AMWA BCP-006-04: NMOS Support for MPEG Transport Streams [Work In Progress]
- Use of Normative Language
- Definitions
- MPEG TS IS-04 Sources, Flows, and Senders
- MPEG TS IS-04 Receivers
- MPEG TS IS-05 Senders and Receivers
- Controllers
MPEG Transport Stream is a standard digital container format specified in ISO/IEC 13818-1, widely used for transmission and storage of audio, video, and data.
SMPTE ST 2022-2 defines the Unidirectional Transport of Constant Bit Rate MPEG-2 Transport Streams using RTP on IP Networks.
The Video Services Forum developed Technical Recommendations TR-01 and TR-07, which cover the encapsulation of JPEG 2000 and JPEG XS video respectively within MPEG TS over IP networks, compliant with ST 2022-2.
AMWA IS-04 and IS-05 have support for RTP transport and can signal the media type video/MP2T as defined in RFC 3555.
This BCP allows for the use of all transport types defined by IS-05 that can carry media type video/MP2T.
Use of Normative Language
The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.
Definitions
The NMOS terms ‘Controller’, ‘Node’, ‘Source’, ‘Flow’, ‘Sender’, ‘Receiver’ are used as defined in the NMOS Glossary.
MPEG TS IS-04 Sources, Flows, and Senders
Nodes capable of transmitting MPEG TS streams, including those carrying JPEG 2000 or JPEG XS content as per VSF TR-01 and TR-07, MUST have Source, Flow, and Sender resources in the IS-04 Node API.
Nodes MUST support IS-04 v1.3 to implement all aspects of this specification.
Partial implementation can be achieved using IS-04 v1.2 and earlier.
Sources
The Source resource MUST indicate urn:x-nmos:format:mux for the format.
Source resources can be associated with many Flows at the same time.
The Source is therefore unaffected by the use of MPEG TS or the encapsulated content.
Flows
The Flow resource MUST indicate video/MP2T in the media_type attribute, and urn:x-nmos:format:mux for the format.
For Nodes implementing IS-04 v1.3 or higher, the following additional attributes defined in the Flow Attributes register of the NMOS Parameter Registers are used for MPEG TS:
- Bit Rate This attribute MUST be present in the flow resource definition.
An example Flow resource is provided in the Examples.
Senders
For Nodes transmitting MPEG TS over RTP transport as defined by ST 2022-2, the Sender transport attribute MUST be urn:x-nmos:transport:rtp or one of its sub-classifications.
The SDP file published at the manifest_href end-point MUST comply with the IS-05 usage guidelines for the specific transport and RFC 4566
An example Sender resource is provided in the Examples.
MPEG TS IS-04 Receivers
Nodes capable of receiving MPEG TS streams, including those carrying JPEG 2000 or JPEG XS content as per VSF TR-01 and TR-07, MUST have a Receiver resource in the IS-04 Node API, which lists video/MP2T in the media_types array within the caps object.
If the Receiver supports RTP transport, it MUST have the transport attribute set to urn:x-nmos:transport:rtp or one of its sub-classifications..
If the Receiver has limitations on or preferences regarding the MPEG TS streams that it supports, the Receiver resource MUST indicate constraints in accordance with the BCP-004-01 Receiver Capabilities specification.
The Receiver SHOULD express its constraints as precisely as possible, to allow a Controller to determine with a high level of confidence the Receiver’s compatibility with the available streams.
It is not always practical for the constraints to indicate every type of stream that a Receiver can or cannot consume successfully; however, they SHOULD describe as many of its commonly used operating points as practical and any preferences among them.
The constraint_sets parameter within the caps object can be used to describe combinations of parameters which the Receiver can support, using the parameter constraints defined in the Capabilities register of the NMOS Parameter Registers.
The following parameter constraints can be used to express limitations on MPEG TS streams:
An example Receiver resource is provided in the Examples.
MPEG TS IS-05 Senders and Receivers
Connection Management using IS-05 proceeds in exactly the same manner as for any other stream format carried over the RTP tranport type.
Any SDP file published at the /transportfile end-point MUST comply with the IS-05 usage guidelines for the RTP transport and RFC 4566.
An example SDP file is provided in the Examples.
Controllers
Controllers MUST use IS-04 to discover MPEG TS Senders and Receivers and IS-05 to manage connections between them.
Controllers MUST support the BCP-004-01 Receiver Capabilities mechanism and all the parameter constraints listed in this specification in order to evaluate the stream compatibility between MPEG TS Senders and Receivers.
Controllers MUST be capable of handling RTP transports as per the NMOS specifications indicated in the Sender and Receiver resources.