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• fate/lavf-* : Add missing dependency on pipe protocol

  18 septembre 2022, par Andreas Rheinhardt

  fate/lavf-* : Add missing dependency on pipe protocol
  Forgotten in bf1337f99c66ac574c6e4da65c305ca878f1d65d.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] tests/fate/lavf-audio.mak
  • [DH] tests/fate/lavf-container.mak
  • [DH] tests/fate/lavf-image.mak
  • [DH] tests/fate/lavf-image2pipe.mak
  • [DH] tests/fate/lavf-video.mak

• ffmpeg process how to read from pipe to pipe in c#

  28 janvier 2024, par greg

  I need to read audio data from stream 1 to stream 2 passing the data through ffmpeg.
It works great when i input data from file and output to pipe :

  


  Process? CreateStream()
{
    return Process.Start(new ProcessStartInfo
    {
        FileName = @"sources\ffmpeg",
        Arguments = @"-i input.mp3 -f s16le pipe:1",
        UseShellExecute = false,
        RedirectStandardOutput = true
    });
}


  


  Or when i input data from pipe and output to file :

  


  Process? CreateStream()
{
    return Process.Start(new ProcessStartInfo
    {
        FileName = @"sources\ffmpeg",
        Arguments = @"-i pipe: -f s16le output.file",
        UseShellExecute = false,
        RedirectStandardInput = true
    });
}


  


  But if i try to do both :

  


  Process? CreateStream()
{
    return Process.Start(new ProcessStartInfo
    {
        FileName = @"sources\ffmpeg",
        Arguments = @"-i pipe:0 -f s16le pipe:1",
        UseShellExecute = false,
        RedirectStandardInput = true,
        RedirectStandardOutput = true
    });
}


  


  Runtime will hang in place printing :

  


  


  Input #0, matroska,webm, from 'pipe:0' :
Metadata :
encoder : google/video-file
Duration : 00:04:15.38, start : -0.007000, bitrate : N/A
Stream #0:0(eng) : Audio : opus, 48000 Hz, stereo, fltp (default)
Stream mapping :
Stream #0:0 -> #0:0 (opus (native) -> pcm_s16le (native))

  


  Output #0, s16le, to 'pipe:1' :
Metadata :
encoder : Lavf59.27.100
Stream #0:0(eng) : Audio : pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s (default)
Metadata :
encoder : Lavc59.37.100 pcm_s16le

  


  


  main function code (it is the same for all examples) :

  


  async Task Do()
{
    using (var ffmpeg = CreateStream())
    {
        if (ffmpeg == null) return;

        using (var audioStream = GetAudioStream())
        {
            await audioStream.CopyToAsync(ffmpeg.StandardInput.BaseStream);
            ffmpeg.StandardInput.Close();
        }

        //runtime will hang in here

        Console.WriteLine("\n\ndone\n\n"); //this won't be printed

        using (var outputStream = CreatePCMStream())
        {
            try
            {
                await ffmpeg.StandardOutput.BaseStream.CopyToAsync(outputStream);
            }
            finally
            {
                await outputStream.FlushAsync();
            }
        }
    }
}


  


  And the most interesting is if i remove RedirectStandardOutput = true string programm will work as expected printing a bunch of raw data to the console.

  


  I'd like to solve this problem without using any intermediate files and so on.

  


• Matplotlib pipe canvas.draw() to ffmpeg - unexpected result [duplicate]

  31 juillet 2022, par Narusan

  I'm using this code from here to try and pipe multiple matplotlib plots into ffmpeg to write a video file :

  


  import numpy as np
import matplotlib.pyplot as plt
import subprocess

xlist = np.random.randint(100,size=100)
ylist = np.random.randint(100, size=100)
color = np.random.randint(2, size=100)

f = plt.figure(figsize=(5,5), dpi = 300)
canvas_width, canvas_height = f.canvas.get_width_height()
ax = f.add_axes([0,0,1,1])
ax.axis('off')


# Open an ffmpeg process
outf = 'ffmpeg.mp4'
cmdstring = ('ffmpeg',
    '-y', '-r', '30', # overwrite, 30fps
    '-s', '%dx%d' % (canvas_width, canvas_height), # size of image string
    '-pix_fmt', 'argb', # format
    '-f', 'rawvideo',  '-i', '-', # tell ffmpeg to expect raw video from the pipe
    '-vcodec', 'mpeg4', outf) # output encoding
p = subprocess.Popen(cmdstring, stdin=subprocess.PIPE)

# Draw 1000 frames and write to the pipe
for frame in range(10):
    print("Working on frame")
    # draw the frame
    f = plt.figure(figsize=(5,5), dpi=300)
    ax = f.add_axes([0,0,1,1])
    ax.scatter(xlist, ylist,
               c=color, cmap = 'viridis')
    f.canvas.draw()
    plt.show()

    # extract the image as an ARGB string
    string = f.canvas.tostring_argb()
    # write to pipe
    p.stdin.write(string)

# Finish up
p.communicate()


  


  While plt.show() does show the correct plot (see image below), the video that ffmpeg creates is a bit different than what plt.show() shows. I am presuming the issue is with f.canvas.draw(), but I'm not sure how to get a look at what canvas.draw() actually plots.

  


  plot.show() :


  


  ffmpeg video (imgur link)