c1_audio&video basic.ppt

Prepared by: AQ First Prepared on:1st September 2007 Last Modified on: -n- Quality checked by: -n-

Copyright 2007 Asia Pacific University College of Technology and Innovation

Chapter 1:Analysis of technical elements in relation toanalogue, digital film and audio production.

Digital Audio and Video(CT018-3-2)

Digital Audio and Video (CT018-3-2) Analysis of technical elements in relation to analogue, digital film and audio production

Topic & Structure of the lesson

• Video basics– Analog and Digital Video – Interlacing and Progressive Scan – Video Standards– Video Resolution– Native Aspect Ratio– Pixel Aspect Ratio– Videotape Formats – VideotapeTracks


Learning Outcomes

At the end of this lecture YOU will be able to:

• Demonstrate an awareness of fundamental knowledge of digital video.

• Discuss the types of digital video and its format.


Key Terms you must be able to use

If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams:

• Analogue and Digital Video• Standards and Resolutions• Native Aspect Ratio


Analogue and digital video

Analog Video:• The original video recording method that

stores continuous waves of red, green and blue intensities.

• In analog video, the number of rows is fixed.

• There are no real columns, and the maximum detail is determined by the frequency response of the analog system.



Analog Video: components• Component video - each primary is sent as a separate video

signal. – The primaries can either be RGB or a luminance-

chrominance transformation of them.– Best color reproduction – Requires more bandwidth and good synchronization of

the three components • Composite video - colour (chrominance) and luminance

signals are mixed into a single carrier wave. Some interference between the two signals is inevitable.

• S-Video (Separated video, e.g., in S-VHS) a compromise between component analog video and the composite video. It uses two lines, one for luminance and another for composite chrominance signal.



Digital Video:• Digital video cameras come in two different

image capture formats: interlaced and progressive scan.

• Interlaced cameras record the image in alternating sets of lines: the odd-numbered lines are scanned, and then the even-numbered lines are scanned, then the odd-numbered lines are scanned again, and so on.

• One set of odd or even lines is referred to as a "field", and a consecutive pairing of two fields of opposite parity is called a frame.


Interlacing• Interlacing was used to reduce the amount of

information sent for each image. • By transferring the odd-numbered lines, followed

by the even-numbered lines• So if you capture AB frame, odd lines come from

picture A and even lines from picture B, the two pictures have a time shift of 1/24 second. Therefore object moving have their odd lines and even lines shifted.

Interlacing and Progressive Scan


interlace

scenes change on an AB or BC frame



• Progressive scanning is any method for displaying, storing or transmitting moving images in which all the lines of each frame are drawn in sequence.



• Although video format is the same throughout the World, the video standard or electronic signal that is recorded on the cassette varies from country to country.

• The three most common video standards used are NTSC, PAL and SECAM.

Video Standards


NTSC (National Television Systems Committee) • A standard for analog television transmission in

the United States and many other counties worldwide

• NTSC provides 482 lines of vertical resolution and 16 million colours.

• NTSC delivers 29.97 frames per second

• NTSC has an aspect ratio of 4:3.

Video Standards


PAL(Phase Alternating Line)• Phase Alternating Line (PAL) is the television

standard popular in Europe and Asia • PAL uses a screen resolution of 720 x 576 pixels

and has a refresh rate of 25 frames per second. • Deliver a better quality picture as compared to

NTSC.SECAM (Sequential Color with Memory)• SECAM use in France. • Similar with PAL standard (25fps) but runs on

625 lines/frame.

Video Standards


• It is common to see video resolutions of 720 × 480 or 1920 × 1080.

• However, those are just the number of horizontal samples and vertical scan lines, and do not necessarily convey the amount of useful information.

• For example, an analog video signal can be sampled at 13.5 MHz to generate 720 samples per line.

• Sampling the same signal at 27 MHz would generate 1440 samples per line. However, only the number of samples per line has changed, not the resolution of the content.

Video Resolution


• Therefore, video is usually measured using “lines of resolution”. In essence, how many distinct black and white vertical lines can be seen across the display?

