FFMPEG C++ select GPU

Question

 AVDictionary* options = nullptr;
 av_dict_set(&options, "hwaccel", "cuvid", 0);
 av_dict_set_int(&options, "hwaccel_device", 2, 0);

Even though I specify hwaccel device to be 2, it still runs on GPU 0. How can I fix this?

Answer 1

Ran into this issue myself. Here is the solution. When you create the hwdevice ctx you can pass in a char* specifying the gpu device.

int gpu_id = 1;
std::string d = std::to_string(gpu_id);
const char * device = d.c_str();
int err = 0;
if ((err = av_hwdevice_ctx_create(&hw_device_ctx, type,
                                      device, NULL, 0)) < 0) {
    return err;
}