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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...

• Carrierwave video not being processsed before uploading to S3

  12 décembre 2013, par Cramps

  I'm using Carrierwave, Carrierwave-video and Carrierwave-video-thumbnailer to process videos and make a thumbnail when they're uploaded. This was all working nicely while I was saving the files on my file system. However, now that I've added uploading to Amazon S3 using the carrierwave-aws gem, the videos are being uploaded to S3 without being processed first. It's as if the process encode_video and version :thumb are being skipped by the uploader.

  Here's what was working for me at first (before adding S3) :

  class VideoUploader < CarrierWave::Uploader::Base
  
  
  
  include CarrierWave::Video
  
  include CarrierWave::Video::Thumbnailer
  
  
  
  storage :file
  
  
  
  def store_dir
  
      "upload/path/"
  
  end
  
  
  
  process encode_video: [{ bunch of video options}]
  
  
  
  version :thumb do
  
      process thumbnail: [{ bunch of thumbnailer options }]
  
      def full_filename for_file
  
          png_name for_file, version_name
  
      end  
  
  end
  
  
  
  def png_name for_file, version_name
  
      %Q{#{version_name}_#{for_file.chomp(File.extname(for_file))}.png}
  
  end

  Now it's really just the same, except it's using storage :aws instead.

• How to record (and process ?) a video that is streamable from Android

  13 mai 2016, par afollestad

  My company’s app relies heavily on video recording and playback of web-based videos. I use the MediaRecorder API to record videos, through this library designed by me : https://github.com/afollestad/material-camera.

  For playback, I use this library which is basically a wrapper around Google’s ExoPlayer library : https://github.com/brianwernick/ExoMedia.

  It works fine for the most part with small videos, especially if I decrease bit rates for audio and video. However, larger and higher quality videos have many issues. Sometimes they seem to buffer forever, sometimes playback doesn’t even start successfully, etc. Again, these videos are being streamed over HTTP from Amazon S3.

  ---

  I’ve read a little bit about FFMPEG, and how it can process MP4’s for "faststart", splitting the files into chunks for DASH, etc. However, FFMPEG solutions for Android seem a bit complex, so...

  Is there anyway to record MP4’s from Android, with MediaRecorder, MediaCodec, or some other API which results in a video file that is fast to stream ? It amazes me how well Snapchat has figured this out.