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• c# how to correctly format an ffmpeg user input stream ?

  6 janvier 2021, par user14527374

  So I'm writing a c# application which allows a user to scale a video in pixels to a custom dimension. I am strugeling to get the user input from a textbox for the mpeg psi arguments :

  


  Here is the code :

  


   var localStoragePath = Path.Combine(Path.GetTempPath(), name);
                            var directoryPath = Path.GetDirectoryName(localStoragePath);
                            Directory.CreateDirectory(directoryPath);
                            File.WriteAllBytes(localStoragePath, bytes);
                            Progress.Text = ($"File copy successful: {File.Exists(localStoragePath)}");
                            var readBack = File.ReadAllBytes(localStoragePath);
                            Progress.Text = ($"Read file Back: {readBack.Length}, {localStoragePath}");
                            var resizedFolderPath = @"C:\upscaledvideohere";
                            Directory.CreateDirectory(resizedFolderPath);
                            var resizedFiePath = Path.Combine(resizedFolderPath, Path.GetFileName(localStoragePath));

                            var psi = new ProcessStartInfo();
                            psi.FileName = @"C:\ffmpeg-2020-12-27-git-bff6fbead8-full_build\bin\ffmpeg.exe";
                            psi.Arguments = $"-i \"{localStoragePath}\" -vf scale=" + pixelsheight.Text  "\"{resizedFiePath}\"";
                            psi.RedirectStandardOutput = false;
                            psi.RedirectStandardError = false;
                            psi.UseShellExecute = true;
                            Progress.Text = ($"Args: {psi.Arguments}");


  


  For

  


   psi.Arguments = $"-i \"{localStoragePath}\" -vf scale=" + pixelsheight.Text  "\"{resizedFiePath}\""


  


  What would be the correct way to input the text for what the user typedin the pixelsheight text box ?

  


  Thanks very much.

  


• Error Exception : You do not have ffmpeg installed on your machine when using python bar_chart_race with reticulate in rstudio

  27 septembre 2020, par Zhiqiang Wang

  I have run python bar_chart_race successfully in jupyter notebook.

  


  import bar_chart_race as bcr
bcr.bar_chart_race(df=wide_1, filename=None, title='Mortality (per million) by Country')


  


  I have ffmpeg installed on my machine.

  


  > Sys.which("ffmpeg")
                       ffmpeg 
"C:\\ffmpeg\\bin\\ffmpeg.exe" 


  


  However, when I tried the same code in rmarkdown with rstudio reticulate,

  


  import bar_chart_race as bcr
bcr.bar_chart_race(wide_1)


  


  I received the following message :

  


  Exception: You do not have ffmpeg installed on your machine. Download
                            ffmpeg from here: https://www.ffmpeg.org/download.html.
                            
                            Matplotlib's original error message below:

                            [WinError 6] The handle is invalid


  


  reticulate::py_config()

  


  > reticulate::py_config()
python:         C:/ProgramData/Anaconda3/python.exe
libpython:      C:/ProgramData/Anaconda3/python38.dll
pythonhome:     C:/ProgramData/Anaconda3
version:        3.8.3 (default, Jul  2 2020, 17:30:36) [MSC v.1916 64 bit (AMD64)]
Architecture:   64bit
numpy:          C:/ProgramData/Anaconda3/Lib/site-packages/numpy
numpy_version:  1.18.5


  


  ffmpeg works fine with R animated graph packages in rstudio, and with python bar_chart_race. I have tried to re-install ffmpeg several times. Any advice would be appreciated.

  


• ffmpeg : video to aligned audio (audio too short)

  16 octobre 2020, par mcb

  I want to extract an aligned audio stream from a video. The goal is to obtain an audio sequence that is precisely aligned with the video.

  


  Issue : The video and audio sequences are not aligned. The output audio duration is shorter than the video input.

  


  Script to reproduce :

  


  fn=TV-20200617-2242-4900.websm.h264
url=https://download.media.tagesschau.de/video/2020/0617/$fn.mp4
wget -nc $url

ffmpeg -y -i "$fn.mp4" -vsync 1 -async 1 -map 0:a "$fn.wav" -map 0:v "$fn.flv"

ffprobe -i $fn.mp4  # Duration: 00:01:51.68
ffprobe -i $fn.flv  # Duration: 00:01:51.68
ffprobe -i $fn.wav  # Duration: 00:01:49.61


  


  What I have tried (without success) :

  


  

  • Adding -async 1 as suggested in this answer.

  


  • Adding -acodec copy and exporting the video at the same time (link).

  


  • Opening the mp4 in Audacity. The duration there is 00:01:49.61.

  


  • Opening the mp4 in VLC. Duration : 00:01:51.68.

  


  • Explicitly setting the framerate.

  


  • Other video files.

  


  


  ffmpeg version 4.2.4-1ubuntu0.1

  


  I would appreciate any hint on how to make this work. Thank you.