LibAV FFmpeg C av_find_input_format("dshow") returning nullptr-CodePudding

I'm trying to use DirectShow devices with FFmpeg in a C program. I'm using DLLs built with vcpkg using the command .\vcpkg install ffmpeg[nvcodec]:x64-windows. The vcpkg log shows Enabled indevs: dshow

av_find_input_format is returning nullptr for me (no "dshow" devices found).

If I query the downloaded FFmpeg executable, I get a list of 14 "dshow" devices.

How can I get FFmpeg to return the list of "dshow" devices? Do I need to manually build FFmpeg using mingw-w64?

extern "C"
{
#include <libavformat/avformat.h>
#include <libavdevice/avdevice.h>
}

int main(int argc, char *argv[])
{
    AVFormatContext* inFormatContext = avformat_alloc_context();
    AVInputFormat* inFormat = av_find_input_format("dshow");

    if (!inFormat || !inFormat->priv_class  || !AV_IS_INPUT_DEVICE(inFormat->priv_class->category))
    {
        return false;
    }

    AVDeviceInfoList* deviceList;
    int deviceCount = avdevice_list_input_sources(inFormat, nullptr, nullptr, &deviceList);

    avdevice_free_list_devices(&deviceList);
    avformat_free_context(inFormatContext);

    return 0;
}

CodePudding user response：

You have to call avdevice_register_all() before av_find_input_format("dshow").

The following code returns a valid pointer:

avdevice_register_all();

AVInputFormat* inFormat = av_find_input_format("dshow");

I don't know much about the subject, but I guess avdevice_register_all() expands the list of available formats.