Method speakersSumFrom

src/core/AudioBus.cpp:367–420

}

void AudioBus::speakersSumFrom(const AudioBus & sourceBus)
{
    // FIXME: Implement down mixing 5.1 && 7.1 to stereo.
    // https://bugs.webkit.org/show_bug.cgi?id=79192

    const int numberOfSourceChannels = sourceBus.numberOfChannels();
    const int numberOfDestinationChannels = numberOfChannels();

    if (numberOfDestinationChannels == Channels::Stereo && numberOfSourceChannels == Channels::Mono)
    {
        // Handle mono -> stereo case (summing mono channel into both left and right).
        const AudioChannel * sourceChannel = sourceBus.channel(0);
        channelByType(Channel::Left)->sumFrom(sourceChannel);
        channelByType(Channel::Right)->sumFrom(sourceChannel);
    }
    else if (numberOfDestinationChannels == Channels::Mono && numberOfSourceChannels == Channels::Stereo)
    {
        // Handle stereo -> mono case. output += 0.5 * (input.L + input.R).
        AudioBus & sourceBusSafe = const_cast<AudioBus &>(sourceBus);

        const float * sourceL = sourceBusSafe.channelByType(Channel::Left)->data();
        const float * sourceR = sourceBusSafe.channelByType(Channel::Right)->data();

        float * destination = channelByType(Channel::Left)->mutableData();
        float scale = 0.5;
        vsma(sourceL, 1, &scale, destination, 1, length());
        vsma(sourceR, 1, &scale, destination, 1, length());
    }
    else if (numberOfDestinationChannels == Channels::Surround_5_1 && numberOfSourceChannels == Channels::Mono)
    {
        // Handle mono -> 5.1 case, sum mono channel into center.
        channelByType(Channel::Center)->sumFrom(sourceBus.channel(0));
    }
    else if (numberOfDestinationChannels == Channels::Mono && numberOfSourceChannels == Channels::Surround_5_1)
    {
        // Handle 5.1 -> mono case.
        speakersSumFrom5_1_ToMono(sourceBus);
    }
    else if (numberOfDestinationChannels == Channels::Surround_7_1 && numberOfSourceChannels == Channels::Mono)
    {
        // Handle mono -> 7.1 case, sum mono channel into center.
        channelByType(Channel::Center)->sumFrom(sourceBus.channel(0));
    }
    else if (numberOfDestinationChannels == Channels::Mono && numberOfSourceChannels == Channels::Surround_7_1)
    {
        // Handle 7.1 -> mono case.
        speakersSumFrom7_1_ToMono(sourceBus);
    }
    else
    {
        // Fallback for unknown combinations.
        discreteSumFrom(sourceBus);
    }
}

void AudioBus::speakersSumFrom5_1_ToMono(const AudioBus & sourceBus)
{