cellar S. Lhomme Internet-Draft Intended status: Standards Track M. Bunkus Expires: 1 March 2025 D. Rice 28 August 2024 Matroska Media Container Chapter Codecs Specifications draft-ietf-cellar-chapter-codecs-05 Abstract This document defines common Matroska Chapter Codecs, the basic Matroska Script and the DVD inspired DVD menu [DVD-Video]. 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 https://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 1 March 2025. Copyright Notice Copyright (c) 2024 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Lhomme, et al. Expires 1 March 2025 [Page 1] Internet-Draft Matroska Chapter Codecs August 2024 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Status of This Document . . . . . . . . . . . . . . . . . . . 2 3. Notation and Conventions . . . . . . . . . . . . . . . . . . 2 4. Matroska Chapter Codecs . . . . . . . . . . . . . . . . . . . 2 4.1. Segment Linking . . . . . . . . . . . . . . . . . . . . . 3 5. Matroska Chapter Codecs and Nested Chapters . . . . . . . . . 3 5.1. Matroska Script . . . . . . . . . . . . . . . . . . . . . 4 5.2. DVD Menu . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction The [Matroska] container can be expanded with Matroska Chapter Codecs. They define a set of instructions that the Matroska Player should execute when entering, leaving or during playback of a Chapter. This allows extra features not provided by the classical linear playback of files. The Matroska Chapter Codecs codec is extensible. So any new codec can be created and support added in players. 2. Status of This Document This document is a work-in-progress specification defining the Matroska file format as part of the IETF Cellar working group (https://datatracker.ietf.org/wg/cellar/charter/). It uses basic elements and concept already defined in the Matroska specifications defined by this workgroup [Matroska]. 3. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 4. Matroska Chapter Codecs Chapter codecs are a way to add more complex playback features than the usual linear playback. Lhomme, et al. Expires 1 March 2025 [Page 2] Internet-Draft Matroska Chapter Codecs August 2024 Some ChapProcess elements hold commands to execute when entering/ leaving a chapter. When chapter codecs are used the EditionFlagOrdered of the edition they belong to MUST be set. Each ChapProcessCodecID value in an edition SHOULD have a single interpreter for the whole EditionEntry, if that ChapProcessCodecID value is supported by the Matroska Player. This is necessary to be able to read/write global variables that can be used between chapters. 4.1. Segment Linking Chapter Codecs can reference another Segment and jump to that Segment. The Chapter Codecs MAY store the Segment information in their own format, possibly not using the SegmentUUID format. The ChapterTranslate element and its child elements SHOULD be used to link the internal chapter codec representation, the chapter codec number and the actual Segment it represents. For example, if a chapter codec of type "1" in SegmentA needs to link to SegmentB, it can store that information as "SegB" in its internal data. The translation ChapterTranslate in SegmentB would use the following elements: * ChapterTranslate\ChapterTranslateCodec = 1 * ChapterTranslate\ChapterTranslateID = "SegB" The Matroska Player MUST use the SegmentFamily to find all Segments that need translation between the chapter codec values and the actual segment it targets. 