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Dr. Ruth Westheimer (Dr. Ruth; born 1928), German-American sex therapist, talk show host, author, professor, Holocaust survivor, and former Haganah sniper. |
Blanche Colton Williams, professor of English literature and head of the English department |
Edwin Zarowin Track and Field Coach. |
A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Notable examples of container formats include archive files (such as the ZIP format) and formats used for multimedia playback (such as Matroska, MP4, and AVI). Among the earliest cross-platform container formats were Distinguished Encoding Rules and the 1985 Interchange File Format. |
Design |
Although containers may identify how data or metadata is encoded, they do not actually provide instructions about how to decode that data. A program that can open a container must also use an appropriate codec to decode its contents. If the program doesn't have the required algorithm, it can't use the contained data. In these cases, programs usually emit an error message that complains of a missing codec, which users may be able to acquire. |
Container formats can be made to wrap any kind of data. Though there are some examples of such file formats (e.g. Microsoft Windows's DLL files), most container formats are specialized for specific data requirements. For example, since audio and video streams can be coded and decoded with many different algorithms, a container format may be used to provide the appearance of a single file format to users of multimedia playback software. |
Considerations |
The differences between various container formats arise from five main issues: |
Popularity; how widely supported a container is. |
Overhead. This is the difference in file-size between two files with the same content in a different container. |
Support for advanced codec functionality. Older formats such as AVI do not support new codec features like B-frames, VBR audio or VFR video natively. The format may be "hacked" to add support, but this creates compatibility problems. |
Support for advanced content, such as chapters, subtitles, meta-tags, user-data. |
Support of streaming media. |
Single coding formats |
In addition to pure container formats, which specify only the wrapper but not the coding, a number of file formats specify both a storage layer and the coding, as part of modular design and forward compatibility. |
Examples include JPEG File Interchange Format (JFIF) for containing JPEG data, and Portable Network Graphics (PNG). |
In principle, coding can be changed while the storage layer is retained; for example, Multiple-image Network Graphics (MNG) uses the PNG container format but provides animation, while JPEG Network Graphics (JNG) puts JPEG encoded data in a PNG container; in both cases however, the different formats have different magic numbers – the format specifies the coding, though a MNG can contain both PNG-encoded images and JPEG-encoded images. |
Multimedia container formats |
The container file is used to identify and interleave different data types. Simpler container formats can contain different types of audio formats, while more advanced container formats can support multiple audio and video streams, subtitles, chapter-information, and meta-data (tags) — along with the synchronization information needed to play back the various streams together. In most cases, the file header, most of the metadata and the synchro chunks are specified by the container format. For example, container formats exist for optimized, low-quality, internet video streaming which differs from high-quality Blu-ray streaming requirements. |
Container format parts have various names: "chunks" as in RIFF and PNG, "atoms" in QuickTime/MP4, "packets" in MPEG-TS (from the communications term), and "segments" in JPEG. The main content of a chunk is called the "data" or "payload". Most container formats have chunks in sequence, each with a header, while TIFF instead stores offsets. Modular chunks make it easy to recover other chunks in case of file corruption or dropped frames or bit slip, while offsets result in framing errors in cases of bit slip. |
Some containers are exclusive to audio: |
AIFF (IFF file format, widely used on Mac OS platform) |
WAV (RIFF file format, widely used on Windows platform) |
XMF (Extensible Music Format)Other containers are exclusive to still images: |
FITS (Flexible Image Transport System) still images, raw data, and associated metadata. |
TIFF (Tag Image File Format) still images and associated metadata. |
Macintosh PICT resource (PICT), superseded by PDF in Mac OS X |
Windows Metafile (WMF) = (EMF) Enhanced Metafile |
Encapsulated PostScript (EPS) |
Computer Graphics Metafile (CGM) |
Portable Document Format (PDF) |
Corel Draw File (CDR) |
Scalable Vector Graphics (SVG) |
Rich Text Format file (RTF)Other flexible containers can hold many types of audio and video, as well as other media. The most popular multi-media containers are: |
