Picture Transfer Protocol
Encyclopedia
Picture Transfer Protocol (PTP) is a widely supported protocol developed by the International Imaging Industry Association
to allow the transfer of images from digital camera
s to computers and other peripheral devices without the need of additional device driver
s. The protocol has been standardised as ISO
15740.
It is further standardized for USB
by the USB Implementers Forum
as the still image capture device class. USB is the default network transport media for PTP devices. USB PTP is a common alternative to USB MSC, as a digital camera connection protocol. Some cameras support both modes.
file. While it is common to think of the objects that PTP handle as files
, they are abstract entities identified solely by a 32-bit object ID. These objects can however have parents and siblings so that a file-system–like view of device contents can be created.
, TIFF/EP
, DCF
, and DPOF, and is commonly implemented over the USB
and FireWire
transport layers.
Images on digital cameras are generally stored as files on a mass storage device
, such as a memory card
, which is formatted with a file system, most commonly FAT
or FAT32, which may be laid out as per the Design rule for Camera File system
(DCF) specification. However, none of these are required, as PTP abstracts from the underlying representation.
By contrast, if a camera is mounted via USB MSC, the physical file system and layout are exposed to the user.
digital cameras by Nikon
, Canon, and Eastman Kodak
, allows data transfer over any IP
-based network.
Media Transfer Protocol
, developed by Microsoft
, allows for transfer over wireless or wired networks based in part on FotoNation's PTP/IP, but also allows users to transfer other media aside from pictures, as well as for tagging objects with extended metadata
(such as title, artist and similar).
and Apple include PTP support in their operating system
s, from Windows Me
onwards (excluding Windows CE
), and Mac OS X v10.1
onwards, respectively. Microsoft implements PTP on Windows through Windows Image Acquisition
.
PTP on Linux
and other free software
/open source
operating systems is supported by a number of libraries, such as libgphoto
and libptp, libraries used by applications such as digiKam
and F-Spot
.
The Poseidon USB stack on Amiga
includes ptp.class.
.
As of the middle of 2008, most devices and operating systems do not yet support PTP v1.1. This updated version of PTP is fully backward-compatible with PTP v1.0, and offers optional performance, compatibility, and feature enhancements including:
International Imaging Industry Association
The International Imaging Industry Association was created by a merger of the PIMA and the Digital Imaging Group in 2001. It is a common forum for the industrial imaging industry....
to allow the transfer of images from digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
s to computers and other peripheral devices without the need of additional device driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....
s. The protocol has been standardised as ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
15740.
It is further standardized for USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
by the USB Implementers Forum
USB Implementers Forum
The USB Implementers Forum is a non-profit organisation to promote and support the Universal Serial Bus. Its main activities are the promotion and marketing of USB, Wireless USB, USB On-The-Go, and the maintenance of the specifications, as well as a compliance program.It was formed in 1995 by the...
as the still image capture device class. USB is the default network transport media for PTP devices. USB PTP is a common alternative to USB MSC, as a digital camera connection protocol. Some cameras support both modes.
Description
PTP specifies a way of creating, transferring and manipulating objects which are typically photographic images such as a JPEGJPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
file. While it is common to think of the objects that PTP handle as files
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...
, they are abstract entities identified solely by a 32-bit object ID. These objects can however have parents and siblings so that a file-system–like view of device contents can be created.
Storage
PTP does not specify a way for objects to be stored – it is a communication protocol. Nor does it specify a transport layer. However, it is designed to support existing standards, such as ExifExchangeable image file format
Exchangeable image file format is a standard that specifies the formats for images, sound, and ancillary tags used by digital cameras , scanners and other systems handling image and sound files recorded by digital cameras...
, TIFF/EP
Tag Image File Format / Electronic Photography
"Tag Image File Format / Electronic Photography" is a digital image file format standard – ISO 12234-2, titled "Electronic still-picture imaging – Removable memory – Part 2: TIFF/EP image data format"...
, DCF
Design rule for Camera File system
Design rule for Camera File system is a JEITA specification which defines a file system for digital cameras, including the directory structure, file naming method, character set, file format, and metadata format. It is currently the de facto industry standard for digital still cameras...
, and DPOF, and is commonly implemented over the USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
and FireWire
IEEE 1394 interface
The IEEE 1394 interface is a serial bus interface standard for high-speed communications and isochronous real-time data transfer, frequently used by personal computers, as well as in digital audio, digital video, automotive, and aeronautics applications. The interface is also known by the brand...
transport layers.
Images on digital cameras are generally stored as files on a mass storage device
Mass storage
In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. Devices and/or systems that have been described as mass storage include tape libraries, RAID systems, hard disk drives, magnetic tape drives, optical disc drives, magneto-optical...
, such as a memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...
, which is formatted with a file system, most commonly FAT
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...
or FAT32, which may be laid out as per the Design rule for Camera File system
Design rule for Camera File system
Design rule for Camera File system is a JEITA specification which defines a file system for digital cameras, including the directory structure, file naming method, character set, file format, and metadata format. It is currently the de facto industry standard for digital still cameras...