• This number is then normalized to a 1:1 display aspect ratio (dividing the number by 3/4 for a 4:3 display, or by 9/16 for a 16:9 display).

Video Resolution


Standard Definition• Standard definition video is usually defined as

having 480 or 576 interlaced active scan lines, and is commonly called “480i” and “576i” respectively.

• For a fixed-pixel (non-CRT) consumer display with a 4:3 aspect ratio, this translates into an active resolution of 720 × 480i or 720 × 576i.

• For a 16:9 aspect ratio, this translates into an active resolution of 960 × 480i or 960 × 576i.

Video Resolution


Enhanced Definition• Enhanced definition video is usually defined as having

480 or 576 progressive active scan lines, and is commonly called “480p” and “576p” respectively.

• For a fixed-pixel (non-CRT) consumer display with a 4:3 aspect ratio, this translates into an active resolution of 720 × 480p or 720 × 576p.

• For a 16:9 aspect ratio, this translates into an active resolution of 960 × 480p or 960 × 576p.

• The difference between standard and enhanced definition is that standard definition is interlaced, while enhanced definition is progressive.

Video Resolution


High Definition• High definition video is usually defined as having 720

progressive (720p) or 1080 interlaced (1080i) active scan lines. For a fixed-pixel (non-CRT) consumer display with a 16:9 aspect ratio, this translates into an active resolution of 1280 × 720p or 1920 × 1080i, respectively.

• However, HDTV displays are technically defined as being capable of displaying a minimum of 720p or 1080i active scan lines.

• They also must be capable of displaying 16:9 content using a minimum of 540 progressive (540p) or 810 interlaced (810i) active scan lines.

Video Resolution


Native Aspect Ratio

• The concept of aspect ratio is the fractional relation of the width of a video image compared to its height.

• The two most common aspect ratios in home video are 4:3 (also known as 4x3, 1.33:1, or standard) and 16:9 (16x9, 1.78:1, or wide-screen )

• All the older TVs and computer monitors had the squarish 4:3 shape. It’s 33 percent wider than it was high.

• On the other hand, 16:9 is the native aspect ratio of most HDTV programming; it is 78 percent wider than it is tall, or fully one-third wider than 4:3.


Native Aspect Ratio

Native Aspect Ratio of 4:3 Native Aspect Ratio of 16:9


Pixel Aspect Ratio

Pixel Aspect Ratio• The frame size of a NTSC standard definition

DV frame is 720 x 480 pixels. • However, based on these numbers, its width to

height ratio is 720:480, i.e. 3:2. It does not match the frame aspect ratio quoted above; it is neither 4:3 nor 16:9.

– What is missing here?


Pixel Aspect Ratio

• In digital image editing, images use square pixels by default. However, some video formats use non-square pixels to make up the frame.

• The shape of the pixel can be described by an attribute called pixel aspect ratio. It is the ratio of a pixel's width to its height.

• For a square pixel, its pixel aspect ratio is equal to 1. A pixel aspect ratio of less than 1 depicts a tall pixel while a pixel aspect ratio of greater than 1 depicts a wide pixel.

• For standard DV, the pixel aspect ratio is 0.9 while the pixel aspect ratio for the wide-screen DV is 1.2.

• The pixel aspect ratio for HDV 720p is 1.0 and HDV 1080i and 1080p is 1.333.


Pixel Aspect Ratio

For pixel aspect ratio = 0.9,• width : height = 720 x 0.9 : 480 = 648 : 480 4 : 3≅For pixel aspect ratio = 1.2,• width : height = 720 x 1.2 : 480 = 864 : 480 16 : 9≅

For HDV, its frame aspect ratio is 16:9.• For 720p, pixel aspect ratio = 1.0,• width : height = 1280 x 1.0 : 720 = 16 : 9

For 1080i and 1080p, pixel aspect ratio = 1.333,• width : height = 1440 x 1.333 : 1080 = 16 : 9


• Super VHS, a full-size format with resolution similar to that of HI-8, is virtually out of the consumer camcorder market.

• This format is used for videographers mostly for shooting and editing.

