SetMixerChannelGain
input->SetMixerChannelGain(0, input->GetMixerChannelGain(0) * f);
input->SetMixerChannelGain(1, input->GetMixerChannelGain(1) * f);
input->SetMixerChannelGain(chan, DB_TO_GAIN(static_cast<const float *>(value)[chan]));
input->SetMixerChannelGain(0, m * fl);
input->SetMixerChannelGain(1, m * fr);
void SetMixerChannelGain(int mixerChannel,