- AudioMapping map = AudioMapping (_film->audio_channels(), _audio_channels);
-
- if (_audio_channels != 2 || _film->audio_channels() < 3) {
- for (int i = 0; i < min (_film->audio_channels(), _audio_channels); ++i) {
- map.set (i, i, 1);
- }
- } else {
- /* Special case: stereo output, at least 3 channel input.
- Map so that Lt = L(-3dB) + Ls(-3dB) + C(-6dB) + Lfe(-10dB)
- Rt = R(-3dB) + Rs(-3dB) + C(-6dB) + Lfe(-10dB)
- */
- if (_film->audio_channels() > 0) {
- map.set (dcp::LEFT, 0, 1 / sqrt(2)); // L -> Lt
- }
- if (_film->audio_channels() > 1) {
- map.set (dcp::RIGHT, 1, 1 / sqrt(2)); // R -> Rt
- }
- if (_film->audio_channels() > 2) {
- map.set (dcp::CENTRE, 0, 1 / 2.0); // C -> Lt
- map.set (dcp::CENTRE, 1, 1 / 2.0); // C -> Rt
- }
- if (_film->audio_channels() > 3) {
- map.set (dcp::LFE, 0, 1 / sqrt(10)); // Lfe -> Lt
- map.set (dcp::LFE, 1, 1 / sqrt(10)); // Lfe -> Rt
- }
- if (_film->audio_channels() > 4) {
- map.set (dcp::LS, 0, 1 / sqrt(2)); // Ls -> Lt
- }
- if (_film->audio_channels() > 5) {
- map.set (dcp::RS, 1, 1 / sqrt(2)); // Rs -> Rt
- }
- }