Dolby Car Experience

Dolby Car Experience products are designed to deliver a Dolby Atmos experience in a wide variety of cars regardless of the audio sound system or number of available speakers inside the car cabin.

Dolby Car Experience in the vehicle

The vehicle is equipped with an IVI system that includes a Dolby Car Experience Implementation. The installation of speakers and amplifiers inside the car cabin has been completed. The car cabin has been tuned, which means that this particular internal car speaker system has been optimized to render and deliver a Dolby Atmos experience. Dolby Atmos qualified streaming services serve as an input to the vehicle. The audio is processed through the chain of components and the output is delivered to the internal car speaker system.

Integration of Dolby Car Experience in a car audio system

A Dolby Car Experience Implementation is integrated in the head unit or in the amplifier unit of a car. This figure is a conceptual diagram that shows the relationship of the Dolby Car Experience Implementation to the other components of an IVI system. It includes the potential input and output interfaces that a head unit in the car may provide.

The Implementation receives a bitstream or a PCM signal as input and then outputs PCM that is carried by the media bus to the amplifier unit, which performs the mapping to the required speaker layout and the cabin tuning. The mixing of system sounds and blending of other sources (for example, the navigation system) is performed in a separate mixer component.

Adaptive bit-rate changing

The Dolby Car Experience Implementation and the Dolby Car Experience system integration support adaptive bit-rate streaming where the bit rate of the encoded bitstream changes at the segment boundaries. In the case of Dolby AC-4, a segment always starts with an independently decodable frame (I-frame) which allows for smooth transitions without introducing artifacts or distortion during playback. For Dolby Digital Plus, bit rate changes occur at Dolby Digital Plus frame boundaries and support switching between multiple bit rates depending on available bandwidth resources. While these transitions between bit rates should be gapless and well aligned in Dolby Digital Plus, they might be audible to listeners.

Products that support adaptive streaming must be able to switch between different bit rates based on available bandwidth. The Dolby Car Experience Implementation enables smooth transitions between Dolby Atmos and Dolby Digital Plus 5.1 content to accommodate lower bit rates when processing Dolby Digital Plus bitstreams. For Dolby AC-4 content, switching between Dolby Atmos and 5.1 formats is not necessary since Dolby AC-4 inherently supports Dolby Atmos content at lower bit rates.

Important: Switching between bit rates is only recommended when the transition is seamless. On Implementation level, switches between 5.1 and Atmos are considered seamless. However, these switches may trigger processing changes downstream of the Implementation during cabin tuning that must also be considered in order to determine if the switch is a valid transition for a particular use case.

System resources

The product must provide adequate processing capacity and memory resources to efficiently handle all implemented features.

Data-rate requirements with respect to streaming

The Dolby Car Experience Implementation and the Dolby Car Experience system integration support adaptive bit-rate streaming, where the bit rate of the encoded bitstream changes at the segment boundaries. The maximum supported bit rate for streaming applications is 1,024 kbps for Dolby Digital Plus and 1,500 kbps for Dolby AC-4. For adaptive streaming applications, the recommended bit-rate ladder is:

Tier	Format	Bit rate in kbps
Dolby Atmos (high bandwidth)	Dolby Digital Plus with Dolby Atmos content 768 kbps	768
Dolby Atmos (low bandwidth)	Dolby Digital Plus with Dolby Atmos content	448
5.1 channel-based	Dolby Digital Plus without Dolby Atmos content	256