Wednesday 4 December 2013

Understanding Video Technology

Ash Mosdell - Media Production Level 3 Year 1
Unit 21: Understanding Video Technology
Analogue and Digital Camera Technology
Analogue camera technology was introduced in the late 19th century, and was the original method of moving picture technology. The first moving picture cameras used a roll of film to capture frames in sequence. The film used exposure to light to capture the images. 

Digital camera technology was introduced in the late 70s, with several types of video production equipment with digital internals. Digital video was first introduced commercially in 1986 with the Sony D1 format. Digital video technology is now an extremely important aspect in every day modern life. 
Camera Functions
  • White Balance 
Changing the white balance changes the colour of a shot. When shooting indoors, the camera will need to compensate for the cooler or warmer colours. 
Auto White Balance (AWB) is a mode which is set to make the camera automatically choose the best setting for the current lighting situation, and generally does a pretty good job. But the camera doesn't know exactly how you want the shot to look, so a manual white balance setting is preferred. When shooting indoors, the type of light bulb that is being used can make the room either seem warmer or cooler. Tungsten bulbs make the colour of the room seem a lot warmer, whereas Fluorescent bulbs make the room seem a lot cooler. By selecting Tungsten and Fluorescent modes on a camera, you are able to compensate for the warmer and cooler colours, as the camera adjusts the colour levels. 
Custom White Balance allows you to tell the camera which area in the scene is supposed to be white. By holding a white piece of paper in front of the subject being filmed, the camera can get an accurate view of true white. Once the camera is set in the custom white balance, it will not change until you set another custom white balance or change it to any of the other white balance modes.
  • Focus
Changing the focus allows you to set what exactly is seen as sharp, and what is blurry in a shot. Auto Focus is the standard setting most cameras have. If Auto Focus is set, then the camera will automatically focus on the subject directly in front of the camera, or whatever the camera is pointing at. If the camera is set to Manual Focus, then the camera operator is able to change what is in focus manually by turning the focus ring on the lens. By having different things in the shot in and out of focus, the camera operator is able to put the attention on one particular subject. Manual focus can be used for a racking focus, which is when the focus moves from one subject to another, with one subject behind the other. 

Manual Focus Tutorial Video 
  • Exposure
Exposure is the amount of light that reaches the sensor in a camera, determined by the aperture. Aperture is a hole through which light travels.



Amateur and professional recording formats.
A very widely used example of an amateur recording format is the VHS, a magnetic tape based, analogue solid state. The VHS was used to record Television by using a Television recorder bo, which connected to the tuner. The quality of the VHS video varied from bad to not good, depending on the quality of the television signal being received by the TV tuner. A more modern way of home recording is using the digital DVD and Blu-ray disc format. The disc recording is made possible by using a Digital DVD or Blu-ray recorder. It connects to the TV Tuner or HDTV digital box. It is a lot higher visual and audio quality than VHS. A profession recording format is Betacam, which was developed by Sony in 1982, which came in both analogue and digital formats. 
The Digital Betacam format records a 3-1 compressed digital component video signal sampling in PAL at 720x576 resolution at a bitrate of 90 Mbit/s plus four channels of uncompressed 48kHz encoded digital audio.
Solid State recording format is SD (Solid State) card which uses flash memory technology. SD technologies have been implemented in more than 400 brands and more that 8,000 models. The capacity of SD cards can range from 1MB to 256GB.
The first video technology used cathode ray tube (CRT) television systems. The first video recorder was created in 1951, which used magnetic video tape on which the electrical  impulses  were  transferred.  

Solid State recording format



  •  Television Standards
PAL (Phase Alternating Line) is a colour encoding system used in analogue television broadcasting systems in most countries (primarily the UK, Austrailia, Brazil, and a majority of Asia and Africa. The resolution of broadcast is 576i. In the 1950s, Europeans countries were planning to introduce colour television, but wanted to overcome NTSC's weaknesses. The PAL and SECAM standards were created. The goal of PAL was to provide a colour television standard which had a picture frequency of 50 hertz, and overcoming the problems faced with NTSC. The signal of the subcarrier is 4.43361875 MHz. PAL has 576 visible lines compared with 480 lines with NTSC, which leaves PAL with 20% higher resolution (768 x 567). PAL uses a frame rate of 60i (half frames per second) or 30p. 

