Interactive media I AudioVideo Data .


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Multimedia I (Audio/Video Data). CS423, Fall 2007 Klara Nahrstedt/Sam King. Administrative . SVN Students need to follow the instructions here  https://agora.cs.uiuc.edu/display/tsg/Subversion+Service MP4 – 10% of the class grade. Video on Demand. Video On Demand: (a) ADSL vs. (b) cable.
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Mixed media I (Audio/Video Data) CS423, Fall 2007 Klara Nahrstedt/Sam King

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Administrative SVN Students need to take after the directions here  https://agora.cs.uiuc.edu/show/tsg/Subversion+Service MP4 – 10% of the class review

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Video on Demand Video On Demand: (an) ADSL versus (b) link

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Multimedia Files A motion picture may comprise of a few documents

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Multimedia Issues Analog to advanced Problem: should be adequate to ears or eyes Jitter Require high information rate Large stockpiling Compression Require ongoing playback Scheduling Quality of administration Resource reservation

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Audio Sound is a ceaseless wave that goes through the air. The wave is comprised of weight contrasts.

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How would we hear sound?

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Basic Sound Concepts Frequency speaks to the quantity of periods in a moment (measured in hertz, cycles/second) Human listening to recurrence go: 20 Hz - 20 kHz (sound), voice is around 500 Hz to 2 kHz. Plentifulness of a sound is the measure of relocation of the gaseous tension wave from its mean.

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Computer Representation of Audio Speech is simple in nature and it is changed over to advanced frame by a simple to-computerized converter (ADC). A transducer changes over weight to voltage levels. Change over simple flag into an advanced stream by discrete inspecting Discretization both in time and abundancy (quantization)

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Audio Encoding (1) Audio Waves Converted to Digital electrical voltage input test voltage levels at interims to get a vector of qualities: (0, 0.2, 0.5, 1.1, 1.5, 2.3, 2.5, 3.1, 3.0, 2.4,...) A PC measures the plentifulness of the waveform at customary time interims to deliver a progression of numbers ( tests ). The ADC procedure is represented by different variables, for example, test rate and quantization : double number as yield

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Audio Encoding (2) Sampling Rate : rate at which a consistent wave is examined (measured in Hertz) Examples: CD standard - 44100 Hz, Telephone quality - 8000 Hz The sound business utilizes 5.0125 kHz, 11.025 kHz, 22.05 kHz, and 44.1 kHz as the standard inspecting frequencies. These frequencies are upheld by most solid cards. How frequently do you have to test a flag to abstain from losing data?

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Audio Encoding (3) Nyquist Sampling Theorem : If a flag f(t) is examined at standard interims of time and at a rate higher than double the most elevated critical flag recurrence, then the examples contain all the data of the first flag. Case: CD\'s real inspecting recurrence - 22050 Hz, Due to Nyquist\'s Theorem - examining recurrence is 44100Hz.

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Audio Encoding (4) The best-known method for voice digitization is Pulse-Code Modulation (PCM) . Voice 4000 Hz What is the PCM examining rate? PCM gives simple examples which must be changed over to computerized representation. Each of these simple specimens must be allocated a double code. Every specimen is approximated by being quantized as clarified next.

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Audio Encoding (5) Quantization (test exactness) : the determination of a specimen esteem. Tests are regularly put away as crude numbers (direct PCM arrange) or as logarithms (u-law or A-law) Quantization relies on upon the quantity of bits utilized measuring the stature of the waveform Example: 16-bit CD quality quantization brings about more than 65536 qualities

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Audio Formats (1) Audio Formats are portrayed by the specimen rate and quantization Voice quality: 8-bit quantization, 8000 Hz u-law mono (8kBytes/s) 22 kHz 8-bit straight mono (22 kBytes/second) and stereo (44 kBytes/s) CD quality 16-bit quantization, 44100 Hz direct stereo (176.4 kBytes/s = 44100 specimens x 16 bits/test x 2 (two channels)/8000)

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Audio Formats (2) Available organizations on SUN au - Sun File Format wav - Microsoft RIFF/waveform Format al - Raw A-law Data Format u - Raw u-law Data Format snd - NeXT File Format Available configurations on Microsoft-Windows-based frameworks ( RIFF positions): Waveform sound record design for computerized sound equipment MIDI document organize for standard MIDI documents Audio Video Interleaved (AVI) Indeo document arrange

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Audio Formats (3) RIFF (Resource Interchange File Format) shapes the premise of various document groups. RIFF (comparatively to TIFF - Tagged Image File Format) is a labeled document organize. Labels permit applications fit for perusing RIFF records to peruse RIFF documents by another application, thus the word trade in RIFF. Different Formats/Players - RealPlayer 7 (Windows NT) with RealAudio, MP3 (MPEG Audio Layer 3) sound, Midi players; MP3 players (MP3.com)

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Video Encoding (1)

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Video (Color) Encoding (2) During the checking, a camera makes three signs: RGB (red, insatiability and blue) signals. For similarity with highly contrasting video and in view of the way that the three shading signs are exceedingly connected, another arrangement of signs of various space are produced. The shading frameworks compare to the principles, for example, NTCS, PAL, SECAM (traditional frameworks).

