Flashcards in IT152_Lecture_2_Multimedia_delivery_2013a Deck (104):
Currently Internet for multimedia on NZ is less suitable than DVD - why?
- Relatively slow connections
- No guarantee that site visitors have multimedia capable computers.
- Plug-ins usually required - problematic
- Security issues
- Data integrity
- Legal ownership of media.
Large files can be unusable through modem connections because...?
- Modem: 56 Kbps
- CDROM (single speed) transfers data to 150Kbps
- 1x speed rating for DVDs is 1.32 Mbps
- To put bandwidth in perspective, most broadband users surf at less than the speed of a single-speed CD-ROM drive.
- Faster Broadband AND technologies such as streaming / compression needed.
Dealing with Slow Transfer Times - What can you do to solve this?
- Compress files using different format GIF, JPEG, MPEG.
- Use a Codec (= 'Co'mpression 'Dec'ompression) to reduce file up to 90% but also reduces quality.
- Use lower-quality elements to reduce sizes.
- Reduce bit-depth/physical size.
- Combine Optical Disk and Internet delivery.
Browsers don't natively support...?
Audio, Video, or Sophisticated animation.
(Additional programs are often needed to view Multimedia elements such as helpers and plug-ins, some organisations don't allow plug-ins, plug-ins often don't work due to version/ OS issues)
How is a helper different to a plug-in?
Helper applications display the element in a separate window, Plug-ins display the element in the browser window. (Fortunately, more than 90% of current browsers view Flash and the Swf or Shockwave format.
Some common viewers-helpers and plug-ins include...?
- Windows Media Player for a range of files such as .avi
- Mpgeplay for .mpg movie files
- QuickTime Viewer 32 for .mov movie files
- RAplayer for RealAudio .rm and .ra files
- Viewer32 for Adobe postscript .pdf files
- Shockwave for Flash .swf files
- Neuron for Asymmetric Toolbook .tbk files
Flash is an authoring tool used in...?
Multimedia mainly for animation. (Can create very small files for Internet playback)
Director, is industry standard optical disk authoring tool and creates...?
Shockwave content for Internet, current browsers have the Shockwave Flash plug-in
Most browsers read only...?
Bitmapped, JPG, GIF, and PNG image files.
PNG is an...?
Open format supported by most image creation programs.
Joint Photographic Experts Group (JPEG) uses lossy compression to ...?
Produce files of small size from natural images.
GIF is useful for..?
Solid blocks of colour limited to 256 colours.
Plug-ins that enable viewing of vector formats (such as Flash) are...?
Vector graphics are...?
Device-independent. (An image is displayed at the correct size and with colors supported by the computer.)
When creating images bound for the Web, use a resolution of...?
72 pixels per inch.
Animated text can be done through...?
DHTML allows for...?
Animated GIFs are...?
small and efficient.
Directory or Flash (SWF format) movie usually require...?
3-D environments (VRML, Quick Time VR) require...?
SWF, GIF89a, MOV, MPEG, AVI, MNG
GIF89a format specification creates...?
Simple animations. (It integrates multiple images, or frames, into a single GIF89a file and displays them with programmable delays between them.
Internet is not suitable for high quality video due to...?
Webcam can record at...?
56kbps but poor quality. Needs 128k+
Broadcast video ...?
384k min needed for watchable quality but ideally 512k needed for smaller screaps and 1Mbps for larger screens.
Formats developed for web include...?
ASF, AVI, MPEG, MP4, MOV, RM and WMV.
Indeo, MPEG (incl. divX), Sorenson, DVI, H264)
Kbps stands for...?
kilobits per second transfer (1000 bits)
WMV is used by...?
Windows Movie Maker
MPEG-1 Part 2: Used for...?
Video CDs, and also sometimes for online video. (The quality is roughly comparable to that of VHS. Almost every computer in the world can play this codec, and very few DVD players do not support it.)
MPEG-2 Used on...?
DVD and in another for for SVCD and used in most digital video broadcasting and cable distribution systems. (When used on a standard DVD, it offers good picture quality and supports widescreen. Will also be used on HD-DVD and Blu-Ray. In terms of technical design, the most significant enhancement in MPEG-2 relative to MPEG-1 was the addition of support for interlaced video. MPEG-2 is now considered an aging codec, but has tremendous market acceptance and a very large installed base.
MPEG-4 Part 2: An MPEG standard that can be used for...?
Internet, broadcast, and on storage media. It offers improved quality relative to MPEG-2. Like MPEG-2, it supports both progressive scan and interlaced video.
