| RFC XXXX | The 'haptics' Top-level Media Type | May 2022 |
| Muthusamy & Ullrich | Expires 23 November 2022 | [Page] |
This memo serves to register and document the 'haptics' top-level media type, under which subtypes for representation formats for haptics may be registered. This document also serves as a registration application for a set of intended subtypes, which are representative of some existing subtypes already in use.¶
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The term 'haptics' refers to the generation of touch-related sensations in a device or interface. Haptics is widely used in consumer devices in order to provide touch-based feedback to users. The most common use of haptics is in mobile devices, where it is used to provide feedback to users interacting with the touchscreen, e.g., typing on a virtual keyboard. Haptic technologies are unlike audio and visual enabling technologies in the sense that they require some form of actuation in order to create a tactile sensation. For mobile phones and game controllers, these actuators are typically small vibrating motors. For large touchscreens in vehicles, these actuators can be specialized piezoelectric materials. Haptic capabilities are found in nearly every modern smartphone and game and virtual reality controller, making these devices an ideal target for enhanced media experiences.¶
Internet Media Types [RFC6838] are used to label content carried over Internet protocols. This document defines a new top-level type 'haptics' according to Section 4.2.7 of [RFC6838]. This top-level type indicates that the content specifies haptic data. Under this top-level type, different representation formats of haptics may be registered.¶
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119].¶
Haptic signals provide an additional layer of entertainment and sensory immersion for the user. Haptic tracks, in separate files, can be combined with audio/video files and played back in sync to provide an overall immersive media experience (audio, visual, tactile) for the user. More recently, haptic tracks embedded in standard file formats such as ISOBMFF (ISO Base Media File Format), enable playback of the haptic signals over one or more actuators, simultaneously with audio and video playback. Haptic signals are also part of media streams that use RTP, such as those for streaming games, XR, and wearables.¶
Historically, there has not been a registration of formats for haptics. However, haptics has been proposed as a first-order media type (at the same level as audio and video) in ISOBMFF. This proposal was made to the MPEG Systems File Format sub-group in April 2020. The proposal was accepted, has since progressed to International Standard, and was published in January 2022 [ISOBMFF-IS]. Haptics is officially part of the ISO/IEC 14496-12 (ISOBMFF) standard, 7th Edition. Given this development, a strong case can be made for haptics to be added to the list of top-level media types recognized by the IETF.¶
We envision the following designations for haptics in mp4 files, once the top-level type 'haptics' is registered:¶
There are multiple sub-modalities of haptics:¶
Therefore, designating 'haptics' as a top-level media type would enable the definition of data formats pertaining to these sub-modalities in a more streamlined manner. This would not be possible if 'haptics' were to be placed under other top-level types like 'audio', 'video', or 'application'.¶
The top-level media type 'audio' pertains to the human sense of hearing, the top-level media type 'video' pertains to the human sense of seeing, so it only makes sense for the (equally important) human sense of touch to be represented by another top-level media type 'haptics'. Placing 'haptics' under 'audio' or 'video' is not reflective of the kinds of files or use cases that would need haptics but have nothing whatsoever to do with audio or video.¶
Haptics is rapidly becoming a standard feature of consumer electronic devices. For example:¶
Haptic media is expected to be commonly exchanged between these devices. Since they represent the majority of CE devices, a strong case can be made for 'haptics' as a top-level media type.¶
There are multiple instances of existing haptic data formats that would live as sub-types under the proposed 'haptics' top-level media type. While these subtypes have *not* been registered with IANA or standardized (yet), the prevalence of these haptic data formats in a large number of devices around the world, pre-dating the standardization of haptic tracks in ISOBMFF, provides a compelling argument for 'haptics' to be designated as a top-level media type:¶
'ivs': The IVS haptic data format is currently a vendor-specific format that is in use:¶
'hapt': The HAPT haptic data format is currently a vendor-specific format that is in use:¶
The following Japanese game developers use the HAPT format as part of Immersion's TouchSense SDK:¶
Given the widespread use of these subtypes, it makes sense for 'haptics' to be a top-level media type.¶
The MPEG ISOBMFF proposal included an informative annex of known haptic coding formats with proposed FourCC codes for them. These codes are not registered yet, but the plan is indeed to standardize these haptic coding formats in the near future. Once standardized, they will also live as subtypes under the proposed 'haptics' top-level media type:¶
