ANSI SCTE 243-1-2017 pdf free download – Next Generation Audio Carriage Constraints for Cable Systems: Part 1 – Common Transport Signaling.
6.1. Audio Preselection Information Audio Preselections are used for offering alternative audio mixes to the user for “User Personalization”. These mixes could include existing service types such as alternative language versions or Video Description Services (VDS), but could also include new services such as “home and away” commentary mix for a sports event or a team channel. NGA systems enable user control of certain aspects of the Audio Scene (e.g., adjusting the relative level of dialogue with respect to the ambient music and effects) by combining the Audio Program Components, present in one or more NGA streams, at the receiver side. In this way several Audio Program Components can be shared between different Audio Preselections, allowing for very efficient delivery of additional services compared to legacy systems (e.g., the multi-language functionality can be achieved using supplementary streams in legacy systems). This is a major advantage of the NGA systems, where one stream contains much more than one complete audio main.
6.2. Carriage of NGA Audio Program Components corresponding to one or more Audio Preselections can be delivered in a single elementary stream (i.e., NGA single-stream delivery) or in multiple elementary streams (i.e., NGA multi- stream delivery). In case of single-stream delivery all Audio Program Components of one Audio Program are carried in a single NGA stream, together with the signaling information of the available Audio Preselections. In case of multi-stream delivery the Audio Program Components of one Audio Program are not carried within one single NGA stream, but in two or more NGA streams. In this case the main NGA stream contains
at least all the Audio Program Components corresponding to one Audio Preselection. The auxiliary streams may contain additional Audio Program Components (e.g., additional language tracks).
The metadata formats embedded in the NGA streams shall be used only for carrying audio related data.
6.3. Audio Specific Capabilities
Typical differentiation of receiver capabilities for the audio decoding and rendering pipeline may use one or multiple of the following properties:
• Codec capabilities:
• Codec, Profile and Level
• Rendering capabilities/environment
• User preferences and settings (accessibility, language, role)
• User interaction and Personalization
7. Signaling of NGA codecs in MPEG-2 TS
7.1. Audio Preselection Information
For signaling the features of NGA systems in MPEG-2 Transport Streams the concept of Audio Preselection is used as defined in ETSI EN 300 468 subclause 6.4 [3]
7.1.1. audio_preselection_descriptor The audio_preselection_descriptor provides information about the available Audio Preselections for one Audio Program contained in one or more NGA associated elementary streams within a transport stream that are to be identified in the PSI PMT sections. The descriptor may be used by the receiver for selection of the appropriate Audio Preselection to present the Audio Program to the user, and to locate the constituent elementary streams. The audio_preselection_descriptor is defined in ETSI EN 300 468 subclause 6.4 [3] and is located in the PMT of the PSI Tables defined in ETSI EN 300 468 [3]. The audio_preselection_descriptor, when present, shall be used as specified in ETSI EN 300 468 subclause 6.4 [3] and shall be included in the program map section at most once in the ES_info descriptor loop that describes the elementary stream carrying the main NGA stream. The audio_preselection_descriptor shall be present for all NGA elementary streams that contain Audio Preselections for the Audio Program.ANSI SCTE 243-1 pdf download.