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51-579: Transport stream specifies a container format encapsulating packetized elementary streams , with error correction and synchronization pattern features for maintaining transmission integrity when the communication channel carrying the stream is degraded . Transport streams differ from the similarly named MPEG program stream in several important ways: program streams are designed for reasonably reliable media, such as discs (like DVDs ), while transport streams are designed for less reliable transmission, namely terrestrial or satellite broadcast . Further,

102-777: A header , that may be followed with optional additional headers; the rest of the packet consists of payload . All header fields are read as big-endian . Packets are 188 bytes in length, but the communication medium may add additional information. The 188-byte packet size was originally chosen for compatibility with Asynchronous Transfer Mode (ATM) systems . This field allows a receiver that started reading mid transmission to know when it can start extracting data. For DVB-CSA and ATSC DES only: '01' (0x40) = Reserved for future use '10' (0x80) = Scrambled with even key '11' (0xC0) = Scrambled with odd key 10 – adaptation field only, no payload, 11 – adaptation field followed by payload, 00 – RESERVED for future use It gives

153-441: A television set , VCR , digital video recorder (DVR), or set-top box which provides audio/video output connectors of various types. Another type of television tuner is a digital television adapter (DTA) with an analog passthrough . The terms "tuner" and "receiver" are used loosely, and it is perhaps more appropriately called an ATSC receiver, with the tuner being part of the receiver (see Metonymy ). The receiver generates

204-500: A 27 MHz clock. The maximum jitter permitted for the PCR is +/- 500 ns . Some transmission schemes, such as those in ATSC and DVB , impose strict constant bitrate requirements on the transport stream. In order to ensure that the stream maintains a constant bitrate, a multiplexer may need to insert some additional packets. The PID 0x1FFF is reserved for this purpose. The null packets have

255-529: A different aspect ratio . The FCC has issued the following mandates for devices entering the US: Devices manufactured before these dates can still be sold without a built-in ATSC DTV tuner; the lack of digital tuners legally must be disclosed to consumers and most name-brand retailers have incurred FCC penalties for non-compliance with these requirements. The current regulations are specified in

306-410: A few seconds in order to receive the extended info). DirecTV receivers with ATSC tuners can download the guide at any time, while other TiVo units download guide data separately. TV Guide On Screen can also be used for this, but very few if any ATSC tuners include this (which requires downloading all guide data for all channels from one particular station). Stations sending the wrong time are also

357-761: A good indoor antenna and an ATSC tuner. US-based ATSC signals can be reliably tuned with an outdoor antenna and an ATSC tuner in Canadian markets within 60 miles of the US broadcast towers. These markets include Toronto (from Buffalo), Windsor (from Detroit and Toledo), Vancouver (from Seattle and Tacoma), Montreal (from Burlington and Plattsburgh), Ottawa (from Watertown and Plattsburgh), and Fredericton (from Presque Isle). Indoor antennas (both passive and amplified) are easier to install, but outdoor antennas are better at tuning stations from further distances. Most ATSC tuners have relatively simple on-screen menus, and automatically bring

408-428: A major problem, as this can skew or ruin guide data for all stations until the correct time is received again from a different and correctly set station. Each digital OTA channel number is composed of a main number and a subchannel, for example 4.1, 4.2, etc. A dash is an alternate form of representation: 4–1, 4–2... The dot and dash are interchangeable; they both mean the same thing. The main channel numbers refer to

459-604: A particular PID appears in the transport stream. Transport stream has a concept of programs . Every program is described by a program map table (PMT). The elementary streams associated with that program have PIDs listed in the PMT. Another PID is associated with the PMT itself. For instance, a transport stream used in digital television might contain three programs, to represent three television channels. Suppose each channel consists of one video stream, one or two audio streams, and any necessary metadata. A receiver wishing to decode one of

