Multimedia by chenmeixiu

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									Lecture Outline - Multimedia


Multimedia                     Media used:
                                    Audio
                                    Video
                                    Animation
                                    Graphics
                                    Text
Problem                             Much of the real world multimedia is in analog form
                                    Computer must store data in digital form
                                    Computers use have limited storage and speed
Sampling                       Used to select parts of an analog signal that will allow the computer
                               to convert it to a digital value and store it.
                               (Analog-To-Digital Converter)
Sample Size                    How many divisions is the sample broken into?
                               8 bit recording allows 256 samples (-128 to 0 to +127)
                               16 bit recording allows 64K samples (-32K to +32K)
                               16 bit sound quality is many (256) times that of 8 bit sound quality
                               but only uses twice as much storage area.
Sample Rate                    How often is it sampled?
                               CD quality = 44KHz
                               Radio quality = 22KHz
                               Phone quality = 11KHz
Compression                    A method used to as much of the important information in
                               multimedia in as small a space as possible.
Storing Sound in files
WAV                            Sound file format – Most multimedia sound
                               Uses standard audio sampling
                               Relative large files
                                      Voice annotation – adding audio notes to documents etc.
                                      Microsoft Sound Recorder
                                      C:\Windows\SNDREC32.EXE
                                      Start/Programs/Accessories/Entertainment/Sound Recorder
                                      From with in Word:

                                      (Insert/Object/Create New/WAV)
MIDI                           Musical Instrument Digital Interface
                               Sound file format – used with most games
                               Uses more advanced method of storing sound
                                      Note Pitch
                                      Note Volume
                                      Note Length
                               Employees compression
                               Used by most synthesizes
                               Relatively smaller files



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Lecture Outline - Multimedia




Video
AVI                        Audio Video Interleave – Video file format
                           Video file
                           Supported by Video for Windows (Microsoft)
MOV                        Quick Time – Apple’s video file format
                           Video file
                           Runs on Mac’s and on PC’s
NTSC                       National Television Standards Committee
                           US standard TV signal
                           The NTSC standard for television defines a composite video
                           signal with a refresh rate of 60 half-frames (interlaced) per
                           second. Each frame contains 525 lines and can contain 16
                           million different colors.
PAL                        Phase Alternating Line
                           International TV signal Standard
                           the dominant television standard in Europe. PAL delivers 625
                           lines at 50 half-frames per second. Many video adapters that
                           enable computer monitors to be used as television screens
                           support both NTSC and PAL signals.
S-Video Cable              Separate
                           Chrona (color) and Luma (brightness) lines
                           Best video
Composite                  RCA jack
                           Good video
VHF/UHF                    Very High Frequency/Ultra High Frequency
                           Audio and Video
                           OK video
Sound
AD Converter               Analog-to-digital Converter
A to D Converter
ADC
DA Converter               Digital-to-analog converter
Sample size                Number of bits used to store sample
                           8bits = +128 to –127
                           16 bits = +32K to –32K
Sample rate                Number of samples taken per second
                           CD = 44KHZ
Hz                         Cycles per Second
WAV                        Sound file format – Most multimedia sound
                           Uses standard audio sampling
                           Large files
MIDI                       Musical Instrument Digital Interface
                           Sound file format – used with most games
                           Uses more advanced method of storing sound
                                   Note Pitch
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Lecture Outline - Multimedia


                                  Note Volume
                                  Note Length
                           Employs compression
                           Used by most synthesizes
                           Smaller files
FM Synthesis               Frequency Modulation
                           Uses mathematical formulas to recreate musical instrument
                           sounds
Wavetable synthesis        Uses musical instrument recording samples (voice)to create
                           instrument sounds
                           More expensive than FM synthesis
MPC3                       Multimedia Personal Computer - 3
                           Current specification for sound card
                           (SB16)


