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• 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;

    }

}


  


• ffmpeg compilation error in windows 10 x64 for Visual Studio 2015 CE

  12 avril 2016, par Anqush

  So i was trying to use FFmpegInterop for win10 UWP application. And followed the specification given on https://trac.ffmpeg.org/wiki/CompilationGuide/WinRT.

  here is some environment information :

  VS2015 Community Edition with 10.0.10240.0 SDK

  OS : Windows 10 Enterprise x64

  PATH were set to:Program Files (x86)/Microsoft Visual Studio 14.0/VC/BIN/x64_ARM

  So when i did this in msys2_shell.bat

  ../../../configure \
  
  --toolchain=msvc \
  
  --disable-programs \
  
  --disable-d3d11va \
  
  --disable-dxva2 \
  
  --arch=x86_64 \
  
  --enable-shared \
  
  --enable-cross-compile \
  
  --target-os=win32 \
  
  --extra-cflags="-MD -DWINAPI_FAMILY=WINAPI_FAMILY_APP -D_WIN32_WINNT=0x0A00" \
  
  --extra-ldflags="-APPCONTAINER WindowsApp.lib" \
  
  --prefix=../../../Build/Windows10/x64

  I got a warning regarding some pkg file that can’t be found and may cause library detection issues.

  For then i ignored it. After that i entered

  make

  this started a series of processing in which there is a lot of possibly harmful warnings. Like :-

  c:\ffmpeginterop\ffmpeg\libavcodec\get_bits.h(307): warning C4101: 're_cache': unreferenced local variable
  
  CC libavformat/srtdec.o
  
  srtdec.c
  
  c:\ffmpeginterop\ffmpeg\libavutil\libm.h(438): warning C4211: nonstandard extension used: redefined extern to static
  
  c:\ffmpeginterop\ffmpeg\libavformat\subtitles.h(189): warning C4267: 'initializing': conversion from 'size_t' to 'int', possible loss of data

  So my question is that. Is this dangerous to proceed with. Can you help me for i should proceed with my project without any worry or not ? And i would be gratefull if anyone can guide me to watc out for specific errors that this could generate.

  I know this is a lot to ask. But i would be gratefull.
  Thanks

  Edit : Now i cant run the samples included in the ffmpeginterop package. The sample project wont debug. saying these are out of date.

• C# Windows Forms Using FFMPEG to change video format got no response

  21 mai 2023, par TSLee

  I am trying to make an exe program to change a video format by using FFMPEG instead of doing it in the terminal. The formatted video will be saved in the download folder. I have tried my code below and got no output response. I wonder if I used process() and StartInfo correctly, as examples I found and the documentation just confused me. I have double-checked the ffmpeg.exe is in the bin folder and the StartInfo() is just for getting information, which is under Process(). This is why Process() can access the information and use Start() to start the process. Please help and correct my understanding.
Below is part of my code :

  


  private void convertButton_Click(object sender, EventArgs e)
    {
        String input = filepathTextBox.Text;
        String outputResolution = resolutionLabel.Text;
        String output;
        String outputFileType;
        int inputLength = input.Length;
        int l = 0;
        for (int i = (inputLength - 1); inputLength > -1; i--)
        {
            if (input[i] == '.')
            {
                l = i;
                break;
            }
        }
        output = input.Substring(0, l - 1);
        outputFileType = input.Substring(l + 1, inputLength - 1);
        Process process = new Process();
        process.StartInfo.UseShellExecute = true;
        process.StartInfo.FileName = "ffmpeg.exe";
        process.StartInfo.WorkingDirectory = @"C:\Users\User\Downloads\ffmpeg-2023-05-15-git-2953ebe7b6-full_build\bin";
        process.StartInfo.Arguments = "ffmpeg -i" + @"C:\Users\User\Downloads\file_example_MP4_640_3MG.mp4" + "-s 320x240 -r 25 -b:v 500000 -pix_fmt yuv420p -c:v libx264     -vprofile baseline -level  2.1 -x264opts  stitchable=1:level=3.0:keyint=15:ref=1:merange=16:mvrange=32 -acodec pcm_s16le -ar 16000 -ac 1" + @"C:\Users\User\Downloads\440.mp4";
        process.Start();
    }


  


  Output :
"myprogram.exe(CoreCLR : clrhost) : Loaded 'C :\Program Files\dotnet\shared\Microsoft.NETCore.App\6.0.15\System.Diagnostics.Process.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled."
The thread 0x79e0 has exited with code 0 (0x0).