3GP (used by many mobile phones; based on the ISO base media file format) |
ASF (container for Microsoft WMA and WMV, which today usually do not use a container) |
AVI (the standard Microsoft Windows container, also based on RIFF) |
DVR-MS ("Microsoft Digital Video Recording", proprietary video container format developed by Microsoft based on ASF) |
Flash Video (FLV, F4V) (container for video and audio from Adobe Systems) |
IFF (first platform-independent container format) |
Matroska (MKV) (not limited to any coding format, as it can hold virtually anything; it is an open standard container format) |
MJ2 - Motion JPEG 2000 file format, based on the ISO base media file format which is defined in MPEG-4 Part 12 and JPEG 2000 Part 12 |
QuickTime File Format (standard QuickTime video container from Apple Inc.) |
MPEG program stream (standard container for MPEG-1 and MPEG-2 elementary streams on reasonably reliable media such as disks; used also on DVD-Video discs) |
MPEG-2 transport stream (a.k.a. MPEG-TS) (standard container for digital broadcasting and for transportation over unreliable media; used also on Blu-ray Disc video; typically contains multiple video and audio streams, and an electronic program guide) |
MP4 (standard audio and video container for the MPEG-4 multimedia portfolio, based on the ISO base media file format defined in MPEG-4 Part 12 and JPEG 2000 Part 12) which in turn was based on the QuickTime file format. |
Ogg (standard container for Xiph.org audio formats Vorbis and Opus and video format Theora) |
RM (RealMedia; standard container for RealVideo and RealAudio) |
WebM (subset of Matroska, used for web-based media distribution on online platforms; container for royalty-free audio formats Vorbis/Opus and video formats VP8/VP9/AV1)There are many other container formats, such as NUT, MXF, GXF, ratDVD, SVI, VOB and DivX Media Format |
An import is the receiving country in an export from the sending country. Importation and exportation are the defining financial transactions of international trade.In international trade, the importation and exportation of goods are limited by import quotas and mandates from the customs authority. The importing and exporting jurisdictions may impose a tariff (tax) on the goods. In addition, the importation and exportation of goods are subject to trade agreements between the importing and exporting jurisdictions. |
History |
Definition |
Imports consist of transactions in goods and services to a resident of a jurisdiction (such as a nation) from non-residents. The exact definition of imports in national accounts includes and excludes specific "borderline" cases. Importation is the action of buying or acquiring products or services from another country or another market other than own. Imports are important for the economy because they allow a country to supply nonexistent, scarce, high cost, or low-quality certain products or services, to its market with products from other countries. |
A general delimitation of imports in national accounts is given below: |
An import of a good occurs when there is a change of ownership from a non-resident to a resident; this does not necessarily imply that the good in question physically crosses the frontier. However, in specific cases, national accounts impute changes of ownership even though in legal terms no change of ownership takes place (e.g. cross border financial leasing, cross border deliveries between affiliates of the same enterprise, goods crossing the border for significant processing to order or repair). Also, smuggled goods must be included in the import measurement. |
Imports of services consist of all services rendered by non-residents to residents. In national accounts any direct purchases by residents outside the economic territory of a country are recorded as imports of services; therefore all expenditure by tourists in the economic territory of another country are considered part of the imports of services. Also, international flows of illegal services must be included.Basic trade statistics often differ in terms of definition and coverage from the requirements in the national accounts: |
Data on international trade in goods are mostly obtained through declarations to custom services. If a country applies the general trade system, all goods entering the country are recorded as imports. If the special trade system (e.g. extra-EU trade statistics) is applied goods that are received into customs warehouses are not recorded in external trade statistics unless they subsequently go into free circulation of the importing country. |
A special case is the intra-EU trade statistics. Since goods move freely between the member states of the EU without customs controls, statistics on trade in goods between the member states must be obtained through surveys. To reduce the statistical burden on the respondent's small-scale traders are excluded from the reporting obligation. |
