par mczarnek

  Currently I am generating a MP4 Bitstream using Intel’s Media SDK library, which uses ffmpeg underneath the covers. I can generate a mp4 file, and play it and it works.

  However, when I try to stream that mp4 across the network, it doesn’t play within the HTML5 video player, as tested within Chrome, Firefox, or IE.

  This much is sent back and forth across the network :

  Sent by Chrome:
  
  GET / HTTP/1.1
  
  Host: localhost:8085
  
  Connection: keep-alive
  
  User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.102 Safari/537.36
  
  Accept-Encoding: identity;q=1, *;q=0
  
  Accept: */*
  
  Accept-Language: en-US,en;q=0.8
  
  Range: bytes=0-
  
  
  
  From my video player:
  
  HTTP/1.1 200 OK
  
  Server: Microsoft-HTTPAPI/2.0
  
  Date: Thu, 09 Jan 2014 17:28:14 GMT
  
  Content-type: video/mp4

  After this, I send a newline, and all the video frames, one after another, while listening to see if I receive anything back from the browser.

  Then nothing happens. Any suggestions to get this playing video ? Thank you !