5. Matroska Chapter Codecs and Nested Chapters When Nested Chapters contain chapters codecs -- via the ChapProcess element -- the enter/leave commands -- ChapProcessTime element -- MUST be executed in a specific order, if the Matroska Player supports the chapter codecs included in the chapters. When starting playback, the Matroska Player MUST start at the ChapterTimeStart of the first chapter of the ordered chapter. The enter commands of that chapter MUST be executed. If that chapter Lhomme, et al. Expires 1 March 2025 [Page 3] Internet-Draft Matroska Chapter Codecs August 2024 contains Nested Chapters, the enter commands of the Nested Chapter with the same ChapterTimeStart MUST be executed. If that chapter contains Nested Chapters, the enter commands of the Nested Chapter with the same ChapterTimeStart MUST be executed, and so on until there is no Nested Chapter with the same ChapterTimeStart. When switching from a chapter to another: * the leave commands (ChapProcessTime=2) of the chapter MUST be executed, then the leave commands of its parent chapter, etc., until the common Parent Chapter or Edition element. The leave command of that Parent Chapter or Edition element MUST NOT be executed. * the enter commands (ChapProcessTime=1) of the Nested Chapter of the common Parent Chapter or Edition element, to reach the chapter we switch to, MUST be executed, then the enter commands of its Nested Chapter to reach the chapter we switch to MUST be executed, until that chapter is the chapter we switch to. The enter commands of that chapter MUST be executed as well. When the last Chapter finished playing, i.e., its ChapterTimeEnd has been reached, the Matroska Player MUST execute its leaved commands, then the leave commands of it's Parent Chapter, until the parent of the chapter is the Edition. 5.1. Matroska Script This is the case when ChapProcessCodecID = 0. This is a script language build for Matroska purposes. The inspiration comes from [ActionScript], [ECMAScript] and other similar scripting languages. The commands are stored as text commands, in UTF-8. The syntax is C like, with commands spanned on many lines, each terminating with a semicolon ";". You can also include comments at the end of lines with "//" or comment many lines using "/* */". The scripts are stored in ChapProcessData. For the moment ChapProcessPrivate is not used. The one and only command existing for the moment is GotoAndPlay( ChapterUID );. As the same suggests, it means that, when this command is encountered, the Matroska Player SHOULD jump to the Chapter specified by the UID and play it, as long as this Chapter exists. Lhomme, et al. Expires 1 March 2025 [Page 4] Internet-Draft Matroska Chapter Codecs August 2024 5.2. DVD Menu This is the case when ChapProcessCodecID = 1. Each level of a chapter corresponds to a logical level in the DVD system [DVD-Video] that is stored in the first octet of the ChapProcessPrivate. This DVD hierarchy is as follows: +====================+======+===========+==========+=============+ | ChapProcessPrivate | DVD | Hierarchy | Commands | Comment | | | Name | | Possible | | +====================+======+===========+==========+=============+ | 0x30 | SS | DVD | - | First Play, | | | | domain | | Video | | | | | | Manager, | | | | | | Video Title | +--------------------+------+-----------+----------+-------------+ | 0x2A | LU | Language | - | Contains | | | | Unit | | only PGCs | +--------------------+------+-----------+----------+-------------+ | 0x28 | TT | Title | - | Contains | | | | | | only PGCs | +--------------------+------+-----------+----------+-------------+ | 0x20 | PGC | Program | * | | | | | Group | | | | | | Chain | | | | | | (PGC) | | | +--------------------+------+-----------+----------+-------------+ | 0x18 | PG | Program 1 | - | | | | | / Program | | | | | | 2 / | | | | | | Program 3 | | | +--------------------+------+-----------+----------+-------------+ | 0x10 | PTT | Part Of | - | Equivalent | | | | Title 1 / | | to the | | | | Part Of | | chapters on | | | | Title 2 | | the sleeve. | +--------------------+------+-----------+----------+-------------+ | 0x08 | CN | Cell 1 / | - | | | | | Cell 2 / | | | | | | Cell 3 / | | | | | | Cell 4 / | | | | | | Cell 5 / | | | | | | Cell 6 | | | +--------------------+------+-----------+----------+-------------+ Table 1 Lhomme, et al. Expires 1 March 2025 [Page 5] Internet-Draft Matroska Chapter Codecs August 2024 You can also recover wether a Segment is a Video Manager (VMG), Video Title Set (VTS) or Video Title Set Menu (VTSM) from the ChapterTranslateID element found in the Segment Info. This field uses 2 octets as follows: 1. Domain Type: 0 for