Digital Media exam 2 GGC

The letters "p" and "I" in 720p or 1080i

"i" means interlaced "p" means progressive this is used in high definition frame resolution through these three picture formats- 720p, 1080i, 1080p - the number designates the pixel height of the frame size, and the letter "p" and "i" specify the video's scan type-- progressive and interlaced

Television broadcast standards in the US (SECAM, PAL, NTSC, etc.)

(digital video resolution, color spaces, frame rate, influenced by analog TV broadcast standards) --NTSC- (u.s. National Television Systems Committee) used in North America, Japan, Taiwan, and parts of the carribean fps= 29.97 (color) or 30 (BnW) --PAL- (Phase Alternative Line) have encoded signals, it is used in Australia, New Zealand, and most of Western Europe and Asian countries, fps= 25 --SECAM - (Séquential Couleur avecc Mémoire) which translates as sequential color with memory. It is used in France, Soviet Union, and Eastern Europe. fps= 25

Progressive vs. interlaced methods of displaying video

(lines are traced across the screen one line at a time, from top to bottom) progressive scan- scans image from top to bottom in one pass Interlaced scan- scans the image in two passes: even-numbered lines first then odd-numbered lines second (the two fields in a frame are captured at a slightly different moment in time) this makes the video lag

decompression

- a compression video file must be decompressed before it is played - the decompression method or algorithm depends how it is originally compressed. - compression and decompression go together as a pair (Codec)

sound intensity/ decibels

- an objective measurement - can be measured with auditory devices - measured in decibles (dB) -higher intensity means higher sound 0 dB- threshold of hearing, minimum sound pressure level at which humans can hear a sound at a given frequency, does not mean zero sound intensity, does not mean absence of sound wave 120 dB- threshold of pain

Human hearing range

- higher frequency: higher pitch - human ear can hear sound ranging from 20 Hz to 20,000 Hz

Pixel aspect ration 1.2 (less than example 0.9)

- if an image is displayed incorrectly on a system of pixel aspect ratio of 0.9 the image looks slightly stretched vertically

Pixel aspect ration of 0.9 (greater than example 1.0)

- if an image is displayed incorrectly on a system of pixel aspect ratio of 1.0 the image looks slightly stretched horizontally

Pixel aspect ration 1.2 (less than example 1.0)

- if an image is displayed incorrectly on a system of pixel aspect ratio of 1.0 the image looks slightly stretched vertically

Pixel aspect ration 0.9 (greater than example 1.2)

- if an image is displayed incorrectly on a system of pixel aspect ratio of 1.2 the image looks slightly stretched horizontally

picel aspect ration of 1 (greater than example)

- if an image is displayed incorrectly on a system of pixel aspect ratio of 1.2 the image looks stretched horizontally

Pixel aspect ration of 1 (less than example)

- if an image is displayed incorrectly on a system of pixels aspect ration of 0.9 the image looks stretched vertically

Audio file size reduction

- reduce sampling rate-file size is reduced in the same proportion as the reduction of the sampling rate (if reduced file size will reduce the same amount) -reduce bit depth- same as above ( if minimize the bit depth the file size will reduce that much) -apply compression- use lossless or lossy (ex. MP3) -reduction of the number of channels- (reducing 2 stereo to 1 mono reduces file size by half

video file size reduction

-Reduce frame size because: you have less pixels for each frame -Reduce frame rate because: you have less frames -Video compression with high compression because: some data are discarded -Lower picture quality option because: some data are discarded (least used reducing bit depth not all video formats support lower bit depth,Reduce sampling rate, bit depth, and channel numbers of the audio)

image file size reduction

-Reducing the pixel dimensions (if reduce the pixels it reduces the file size the same number) -lowering bit depth- file size directly proportional -compression- reduction of bits

Types of compression (Spatial, Temporal, etc.)

-Spatial compression -Temporal compression -Lossless vs. Lossy compression -symmetrical and asymmetrical compression

bit depth

-bit depth of a digital audio is also referred to as resolution. - for digital audio, higher resolution means higher bit depth

Spatial compression

-compact individual frames as if they are independent digital images (algorithms: run-length encoding RLE, JPEG compression -Spatial compression is good for videos that contain large areas of solid colors such as cartoon animation -the disadvantages are less compressed, relatively large file size compared to other types of compression

Temporal compression

-exploits the repetitious nature of the image content over time and the possibility of predicting one frame from the other -Saving more information for selected frames; less compressed known as key frames -all other frames store only the difference from previous key frames, instead of the full frame -effective if the change between a frame and its previous key frame is small - good for videos that contain continuous motion and bad for video with frequent flicking and scene change (codecs used with Temporal are H.264 and Sorenson Video

MIDI

-is another method of storing music information (Musical Instrument Digital Interface) -it is a communications protocol, not a physical object, it defines the common interface for electronic digital musical instruments to communicate with computers or other instruments or devices containing microprocessors. it specifies the configurations of cables and cable plugs and the format of the data. -also MIDI keyboards are available to connect to a computer, MIDI requires a sound card

MPEG-4

-newest standard of MPEG family -different encoding approach from MPEG-1 and MPEG-2 -cover a wide range of data rate, low end of the data rate: video playback on mobile devices -high end of the data rate: HDTV, Handheld and portable game devices (Sony PSP)

Pixel aspect ratio - result of displaying ratio larger than 1 or smaller than 1 on a device with ratio of 1

