mmusic P. Yue Internet-Draft Huawei Technologies Intended status: Standards Track October 21, 2011 Expires: April 23, 2012 RTSP Extension for Substream Control draft-yue-mmusic-rtsp-substream-control-extension-00 Abstract This document defines extensions to RTSP 2.0 protocol, including header "Substream", feature tag "Play.substream" , and related new status codes. These extensions enables the playback control of a media stream on substream basis. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 23, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Yue Expires April 23, 2012 [Page 1] Internet-Draft RTSP Extension for Substream Control October 2011 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 3. Definitions and Abbreviations . . . . . . . . . . . . . . 3 3.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . 4 4.1. Substream Annotation . . . . . . . . . . . . . . . . . . . 4 4.2. Capability Negotiation . . . . . . . . . . . . . . . . . . 5 4.3. Substream Playback Control . . . . . . . . . . . . . . . . 5 4.3.1. Play a Substream . . . . . . . . . . . . . . . . . . . . . 5 4.3.2. Pause a Substream . . . . . . . . . . . . . . . . . . . . 7 5. RTSP Extensions . . . . . . . . . . . . . . . . . . . . . 7 5.1. Substream Header . . . . . . . . . . . . . . . . . . . . . 7 5.2. Play.substream Feature Tag . . . . . . . . . . . . . . . . 8 5.3. Status Code Extension . . . . . . . . . . . . . . . . . . 8 5.3.1. 552 Substream Type Not Recognized . . . . . . . . . . . . 8 5.3.2. 553 Substream Control Not Allowed . . . . . . . . . . . . 8 5.3.3. 554 Substream Id Not Valid . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . 9 7.1. RTSP Feature-tag Extensions . . . . . . . . . . . . . . . 9 7.2. RTSP Status Code Extension . . . . . . . . . . . . . . . . 9 7.3. RTSP Header Extensions . . . . . . . . . . . . . . . . . . 10 7.4. Hold of Substream Type Registration . . . . . . . . . . . 10 7.4.1. Guidance of Substream Type Registration . . . . . . . . . 10 7.4.2. Registration of Substream Types . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . 11 Yue Expires April 23, 2012 [Page 2] Internet-Draft RTSP Extension for Substream Control October 2011 1. Introduction Single Session Transmission (SST) is recommended for the SVC ( Scalable Video Codec) video transport [RFC6190] and MVC (Multiview Video Codec) video transport [I-D.ietf-payload-rtp-mvc] . In SST, a single RTP session conveys all the related media data, namely all the bitstream components. A bitstream component here is part of a media stram that has a common property which could be: o Layer: in SVC media stream; In this case, a bitstream component is media data of a specific layer. o View: in MVC media stream; In this case, a bitstream component is media data of a specific view. In such a SST session,one or several bitstream components together may be decodable by themselves and therefore make sense to the receiver. These bitstream component(s) combinations are here called Substream. In SVC and MVC RTP sessions, such a Substream is identified by an Operation Point. There are cases that a client wants to retrieve a specific substream in such a SST session. However, in the current RTSP 2.0 protocol, the control of the media is on media stream basis, e.g. as an RTP session when RTP is used. This prevents a client to receive only certain substream(s) from the media. This memo extends the RTSP 2.0[I-D.ietf-mmusic-rfc2326bis] to establish a substream playback control framework, which enables a client to play a part of a media stream. This memo also defines the substream usage for SVC and MVC. 2. Terminology 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 [RFC2119]. 3. Definitions and Abbreviations 3.1. Definitions The following terms are used in this document and have specific meaning within the context of this document. Yue Expires April 23, 2012 [Page 3] Internet-Draft RTSP Extension for Substream Control October 2011 o Substream: a part of a media stream containing one or more bitstream components, which can be independently decoded. Typically a Substream is identified by one operation point. o Substream type: the compound mode of the bitstream components in a substream, e.g. SVC, MVC, etc 3.2. Abbreviations SVC: Scalable Video Coding MVC: Multiview Video Coding SST: Single Session Transmission 4. Protocol Overview The whole framework includes substream annotation, capability negotiation and substream playback control. This section provides an overview of substream control. 