private void ShitboxAlignVideoAudio_MouseMove(object sender, MouseEventArgs e)
        {
            if (!isDown)
            {
                return;
            }
            if (vclip == null)
            {
                return;
            }
            var dX  = e.X - mouseX1;
            var dTs = dimdim.convert_AbsX2Seconds(dX);

            vclip.CustomAudioOffset = originalOffset + dTs;
            if (OffsetUpdated != null)
            {
                OffsetUpdated(vclip.CustomAudioOffset);
            }
        }