-pixel aspect ration- it is the ratio of a pixel's width to its height video image will be distorted if it is displayed on a system with a different pixel aspect ration -standard format (720x 480/ 4:3) is 0.9 -wide-screen format (frame size: 720x480/ frame aspect ratio16:9) is 1.2 (pixel aspect ratio)

Streaming video

-play video as soon as enough data has arrived (streaming Quicktime, real video, window Media Video) - require a streaming server to stream video, allow saving several different compression levels on a video in a single life, the server chooses the compression level to match the speed of network connection, buffering: wait time depends on network speed

MPEG-2

-supports DVD-video, HDTV, HDV standards -for DVD video production: Export video into DVD MPEG-2 format -For HDV video production: Export video into HDV's MPEG-2 format

Omnidirectional vs. unidirectional microphones

-unidirectional- most sensitive to sound coming from the front, advantages: ignore noise coming from the rear (cardioid means unidirectional) -omnidirectional- sensitive to sound coming from all directions

MPEG-1

-video quality comparable to VHS -originally intended for web and CD-ROM playback -frames size up to 352 x 240 pixels -video format for VCD (VideoCD) before DVD became widespread

File extensions for video

.mov (audio-only, common compression methods: H.264, Sorenson Video, Animation; Mac and Windows) -avi (Intel, common compression methods: Microsoft RLE, Intel Indeo Video

.wma; .mp3;.wav file extensions

.wav- ( created by Microsoft, IBM) compressed/uncompressed, used by windows .mp3- (created by Moving Pictures, Experts Group) good compression rate with perceivably high quality sound, (used by Cross-platform) .wma- (created by window Media audio) orginally created by Microsoft

Frame rate for NTSC

29.97 Frame rate- how fast the pictures are captured, how fast the frames are played back is determined by frames per second

sampling rate/ cd quality

44,100 Hz (44,100 samples per second) -the more sample points, and thus larger the file size -44,100-Hz sampling rate, 16 bits, and stereo

What kind of code would you use to put audio on a web page?

HTML code <audio src= "media/demo.oga" controls></ audio>

Lossy vs. Lossless compression

Lossy compression- reduce data by discarding or altering some of the original data -has smaller file size than lossless, has lower picture quality, often try to maintain perceptual quality when deciding what data are to be discarded, discarded data cannot be recovered Lossless compression- preserve the original data but reduce file size by encoding the data specially -usually much larger file size than lossy compression -Example codecs: QuickTime Animation, planarRGB (set at the maximum quality setting)

Luminance and chrominance

Luminance- brightness chrominance- color or hue

MPEG

MPEG (Moving Picture Experts Group Committee who derives standards for encoding video, allow high compression)

Symmetrical and asymmetrical compression

Symmetrical compression- requires the same amount of time in compression and decompression Asymmetrical codec- amount of time to compress and decompress are significantly different (takes video longer to compress than decompress) - preferable: fast decompression so less wait time to play back the video

YIQ color model

Y: luminance component I and Q: chrominance components -used for NTSC broadcast

YUV color models

YUV- a color model that digital video uses to represent the color of each pixel Y: luminance (brightness) component U: a chrominance (color or hue) component V: a chrominance (color or hue) component -we can assign fewer bits to store the chrominance component, meaning smaller file size, used for PAL broadcast

waveforms

a waveform serves as a means for us to "see" the information that we hear by providing quantitive properties of a sound, such as its amplitude and frequency.

Data rate

amount of video data to be processed per second, also known as bit rate because it is measured in bits per second. -larger file size can have a low data rate if it is a long video -smaller file size can have a high data rate if it is a short video - data rate is related to the smoothness of the video playback

clipping

areas of the waveform where this occurs will looks chopped off and cause distortion of your recording

Compression

common video compressors H.264 and Sorenson Video 3 -compression- want to represent the same content by using less data - reduces file size, takes time, often takes more time for higher compression - compression and decompression go together as a pair (Codec)

Codec

compression and decompression always go together as a pair COmpression/ DECompression

Frame aspect ratio (4:3, 16:9) standard definition? HD? Wide format?

frame aspect ratio- the ratio of a frame's viewing width to height, not equivalent to ratio of the frame's pixel width to height. Ex. 4.3 is standard definition NTSC standard format Ex. 16.9 is standard definition NTSC wide-screen format, high definition digital video/ High-definition TV

podcast

is a collection of files available on a Web server. The files in a podcast are usually audio and video, but they also can be web pages, text, pdf, images, or any file type. each file is called an episode

loop music

is music that is created from short music clips that are repeated.usually loop seamlessly

Noise reduction/removal

noise reduction- useful for removing background noises such as: computer fan noise, hissing noise of the microphone (you select a segment that contains pure noise, the program performs a statistical analysis of the noise to generate a profile where it reduces the noise of the selected or whole audio (Adobe Audition) Noise removal- (audacity)

progressive download

play video as soon as enough data has arrived, does not require special servers EX. Quicktime fast start- created by saving the QuickTime movie as self-contained using Quicktime Pro

frequency

refers to the number of complete back-and-forth cycles of vibrational motion of the medium particles per unit of time. -Unit for frequency: Hz (Hertz) - 1 Hz = 1 cycle/second

Hertz (Hz)

unit for frequency and sampling rate

nyquist's theorem

we must sample at least 2 points in each sound wave cycle to be able to reconstruct the sound wave satisfactorily. In other words, the sampling rate of the audio must be at least twice that of the audio frequency-- called a Nyquist rate. So sampling rate of an audio that is higher will have audio with higher pitch

overscan

when a video is displayed on a television set, the edge areas of the picture may not be displayed within the viewing area. This is the area that is outside of the screen.