NTSC (National Television System Committee) is another analogue television system which is used primarily in the USA, Canada and a majority of South America. The typical resolution of NTSC is 640x480. The first colour standard of NTSC was created in 1953. After nearly 70 years of use, the majority of NTSC transmissions were turned off in 2009 and 2011. The signal of the sub carrier is 3.579545 MHz. 

SECAM (Sequential Colour with Memory) is also an analogue television system which was first used in France. It is the first colour television standard in Europe, with development starting in 1956. The first proposed system was a system named 'SECAM I' in 1961. The system uses the existing monochrome television receivers, but adds a second signal which carries the colour information. This is called chrominance. The signal of the sub carriers are 4.41 MHz and 4.25 MHz. SECAM typically displays half the vertical resolution of NTSC. 
  • Aspect Ratios
4:3 is the traditional television aspect ratio standard for video. It has been used since moving picture cameras (video cameras) were invented. 4:3 is the aspect ratio of 35mm films. Nowadays the aspect ratio of 4:3 is becoming less of a standard for television, and modern technology is moving on to the more favorable aspect of 16:9/16:10. 

16:9 is the standard format of HDTV, digital television, and PALplus. 16:9 is the only widescreen aspect ratio to be supported by the DVD standard. Even wider ratios can be achieved (in the DVD standard) by adding black bars the the image. 
1.85:1 is the UK and US widescreen standard for theatrical film, and was introduced by Universal Pictures in May, 1953. 


 2.39:1 is the aspect ratio of current anamorphic widescreen theatrical showings. It is a current cinema standard. Below is a film in the aspect ratio of 2.39:1, displayed on a screen of 16:9 aspect ratio (hence the black bars at the top and bottom). 


  • Video Signals 
DVI (Digital Visual Interface) is a video display interface developed by the DDWG (Digital Display Working Group). It is used to connect the video source to a display such as a monitor. It allows a maximum resolution of 1920 x 1080 at 60Hz displayed in 16:9 (1915 x 1436 at 4:3 aspect ratio).


HDMI (right) and DVI (left)

HDMI (High Definition Multimedia Interface) is a compact interface which carries uncompressed audio and video data. It carries uncompressed video and uncompressed/compressed audio from the source device to a compatible computer monitor, digital video projector or HD television. HDMI connections allow up to 8 channels of either uncompressed or compressed digital audio. HDMI 1.3 can allow for a maximum resolution of 2560x1600, which is possible because of the increased pixel clock rate to 340MHz. 


HDTV (High Definition Television) provides up to five times as many pixels as SDTV (Standard Definition Television). The maximum resolution which HDTV can transmit is 1080p (the standard HD resolution of 1920x1080p). (1080 pixels in height and 1920 pixels in width).
The 'p' stands for progressive scar, while 'i' stands for interlaced. For example, 1080p will be alot higher picture quality because it draws all the lines in a frame in sequence. 1080i draws only the odd lines in each frame, halving the quality. 


  • Broadcasting Systems
Terrestrial Television is a type of television broadcasting. It does not involve either satellite transmission or cables. Transmission is done by using radio waves, and antennas. In North America it is referred to as OTA (over-the-air television) and requires a tuner to view content. The first non-terrestrial way of transmitting television was in the 1960s and 70s by using satellites. Nowadays, analog terrestrial television is under threat from cable and satellite television, as well as the distribution of video and film content over the internet. 

Digital Television (DTV) is the transmission of audio and video by digitally processed and multiplexed signal. 

Internet Television is the distribution of television content, often in an 'on-demand' format, enabled by the use of the internet. It uses video streaming, and is used by many broadcasters.

  • Domestic, Professional and Broadcast differences?