(DCF) specification. However, none of these are required, as PTP abstracts from the underlying representation.
By contrast, if a camera is mounted via USB MSC, the physical file system and layout are exposed to the user.
Extensions
A number of protocols have been developed that extend PTP. PTP/IP, developed by FotoNation and first implemented in a round of Wi-FiWi-Fi
Wi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
digital cameras by Nikon
Nikon
, also known as just Nikon, is a multinational corporation headquartered in Tokyo, Japan, specializing in optics and imaging. Its products include cameras, binoculars, microscopes, measurement instruments, and the steppers used in the photolithography steps of semiconductor fabrication, of which...
, Canon, and Eastman Kodak
Eastman Kodak
Eastman Kodak Company is a multinational imaging and photographic equipment, materials and services company headquarted in Rochester, New York, United States. It was founded by George Eastman in 1892....
, allows data transfer over any IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
-based network.
Media Transfer Protocol
Media Transfer Protocol
The Media Transfer Protocol is a devised set of custom extensions to the Picture Transfer Protocol . Whereas PTP was designed for downloading photographs from digital cameras, Media Transfer Protocol supports the transfer of music files on digital audio players and media files on portable media...
, developed by Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
, allows for transfer over wireless or wired networks based in part on FotoNation's PTP/IP, but also allows users to transfer other media aside from pictures, as well as for tagging objects with extended metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
(such as title, artist and similar).
Operating-system support
Both MicrosoftMicrosoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
and Apple include PTP support in their operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s, from Windows Me
Windows Me
Windows Millennium Edition, or Windows Me , is a graphical operating system released on September 14, 2000 by Microsoft, and was the last operating system released in the Windows 9x series. Support for Windows Me ended on July 11, 2006....
onwards (excluding Windows CE
Windows CE
Microsoft Windows CE is an operating system developed by Microsoft for embedded systems. Windows CE is a distinct operating system and kernel, rather than a trimmed-down version of desktop Windows...
), and Mac OS X v10.1
Mac OS X v10.1
Mac OS X version 10.1, code named "Puma", is the second major release of Mac OS X, Apple's desktop and server operating system. It superseded Mac OS X v10.0 and preceded Mac OS X v10.2. Version 10.1 was released on 25 September 2001 as a 'free update' to version 10.0...
onwards, respectively. Microsoft implements PTP on Windows through Windows Image Acquisition
Windows Image Acquisition
Windows Image Acquisition is a Microsoft driver model and application programming interface for Microsoft Windows Me and later Windows operating systems that enables graphics software to communicate with imaging hardware such as scanners, digital cameras and Digital Video-equipment...
.
PTP on Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
and other free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
/open source
Open-source software
Open-source software is computer software that is available in source code form: the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, improve and at times also to distribute the software.Open...
operating systems is supported by a number of libraries, such as libgphoto
GPhoto
gPhoto is a set of software applications and libraries for use in digital photography. gPhoto supports not just retrieving of images from camera devices, but also upload and remote controlled configuration and capture, depending on whether the camera supports those features.Released under the GNU...
and libptp, libraries used by applications such as digiKam
DigiKam
digiKam is an image organizer and editor using KDE Platform. It runs on most known desktop environments and window managers if the required libraries are installed. It supports all major image file formats, and can organize collections of photographs in directory-based albums, or dynamic albums by...
and F-Spot
F-Spot
F-Spot is an image organizer, designed to provide personal photo management for the GNOME desktop environment. The name is a play on the words F-Stop and G-Spot.-Features:...
.
The Poseidon USB stack on Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...
includes ptp.class.
Version 1.1
PTP v1.1 (ISO15740:2008) is an update to PTP that has recently been published by ISOInternational Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
.
As of the middle of 2008, most devices and operating systems do not yet support PTP v1.1. This updated version of PTP is fully backward-compatible with PTP v1.0, and offers optional performance, compatibility, and feature enhancements including:
- A mechanism for handling streaming content
- A mechanism to support multiple vendor extension sets
- Support for objects larger than the 4GiB size limit set by PTP v1.0, by requiring 64 bits (8 bytes) for object size
- Support for retrieval of ObjectHandles in enumerated chunks. This may reduce long response times for some devices that possess large numbers of objects
- Support for arbitrary resizing prior to image transmission (responder scaling). In PTP v1.0, image sizes might be requested in full-resolution or thumbnail size only
- Support for arrays of datasets. This can be used to reduce the number of required transactions necessary for device characterization from being a function of the number of objects on the device down to one
- A fast file characterization operation that exploits dataset arrays to request, in a single transaction, only the minimum data required to characterize a typical filesystem
- A new standard ObjectFormatCode to support the Digital Negative (DNG)Digital Negative (file format)Digital Negative is an open raw image format owned by Adobe used for digital photography. It was launched on September 27, 2004. The launch was accompanied by the first version of the DNG specification, plus various products including a free of charge DNG Converter utility...
file format
Drawbacks
- Renaming file objects directly is not possible without copying or rewriting them
- Modification of file contents is not supported (the file needs to be re-transferred completely)