The 'haptics' Top-level Media Type

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DISPATCH                                                 Y. K. Muthusamy
Internet-Draft                                                C. Ullrich
Intended status: Standards Track                   Immersion Corporation
Expires: 15 April 2021                                   12 October 2020

                   The 'haptics' Top-level Media Type


   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.

Status of This Memo

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Background and Justification  . . . . . . . . . . . . . . . .   3
     2.1.  MPEG ISOBMFF  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Haptic Sub-modalities . . . . . . . . . . . . . . . . . .   3
     2.3.  Another Human Sense . . . . . . . . . . . . . . . . . . .   4
     2.4.  Commercial Uptake . . . . . . . . . . . . . . . . . . . .   4
     2.5.  Haptic Sub-types (in use) . . . . . . . . . . . . . . . .   5
     2.6.  Haptic Sub-types (envisioned standards) . . . . . . . . .   6
     2.7.  'application' top-level type not suitable . . . . . . . .   6
   3.  Definition and Encoding . . . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  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 [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

1.1.  Terminology

   in this document, are to be interpreted as described in [RFC2119].

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2.  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.


   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 and is scheduled to progress to DIS
   (Draft International Standard) in late October 2020.  Once it
   completes its progression through the MPEG standardization stages
   (expected in January 2022), haptics will become part of the ISO/IEC
   14496-12 (ISOBMFF) standard.  Given this development, a strong case
   can be made for haptics to be added to the list of top-level media
   type recognized by the IETF.

   We envision the following designations for haptics in mp4 files:

   1.  'haptics/mp4' - mp4 files with just haptic tracks in them (e.g.,
       streaming games, haptics files for haptic vests, belts, gloves,

   2.  'video/mp4' - mp4 files with video, audio, and haptics (to ensure
       consistency with existing mp4 files with video content)

   3.  'audio/mp4' - mp4 files with audio and haptics (to ensure
       consistency with existing mp4 files with audio content without
       any video)

2.2.  Haptic Sub-modalities

   There are multiple sub-modalities of haptics:

   *  Vibrotactile (touch, vibration)

   *  Kinesthetic (force feedback)

   *  Surface (surface friction)

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   *  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'.

2.3.  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.

2.4.  Commercial Uptake

   Haptics is rapidly becoming a standard feature of consumer electronic
   devices.  For example:

   *  iPhone (191+ million units sold in 2019): native support for
      haptic encoded data

   *  Android (1.18+ billion units sold in 2019): API support of haptic

   *  W3C (HTML vibration API): Optionally supported in mobile web

   *  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.

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2.5.  Haptic Sub-types (in use)

   There are multiple instances of existing haptic sub-types (data
   formats) that would live under the proposed 'haptics' top-level media
   type.  While these sub-types 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:

   *  haptics/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

   *  haptics/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.

   *  haptics/ivt: The IVT haptic data format is currently an Immersion-
      proprietary format that has been licensed and 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

   *  haptics/hapt: The HAPT haptic data format is currently an
      Immersion-proprietary format that has been licensed and 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:

         o  KLAB: (

         o  Craft&Meister:
            company_en.html (

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      -  Tencent is using the TouchSense SDK for their popular social
         media application QQ and live streaming application NOW:

   Given the widespread use of these sub-types, it makes sense for
   'haptics' to be a top-level media type.

2.6.  Haptic Sub-types (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:

   *  haptics/hstr: would be the standards version of Immersion's HAPT

   *  haptics/hiee: IEEE P1918.1.1 vibrotactile coding standard being
      developed under the IEEE Tactile Internet initiative as part of
      the 5G URLL profile.

   *  haptics/henm: enumerated effects haptic coding format (based on

   *  haptics/havc: audio-to-vibe haptic coding format (automatic audio
      to vibration conversion algorithms)

2.7.  '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 two 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.

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3.  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.

4.  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 [Media-Type-Registration], and
   registers several subtypes for it.

5.  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.  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.

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   As with any synthesized media data (audio, visual and haptic), 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

   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.

6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,

Authors' Addresses

   Yeshwant K. Muthusamy
   Immersion Corporation
   330 Townsend St. Suite 234
   San Francisco

   Phone: +1 469-583-2171

   Chris Ullrich
   Immersion Corporation
   330 Townsend St. Suite 234
   San Francisco

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   Phone: +1 805-320-0774

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