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• FFmpeg file size while recording multiple windows at same time

  29 août 2021, par RuanS

  I'm currently recording 3 windows at once, and placing them next to each other, windows dimensions are : 400x500, 830x500, 830x500, using -c:v h264_nvenc to reduce the use of CPU.

  


  The first and second windows have very low frames change, the third window does change frames frequently.

  


  ffmpeg -f gdigrab -framerate 30 -i title="" -f gdigrab -framerate 30 -i title="" -f gdigrab -framerate 30 -i title="" -c:v h264_nvenc -qp 0 -c:a copy -vsync vfr -filter_complex hstack=inputs=3 output.mp4


  


  Doesn't need to be great quality, 'normal/medium' quality is enough, also, I'm recording only video, no audio.

  


  After 3min the file size was over 340MB, would like to ask if there are any better options in which I could be used to reduce the file size also CPU use (if possible).

  


• Apply Multiple overlay at different time using ffmpeg

  9 juillet 2021, par Abhay Koradiya

  I need to enable multiple overlays on video at different times whcih contain alpha.

  


  I am trying the below command. But no success, only 1st image shows all time.

  


  ffmpeg -i img_0.jpg -i img_1.jpg -i img_2.jpg -i img_3.jpg -i img_4.jpg -i img_5.jpg -i img_6.jpg -i img_7.jpg -i background_video.mp4 
    -filter_complex 
    "[8]split=2[color][alpha];[color]crop=iw/2:ih:0:0[color];[alpha]crop=iw/2:ih:iw/2:0[alpha];[color][alpha]alphamerge[ovrly];[0]scale=540:960[0_scalled];
[1]scale=540:960[1_scalled];
[2]scale=540:960[2_scalled];
[3]scale=540:960[3_scalled];
[4]scale=540:960[4_scalled];
[5]scale=540:960[5_scalled];
[6]scale=540:960[6_scalled];
[7]scale=540:960[7_scalled];
[0_scalled][0]overlay=enable='between=(t,0,5)':x=0:y=0[v0];
[v0][1_scalled]overlay=enable='between=(t,3.5,8.5)':x=0:y=0[v1];
[v1][2_scalled]overlay=enable='between=(t,7,12)':x=0:y=0[v2];
[v2][3_scalled]overlay=enable='between=(t,10.5,15.5)':x=0:y=0[v3];
[v3][4_scalled]overlay=enable='between=(t,14,19)':x=0:y=0[v4];
[v4][5_scalled]overlay=enable='between=(t,17.5,22.5)':x=0:y=0[v5];
[v5][6_scalled]overlay=enable='between=(t,21,26)':x=0:y=0[v6];
[v6][7_scalled]overlay=enable='between=(t,24.5,30)':x=0:y=0[v7];
[v7][ovrly]overlay=0:0"
-t 30 -strict -2 -preset ultrafast out.mp4


  


• Slient crash when calls to ffmpeg's libav exist

  9 juin 2021, par William Lohan

  I have a fairly simple example.

  


  #include <iostream>&#xA;&#xA;extern "C"&#xA;{&#xA;#include <libavutil></libavutil>opt.h>&#xA;#include <libavutil></libavutil>avutil.h>&#xA;#include <libavcodec></libavcodec>avcodec.h>&#xA;#include <libavformat></libavformat>avformat.h>&#xA;}&#xA;&#xA;int main(int, char **)&#xA;{&#xA;  AVFormatContext *format = 0; // avformat_alloc_context();&#xA;&#xA;  // avformat_open_input(&amp;format, "http://s5radio.ponyvillelive.com:8026/stream.mp3", NULL, NULL);&#xA;  // avformat_find_stream_info(format, NULL);&#xA;&#xA;  std::cout &lt;&lt; "Hello, world!" &lt;&lt; std::endl;&#xA;&#xA;  return 0;&#xA;}&#xA;</iostream>

  


  I this outputs "Hello, world !" and I can set break points but the moment I uncomment anything calling avformat code the program silently closes with no error and no break points are hit making it impossible to debug.

  


  An example would be changing AVFormatContext *format = 0; to AVFormatContext *format = avformat_alloc_context(); or uncommenting avformat_open_input(&format, "http://s5radio.ponyvillelive.com:8026/stream.mp3", NULL, NULL);. Without breakpoints or errors how do I solve ?

  


  Update :
This is what I get from the debugger :

  


  


  ERROR : Unable to start debugging. Unexpected GDB output from command "-exec-run". During startup program exited with code 0xc0000139.
The program 'path\to\my\project\LibavPlayground.exe' has exited with code 0 (0x00000000).

  


  


  Update2 :

  


  this is my cmake :

  


  cmake_minimum_required(VERSION 3.0.0)
project(LibavPlayground VERSION 0.1.0 LANGUAGES CXX C)

find_package(PkgConfig REQUIRED) 
pkg_check_modules(LIBAV REQUIRED libavutil libavcodec libavformat)
include_directories(${LIBAV_INCLUDE_DIRS})
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D__STDC_CONSTANT_MACROS -Wno-deprecated-declarations")

include_directories(include PUBLIC)
include_directories(src PRIVATE)

file(GLOB SRC_FILES ${PROJECT_SOURCE_DIR}/src/*.cpp)

add_executable(LibavPlayground ${SRC_FILES})
target_link_libraries(LibavPlayground ${LIBAV_LIBRARIES})


  


  and all the libav* libraries were installed with a single pacman -S mingw-w64-x86_64-ffmpeg command