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• Error while trying to get output from command [C++]

  8 septembre 2021, par Jilijou

  I am trying to get the duration of a video using ffmpeg in C++ and I tried using a pipe to get the output from a command. I can't compile my code, getting this error :

  


  video_concat.cpp: In function 'int main()':
video_concat.cpp:17:41: error: expected ',' or ';' before '{' token
   std::string exec(commande_duration_2) {
                                         ^
video_concat.cpp:51:1: error: expected '}' at end of input
 }
 ^


  


  And this is my code :

  


  #include <iostream>&#xA;#include <memory>&#xA;#include <stdexcept>&#xA;#include <array>&#xA;#include <cstdio>&#xA;#include &#xA;#include <string>&#xA;#include <sstream>&#xA;&#xA;using namespace std;&#xA;&#xA;int main() {&#xA;  float duration_1, duration_2, full_duration;&#xA;  duration_1 = system("ffprobe -i goal1_25.mp4 -show_entries format=duration -v quiet -of csv=\"p=0\"");&#xA;  //duration_2 = system("ffprobe -i goal2_25.mp4 -show_entries format=duration -v quiet -of csv=\"p=0\"");&#xA;  const char* command_duration_2 = "ffprobe -i goal2_25.mp4 -show_entries format=duration -v quiet -of csv=\"p=0\"";&#xA;  std::string exec(commande_duration_2) {&#xA;    std::shared_ptr<file> pipe(popen(command_duration_2, "r"), pclose);&#xA;    if (!pipe) return "ERROR";&#xA;    char buffer[128];&#xA;    std::string result = "";&#xA;    while (!feof(pipe.get())) {&#xA;        if (fgets(buffer, 128, pipe.get()) != NULL) {&#xA;            duration_2 &#x2B;= buffer;&#xA;        }&#xA;    }&#xA;    return duration_2;&#xA;  }&#xA;&#xA;&#xA;  cout &lt;&lt; duration_1 &lt;&lt; " | " &lt;&lt; duration_2;&#xA;  return 0;&#xA;}&#xA;</file></sstream></string></cstdio></array></stdexcept></memory></iostream>

  


  If I put between /.../ the pipe section, everything works fine but I don't get any result (Output : 0 | 0). Can anyone help me ? Thanks !

  


• How to rotate an image overlay in ffmpeg around the image center ?

  14 mars 2023, par ktrace

  I'm using ffmpeg to scale, rotate and overlay an image on a video. I'm able to rotate the image by the desired angle but the overlay ends up being moved both vertically and horizontally from the expected position.

  


  The commands I've tried and their corresponding outputs are shown below. Command 1 gives the expected output, 2 and 3 do not.

  


  How can I modify my commands in general, to rotate the overlay image around the image center, to get the expected output ?

  


  

  


  


  ffmpeg -i graphpaper.mp4 -i arrow.png -y -filter_complex [1:v]scale=w=364:h=370[overlay0] ;[overlay0]rotate=a=0:c=none:ow=rotw(0):oh=roth(0)[rotate0] ;[0:v][rotate0]overlay=x=419:y=168[output0] -map [output0] sample-overlay-on-graph-paper.mp4

  


  


  

  


  


  ffmpeg -i graphpaper.mp4 -i arrow.png -y -filter_complex [1:v]scale=w=364:h=370[overlay0] ;[overlay0]rotate=a=0.8017360589297406:c=none:ow=rotw(0.8017360589297406):oh=roth(0.8017360589297406)[rotate0] ;[0:v][rotate0]overlay=x=419:y=168[output0] -map [output0] sample-overlay-on-graph-paper.mp4

  


  


  

  


  


  ffmpeg -i graphpaper.mp4 -i arrow.png -y -filter_complex [1:v]scale=w=364:h=370[overlay0] ;[overlay0]rotate=a=5.493783719179012:c=none:ow=rotw(5.493783719179012):oh=roth(5.493783719179012)[rotate0] ;[0:v][rotate0]overlay=x=419:y=168[output0] -map [output0] sample-overlay-on-graph-paper.mp4

  


  


  Links to input files :

  


  

  • graphpaper.mp4 https://imgur.com/a/daHI7j0

  


  • arrow.png https://imgur.com/a/wWwnnfq

  


  


• OpenCV 3.0.0 "configure" fails, ffmpeg not downloaded

  19 avril 2017, par S.H

  I get the following error when trying to configure OpenCV using CMAKE on windows :

  CMake Warning at cmake/OpenCVUtils.cmake:865 (message):
  
  Download: Local copy of opencv_ffmpeg.dll has invalid MD5 hash:
  
  d41d8cd98f00b204e9800998ecf8427e (expected:
  
  89c783eee1c47bfc733f08334ec2e31c)
  
  
  
  Call Stack (most recent call first):
  
  3rdparty/ffmpeg/ffmpeg.cmake:10 (ocv_download)
  
  cmake/OpenCVFindLibsVideo.cmake:193 (include)
  
  CMakeLists.txt:527 (include)
  
  
  
  
  
  Downloading opencv_ffmpeg.dll...
  
  CMake Error at cmake/OpenCVUtils.cmake:888 (file):
  
  file DOWNLOAD MD5 mismatch
  
  
  
  for file: [C:/research/opencv300/sources/3rdparty/ffmpeg/downloads/89c783eee1c47bfc733f08334ec2e31c/opencv_ffmpeg.dll]
  
  expected MD5 sum: [89c783eee1c47bfc733f08334ec2e31c]
  
  actual MD5 sum: [d41d8cd98f00b204e9800998ecf8427e]
  
  
  
  Call Stack (most recent call first):
  
  3rdparty/ffmpeg/ffmpeg.cmake:10 (ocv_download)
  
  cmake/OpenCVFindLibsVideo.cmake:193 (include)
  
  CMakeLists.txt:527 (include)
  
  
  
  
  
  CMake Error at cmake/OpenCVUtils.cmake:892 (message):
  
  Failed to download opencv_ffmpeg.dll.  Status=1;"unsupported protocol"
  
  Call Stack (most recent call first):
  
  3rdparty/ffmpeg/ffmpeg.cmake:10 (ocv_download)
  
  cmake/OpenCVFindLibsVideo.cmake:193 (include)
  
  CMakeLists.txt:527 (include)
  
  
  
  
  
  Configuring incomplete, errors occurred!

  I tried downloading opencv_ffmpeg.dll manually, but the configure process didn’t work.

  Can you help me, how to fix that ?