4.1. Substream Annotation Substream annotation is used to announce identifiers for all substreams available in a media stream. which can be retrieved selectively. It is done through a presentation description, typically using an SDP description. Substream annotation based on SDP is described in this section. Substream annotation based on other formats is out of scope of this document. In SVC, a substream is described as an operation point, which consists of the bitstream components required to be able to decode a particular dependency_id, quality_id, and temporal_id combination. SVC operation points are described through the sprop-operation-point- info attribute in SDP as defined in [RFC6190]. According to [RFC6190], the value of sprop-operation-point-info consists of a comma-separated list of operation-point-description vectors. Each operation-point-description vector represents a substream. Each operation-point-description vector has ten elements,where the first element layer-ID is the identifier of the operation point. This layer-ID can be taken as the identifier for the SVC substream. Since the layer-ID is optional, it may not be included. In this case, a [dependency-ID, temporal_ID, quality-ID] combination is taken as the identifier instead. Annocation of MVC substreams is specified in [I-D.ietf-payload-rtp-mvc]. editor notes: pending on the complement of Yue Expires April 23, 2012 [Page 4] Internet-Draft RTSP Extension for Substream Control October 2011 [I-D.ietf-payload-rtp-mvc]. 4.2. Capability Negotiation Capability negotiation can be used to negotiate support of substream control between RTSP client and server. It makes use of the RTSP feature tag mechanism defined in RTSP 2.0[I-D.ietf-mmusic-rfc2326bis]. A new feature tag (play.substream) is defined in Section 5.2. Whenever it has received a media presentation with substream annotation, a substream control capable RTSP client SHALL include play.substream in the SUPPORTED header of the RTSP SETUP request. This indicates that the client is able to control the playback of the media on substream basis. A 2xx response implies that the server is capable of substream control. A server MAY refuse the request with a 551 "Option not supported" response, with an UNSUPPORT header including play.substream. The receiving client may try to setup a session without this feature later. This means that the client will not perform substream control and play the media as a whole. In the SVC case, the client will play all the layers in the session, whereas in the MVC case it will play all the views in the session. 4.3. Substream Playback Control In case the session is setup correctly, the client may control the play back on substream basis, including: o start to play a substream o pause a substream. Note that this means it will pause the play back of the whole session. 4.3.1. Play a Substream After successful set up of an RTSP session, the client may perform substream playback control. The playback of a substream is similar with the normal playback of a session, except that the PLAY request shall contain a "SubstreamCtrl" header with substream type and the substream id corresponding to the substream that the client intends to play. Here the substream id idetifies a specific operation point. The actual definition of the substream id is defined by each substream type. When more than one media stream are controlled, the header shall further contain Request-URIs for each of the the substreams. Yue Expires April 23, 2012 [Page 5] Internet-Draft RTSP Extension for Substream Control October 2011 Following is the specification of substream types for SVC and MVC media stream. Specification for other substream type is out of scope of current document and should be registered in IANA, as described in Section 7.4. When the media stream is an SVC stream as defined in [RFC6190], the substream type shall be "SVC"; The substream id could be either a layer-id or a [dependency-ID, temporal_ID, quality-ID] combination, which comes from an operation-point-description vector. When the media stream is an MVC stream as defined in [I-D.ietf-payload-rtp-mvc], the substream type shall be "MVC". For MVC, substream id is... editor's note: substream id for MVC is