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Video Tape Formats

Tracy Pettigrue
Tracy Pettigrue
Oct 3, 2009
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Video Tape Formats:

Video tape formats can be categorized in two types:

1.   Analog Formats

2.   Digital Formats

 

Analog Formats:

VHS:

It is the lowest quality format in use today, with 250 lines of resolution. VHS should only be used for making final dubs for home use. It should never be used for acquisition (shooting) or editing. All analog formats are subject to generation loss, which means that it decreases in quality as it is copied. VHS is highly susceptible to generation loss.

8MM:

8mm tapes look like Hi8 tapes (see below) but they record only 270 lines of resolution. It is of no professional value

S-VHS (Super-VHS):

A marked improvement over regular VHS, S-VHS achieves this quality improvement by recording the luminance and chrominance separately and using 400 lines of resolution. Compared to other formats, S-VHS is still rather low quality, yet it is used rather widely by low-level professionals such as public access or event videography. While S-VHS decks can play regular VHS tapes, regular VHS VCRs cannot play S-VHS tapes.

Hi8:

Hi8 produces quality about on par with S-VHS yet its tape and equipment are usually smaller, making it a more portable format. Hi8 inhabits a middle ground between consumers and professionals, so it never quite caught on with either. It is usually used by small local cable stations or in educational programs, although many places are replacing Hi8 with DV.

¾" (U-matic):

At one time, ¾" was the standard tape format of broadcast news, yet it was officially discontinued in the 1970's and most places have replaced it with BetaSP. That said, it continues to hang on in environments that couldn't afford or didn't care to upgrade, such as local cable stations, small market broadcast stations, and in corporate video

Betacam SP (BetaSP):

BetaSP has long been the standard format of choice for broadcast work and it is as ubiquitous in the professional world as VHS is among consumers. BetaSP replaced the older Betacam format. It is a component format, meaning that the red, green, and blue signals are recorded separately, yielding better color reproduction and a sharper image. It can also be copied more times than the previous formats before image degradation is noticeable. While Sony (the manufacturer of BetaSP) has very slowly been trying to get people to switch their newer, digital formats,

1 Inch (Type-C):

It is an old and very durable format that uses large, reel-to-reel tape machines. Very expensive, and only found in the upper levels of TV broadcasting.

Digital Formats

DV25 (DV): DV25 is commonly referred to as just DV. DV25 has a data rate of 25 Mbps. MiniDV, DVCAM, and DVCPro (D-7) are all DV25 formats.

Data Rate: 25 Mbps - Compression Ratio: 5:1 - Color Sampling: 4:1:1

Digital 8 (D-8): D-8 uses the same compression scheme as DV25, yet it records it onto a 8mm tape the same size as the analog 8mm and Hi8 format. Thus, D-8 decks can also play 8mm and Hi8 tapes.

Data Rate: 25 Mbps - Compression Ratio: 5:1 - Color Sampling: 4:1:1

DV50: DV50 is similar to DV25, except that it has double the data rate and color sampling. The main supporter of DV50 is Panasonic, who call it DVCPRO50.

Data Rate: 50 Mbps - Compression Ratio: 3.3:1 - Color Sampling: 4:2:2

Digital-S (D-9): Digital-S is a pro format supported mainly by JVC that is equivalent to DV50. Digital-S uses tapes that look like VHS and S-VHS tapes, although it offers vastly improved quality over both of those formats. Some Digital-S decks can play S- VHS. Now more commonly called D-9, since JVC is trying to move it away from any VHS connotations implied by the Digital-S name.

Data Rate: 50 Mbps - Compression Ratio: 3.3:1 - Color Sampling: 4:2:2

Digital Betacam (DigiBeta): DigiBeta has become the de facto standard format for high- end digital production, and has replaced BetaSP in environments that can afford to upgrade. It has high data rate and very light compression. Like other Beta formats, it is manufactured by Sony.