510-709: A payload that is filled with 0xFF, and the receiver is expected to ignore its contents. Transport Stream was originally designed for broadcast. Later it was adapted for use with digital video cameras, recorders and players by adding a 4-byte timecode (TC) field to the standard 188-byte packets, resulting in a 192-byte packet. This is what is informally called M2TS stream, commonly found in HDV cameras. The Blu-ray Disc Association calls it " BDAV MPEG-2 transport stream ". JVC called it TOD when used in HDD-based camcorders like GZ-HD7 . The timecode allows quick access to any part of

561-496: A poor-quality signal will cause the loss of some data that the ATSC tuner receives. With error correction, the tuner has the ability to perform a number of checks and repair data so that a signal can be viewed on a TV set. Error correction works by adding some extra information to the signal before transmission that can be used upon reception to fill in gaps. Therefore, error correction has the opposite effect of compression—it increases

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612-401: A television with a digital tuner or a set-top box, ended up losing their only source of television, unless they relied only upon the aforementioned non-full-power broadcasters. A Congressional bill authorized subsidized converter boxes in a way that allowed viewers to receive the new digital broadcasts on their old TVs. The transition proceeded with about 235,000 people requesting coupons after

663-521: A third channel (sometimes the former analog of another local station), chosen in the digital channel election in the U.S. This requires all viewers to re-scan or manually add the new channel and possibly delete the old one. Doing a full re-scan will usually cause other channels to be dropped if they cannot be received at the moment the scan passes their physical channel, so this is typically undesirable, although many ATSC tuners only have this option. Some have an "easy-add" feature which does not delete what

714-616: A transport stream may carry multiple programs. Transport stream is specified in MPEG-2 Part 1, Systems , formally known as ISO/IEC standard 13818-1 or ITU-T Rec. H.222.0 . A transport stream encapsulates a number of other substreams, often packetized elementary streams (PESs) which in turn wrap the main data stream using the MPEG codec or any number of non-MPEG codecs (such as AC3 or DTS audio, and MJPEG or JPEG 2000 video), text and pictures for subtitles, tables identifying

765-516: A video or audio encoder is to first create PES packets from the elementary stream data and then to encapsulate these PES packets inside Transport Stream (TS) packets or Program Stream (PS) packets. The TS packets can then be multiplexed and transmitted using broadcasting techniques, such as those used in an ATSC and DVB . Transport Streams and Program Streams are each logically constructed from PES packets. PES packets shall be used to convert between Transport Streams and Program Streams. In some cases

816-477: Is already mapped in memory. Some allow the user to enter the physical channel and an unmapped subchannel, causing the tuner to search the physical channel. Depending on the tuner, this may or may not automatically add the station and its digital subchannels to the map, and/or to the user's " favorites ". This may also leave the old "dead" channel mapping in place, so that there is the new 8.1, dead 8.1, new 8.2, dead 8.2, etc. In most cases, TV stations will not have

867-665: Is an example of resolution change. It is commonly used to convert a low-resolution picture to a high-resolution display. This lets the user eliminate letterboxing or pillarboxing by stretching or cropping the picture. Some ATSC receivers, mostly those in HDTV TV sets , will stretch automatically, either by detecting black bars or by reading the Active Format Description (AFD). An ATSC tuner works by generating audio and video signals that are picked up from over-the-air broadcast television . ATSC tuners provide

918-490: Is employed to generate a system_timing_clock in the decoder. The system time clock (STC) decoder, when properly implemented, provides a highly accurate time base that is used to synchronize audio and video elementary streams. Timing in MPEG-2 references this clock. For example, the presentation time stamp (PTS) is intended to be relative to the PCR. The first 33 bits are based on a 90 kHz clock. The last 9 bits are based on

969-403: Is particularly important for videoconferencing, where large frames may introduce unacceptable audio delay. Transport streams tend to be broadcast as constant bitrate (CBR) and filled with padding bytes when not enough data exists. A network packet is the basic unit of data in a transport stream, and a transport stream is merely a sequence of packets. Each packet starts with a sync byte and