MPEG-4 Part 10. This emerging new standard is the current state of the art and is rapidly gaining adoption into a wide variety of applications. It contains...?
a number of significant advances in compression capability, and it has recently been adopted into a number of company products, including for example the Playstation Portable, the Nero Digital product suite, Mac OS X v10.4, as well as HD-DVD/Blu-Ray.
DivX, XviD and 3ivx are...?
Video codec packages basically using MPEG-4 Part 2 video codec, with the *.avi, *.mp4, *.ogm, or *.mkv file container formats.
High quality music is not suitable for the Internet because...?
- Is encoded at 256-384+kbps which is ok for CD player (reads at 300kbps) but not general Web.
MIDI sound files are more...?
compact, but they depend upon the computer's MID setup for quality.
Sound elements may also...?
Be embedded into projects made with various authoring tools.
Digitized sound files in MP3, WAV, AIF, or AU formats may be send and played on a users computer from...?
Plug-ins allows embedding of...?
sounds into HTML documents.
Internet Explorer offers the tag to play...?
an AU, WAV, or MIDI sound track in a document background.
Netscape and Internet Explorer offer the QuickTime plug-in for...?
Playing AIFF, MIDI, WAV, and AU formats. (Streaming audio is more useful for the Web, where a sound file can start playing as soon as data begins to download.)
Uncompressed audio as stored on a compact disc has a bit rate of 1411.2 kbps.
MP3 is a lossy compression format it is able to provide a number of...?
different options for its "bit rates"
(Typically rates chosen are between 128 and 320 kbps, 128 kbps is close to CD quality for average user but lack of quality is noticeable, provides compression ratio of approx 11:1)
The quality of MP3 files also depend on the quality of the...?
Encoder and the difficulty of the signal being encoded.
bit rate is ...?
the number of bits of encoded data that are used to represent each second of audio. (Uncompressed audio stored on a compact disc has a bit rate of 1411.2 kbit/s. MP3 files encoded with a lower bit rate will generally play back at a lower quality)
Source code (XHTML) provides info the browser needs in order to display the...?
Web pages correctly.
XHTML can be written from scratch or you can use...?
tools to help write the code.
Official standards committee for the Web called the...?
World Wide Web Consortium (W3W)
Hypertext Markup Language.
XHTML is platform...?
Markup tags specify how...?
Browser displays content.
Tags are paired and consist of a ...?
Beginning tag and an end tag.
Information between tags is...?
Content; affected by tags. ( my web page )
(value follows an attribute , An element is a beginning tag along with its attributes and values)
- Requires tags in lower case
- Attribute values in "quotes"
- All tags must be closed
- XML is stricter standard that allows you to create your own tags.
Advantages of writing in XHTML...?
Power/Control, Clean Code, No Dependent on a Tool with Limitations.
Disadvantages of writing in XHTML...?
Learning Curve, Time-consuming to Write, Easy to make mistakes.
Writing in HTML...?
- Conversion tools
- MS Office Applications
- Web page editors
- Web page authoring programs
High performance XHTML editor for Macs
Authoring tools like MS Expression and Dreamweaver are...?
WYSIWYG HTML editors that allow for multimedia.
Basic HTML allows for...?
video and audio files as well as animated gifs using these tags:.
HTML 5 will provide native support for...?
Video and Sound in the appropriate format. The current discussion is over what those formats should be. Flash is not one of them.
Currently there is on standardized video format so...?
Different browsers support different formats.
(- Firefox supports Ogg Vorbis format.
- Google Chrome supports MP4 videos. In order for a video to display properly on all browsers, the video must be provided in both formats. This is a hassle for developers, and in reality doesn't make catering for HTML5 any more attractive than catering for third-party plug-ins. The W3C is working on either developing a standardized format, or agreeing upon using an existing format.)
Blu-ray Disc (also known as Blu-ray or BD) is an..?
Optical disc storage media format. With currently expensive but getting cheaper players and discs.
A single layer disk on Blu-ray can hold...?
25GB, feature length movies with add ons typically on a dual layer 50 GB disk.
Blu-ray supports more...?
Advanced video encoding algorithms (codecs) as well as MPEG-2, which is used for DVD, the highest HDTV resolution.
Includes a _________________ to allow updates to Blu-ray via the Internet, adding content such as promotional features that are not included on the disc at pressing time.
Java Virtual Machine (BD-J)
Blu ray won the format battle over HD DVD because...?
- The playstation3 used a Blu-ray Disc drive as its primary info storage medium.
- Sony's influential marketing campaign.
- Several studios have cited Blu-ray's adoption of the BD+ anti-copying system as main reason.
Mini-BD (Mini Blu-ray Disc is a ....?
