Suppress the recording sound in the recorded video

        // After the initial mute, we raise the volume linearly

        // over kAutoRampDurationUs.

        kAutoRampDurationUs = 300000,

        kAutoRampDurationUs = 700000,

        // This is the initial mute duration to suppress

        // the video recording signal tone

        kAutoRampStartUs = 700000,

        kAutoRampStartUs = 1000000,

      };

    AudioRecord *mRecord;