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• What is a correct way of ffmpeg dshow webcamera properties save and load ?

  12 juin 2020, par C0oo1D

  Command (PS == Windows PowerShell) :

  



  PS D:\> ffmpeg -f dshow -show_video_device_dialog True -video_device_save some_profile.txt -i 'video=MicrosoftR LifeCam Studio(TM)'


  



  FFmpeg Header :

  



  ffmpeg version git-2020-06-04-7f81785 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9.3.1 (GCC) 20200523
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libsrt --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --disable-w32threads --enable-libmfx --enable-ffnvcodec --enable-cuda-llvm --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
  libavutil      56. 49.100 / 56. 49.100
  libavcodec     58. 90.100 / 58. 90.100
  libavformat    58. 44.100 / 58. 44.100
  libavdevice    58.  9.103 / 58.  9.103
  libavfilter     7. 84.100 /  7. 84.100
  libswscale      5.  6.101 /  5.  6.101
  libswresample   3.  6.100 /  3.  6.100
  libpostproc    55.  6.100 / 55.  6.100


  



  Error after OK/Cancel/Close in camera settings dialog (empty file was created). Also tried without dialog - the same problem :

  



  [dshow @ 0715de40] Query for IPersistStream failed.
video=Microsoft® LifeCam Studio(TM): I/O error


  



  I assume that problem at the camera side, but I don't exclude my blindness (didn’t find any examples of saving settings or required command options in the documentation).

  



  Perhaps there is another way to save / load webcamera properties ?

  


• configure : Define feature test macros for —std=gnu99

  31 janvier 2016, par Henrik Gramner

  configure : Define feature test macros for —std=gnu99
  Makes the printf() family functions on MinGW use the correct C99 POSIX
  
  versions instead of the broken pre-VS2015 Microsoft ones.
  Also allows us to get rid of some _GNU_SOURCE and _ISOC99_SOURCE defines.
  

  • [DH] common/cpu.c
  • [DH] common/set.c
  • [DH] configure
  • [DH] encoder/analyse.c
  • [DH] encoder/ratecontrol.c
  • [DH] x264.c

• FFmpeg function avdevice_list_devices causes C++ Runtime error

  29 mai 2023, par ffvideoner

  I use Windows, C#, FFmpeg.AutoGen.
I want to get list of devices.

  


  public static class Helpers
{

    private static unsafe AVDeviceInfoList** _devicesList;

    public static unsafe void GetMediaSourceNames()
    {

        ffmpeg.avdevice_register_all();

        AVFormatContext* context = ffmpeg.avformat_alloc_context();

        ffmpeg.avdevice_list_devices(context, _devicesList);

    }

}


  


  Function avdevice_list_devices() causes error :

  


  


  Microsoft Visual C++ Runtime Library.
This application has requested the Runtime to terminate it in an unusual way.

  


  


  What am I doing wrong ?

  


  UPDATE

  


  Another reason for the error :

  


  Assertion s->oformat || s->iformat failed at src/libavdevice/avdevice.c:192


  


  If we look at the context in debugging, we will see that context.oformat and context.iformat are equal to zero.

  


  UPDATE 2

  


  If set some non-zero value, then the error will disappear.
Like this :

  


  AVInputFormat avformat = new AVInputFormat();

(*context).iformat = &avformat;


  


  But can't get list of devices.
Now the code looks like this. The last line throws an exception "Object reference not set to an instance of an object". But in debugging can see the value of nb_devices is ten (in fact, there are no devices at all).

  


  public static class Helpers
{

    private static unsafe AVDeviceInfoList* _devicesList;


    public static unsafe void GetMediaSourcesNames()
    {

        ffmpeg.avdevice_register_all();

        AVFormatContext* context = ffmpeg.avformat_alloc_context();


        AVInputFormat avformat = new AVInputFormat();

        (*context).iformat = &avformat;


        fixed (AVDeviceInfoList** devicesListPointer = &_devicesList)
        {
            ffmpeg.avdevice_list_devices(context, devicesListPointer);
        }


        int devicesQuantity = (*_devicesList).nb_devices;

    }

}