Statistical recording of trade in services is based on declarations by banks to their central banks or by surveys of the main operators. In a globalized economy where services can be rendered via electronic means (e.g. internet) the related international flows of services are difficult to identify. |
Basic statistics on international trade normally do not record smuggled goods or international flows of illegal services. A small fraction of the smuggled goods and illegal services may nevertheless be included in official trade statistics through dummy shipments or dummy declarations that serve to conceal the illegal nature of the activities. |
Balance of trade |
A country has demand for an import when the price of the good (or service) on the world market is less than the price on the domestic market. |
The balance of trade, usually denoted |
NX , is the difference between the value of all the goods (and services) a country exports and the value of the goods the country imports. A trade deficit occurs when imports are larger than exports. Imports are impacted principally by a country's income and its productive resources. For example, the US imports oil from Canada even though the US has oil and Canada uses oil. However, consumers in the US are willing to pay more for the marginal barrel of oil than Canadian consumers are, because there is more oil demanded in the US than there is oil produced. |
In macroeconomic theory, the value of imports can be modeled as a function of domestic absorption (spending on everything, regardless of source) and the real exchange rate. These are the two most important factors affecting imports and they both affect imports positively. |
Types of import |
There are two basic types of import: |
Industrial and consumer goods |
Intermediate goods and servicesCompanies import goods and services to supply to the domestic market at a cheaper price and better quality than competing goods manufactured in the domestic market. Companies import products that are not available in the local market. |
There are three broad types of importers: |
Those looking for any product around the world to import and sell |
Those looking for foreign sourcing to get their products at the cheapest price |
Those who using foreign sourcing as part of their global supply chainDirect-import refers to a type of business importation involving a major retailer (e.g. Wal-Mart) and an overseas manufacturer. A retailer typically purchases products designed by local companies that can be manufactured overseas. In a direct-import program, the retailer bypasses the local supplier (colloquial: "middle-man") and buys the final product directly from the manufacturer, possibly saving in added cost |
data on the value of imports and their quantities often broken down by detailed lists of products are available in statistical collections on international trade published by the statistical services of intergovernmental organisations (e.g. UNSD, FAOSTAT, OECD), supranational statistical institutes (e.g. Eurostat) and national statistical institutes. |
Import of goods |
Importation and declaration and payment of customs duties is done by the importer of record, which may be the owner of the goods, the purchaser, or a licensed customs broker. |
Paul Delaney is a senior lecturer and professor of physics and astronomy at York University in Toronto. He is also the director of the Division of Natural Science within the Faculty of Science at York, as well as the Master of Bethune College at York.Delaney has his master's degree in science. He has taught at York University since 1986. He earned his Bachelor of Science in experimental physics at the Australian National University in Canberra and his master's degree in astronomy at the University of Victoria. Delaney has been the recipient of many faculty of science and engineering awards at York University. One of his classes deals with the possibility of life on Mars. Delaney is also the director of the observatory at the York University, and its outreach program. In the past, he has also worked as a nuclear physicist at the Atomic Energy of Canada, and a support astronomer with the McGraw-Hill Observatory in Tucson, Arizona.He holds both Australian and Canadian citizenship, and resides in Simcoe County with his wife - whom he met while attending the University of Victoria - and their two sons. |
ISO 3166-2 is part of the ISO 3166 standard published by the International Organization for Standardization (ISO), and defines codes for identifying the principal subdivisions (e.g., provinces or states) of all countries coded in ISO 3166-1. The official name of the standard is Codes for the representation of names of countries and their subdivisions – Part 2: Country subdivision code. It was first published in 1998. |
The purpose of ISO 3166-2 is to establish an international standard of short and unique alphanumeric codes to represent the relevant administrative divisions and dependent territories of all countries in a more convenient and less ambiguous form than their full names. Each complete ISO 3166-2 code consists of two parts, separated by a hyphen: |
Subsets and Splits