Real Player                (Real Audio + Real Video)
TAPI                       Telephony Application Programming Interface
                             Telephone standard
MP3                        (Replace - This is un-cited copy from the Internet)
                           Is the file extension for MPEG, audio layer 3. Layer 3 is one of
                           three coding schemes (layer 1, layer 2 and layer 3) for the
                           compression of audio signals. Layer 3 uses perceptual audio
                           coding and psychoacoustic compression to remove all
                           superfluous information (more specifically, the redundant and
                           irrelevant parts of a sound signal. The stuff the human ear doesn't
                           hear anyway). It also adds a MDCT (Modified Discrete Cosine
                           Transform) that implements a filter bank, increasing the
                           frequency resolution 18 times higher than that of layer 2.
                           The result in real terms is layer 3 shrinks the original sound data
                           from a CD (with a *bitrate of 1411.2 kilobits per one second of
                           stereo music) by a factor of 12 (down to 112-128kbps) without
                           sacrificing sound quality.
                           *Bitrate denotes the average number of bits that one second of
                           audio data will consume.
                           Because MP3 files are small, they can easily be transferred
                           across the Internet. Controversy arises when copyrighted songs
                           are sold and distributed illegally off of Web sites. On the other
                           hand, musicians may be able to use this technology to distribute
                           their own songs from their own Web sites to their listeners, thus
                           eliminating the need for record companies. Costs to the
                           consumer would decrease, and profits for the musicians would
                           increase.




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Lecture Outline - Multimedia




Ogg Vorbis                 “Dancing Weasel”
                           (Replace - This is un-cited copy from the Internet)
                           From: ZDNET.COM - Open-source music format ready to play
                               . A team of independent software developers from the ranks
                           of the open-source movement has been toiling away on a
                           program called Ogg Vorbis that, like MP3, compresses standard
                           audio tracks into easily shared and distributed files. This Sunday
                           the team was set to officially debut a version 1.0 "release
                           candidate." It includes all the features of a final version--but is
                           still being vetted for glitches. Go to the full story by John
                           Borland.
                              The skinny: Software developers or music distributors that
                           utilize MP3 have to pay a royalty for the privilege. Ogg Vorbis
                           will carry no such levy. But just because it's price is right doesn't
                           mean Ogg Vorbis is going to overcome MP3 anytime soon. MP3
                           is in widespread use. What's more, just last week, the two
                           companies behind it, Thomson Multimedia and the Fraunhofer
                           Institute, released an upgraded version of the format capable of
                           creating better quality music files in less space. The most
                           significant thing to note about this effort isn't its potential.
                           Instead, it's this: The grassroots, open-source movement has
                           planted a seed in yet another fertile segment of the software
                           market--and it's taking sprout.
Multimedia
MMX                        MultiMedia Extension
                           SIMD - Single-instruction, Multiple-data
                           Also new instructions and increased internal cache
                           200MHz –Pentium-Pro, PII
SSE                        Streaming SIMD Extension
                           PIII

Graphics Accelerator           Video Card with a processor(s)
                               Frees up MB CPU
                               Provides faster video processing
                               Video Bus – Bus on video card
                                      32, 64, 128, 256 bits wide
                               My include special circuits/design features for
                                       2D/3D graphics
                                       Specific application support
                                       Dual monitors
                                       Etc.
Video Memory                   Frame Buffer
                               Also used to store fonts & other info
                               Dual ported video Ram = VRAM – read and write at the
                               same time
                               Determined by screen resolution (horiz X vert) and color
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Lecture Outline - Multimedia


                               depth (number of colors)
                                      Color Depth (bytes per pixel)
                                             4 – 16 colors (1MB @ 1024X768 - XGA)
                                             8 – 256 colors (1MB @ 1024X768 - XGA)
                                             16 – 65,000 colors (2MB @ 1024X768 -
                                             XGA)
                                             24 – True color – 16.7 million colors (4MB
                                             @ 1024X768 - XGA)
                               Specialized Video RAM
                                      SGRAM – Synchronous Graphics
                                      WRAM – Window RAM – full-motion video
                                      3D RAM – 3D logic contained in the chip

MPEG Standards                 Motion Picture Experts Group
MPEG-1                         Image Compression (home & business)
MPEG-2                         Film Compression (to digital video for DVD’s)
MPEG-3                         Audio Compression
MPEG-4                         Video Transmission over the Internet




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