
Add ctts box implementation to handle muxing B-frame videos. Add method convertPresentationTimestampsToCompositionOffset to provide sample offsets. Return empty ctts box in case of video does not contain B-frame. Add ctts box to MoovStructure to handle muxing the video containing B-frames. PiperOrigin-RevId: 628346257
Test data module
Provides sample data for media unit and instrumentation tests.