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• bash script with conditional arguments and output pipe not working [duplicate]

  19 décembre 2022, par Pavel

  Can u please help me with bash script for ffmpeg ?
Trying to create condition based on args to play OR save media to file, so I've created this kind of IF :

  


  #!/bin/bash

if [ "$1" == "play" ]; then
    POSTFIX="-f matroska - | mpv -"
else
    POSTFIX="-y $OUTPUT"
fi

ffmpeg \
  # skipped personal ffmpeg stuff
  "$POSTFIX"


  


  Now when I try to run it with "play" argument it says :

  


  Unrecognized option 'f matroska - | mpv -'.


  


  So if I add this POSTFIX both variants to command everything works fine...

  


  It looks like something in my bash screens this args or something like that ? Also I don't see in error this dash symbol before f option

  


• ffmpeg record video from image pipe with constant framerate

  4 janvier 2023, par Michael

  I'm trying to record a lossless video with ffmpeg, feeding it image data through standard input.

  


  The process is started like this (C#) :

  


  string inputArgs = "-y -f image2pipe -pix_fmt yuyv422 -i -";
string outputArgs = "-r 20 -c:v libx264 -crf 0 -pix_fmt yuv422p -preset ultrafast C:\\temp\\out.mp4";

process = new Process
{
    StartInfo =
        {
           FileName = "ffmpeg.exe",
           Arguments = $"{inputArgs} {outputArgs}",
           UseShellExecute = false,
           CreateNoWindow = true,
           RedirectStandardInput = true
        }
};

process.Start();


  


  The above works, but I have a problem with framerate. The rate I'm feeding images to ffmpeg is different over time, but I need ffmpeg to keep output rate constant. According to ffmpeg documentation, if set like this "-r 20" it should "duplicate or drop input frames to achieve constant output frame rate fps". But it doesn't. If I feed the images to the ffmpeg too slow, I'm getting fast playing video and vice versa.

  


  Am I providing wrong arguments ? Or it's somehow has to deal with ffmpeg getting images from Standard Input ?

  


  I tried these options in the output settings block : "vsync" (setting it to 1) and "fps_mode" (setting it to cfr). "vsync" doesn't have any effect, with "fps_mode" nothing works (video not recorded at all).

  


• avformat/file : add fd option for pipe

  14 décembre 2022, par Zhao Zhili

  avformat/file : add fd option for pipe
  Signed-off-by : Zhao Zhili <zhilizhao@tencent.com>
  

  • [DH] doc/protocols.texi
  • [DH] libavformat/file.c
  • [DH] libavformat/version.h