map<DeviceSpec, DeviceInfo> devices;
for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
const DeviceSpec spec{ InputSourceType::CAPTURE_CARD, card_index };
map<DeviceSpec, DeviceInfo> devices;
for (unsigned card_index = 0; card_index < num_cards; ++card_index) {
const DeviceSpec spec{ InputSourceType::CAPTURE_CARD, card_index };