Lip-sync animation is implemented as a special type of action clip (the Speech Action clip) in the mixer, but in every other respect it acts like a normal action clip and can be treated as one as far as mixing goes.
You can add action clips of head movements, eye blinking, etc. to the animation mixer on different tracks, then have that animation running at the same time as the lip-sync animation that's in the Speech Action clip.
If you want to blend lip-sync animation with mocap data, it's best to do the lip sync first. Then when you add the mocap, its data is driven by the retargeting operators so that it's still "live". This allows you to adjust the mocap using the options in the Adjust panel (see ) while editing the lip sync at the same time.The different types of data will each affect the animation controls as they should. You can then control the amount that each type of animation contributes to the result.
The mocap and the lip-sync animation each contribute equally to the result, but what you usually want is to use the mouth animation from one source and the jaw animation from the other. To do this, you can have either source controlling the animation as you like:
To have the lip-sync animation drive the animation, you can open the Adjust panel and reduce the weight of the Upper Lip, Lower Lip, and Jaw channels in the Global Controls group. Setting these values to zero means that the lip-sync operator (SpeechBlend) is the only thing affecting those animation controls. Of course, you can set these values to any number and even animate them.
To have the mocap drive the animation, you can reduce the weight of the Lip, Jaw, and Tongue channels in the Speech Blend property editor (see ). As with the Adjust controls, you can set these values to any number you like and animate them.
You may also choose to use only parts of the lip sync with the mocap. For instance, you can disable the lips and jaw channels of the lip sync so that you are using only the tongue lip-sync animation with the mocap.
Lip-sync animation works in conjunction with keyframe animation. You can set keys on the animation controls using animation layers (see ), store that animation as a clip in the mixer (see ), or key the animation controls directly.
To add keyframes on top of the lip-sync animation, add an animation layer and set keyframes in that layer. These are considered to be an offset from the base layer of animation (the lip-sync animation).
If you key the lip, jaw, or tongue animation controls directly, the speech operator (which drives the Speech action clip) will override this animation because clips in the mixer always override other animation at the same frames. However, you can set the mixer options to allow this clip to blend with the fcurves - see for more information.