pending on the complement of draft-ietf-payload-rtp-mvc-00. A client should not perform substream play if the server has not indicated support of substream control in an ealier message exchange. Upon receiving a PLAY request with a "SubstreamCtrl" header, the server SHALL identify the substream(s) according to the id(s) and Request-URI(s) in the request, and then provides the indicated substream(s) after sending a 200 OK response. If the server doesn't support substream control, it should respond a 551 "Option not supported" response as defined in RTSP 2.0[I-D.ietf-mmusic-rfc2326bis]. If the server supports substream control but the substream type indicated in the "SubstreamCtrl" header is not recognized, it shall response wth a 552 "Substream Type Not Recognizable" response, see Section 5.3.1. If the server supports substream control but the substream type indicated in the "SubstreamCtrl" header is not recognized, it shall response wth 552 "Substream Type Not Recognizable", see Section 5.3.1. If a requested media is not allowed to be played on substream basis as requested, the server SHALL respond with a 553 "Substream Control Not Allowed" response, see Section 5.3.2. If the requested substream id is not valid, the server shall response with 554 "Substream id not valid", see Section 5.3.3. Yue Expires April 23, 2012 [Page 6] Internet-Draft RTSP Extension for Substream Control October 2011 4.3.2. Pause a Substream The pause operation of a substream is identical to the pause operation of a normal session. It is not necessary for the client to include a "SubstreamCtrl" header in the pause request message. However, if the request includes a "SubstreamCtrl" header, it shall list all the substreams are currently played. If aggregated control is used, it is not allowed to pause only a part of a session. It is also not allowed to pause only a specific substream from a media stream. 5. RTSP Extensions This section documentsthe extension to the RTSP 2.0 specification. Specifically Section 5.1 specifies the SubstreamCtrl header, Section 5.2 specifies the substream control feature tag, Section 5.3 specifies the status codes extentions for the substream control feature. 5.1. Substream Header SustreamCtrl header is used to indicate the substream(s) of a media stream that the client intends to play. It contains one or more [stream uri, substream type, substream id] triple. The syntax is: substream = "substream:" substream-id * (";" sustream-id) substream-id = stream-uri "," substream-type "," substream_id stream-uri = RTSP-URI substream-type = "SVC" / "MVC" / token When the substream-type is SVC, the syntax of substream_id is: substream_id = layer-id /dependency-id "," temporal-id "," quality-id layer-id = "layer_id=" layer_id_value layer_id_value = 1*4DIGIT; 0~2047 dependency-id = "dependency_id=" dependency_id_value dependency_id_value = DIGIT ; 0~7 temporal-id = "temporal_id=" temporal_id_value temporal_id_value = DIGIT ; 0~7 quality-id = "quality_id=" quality_id_value quality_id_value = 1*2DIGIT; 0~15 DIGIT = %x30-39 ; any US-ASCII digit "0".."9" Yue Expires April 23, 2012 [Page 7] Internet-Draft RTSP Extension for Substream Control October 2011 An example of Substream header is: substream: rtsp://example.com/svc.mp4, SVC, lay-id=1 For the MVC case, the syntax of substream_id is: editor's notes: pending on the complement of mvc-operation-point-id HCOLON = *( SP / HT ) ":" SWS SEMI = SWS ";" SVS ; semicolon SWS = [LWS] ; Separating White Space DIGIT = %x30-39 ; any US-ASCII digit "0".."9" COMMA = SWS "," SWS ; comma EQUAL = SWS "=" SWS ; equal SubstreamCtrl header can be used in PLAY and PAUSE request. Proxies shall not modify this header and pass through to the server. 5.2. Play.substream Feature Tag The following feature-tag is defined in this specification and hereby registered. The change control belongs to the IETF. play.substream: Support of substream control operations for media playback. Applies only for servers. 5.3. Status Code Extension This clause defines the status code extended for the substream control feature. They are: o 552 Substream Type Not Recognized o 553 Substream Control Not Allowed o 554 Substream Id Not Valid 5.3.1. 552 Substream Type Not Recognized The server can not understand the substream type. 5.3.2. 