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• How can I transform a sequence of images into a playable video using LibVLCSharp ?

  9 février 2021, par adamasan

  I have a sequence of images that I was able to extract from a video using LibVLCSharp. This sample to be more specific. I'm creating a small video library manager for learning purposes, and I would like to extract frames and create thumbnails to play when the user hovers the mouse over the previewer.

  


  Using the aforementioned sample I was able to create a WPF UI around the same loging and extract the frames from a video file. However what I want now is to convert these extracted frames into a video file, using them as preview for the video, just like happens on YouTube.

  


  I wasn't able, however, to find out how to achieve this using LibVLCSharp or just LibVLC. Using this answer on Super User I was able to achieve my goal and put those frames together into a video using ffmpeg.

  


  I haven't taken the time yet to study FFmpeg.Autogen, so I don't know if I would be able to extract the frames from the video files in the same way I can do with LibVLCSharp, but I don't see with good eyes using both libraries on my application, one to export the frames and one to generate these frames into a video.

  


  So, is there a way to get the output frames and convert them into a playable video using LibVLCSharp (or libvlc) itself ?

  


• AVPlayer won't play audio files from FFMPEG

  18 janvier 2021, par Marcus

  Before requesting audio data AVPlayer requests byte range 0-1 from FFMPEG.

  


  FFMPEG gives a 200 response, but AVPlayer requires a 206 response.

  


  This results in the request failing and audio can't be played.

  


  Expected behavior :
Play tracks when streaming through ffmpeg

  


  Current behavior : When trying to stream with ffmpeg we get "Operation Stopped"

  


  Sample FFMPEG command :

  


  ffmpeg -i "/path/to/audio/track.mp3" -vn -strict -2 -acodec pcm_u8 -f wav -listen 1 -seekable 1 http://localhost:8090/restream.wav


  


  Player Log :

  


  Error Domain=AVFoundationErrorDomain Code=-11850 "Operation Stopped" UserInfo={NSLocalizedFailureReason=The server is not correctly configured., NSLocalizedDescription=Operation Stopped, NSUnderlyingError=0x600003bcc4b0 {Error Domain=NSOSStatusErrorDomain Code=-12939 "(null)"}}
!av_interleaved_write_frame(): Broken pipe

!Connection to tcp://localhost:8090 failed: Connection refused

!Connection to tcp://localhost:8090 failed: Connection refused

!Connection to tcp://localhost:8090 failed: Connection refused

!Error writing trailer of http://localhost:8090/restream.wav: Broken pipe


  


  This error is defined by Apple as :

  


  +"The HTTP server sending the media resource is not configured as expected. This might mean that the server does not support byte range requests."


  


  And summarised nicely in this StackOverflow post :

  


  when AVPlayerItem receive a video URL , it do the following task:

    Send a bytes request HTTP Request, and range = 0 -1
    If the response code is 206 and return 1 bytes data, It do the 3th task, if not, AVErrorServerIncorrectlyConfigured error occurred.
    continue send other HTTP Request, to download segment of All duration. and the response of VideoData code must be 206

In my situation , when send range[0-1] HTTP request, the server side give me a 200 OK response, So error occurred.


  


  Network Log :

  


  GET /file.wav HTTP/1.1
Host: localhost:1234
X-Playback-Session-Id: F72F1139-6F4C-4A22-B334-407672045A86
Range: bytes=0-1
Accept: */*
User-Agent: AppleCoreMedia/1.0.0.18C61 (iPhone; U; CPU OS 14_3 like Mac OS X; en_us)
Accept-Language: en-us
Accept-Encoding: identity
Connection: keep-alive

HTTP/1.1 200 OK
Content-Type: application/octet-stream
Transfer-Encoding: chunked


  


  Reproduce using this sample app :

  


  This can also be reproduced using standard ffmpeg and adding URL to local or remote ffmpeg URL

  


  Can we solve this by making changes to FFMPEG or AVPlayer ?

  


• FFMPEG throws error can not open display error for :1

  2 décembre 2020, par Krishna

  i am using Xvfb for starting X server on display 1 and x11vnc is also set for -display :1 along with fluxbox as window manager on Ubuntu 20.04 LTS like using below commands

  


  sudo -i -u ubuntu Xvfb :1 +extension GLX -screen 0 1440x1080x16 -ac sudo -i -u ubuntu DISPLAY=:1 fluxbox sudo -i -u ubuntu x11vnc -forever -display :1

  


  and when i run command : "ffmpeg -video_size 1440x1080 -framerate 25 -f x11grab -i :1.0 -c:v libx264rgb -crf 0 -preset ultrafast sample.mp4" it runs, however when i execute programmatically through processbuilder i see that in output buffer stream log file as :1 : Invalid argument and doesn't start recording,

  


  Command sent to processBuilder is like below :

  


  pb = new ProcessBuilder(ffmpegLocation, "-video_size", "1440x1080x16",
"-f", "x11grab", "-i", ":1", "-c:v libx264 -crf 0 -preset ultrafast", "-framerate","25", outputfilepath()) ;

  


  -FYI i have tried setting environmental variable as export DISPLAY=:1 , but still same error and also do i need to set the DISPLAY=:1, since i am setting up display number when i start Xvfb ? this used to work using avconv on older version of ubuntu but i am stuck on display issue for ffmpeg, anyone has idea how to resolve this ?