VMG, the domain number for VTS and VTSM 2. Domain Value: 0 for VMG and VTSM, 1 for the VTS source. For instance, the menu part from VTS_01_0.VOB would be coded [1,0] and the content part from VTS_02_3.VOB would be [2,1]. The VMG is always [0,0] The following octets of ChapProcessPrivate are as follows: +=========+======+=================================================+ | Octet 1 | DVD | Following Octets | | | Name | | +=========+======+=================================================+ | 0x30 | SS | Domain name code (1: 0x00= First play, 0xC0= | | | | VMG, 0x40= VTSM, 0x80= VTS) + VTS(M) number (2) | +---------+------+-------------------------------------------------+ | 0x2A | LU | Language code (2) + Language extension (1) | +---------+------+-------------------------------------------------+ | 0x28 | TT | global Title number (2) + corresponding TTN of | | | | the VTS (1) | +---------+------+-------------------------------------------------+ | 0x20 | PGC | PGC number (2) + Playback Type (1) + Disabled | | | | User Operations (4) | +---------+------+-------------------------------------------------+ | 0x18 | PG | Program number (2) | +---------+------+-------------------------------------------------+ | 0x10 | PTT | PTT-chapter number (1) | +---------+------+-------------------------------------------------+ | 0x08 | CN | Cell number [VOB ID(2)][Cell ID(1)][Angle | | | | Num(1)] | +---------+------+-------------------------------------------------+ Table 2 If the level specified in ChapProcessPrivate is a PGC (0x20), there is an octet called the Playback Type, specifying the kind of PGC defined: * 0x00: entry only/basic PGC * 0x82: Title+Entry Menu (only found in the Video Manager domain) * 0x83: Root Menu (only found in the VTSM domain) Lhomme, et al. Expires 1 March 2025 [Page 6] Internet-Draft Matroska Chapter Codecs August 2024 * 0x84: Subpicture Menu (only found in the VTSM domain) * 0x85: Audio Menu (only found in the VTSM domain) * 0x86: Angle Menu (only found in the VTSM domain) * 0x87: Chapter Menu (only found in the VTSM domain) The next 4 following octets correspond to the User Operation flags in the standard PGC. When a bit is set, the command SHOULD be disabled. ChapProcessData contains the pre/post/cell commands in binary format as there are stored on a DVD. There is just an octet preceding these data to specify the number of commands in the element. As follows: [# of commands(1)][command 1 (8)][command 2 (8)][command 3 (8)]. More information on the DVD commands and format on DVD from the [DVD-Info] project and [Inside-DVD-Video]. 6. Security Considerations Tag values can be either strings or binary blobs. This document inherits security considerations from the EBML [RFC8794] and Matroska [Matroska] documents. 7. IANA Considerations The Chapter Codec ID values set in ChapProcessCodecID use the Matroska Chapter Codec IDs Registry defined in [Matroska]. The initial values 0 and 1 are defined in Section 5.1 and Section 5.2 respectively. 8. References 8.1. Normative References [Matroska] Lhomme, S., Bunkus, M., and D. Rice, "Media Container Specifications", Work in Progress, Internet-Draft, draft- ietf-cellar-matroska-21, 24 April 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Lhomme, et al. Expires 1 March 2025 [Page 7] Internet-Draft Matroska Chapter Codecs August 2024 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8794] Lhomme, S., Rice, D., and M. Bunkus, "Extensible Binary Meta Language", RFC 8794, DOI 10.17487/RFC8794, July 2020, . 8.2. Informative References [ActionScript] Wikipedia, "ActionScript", . [DVD-Info] "DVD-Video Information", . [DVD-Video] DVD Forum, "DVD-Books: Part 3 DVD-Video Book", November 1995, . [ECMAScript] Ecma International, "ECMA-262 14th Edition, June 2022. ECMAScript 2023 language specification", June 2023, . [Inside-DVD-Video] Wikibooks, "Inside DVD-Video/Instruction Set Details", . Authors' Addresses Steve Lhomme Email: slhomme@matroska.org Moritz Bunkus Email: moritz@bunkus.org Dave Rice Email: dave@dericed.com Lhomme, et al. Expires 1 March 2025 [Page 8]