From the above arguments, it is clear that haptics does not really belong under any other media type. To reiterate, there are three main reasons why the 'haptics' media type does not fit under the 'application' top-level type:¶
Haptics are interpreted data structures that represent collections of different media rendering instructions intended to be decoded and rendered on target device hardware. Haptic data can be represented as collections of signal data and/or descriptive text in XML/JSON or similar format. Signal data is typically not executed by endpoint processors and represents minimal security risk. Descriptive text is typically parsed and represented in memory using standard XML data structures. This data is utilized to construct one or more signals that are sent to the endpoint device hardware.¶
Because of the media/rendering nature of the data path for haptic coded data the security profile of haptic data is expected to be largely consistent with the security profile of visual and audio media data.¶
As with any synthesized media data (audio, video, and haptics), there is a security risk associated with execution of commands based on the descriptive encoding either through its inherent extensibility or through the insertion of arbitrary executable data in the descriptive format itself. Indeed, media rendering systems are normally implemented with a mix of user and kernel space execution since these media must ultimately make their way to a hardware system. In theory, malicious instructions present in descriptive haptic media have the potential to execute arbitrary code in kernel space, effectively bypassing system permissions structures and/or execution sandboxes.¶
Haptics, audio, and video media have widespread use and careful attention should be paid by operating system and device driver implementors to ensure that synthesis and rendering signal paths do not provide attack surfaces for malicious payloads. Ultimately, any coded representation of haptic media is insufficient to implicitly provide sufficient security and this protection should be enforced by the operating system implementor.¶
This specification registers a new top-level type, 'haptics', in the standards tree, adds it as an alternative value of "Type Name" in the media types registration form [Media-Type-Registration], and registers several subtypes for it.¶
'haptics' as the primary media content type indicates that the content identified by it requires a certain haptics subsystem such as low-level haptics APIs, which in turn will require hardware capabilities such as one or more actuators to render the haptics media. The 'haptics' media type does not provide any specific information about the underlying data format and how the haptics information should be interpreted -- the subtypes defined within a 'haptics' tree name the specific haptic formats. Unrecognized subtypes of 'haptics' should be treated as 'application/octet-stream'. Implementations may still pass unrecognized subtypes to the haptics subsystem and associated rendering hardware.¶
New haptics formats should be registered using the online form [Media-Type-Registration]. [RFC6838] should be consulted on registration procedures. In particular, the haptics specification should preferably be freely available.¶
Note that new parameter sub-values may be defined in the future. If an implementation does not recognize a sub-value in the comma- separated list, it should ignore the sub-value and continue processing the other sub-values in the list.¶
In this section, the initial entries under the top-level 'haptics' media type are specified. They also serve as examples for future registrations.¶
Type name: haptics¶
Subtype name: ivs¶
Required parameters: None¶
Optional parameters: None¶
Encoding considerations: Text/binary¶
Interoperability considerations: The IVS format is a device-independent haptic effect coding. It is designed to enable interoperability between distinct physical endpoints. Not all devices may be able to render all effects present in an IVS file.¶
Published specification: ISO/IEC JTC 1/SC 29/WG 2 N 72 "Encoder Input Format for MPEG Haptics" being developed by ISO/IEC JTC1/SC29 WG 2 [MPEG-Haptics-Encoder].¶
Applications that use this media type: All applications that are able to create, edit, or display haptic media content.¶
Additional information:¶
Person & email address to contact for further information: Yeshwant Muthusamy(ymuthusamy@immersion.com)¶
Change controller: Immersion Corporation¶
Type name: haptics¶
Subtype name: hapt¶
Required parameters: None¶
Optional parameters: None¶
Encoding considerations: Text/binary¶
Interoperability considerations: The HAPT format is a device-dependent haptic effect coding based on the RIFF coding standard. It is designed to enable efficient coding of a device-specific haptic effect.¶
Published specification: HAPT is a logical extension of the RIFF standard [RIFF].¶
Applications that use this media type: All applications that are able to create, edit, or display haptic media content.¶
Additional information:¶
Person & email address to contact for further information: Yeshwant Muthusamy(ymuthusamy@immersion.com)¶
Change controller: Immersion Corporation¶