• The S stands for super, as the resolution jumps from the VHS standard of 250 lines to around 400 lines.

• Unfortunately, most VCR's will not play a super VHS tape and has to be transferred to a regular VHS format in order for it to be viewed on non-S-VHS machines.

• Camcorder users who prefer to insert their video tapes directly into their VCR may want to consider using the VHS/C compact format. VHS/C is regular VHS video tape wound into a smaller cartridge.

Video Format


• Since the cartridge is smaller, the length of VHS/C tape is limited to a maximum of 45 minutes - though longer times can be achieved using a long play mode, the quality usually is poor compared to the faster (sp) speed.

• The compact tapes are inserted into your VCR using a cassette adapter which comes with each VHS/C camera. Once inserted, the tape plays just like any other VHS tape you’ve ever used.

Video Format


• VHS/C and full size VHS record at a slightly lower resolution than 8MM.

• A standard T-120 VHS tape has a recording time of 2 hrs, and the resolution is 250 lines.

• Their appeal, or course, is the convenience of easy playback.

• The large VHS camcorders are almost a thing of the past at this point.

• There are still a few models available, but their substantial size and weight make them a difficult sell against smaller camcorders.

Video Format


• 8MM camcorders often have many of the best features found in higher priced HI-8 units, including image stabilisation, strong optical and digital zooms and innovative special effects.

• Regular 8mm tapes are the exact size and shape as their HI8 counterparts, but record video at a lower resolution level, and therefore, are less expensive than camcorders which product better image quality.

• 8mm can record for up to 2 hours and has a resolution of 270 lines.

• HI-8 and regular 8MM tapes cannot be put into a standard VHS video recorder, a common misconception. There are no adapters to achieve this.

• They must be transferred to VHS in order to be viewed on a regular VCR.

Video Format


• HI-8 camcorders record their signal at about 400 lines of resolution, slightly less than Mini DV, but substantially higher than 8mm or regular VHS formats.

• Most often, HI-8 camcorders record sound in hi-fi stereo. Slight quality loss is suffered when copying or editing from HI-8, but a better than average image is maintained.

• Tapes from HI-8 camcorders generally must be played using the camera as the source, which means the user often must connect cables to their television or VCR.

• HI-8 tapes can be bought in 30, 60, and 120-minute lengths.

Video Format


• DIGITAL8 is a format that is far superior to HI-8 or 8MM.

• Sony was the first to introduce this format and has done a great job.

• It is backwardly compatible, meaning that the new Digital8 camcorders and VCR's will also play your 8MM and HI-8 tapes.

• No special tapes to record in Digital8 is required. A regular 8MM or HI-8 tape will record up to 60 minutes of digital video and audio.

• Because of the design, using regular tapes is not a problem, but it uses twice as much tape. A 2 hour HI-8 or 8MM tape will record 60 minutes when done in the Digital mode and records up to 500 lines of resolution

Video Format


• Mini DV tapes are the smallest of the video formats. • They take and maintain crystal clear images because of

the nature of a digital format. • Editing enthusiasts benefit from Mini DV as well, since

copying between two units is done with no quality loss.

• Mini DV tapes are available in 30, 60,63 and 80 minute lengths.

• Digital camcorders have the highest resolution of all the camcorders, starting at 500 lines.

Video Format


Videotape Tracks

The standard VHS put four separate tracks on the tape;• Video track

– Containing the picture information– The video track takes up about three-quarters of the

space on a videotape. It is recorded as a series of diagonal lines by one or two rapidly spinning tape heads on the head drum of the VCR

• Two sound track– Containing the sound information– Analog audio information is generally recorded on

longitudinal tracks near the edge of the tape. Because of the demand for stereo audio for keeping the sound separated from monophonic sound.


• Control track– The sync pulse synchronise the tape speed and the

rotation speed of the record heads so that tape made on similar machine can be played back without picture breakups

– Some VTRs have a sync track (reserving the control track for editing purposes.

• Time Code Track– The time code address track is used to record cuing

information for editing. This information may consist of audio or visual time/frame identification.

Videotape Tracks


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