Dissolves and Transitions in Dolby Vision

When moving from one shot (or scene) to another, editors and colorists often use various types of transitions and transition effects as part of the creative process. Dolby Vision metadata, which is normally created per shot, uses per frame metadata in such cases to produce smooth changes across the several frames of such transitions. A few scenarios where this would be applicable are:
 

Cross Dissolves and Fades

When a dissolve or cross fade is applied between two shots, per-frame metadata is generated to create a smooth transition in the metadata from one shot to the next. The per-frame metadata on each frame of the dissolve will include L1 (analysis) as well as L2/L3/L8 (trims), depending on the metadata pertaining to the shots on either side of the dissolve. Over the course of the transition, the metadata of the incoming shot changes to that of the outgoing shot over every frame of the transition. Every frame of the transition is treated as a separate shot or event in the resulting/exported Dolby Vision metadata (XML).





Different systems work differently in the way a dissolve or transition must be setup to ensure that the resulting Dolby Vision metadata is correct. For example, setting up a dissolve correctly (for Dolby Vision) in Resolve is different from the way it must be done in a layer-based system like Baselight. Refer to the documentation provided with your color correction or mastering system for detailed instructions on how to setup dissolves correctly.

Dynamic or Animated Trims

Whenever there is a need to create a dynamic or animated trim within a shot due to a transition in the grade or the light/color composition of the shot, the metadata is generated per frame to create a smooth transition from one state of the image to the other. The per-frame metadata on each frame of the animation or dynamic will include all the adjusted trims(L2/L3/L8), depending on the trim parameters that are being changed across the range of frames.  
 


On other systems like Baselight and Nucoda, the colorist can animate trim settings across a set of frames by assigning one set of trims (keyframe) at the beginning of a shot and a different set of trims (keyframe) at the end of the same shot, and the system will automatically generate per-frame metadata that creates a smooth transition in the mapping from the beginning of the shot to the end.

The per frame metadata will be tagged in the exported XML as <Frame> events instead of <Shot> as they normally are for per shot metadata.




 

Exceptions

If the transition is anything other than a simple cross dissolve, it may require some additional workflow steps to ensure that correct metadata is created.

Example #1

If there is a single shot that has a single, smooth camera move from a dark interior to a bright exterior, the Dolby Vision analysis would average the dark and bright side of the shot, resulting in mapping that would not faithfully reproduce either side of the shot correctly. This problem can be corrected using trims if the color grading system used supports animated or dynamic trims. In that case, the colorist can set a different set of trims at different points in the shot (like keyframes) to create the desired effect in the mapped result.

If the color correction system does not support animated trims, the steps to take are as follows,

1. Insert a cut at the mid-point of the transition in the shot.
2. Analyze the two shots thus formed to create L1 metadata for each of them, check the resulting mapping and perform the required trims (L2/L3/L8).
3. Add a dissolve across this cut and adjust the duration of the dissolve to match the transition.
4. Check the mapping across the dissolve and adjust the length of the dissolve as required.
5. The dissolve will create per frame metadata that will produce a smooth transition between the two shots.

 

Example #2

If there happens to be a special transition like a wipe or a custom transition of some sort, this again can be addressed by using trims, if the color correction system used supports animated or dynamic trims. In that case, the colorist can set a different set of trims at different points in the shot to create the desired effect in the mapped result.

If the color correction system does not support animated trims, the steps to take are as follows,

1. Render out or flatten the two shots with the custom transition and create a single shot/clip with the transition baked in.
2. Bring the rendered clip back on to the timeline and insert a cut at the midpoint of the transition.
3. Analyze the two shots thus formed to create L1 metadata for each of them, check the resulting mapping and perform the required trims (L2/L3/L8).
4. Add a dissolve across this cut and adjust the duration of the dissolve to match the transition.
5. Check the mapping across the dissolve and adjust the length of the dissolve as required. Some adjustment of the trims on both the shots maybe required to smoothen out the transition while mapping.
6. The dissolve will create per frame metadata that will produce a smooth transition between the two shots.