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• Can you think of a reason why windows might not enable audio if noone is logged in ?

  3 juillet 2017, par Caius Jard

  I’m having a bizarre problem with some virtual servers created to record podcasts. They run on amazon AWS as windows server 2012 instances and a small c# app tells FFMPEG to do the heavy lifting of capturing from the virtual screen and reading from the virtual sound card (Virtual Audio Cable : https://en.wikipedia.org/wiki/Virtual_Audio_Cable) via DirectShow filters

  The problem I have is if I leave the machine to do its stuff unattended, the recordings are sometimes silent. If I log in via VNC and watch it doing its stuff the audio is recorded just fine. All other aspects of the test op are the same, and the virtual machine is shut down between successive recordings so each one should theoretically be a clean slate. The app runs under a logged in session (hence the use of VNC rather than RDP)

  I’m now wondering if there is some optimisation of the windows sound engine whereby it doesn’t bother playing audio if it thinks noone is listening. The confusing thing to me is that not every virtual machine suffers these problems ; some of them record fine (and they’re all created from the same seed virtual hard disk image) in unattended mode

  I’m asking this question with the aim of getting together a list of things I can check/look into/debug.. I don’t have much knowledge of how MME/DirectSound/WASAPI work internally...

• Creating a PowerShell Streamer Function w/youtube-dl, ffmpeg & ffplay

  11 juillet 2017, par Adam Chilcott

  My question is in regards to combining youtube-dl, ffmpeg, ffplay and PowerShell to handle video URLs.

  Some examples I’ve seen have piped a binary stream from youtube-dl to an external player using the Windows Command Prompt as demonstrated :

  youtube-dl --output - "https://youtube.com/mygroovycontent" | mpc-hc.exe /play /close -

  This works fine in Command Prompt as it does not mangle the binary stream. If you try and run the same command in PowerShell it doesn’t handle the binary stream so well and modifies the output, making it unreadable to the external player.

  In light of this I’ve written the following PowerShell function to get around this issue. It tries to mirror a similar function I’ve written in Bash (See : https://github.com/adamchilcott/.dotfiles/blob/master/.bash_functions.d/streamer.sh)

  The reason I’ve handled youtube-dl, ffmpeg and ffplay seperately is that defining the ffmpeg binary location in youtube-dl as an external program creates some issues when passing it in PowerShell.

  I was hoping that someone could take a look at my script and provide some feedback on what I have done here and if it can be improved upon or if a better implementation is already available ?

  Best,

  Adam.

  BEGIN POWERSHELL

  Function streamer
  
  {
  
  
  
  Param
  
  (
  
  [string] $streamURL
  
  )
  
  
  
  Begin
  
  {
  
  }
  
  
  
  Process
  
  {
  
  $streamDir = "$env:TEMP\YTD.d"
  
  
  
  $ytdBin = "Z:\PortableApps\CommandLineApps\youtube-dl\youtube-dl.exe"
  
  $streamExtractor = &$ytdBin --no-warnings --get-url $streamURL
  
  
  
  $ffmpegBin = "Z:\PortableApps\CommandLineApps\ffmpeg-20170702-c885356-win64-static\bin\ffmpeg.exe"
  
  $ffplayBin = "Z:\PortableApps\CommandLineApps\ffmpeg-20170702-c885356-win64-static\bin\ffplay.exe"
  
  
  
  if 
  
  (
  
  -not (Test-Path -Path $streamDir -PathType Any)
  
  )
  
  
  
  {
  
  New-Item $streamDir -type directory -ErrorAction SilentlyContinue
  
  }
  
  
  
  Start-Process -FilePath $ffmpegBin -ArgumentList "-loglevel quiet -i $streamExtractor -c copy $streamDir\streamContainer.m2ts" -NoNewWindow -ErrorAction SilentlyContinue
  
  
  
  Do
  
  {
  
  Start-Sleep -Seconds 1
  
  } 
  
  
  
  Until 
  
  (
  
  (Get-Item $streamDir\streamContainer.m2ts -ErrorAction SilentlyContinue).Length -gt 256kb
  
  )
  
  
  
  &$ffplayBin -loglevel quiet $streamDir\streamContainer.m2ts
  
  
  
  if 
  
  (
  
  (Test-Path -Path $streamDir -PathType Any) -eq $true -and (Get-Process -Name ffplay -ErrorAction SilentlyContinue) -eq $null
  
  ) 
  
  
  
  {
  
  
  
  Do
  
  {
  
  Stop-Process -Name ffmpeg -ErrorAction SilentlyContinue
  
  }
  
  
  
  Until
  
  (
  
  (Get-Process -Name ffmpeg -ErrorAction SilentlyContinue) -eq $null
  
  )
  
  
  
  Remove-Item $streamDir -Recurse -ErrorAction SilentlyContinue
  
  }
  
  }
  
  
  
  End
  
  {
  
  }
  
  
  
  }
  
  
  
  streamer -streamURL https://www.youtube.com/watch?v=9uFXw7vKz14

  END POWERSHELL

• Streaming from Icecast to Facebook Live with ffmpeg on Ubuntu 16.04

  24 juillet 2017, par Matthieu

  I have a webradio streamed by Liquidsoap+Icecast on a DigitalOcean droplet (Ubuntu 16.04), and I want to combine this audio stream with a simple jpeg image with ffmpeg, transform it to a video stream and send it to Facebook live.

  Facebook Live specifications :

  Video Format :

  We accept video in maximum 720p (1280 x 720) resolution, at 30 frames
  per second. (or 1 key frame every 2 seconds). You must send an I-frame
  (keyframe) at least once every two seconds throughout the stream..
  Recommended max bit rate is 4000 Kbps. Titles must be less than 255
  characters otherwise the stream will fail. The Live API accepts H264
  encoded video and AAC encoded audio only.

  Video Length :

  240 minute maximum length, with the exception of continuous live (see
  above). 240 minute maximum length for preview streams (either through
  Live dialog or publisher tools). After 240 minutes, a new stream key
  must be generated.

  Advanced Settings :

  Pixel Aspect Ratio : Square. Frame Types : Progressive Scan. Audio
  Sample Rate : 44.1 KHz. Audio Bitrate : 128 Kbps stereo. Bitrate
  Encoding : CBR.

  And the ffmpeg command I tried :

  ffmpeg -loop 1 -i radio-background.jpg -thread_queue_size 20480 -i http://localhost:8000/radio -framerate 30 -r 30 -acodec aac -strict -2 -c:v libx264 -strict experimental -b:a 128k -pix_fmt yuvj444p -x264-params keyint=60 -b:v 256k -minrate 128k -maxrate 512k -bufsize 768k -f flv 'rtmp://rtmp-api.facebook.com:80/rtmp/'

  This is actually working, as Facebook receives the live video and allows me to publish it. But I can’t figured out why there is a lag almost every 2 or 3 seconds. I asked different people to watch the test video, and everyone gets the same problem : every 2 or 3 seconds the playing "freezes" for half a second and seems to load the video, I even can see the loading icon spinning on the screen.

  I tried different combinations of values for the following options : -thread_queue_size / -b:v / -minrate / -maxrate / -bufsize. Nothing seems to produce any change.

  Video streaming is new for me, I’m not really confortable with the options listed before, so I think I’m missing something here...

  Also, note that the icecast audio stream perfectly works, and according to DigitalOcean graphs, the server is not overloaded. So I think my ffmpeg command is wrong.

  What ffmpeg parameters would be working for that case ?