1020-432: Is that error correction systems are specially designed to get the maximum benefit out of a very small amount of redundant data, whereas the natural redundancy of the data doesn't do this job as efficiently, so with error correction the net amount of data needed is still smaller. AV synchronization is the coordination of audio and video signals being displayed on a digital TV in proper time. AV synchronization ensures that

1071-538: The MPEG-2 Part 1 (Systems) (ISO/IEC 13818-1) and ITU-T H.222.0 that defines carrying of elementary streams (usually the output of an audio or video encoder) in packets within MPEG program streams and MPEG transport streams . The elementary stream is packetized by encapsulating sequential data bytes from the elementary stream inside PES packet headers. A typical method of transmitting elementary stream data from

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1122-505: The June 12, 2009, transition date. Two $ 40 coupons were made available per US address nominally from January 1, 2008, through March 31, 2009; each coupon could be used toward the purchase of one approved coupon-eligible converter box . The coupons expired 90 days after initial mailing and were not renewable. All households were eligible to receive coupons from the initial $ 990 million allocated, after which an additional $ 510 million in coupons

1173-576: The PES packets need not be modified when performing such conversions. PES packets may be much larger than the size of a Transport Stream packet. While above flags indicate that values are appended into variable length optional fields, they are not just simply written out. For example, PTS (and DTS) is expanded from 33 bits to 5 bytes (40 bits). If only PTS is present, this is done by catenating 0010b, most significant 3 bits from PTS, 1, following next 15 bits, 1, rest 15 bits and 1. If both PTS and DTS are present

1224-750: The U.S. Code of Federal Regulations (CFR). In early 2006 the US Deficit Reduction Act of 2005 became law, which calls for full-power over-the-air television stations to cease their analog broadcasts by February 17, 2009 (this cut-off date had been moved several times previously). On February 11, 2009, the mandatory DTV broadcast date was moved again to June 12, 2009, although stations were allowed to switch earlier. The delay enabled distribution of more coupons for purchase of converter boxes. As of June 12, 2009, TVs and other equipment with legacy NTSC tuners are unable to receive over-the-air broadcasts from United States TV stations, unless

1275-433: The US with no government subsidies. ATSC tuners may also be present in most recently manufactured televisions, as well as DVD recorders , HDTV FTA receivers , and personal computer TV tuner cards . As of the beginning of 2012, almost all Canadian broadcasters are broadcasting an ATSC signal, with a handful of exceptions granted for low-power and regional stations. These signals can be reliably tuned in most cities with

1326-787: The United States, there is no plan to subsidise ATSC converter purchases and no requirement that newly imported receivers decode the digital signal. Canadian retailers are also not required to disclose the inability of new equipment to receive DTV. The Canadian market therefore has been flooded with obsolete new NTSC equipment which lawfully cannot be exported to the US. A limited number of ATSC receivers are in Canadian retail stores as high-definition television (HDTV) receivers. ATSC CECB converter boxes were first carried nationally in October 2008, with chains such as Best Buy and Home Hardware offering limited selection at higher prices than in

1377-443: The actual frequency they are currently using on their website. If the auto scan does not pick up the signal and the tuner has manual frequency scan capability try to get the actual frequency from the station engineer. This may allow one to stay on one frequency (channel) versus "scanning" (moving too quickly through) and allow one to make antenna adjustments while observing only a problematic channel. Other errors which appear to be in

1428-514: The air (or down a coaxial cable or other long-distance medium.) ATSC as implemented in the US uses 8VSB modulation, which requires less power to transmit, as opposed to the also proposed COFDM modulation (used in European DVB-T , which is less prone to multipath distortion and therefore better received in mobile installations). In the US, multiple digital signals are combined and then transmitted from one antenna source to create over

1479-489: The air broadcasts. By the reverse process ( demultiplexing ), an ATSC receiver first receives the combined MPEG transport stream and then decodes it to display one of its component signals on a TV set. Since digital signals that are broadcast over the air are compressed (packed smaller), once they are received by the ATSC tuner, these compressed packets of digital data are then decompressed (unpacked to their original size). The ATSC system uses lossy compression , so while