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Video Encoding (3) For transmission of the visual flag we utilize three signs: 1 luminance (shine essential flag) and 2 chrominance (shading signals). In NTSC flag the luminance and chrominance signs are interleaved; The objective at the recipient is : (1) isolate luminance from chrominance parts, and (2) stay away from impedance between them (cross-shading, cross luminance)

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Image Formats (1) Important Parameters for Captured Image Formats : Spatial Resolution (pixels x pixels) Color encoding (quantization level of a pixel: e.g., 8-bit, 24-bit) Examples: `SunVideo\' Video Digitizer Board permits pictures of 320 by 240 pixels with 8-bit dim scale or shading determination. For an exact exhibition of picture fundamental ideas attempt the program xv which shows pictures and permits to appear, alter and control the picture attributes.

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Image Formats (2) Important Parameters for Stored Image Formats : Images are put away as a 2D exhibit of qualities where every esteem speaks to the information connected with a pixel in the picture (bitmap or a shading picture). The put away pictures can utilize adaptable arrangements, for example, the RIFF (Resource Interchange File Format). RIFF incorporates organizations, for example, bitmats, vector-representations, livelinesss, sound and video. At present, most utilized picture stockpiling arrangements are GIF (Graphics Interchange Format), XBM (X11 Bitmap), Postscript, JPEG (see pressure part), TIFF (Tagged Image File Format), PBM (Portable Bitmap), BMP (Bitmap).

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Video Format (1) NTCS (National Television Systems Committee) TV Format (USA TV Standard) Analog video design Color transporter 4.429 MHz; invigorate rate 30 Hz (29.92Hz); 4.2 MHz for luminance, 1.5 MHz for eac of the two chrominance stations Resolution: 833x635 picture components Refresh Rate: 30 Hz Aspect Ratio: 4:3 Interlaced organization : Each edge is made out of two sequential fields, each containing a large portion of the checking lines of a photo, which are examined and exhibited in joined mode.

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Video Format (2) Digital Video Format Video Digitizer - is a simple to-advanced converter Important parameters coming about because of a digitizer: computerized picture determination (stature x width) in pixels quantization (bits per pixel) outline rate (outlines every second) Examples: Parallax XVideo 640x480 pixels spatial determination; 24 bits for each pixel determination (16777216 shades of dim or shading) 20 fps; if the picture determination is 320x240 pixels then this video board can give even 30 fps. Yield of computerized video goes for the most part to raster shows which have vast video RAM recollections. These showcases use for presentation of shading frameworks the Color Look Up Table (lut).

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Video Formats (2) High Definition TV (HDTV) Research on HDTV began in Japan 1968 Current TV standard Resolution: twice the same number of flat and vertical segments and lines than customary frameworks (NTSC) Two determination frameworks High 1440 Level with 1,440x1,152 pixels High Level with 1,920x1,152 pixels Frame rate: 50 or 60 outlines for each second Aspect Ratio: 16:9 Interlaced and additionally dynamic filtering designs Conventional frameworks utilize joined (shift of examining lines) arrange HDTV like PC presentations, utilizes dynamic checking

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Digital Transmission Bandwidth prerequisites for Images : Raw Image Transmission Bandwidth:= size of the image:= spatial determination x pixel determination; Compressed Image Transmission Bandwidth: = relies on upon the pressure plot (e.g., JPEG) and substance of the picture; Symbolic Image Transmission bandwidth:= size of the guidelines and factors conveying representation primitives and properties. Transfer speed Requirements for Video : Uncompressed Video Bandwidth:= picture estimate x outline rate; Compressed Video Bandwidth:= relies on upon the pressure plot (e.g., Motion JPEG, MPEG) and substance of the video (scene changes).

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Digital Transmission Bandwidth Example: Assume the accompanying video attributes - 720,000 pixels for every picture (outline), 8 bits for each pixel quantization, and 60 outlines for every second edge rate. The Video Bandwidth := 720,000 pixels for each edge x 8 bits for every pixel x 60 fps which brings about HDTV information rate of 43,200,000 bytes for every second = 345.6 Mbps When we utilize MPEG pressure, the data transfer capacity goes to 34 Mbps mind some misfortune in picture/video quality.

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Summary Audio and Video Encoding standards are essential, set the reason for digitization Different Digital Audio, Image and Video Formats, very little institutionalization crosswise over mainlands/nations, subsequently hard to construct media frameworks Multimedia frameworks are behind different frameworks, for example, web frameworks, lattice frameworks, working frameworks, … because of the vast space in sound and video groups.

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