Data Rate: 90 Mbps - Compression Ratio: 2:1 - Color Sampling: 4:2:2

D-2, D-3: These two formats are essentially the same signal, the only difference is that D-2 records on a ¾" tape while D-3 uses a ½" tape. These formats  are only used in high end production environments, such as at large broadcast stations. D-2/D-3 is a composite format. Composite is usually seen as low quality, yet here the signal is sampled so finely that it is still a very high quality signal.

Data Rate: 143 Mbps - Uncompressed - Color Sampling: 4:0:0 (composite)

D-5: Another extremely high-end uncompressed format. It is supported by Panasonic. D-5 machines can play D-3 tapes.

Data Rate: 170 Mbps - Uncompressed - Color Sampling: 4:2:2

D-1: Ultra high-end. D-1 is so expensive that it even many high-level productions don't use it because of its cost. Its data rate is a whopping 270 Mbps, over ten times that of DV25. It also can record an alpha channel for transparency and keying (this is signified by the extra 4 at the end of the color sampling stat).

Data Rate: 270 Mbps(!) - Uncompressed - Color Sampling: 4:2:2:4

D-6: D-6 is a HDTV signal recorded on a D-1 tape.

Television Transmission schemes:

TV Broadcast concerns both digital and analog systems and includes systems like DVB, ATSC, DSS, NTSC, and PAL.

DVB

Digital Video Broadcasting (DVB) is a transmission scheme based on the MPEG-2 video compression / transmission scheme and utilising the standard MPEG-2 Transmission scheme.

DVB provides superior picture quality with the opportunity to view pictures in standard format or wide screen (16:9) format, along with mono, stereo or surround sound. It also allows a range of new features and services including subtitling, multiple audio tracks, interactive content, multimedia content - where, for instance, programs may be linked to world wide web material. The DVB system is based on a generic transport system which does not impose any restriction on the type of material being sent.

ATSC

The ATSC standards are intended to replace the NTSC system used mostly in North America. The high definition television standards under the ATSC regime produce wide screen 16:9 images up to 1920×1080 pixels in size.

The ATSC system supports a number of different display resolutions, aspect ratios, and frame rates. The different resolutions can operate in progressive scan or interlaced mode.

ATSC signals are designed to use the same 6 MHz bandwidth as NTSC television channels. Once the video and audio signals have been compressed and multiplexed, the transport stream can be modulated in different ways depending on the method of transmission.

NTSC

NTSC is the analog television system used with the M format which consists of 29.97 interlaced frames of video per second. Each frame consists of 484 lines out of a total of 525 (the rest are used for sync, vertical retrace, and other data such as captioning).

The NTSC system interlaces its scanlines, drawing odd-numbered scanlines in odd-numbered fields and even-numbered scanlines in even-numbered fields, yielding a nearly flicker-free image at its approximately 59.94 hertz (nominally 60 Hz/100.1%) refresh frequency.

There is a large difference in framerate between NTSC and film, the latter consisting of 24.0 frames per second whereas NTSC is displayed at approximately 29.97 frames per second.

An NTSC television channel as transmitted occupies a total bandwidth of 6 MHz.

One odd thing about NTSC is the Cvbs (Composite vertical blanking signal) is something called "setup." This is a voltage offset between the "black" and "blanking" levels. Cvbs is unique to NTSC.

PAL

PAL, short for Phase Alternating Line, is a colour encoding system used in broadcast television systems.

A quadrature amplitude modulated subcarrier carrying the chrominance information is added to the luminance video signal to form a composite video baseband signal (CVBS) in case of PAL. The frequency of this subcarrier is typically 4433618.75 Hz (approximately 4.43 MHz) for PAL

SECAM 

SECAM is an analog color television system first used in France.

SECAM differs from the other color systems by the way the R-Y and B-Y signals are carried.

First, SECAM uses frequency modulation to encode chrominance information on the sub carrier.

Second, instead of transmitting the red and blue information together, it only sends one of them at a time, and uses the information about the other color from the preceding line. It uses a delay line, an analog memory device, for storing one line of color information. This justifies the "Sequential, With Memory" name.

 




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