1530-400: The amount of data to transmit, rather than reducing it like compression does, and it improves the quality and robustness of the signal rather than reducing it. Compression removes redundant (and some non-redundant) data, while error correction adds some redundant data. The reason for using error correction rather than just using less compression and keeping the redundancy that was already there

1581-488: The audio and video (AV) signals needed for television, and performs the following tasks: demodulation ; error correction ; MPEG transport stream demultiplexing ; decompression ; AV synchronization ; and media reformatting to match what is optimal input for one's TV. Examples of media reformatting include: interlace to progressive scan or vice versa; picture resolutions; aspect ratio conversions (16:9 to or from 4:3); frame rate conversion; and image scaling . Zooming

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1632-471: The audio does not lag behind the video that is being displayed on the TV set or vice versa, so that both audio and video are in sync. Media reformatting is extremely important because the formatting of images on TV sets differs significantly according to the technology employed. For instance, some televisions have an interlaced picture, whereas others have a progressive-scan picture. Different televisions have

1683-507: The broadcast is from a repeater or low-power transmitter. However, Class-A stations shut down analog transmissions on September 1, 2015 followed by a complete shutdown of all low-power and repeater stations by July 13, 2021. Canada had a similar analog TV termination date set to September 1, 2011 (except in some remote northern regions). It was feared that the US switch-off would cause millions of non-cable- and non-satellite-connected TV sets to "go dark ". Viewers who did not upgrade, either to

1734-469: The channel map. If no PSIP is transmitted, the physical channel number is used, and each transport stream is enumerated according to its TSID (converted from hexadecimal ), or starting sequentially at .1, .2, .3, and so forth, depending on the tuner. Several TV stations are using or have used a temporary channel to send their DTV signals and, upon terminating analog transmission, move their digital transmission either back to their old analog channel, or to

1785-414: The country, including all provincial capitals, plus Ottawa (the national capital), and most other major urban centers. As of the end of 2008, there were 22 Canadian DTV transmitters on-air and all existing digital transitional television licenses explicitly proscribe, as a condition of license, the broadcast of more than fourteen hours a week of programming not already on the analogue service. Unlike in

1836-426: The decompressed data size is the same as the original compressed data size, the data produced is not exactly the same as the original data fed into the system at the transmitting site, but it is close enough that most people will not notice a difference. Error correction is a technology that is used by the ATSC tuner to make sure that any data that is missing can be corrected. For instance, sometimes interference or

1887-540: The extra transport overhead. There is also the BDAV (Blu-ray Disc Audio/Visual) format, the consumer-oriented alternative to the BDMV format used for movie releases. The BDAV format is used on Blu-ray Disc recordable for audio/video recording. Blu-ray Disc employs the MPEG-2 transport stream recording method. This enables transport streams of a BDAV converted digital broadcast to be recorded as they are with minimal alteration of

1938-446: The following functions: selective tuning; demodulation; transport stream demultiplexing; decompression; error correction; analog-to-digital conversion; AV synchronization; and media reformatting to fit the specific type of TV screen optimally. Selective tuning is the process by which the radio frequency (RF) of the television channel is selected by a receiver from within a band of transmitted RF signals. The tuner usually performs

1989-474: The format of the CAT and NIT. To enable a decoder to present synchronized content, such as audio tracks matching the associated video, at least once each 100 ms, a program clock reference (PCR) is transmitted in the adaptation field of an MPEG-2 transport stream packet. The PID with the PCR for an MPEG-2 program is identified by the pcr_pid value in the associated PMT. The value of the PCR, when properly used,

2040-455: The function of frequency-agile selection, along with rejection of unwanted out-of-band signals. "Demodulation" means transforming the signal from the tuner into a signal that a TV set can use to produce images and sound without further consideration for the frequency at which it was transmitted. It is separation of a standard baseband signal from the RF carrier that was used to transmit it through

2091-457: The index after this byte at which the new payload unit starts. Any payload byte before the index is part of the previous payload unit. Each table or elementary stream in a transport stream is identified by a 13-bit packet identifier (PID). A demultiplexer extracts elementary streams from the transport stream in part by looking for packets identified by the same PID. In most applications, time-division multiplexing will be used to decide how often

