The 'haptics' Top-level Media Type
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Internet
MEDIAMAN
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.
Introduction
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 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 . This top-level type indicates
that the content specifies haptic data. Under this top-level type,
different representation formats of haptics may be registered.
Terminology
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 .
Background and Justification
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.
MPEG ISOBMFF
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 . 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:
- 'haptics/mp4' - mp4 files with just haptic tracks and no audio or video in them (e.g.,
streaming games, haptics files for haptic vests, belts, gloves, etc.)
- 'video/mp4' - mp4 files with video, audio, and haptics (to ensure
consistency with existing mp4 files with video content)
- 'audio/mp4' - mp4 files with audio and haptics (to ensure
consistency with existing mp4 files with audio content without any video)
Haptic Sub-modalities
There are multiple sub-modalities of haptics:
- Vibrotactile (touch, vibration)
- Kinesthetic (force feedback)
- Surface (surface friction)
- Spatial, non-contact (ultrasound)
- Thermal (temperature)
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'.
Another Human Sense
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.
Commercial Uptake
Haptics is rapidly becoming a standard feature of consumer electronic
devices. For example:
- iPhone (206+ million units sold in 2020): native support for haptic
encoded data
- Android (1.38+ billion units sold in 2020): API support of haptic
buffers
- W3C (HTML vibration API ): Optionally supported in mobile web
browsers. W3C has also defined vibration extensions for gamepads
- Game consoles (39+ million units sold in 2019): MS Xbox, Sony
PlayStation, Nintendo Switch, etc.
- XR devices (9+ million units sold in 2019): OpenXR haptic API
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.
Haptic Data Formats in Use
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:
- 'ahap': The AHAP haptic data format is currently the standard
encoding on all iOS devices + iOS connected game peripherals. The format has
seen usage and adoption beyond Apple devices as well, with decoders available
for Android and other XR systems.
- 'ogg': Google has introduced a proprietary extension to the OGG format
in the latest version of Android 11. This encoding enables haptic media to be
stored in OGG files.
- 'ivs': The IVS haptic data format is currently a
vendor-specific format that is in use:
- In mobile phones from LG Electronics (specifically, the models V30,
V40, and the newest V50) that are sold worldwide
- In gaming phones from ASUS (specifically, models ROG, ROG Phone II,
ROG Phone 3) that are sold worldwide
- 'hapt': The HAPT haptic data format is currently a vendor-specific format that is in use:
- In mobile haptic advertising (for W3C devices)
- The following Japanese game developers use the HAPT format as part
of Immersion's TouchSense SDK:
- KLAB: https://www.klab.com/en/
- Craft&Meister: http://www.crafts-meister.co.jp/pc/company_en.html
- Tencent is using the TouchSense SDK for their popular social media
application QQ and live streaming application NOW:
Immersion-Announces-Tencent-Licenses-TouchSense-Technology-Deliver
Given the widespread use of these subtypes, it makes sense for 'haptics'
to be a top-level media type.
Haptic Subtypes (envisioned standards)
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:
- 'hmpg': the selected coding format from the MPEG Call for Proposals on the Coded Representation of Haptics
- 'hiee': IEEE P1918.1.1 vibrotactile coding standard being developed under the IEEE Tactile
Internet initiative as part of the 5G URLL profile
- 'henm': enumerated effects haptic coding format (based on MIDI)
- 'havc': audio-to-vibe haptic coding format (automatic audio
to vibration conversion algorithms)
'application' top-level type not suitable
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 connects to a sensory system, touch/motion, directly, and is
more specific than the abstract 'application' type, and
- 'application' has historically been used for applications, i.e., code,
which means it is viewed and treated with great care for security.
'haptics' is not code, just as 'audio' and 'video' are not code
either.
- haptics is a property of a media stream, it is not an application under
any normal definition. As such, it should be its own type.
Security Considerations
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.
IANA Considerations
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 ,
and registers several subtypes for it.
Definition and Encoding
'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.
Registration Procedure
New haptics formats should be registered using the online form
. 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.
Subtype Registrations
In this section, the initial entries under the top-level 'haptics'
media type are specified. They also serve as examples for future
registrations.
IVS Haptics Type
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 .
Applications that use this media type: All applications that are able to create, edit, or display haptic media content.
Additional information:
- File extension(s): Haptic file extensions used for IVS files: .ivs (xml) and .ivt (binary)
- Macintosh file type code(s): (no code specified)
- Macintosh Universal Type Identifier code: None
- Fragment Identifier: None
- Deprecated Alias: None
Person & email address to contact for further information: Yeshwant Muthusamy(ymuthusamy@immersion.com)
Change controller: Immersion Corporation
HAPT Haptics Type
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 .
Applications that use this media type: All applications that are able to create, edit, or display haptic media content.
Additional information:
- File extension(s): Haptic file extensions used for HAPT files: .hapt
- Macintosh file type code(s): (no code specified)
- Macintosh Universal Type Identifier code: None
- Fragment Identifier: None
- Deprecated Alias: None
Person & email address to contact for further information: Yeshwant Muthusamy(ymuthusamy@immersion.com)
Change controller: Immersion Corporation
Normative References
Informative References
ISO/IEC 14496-12 (7th Edition) Information technology — Coding of audio-visual objects — Part 12: ISO base media file format
Encoder Input Format for MPEG Haptics
Apple Haptic Audio Pattern
MPEG Evaluates Responses to the Haptics Phase 1 Call for Proposals
W3C Vibration API (Second Edition)
W3C Gamepad Extensions
P1918.1.1 - Haptic Codecs for the Tactile Internet
IANA, Application for a Media Type
Resource Interchange File Format