Recherche avancée

Sur d’autres sites (10480)

• ffplay playback h264 encoded camera preview blur

  11 juillet 2019, par doufu

  I use the ffplay tool provided by ffmpeg to play an h264 encoded camera. When the camera is still, the interface will be very clear, but when I cover the camera for a while to remove the occlusion or move the camera quickly, the interface will be blurred, resulting in a mosaic-like picture, but the interface will become clear after a few seconds.
  Why is this happening ?
  Am I missing some options to run ffplay ?
  PS：Using AMCap will not have the above problem.
  The command opening my camera I used :

  ffplay.exe -f dshow -i video="camera name"

  Preview screencast video is uploaded to youtube

  The following is the printout information of ffplay：
  

• ffmpeg - How to convert massive amounts of files in parallel ?

  15 juillet 2019, par Forivin

  I need to convert about 1.5TiB or audio files which are in either flac or wav format. They need to be converted into mp3 files, keeping important meta data and the cover art etc. and the bitrate needs to be 320k.

  This alone is easy :

  ffmpeg -i "$flacFile" -ab 320k -map_metadata 0 -id3v2_version 3 -vsync 2 "$mp3File" < /dev/null

  But the problem is making it faster. The command from above only uses 12.5% of the CPU. I’d much rather use like 80%. So I played around with the threads flag, but it doesn’t make it faster or slower :

  ffmpeg -i "$flacFile" -ab 320k -map_metadata 0 -id3v2_version 3 -vsync 2 -threads 4 "$mp3File" < /dev/null

  But it only utilizes my CPU by 13%. I think it only uses one thread. My CPU has 8 physical cores btw (+ hyperthreading).

  So my idea now is to somehow have multiple instances of ffmpeg running at the same time, but I have no clue how to do that properly.

  This is my current script to take all flac/wav files from one directory (recursively) and convert them to mp3 files in a new directory with the exact same structure :

  #!/bin/bash
  
  
  
  SOURCE_DIR="/home/fedora/audiodata_flac"
  
  TARGET_DIR="/home/fedora/audiodata_mp3"
  
  
  
  echo "FLAC/WAV files will be read from '$SOURCE_DIR' and MP3 files will be written to '$TARGET_DIR'!"
  
  read -p "Are you sure? (y/N)" -n 1 -r
  
  echo    # (optional) move to a new line
  
  if [[ $REPLY =~ ^[Yy]$ ]] ; then # Continue if user enters "y"
  
  
  
      # Find all flac/wav files in the given SOURCE_DIR and iterate over them:
  
      find "${SOURCE_DIR}" -type f \( -iname "*.flac" -or -iname "*.wav" \) -print0 | while IFS= read -r -d '' flacFile; do
  
          if [[ "$(basename "${flacFile}")" != ._* ]] ; then # Skip files starting with "._"
  
              tmpVar="${flacFile%.*}.mp3"
  
              mp3File="${tmpVar/$SOURCE_DIR/$TARGET_DIR}"
  
              mp3FilePath=$(dirname "${mp3File}")
  
              mkdir -p "${mp3FilePath}"
  
              if [ ! -f "$mp3File" ]; then # If the mp3 file doesn't exist already
  
                  echo "Input: $flacFile"
  
                  echo "Output: $mp3File"
  
                  ffmpeg -i "$flacFile" -ab 320k -map_metadata 0 -id3v2_version 3 -vsync 2 "$mp3File" < /dev/null
  
              fi
  
          fi
  
      done
  
  fi

  I mean I guess I could append an & to the ffmpeg command, but that would cause throusands of ffmpeg instances to run at the same time, which is too much.

• Most efficient way to render bitmap to screen on Linux [on hold]

  22 juillet 2019, par Maximus

  My goal is to receive a video feed from wifi and display it on my screen. For this, I’ve created a couple of small programs and a bash script to automate them running. It works like this :

  UDPBitmap/Plotter & ffplay -i - < UDPBitmap/pipe & python requester.py;

  Translation : There is a C++ program called Plotter, its job is to receive packets on an assigned UDP port, process them and write it to pipe (named : UDPBitmap/pipe). The pipe is accessed by ffplay, and ffplay renders the video on screen. The python file is solely responsible for accessing and controlling the camera with various HTTP requests.

  The above command works fine, everything works as expected. However, the resulting latency and framerate is a bit lower than what I’ve wanted. The bottleneck of this program is not the pipe, it is fast enough. Wifi transmission is also fast enough. The only thing left is ffplay.

  Question :

  What is the most efficient way to render a bitmap to screen, on Linux ? Is there a de facto library for this that I can use ?

  Note :

  • Language/framework/library does not matter (C, C++, Java, Python, native linux tools and so on...)
  • I do not need a window handle, but is SDL+OpenGL the way to go ?
  • Writing directly to the framebuffer would be super cool...