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2142-410: The packets. It also enables simple stream cut style editing of a BDAV converted digital broadcast that is recorded as is and where the data can be edited just by discarding unwanted packets from the stream. Although it is quite natural, a function for high-speed and easy-to-use retrieval is built in. Packetized elementary stream Packetized Elementary Stream ( PES ) is a specification in

2193-670: The same is done, but first 4 bits before start of PTS bits are 0011b (and not 0010b) and first 4 bits before start of DTS bits are 0001b. Other appended bytes have similar but different encoding. ATSC tuner An ATSC ( Advanced Television Systems Committee ) tuner , often called an ATSC receiver or HDTV tuner , is a type of television tuner that allows reception of digital television (DTV) television channels that use ATSC standards , as transmitted by television stations in North America , parts of Central America , and South Korea . Such tuners are usually integrated into

2244-428: The same radio frequencies as previously. However, now " virtual channel " (technically known as logical channel number ) numbers are common. So, Channel 4 digital signals may now actually be broadcast on channel 43, or any other frequency. When the ATSC tuner does a channel scan, it finds the signal on channel 43, learns that this material is called "Channel 4", and remembers that mapping. The user can tune to "4", and

2295-580: The stream either from a media player, or from a non-linear video editing system. It is also used to synchronize video streams from several cameras in a multiple-camera setup . Blu-ray Disc video titles authored with menu support are in the Blu-ray Disc Movie (BDMV) format and contain audio, video, and other streams in a BDAV container, which is based on the MPEG-2 transport stream format. Blu-ray Disc video uses these modified MPEG-2 transport streams, compared to DVD's program streams that don't have

2346-551: The streams, and even broadcaster-specific information such as an electronic program guide . Many streams are often mixed together, such as several different television channels, or multiple angles of a movie. Each stream is chopped into (at most) 188-byte sections and interleaved together. Due to the tiny packet size, streams can be interleaved with less latency and greater error resilience compared to program streams and other common containers such as AVI , MOV / MP4 , and MKV , which generally wrap each frame into one packet. This

2397-541: The three channels merely has to decode the payloads of each PID associated with its program. It can discard the contents of all other PIDs. A transport stream with more than one program is referred to as a multi-program transport stream (MPTS). A single program transport stream is referred to as a single-program transport stream (SPTS). There are 4 program specific information (PSI) tables: program association (PAT), program map (PMT), conditional access (CAT), and network information (NIT). The MPEG-2 specification does not specify

2448-458: The tuner are actually the result of incorrect data sent by one or more stations, often including missing electronic program guide data. Many ATSC tuners will remember EPG info for each station, but only for a few hours after viewing a channel on that station. Some will not remember at all (displaying only the required channel banner), while a very few others will store data for days (although this requires staying tuned to each station for more than

2499-445: The tuner will know to tune in 43. Before a scan is done, it may be possible to access the programs directly by manual tuning, by entering 43–1, 43–2... After the scan, the programs would usually be accessed by entering 4–1, 4-2 etc., but it may still be possible to also access them directly at 43 as long as it is also not the same as an already assigned channel. If stations change their broadcast frequencies, it may be possible to access

2550-463: The user to a setup screen when turned on for the first time. This allows the user to pick the time zone and daylight-saving time mode (as all stations transmit time in UTC ), and bandscan for stations. The scan "listens" on every channel from 2 to 69 , and pauses when it detects a digital carrier wave . If it is able to decode the station, it reads its PSIP data, and adds its virtual channels to

2601-526: Was to be available to households that rely exclusively on over-the-air television reception. On January 4, 2009, the coupon program reached its US$ 1.34 billion ceiling and any further consumer requests were placed on a waiting list. In Canada , the Canadian Radio-television and Telecommunications Commission (CRTC) had set August 31, 2011, as the date on which over-the-air analog TV transmission service would cease in 31 major markets of

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