553 Substream Control Not Allowed The substream specified in the request is not allowed for the media identified by the Request-URI. The response shall include a xxxx header to indicate the substream information. Editor notes: whether there is a need to return substream information is pending for discussion. Yue Expires April 23, 2012 [Page 8] Internet-Draft RTSP Extension for Substream Control October 2011 5.3.3. 554 Substream Id Not Valid The substream id specified in the request is not valid for the media identified by the Request-URI. The response shall include a xxxx header to indicate the substream information. Editor notes: whether there is a need to return substream information is pending for discussion. 6. Security Considerations Editor notes: pending for more discussion. 7. IANA Considerations Registration is requested for the newly defined RTSP header extensions, RTSP status code extensions and RTSP feature tag extensions, according to the instructions in section 22 of the base specification [I-D.ietf-mmusic-rfc2326bis]. This section also sets up a registry for substream type that should be maintained by IANA. 7.1. RTSP Feature-tag Extensions The following feature-tag is defined in this specification and hereby registered according to the section 22.1.2 of the base specification [I-D.ietf-mmusic-rfc2326bis]. The change control belongs to the IETF. o Feature tag: substream.control o Description:Support of control the media playback on substream basis.Applies for both clients, servers and proxies. o Contact person: Peiyu YUE o Change control: IETF o Reference specification: present document. 7.2. RTSP Status Code Extension The following RTSP status codes are in defined this specification and hereby registered according to section 22.3.2 of the base specification [I-D.ietf-mmusic-rfc2326bis]. The change control belongs to the IETF. Yue Expires April 23, 2012 [Page 9] Internet-Draft RTSP Extension for Substream Control October 2011 o Request number: 552 o Description: as described in Section 5.3.1 o Request number: 553 o Description: as described in Section 5.3.2 o Request number: 554 o Description: as described in Section 5.3.3 7.3. RTSP Header Extensions The following RTSP header is defined in this specification and hereby registered according to section 22.4.2 of the base specification [I-D.ietf-mmusic-rfc2326bis]. The change control belongs to the IETF. o The name of the header: SubstreamCtrl o Description: o The syntax of the header: as described in Section 5.1. o Where to use: as described in Section 5.1. o Handle by proxy: as described in Section 5.1. 7.4. Hold of Substream Type Registration 7.4.1. Guidance of Substream Type Registration IANA should take the responsibility for the registration of the substream type. A new substream type MUST be registered through an IETF Standards Action. A specification for a new substream type MUST consist of the following items: o A substream type; o A description of the substream type; o A substream id definition 7.4.2. Registration of Substream Types This specification registers two substream types: SVC and MVC: o Substream Type: SVC o Description: Scalable Video Codec stream as defined in [RFC6190]. o Substream id definition: could be layer-id or [dependency-ID, temporal_ID, quality-ID] combination, as described in Section 4.1. o Substream Type: MVC o Description: Multiview Video Codec stream as defined in [I-D.ietf-payload-rtp-mvc]. Yue Expires April 23, 2012 [Page 10] Internet-Draft RTSP Extension for Substream Control October 2011 o Substream id definition: as described in Section 4.1. 8. References 8.1. Normative References [I-D.ietf-mmusic-rfc2326bis] Schulzrinne, H., Rao, A., Lanphier, R., Westerlund, M., and M. Stiemerling, "Real Time Streaming Protocol 2.0 (RTSP)", draft-ietf-mmusic-rfc2326bis-27 (work in progress), March 2011. [I-D.ietf-payload-rtp-mvc] Wang, Y. and T. Schierl, "RTP Payload Format for MVC Video", draft-ietf-payload-rtp-mvc-00 (work in progress), March 2011. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6190] Wenger, S., Wang, Y., Schierl, T., and A. Eleftheriadis, "RTP Payload Format for Scalable Video Coding", RFC 6190, May 2011. 8.2. Informative References [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. Author's Address Peiyu Yue Huawei Technologies Huawei Base 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Phone: +86-25-56620258 Email: yuepeiyu@huawei.com Yue Expires April 23, 2012 [Page 11]