  • Audio Equipment
Radio mics are battery powered microphones which are small and portable, lightweight and discrete. The mic itself is attached to a long wire which attaches to a battery pack and transmitter which is small and light enough to comfortably fit into a subject's pocket. Radio mics can be especially uselful when the individual is in a crowded area with alot of surrounding noise, it allowes the subject to be the main thing that is heard. The radio mics are connected directly to the cameras so that further syncing of audio and video later on is not required. 


Directional mics concentrate the audio which is being recorded in the area that they are being pointed at. Directional mics are long and thin, so it is easy to see where the mic is pointing when recording audio. The mics are usually used on the end of a boom pole, so that the sound operator can easily point the directional mic above a person, for example, without interrupting the shot. 


Voiceover mics eliminate any surrounding noise, which can be critical in a voiceover. Any distracting background noise can distract the viewer from what the narrative is saying, which can hinder the production. The voiceover mics are positioned infront and slightly above the person's head. The position is adjustable to get optimal sound. 


Audio Levels are vital to any sound recording. If the levels are set too loud, it can cause the audio to peak, which may cause distortion later on in the production stage. If the levels are set too quietly when recording, the sound quality will be negatively affected when it comes to try and correct it (louder). It can cause noisy and bad quality audio. 

  • Export Formats
AVI (Audio Video Interleaved) is a multimedia format created by Microsoft in 1992. AVI files contain both audio and video data. AVI is now somewhat outdated, and has some limitations, in that it cannot select the right aspect ratio automatically and that it cannot contain specific types of variable bit rate data reliably. AVI files can support multiple streaming audio and video, but it is rarely used.

DVD (Digital Versatile Disc) is an optical disc format, developed by Philips, Sony, Toshiba and Panasonic in 1995. DVDs have a much larger storage capacity than CDs while having the same physical dimensions. Data on DVD-ROM discs can only be read. DVD-R and DVD+R can be recorded onto once, then function as DVD-ROM. DVD-RW and DVD+RW discs can be recorded onto and erased multiple times. The most common type of DVD is the 4.7GB, which has a single-sided, single layer format. Double layer, and double sided DVDs have a higher capacity, ranging from 8.5GB - 17.08 GB. The weight of one DVD is 16g. 


H.264 (H.264/MPEG-4 AVC) is a video compression format, and is one of the most commonly used formats for recording, compression and distribution of video content. H.264 is best known as being one of the codec standards for Blu-ray discs. It is widely used by internet streaming sources, such as YouTube, Vimeo and the iTunes Store. It is possible to create lossless H.264 video. AVCHD uses H.264. XAVC is a recording format designed by Sony that uses level 5.2 of the H.264 format which is the highest level supported. XAVC can support 4K resolution (4096 x 2160) at up to 60 frames per second. Canon and Nikon DSLRs also use H.264.

MPEG is a working group of experts, that set the standards of audio and video compression and transmission. MPEG has standardized the following compression formats: MPEG-1 was the first MPEG compression standard for audio and video, commonly limited to about 1.5 Mbit/s. It was designed so that video and sound could be encoded into the bitrate of a CD. It can be used for low-quality video on DVD video. MPEG-2 is considered important, because is has been chosen as the compression scheme for over-the-air television signals on a variety of networks. It has also been chosen on some satellite networks and digital cable networks, SVCD and DVD video. MPEG-3 standardized scalable and multi-resolution compression, was intended for HDTV compression but was found redundant. MPEG-4 is more efficient than MPEG-2, and moves closer to computer graphics application. MPEG-4 supports DRM (Digital Rights Management). 


Digital Data Transfer

IEEE 1394 interface (AKA. Firewire) is a serial bus interface standard for high-speed communications and real-time data transfer. It was developed by Apple, in the late 1980s and early 90s. It is comparable to USB, though USB has more market share. Firewire has a higher data transfer rate that USB 2.0, but lower than USB 3.0. 

 SD Card (Secure Digital) is a solid state recording format. An SD Card is a memory card which uses flash memory technology. SD technologies have been implemented in more than 400 brands and more that 8,000 models. The capacity of SD cards can range from 1MB to 256GB. They have particular advantages which include their small size, high capacity and high reliability thanks to their no moving parts (solid state) format. 
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