Compact variant storing 7.5GB of data for camcorders.
Blue Ray recording speed...?
Drive speed x 1 Data rate 36 Mbit/s 4.5 MB/s Write time 1 h 30 min. -- 3 hour. 10 speed 45 MB/s 9 mins.
Digital rights management (DRM) is an...?
Umbrella term that refers to access control technologies used by publishers and copyright holders to limit usage of digital media or devices.
The analogue TV standard has been in use for about...?
Analogue tv standard works like..?
A video camera takes a picture of a scene. It does this at a frame rate of up to 30 frames per second. (The camera rasterizes the scene. That is, the camera turns the picture into rows of individual dots called pixels. This final signal, containing the colour and intensity of each pixel in a set of rows, along with horizontal and vertical sync signals , is called a composite video signal.)
a Composite video signal and a sound signal can be broadcast.
When a composite video signal is broadcast over the airwaves by a TV station, it happens on a ...?
Specific frequency via VHF+UHF channels.
Composite video signal is transmitted as an...?
AM signal and the sound as an FM signal on some channels.
What is wrong with analogue TV:
The main problem is...?
Resolution, which controls the crispness and etail in the picture you see. (It is determined by the number of pixels on the screen.)
An analogue TV set can display...?
535 horizontal lines or resolution every thirtieth of a second. (In reality, however, an analogue TV displays half of those lines in a 16th of a second, and then displays the other half in the next 16th, so the whole frame is updated every 13th of a second. This process is called "interlacing".
Digital satellite systems are...?
NOT Digital TV
(The set-top box does receive a digital signal from the satellite or cable; but once received, the signal is converted to an analogue signal and sent to your analogue TV . This is not "digital television" -- it is a normal composite video signal for analogue television converted to a digital format for transmission and then converted back to analogue for display.)
True digital TV is completely....?
Digital and involves:
- Digital Cameras working at a much higher resolution than analog cameras.
- Digital transmission.
- Digital display at a much higher resoultion
On its digital channel, each broadcaster sends a...?
19.39-megabit-per-second (Mbps) stream of digital data.
(Broadcasters have the ability to use this stream in several different ways. E.g.: A broadcaster can send a single program at 19.39 Mbps or 4 streams of 4.85 Mbps each. )
Formats of digital TV have different...?
Aspect ratio. (Analogue TV has a 4:3 aspect ratio, the screen is 4 units wide and 3 units high, the HD format for digital TV has a 16:9 aspect ratio)
To compress the image for transmission (19.39-Mbps stream, broadcasters use...?
MPEG-2 compression, and MPEG-2 allows you to pick both the screen size and bit rate when encoding.
(You see MPEG-2 all the time on the Web, on Web sites that offer streaming video. MPEG-2 allows a technician to pick any bit rate and resolution when encoding a file.)
There are 4 types of tv sets you will see for sale now days... they are...?
- Analog TV sets
- Digital-ready sets
- HDTV-ready sets
- Integrated HDTV sets
High-definition television (HDTV) is a ...?
Digital television broadcasting system with greater resolution than traditional television systems. (HDTV is digitally broadcast because digital television (DTV) requires les bandwidth if sufficient video compression is used.
To display a superior picture, high definition television require a...?
High definition (HD) signal via antenna, set top box, etc.
HDTV is capable of "theater-quality" audio because it uses the...?
Dolby Digital (AC-3) format to support "5.1" surround sound.
HDTV broadcast systems are defined threefold, by...?
1. the number of lines in the vertical display resolution.
2. the scanning system
3. Progressive scanning (p) or interlaced scanning (i). Progressive scanning simply draws a complete image frame (all the lines) per image refresh, whereas interlaced scanning draws a partial image field (every second line).
Interlaced is a technique of...?
improving the picture quality of a video signal by removing flicker without consuming any extra bandwidth.
With progressive scan, an image is captured, transmitted and displayed in ...?
a path similar to text on a page: line by line, from top to bottom. Progressive scan differs from interlaced scan in the way that the image is displayed on a screen by scanning each row of pixels in a sequence rather than an alternately as is done with interlaced scan.
- 720p60 format is 1280 x 720 pixels progressive scanning with 60 fields per second (60 Hz).
- 1080i50 format is 1920 x 1080 pixels (ie 2 MP) interlaced scanning with 50 fields per second.
- NB MySky decoder using 1080i for HD movies while Blu-ray uses 1080p (better)
- For commerical naming of the product, either the frame rate of the field is often dropped, e.g. a "1080i television set" label indicates only the image resolution.
- HDTV is capable of "theater-quality" audio because it uses the Dolby Digital (AC-3) format to support "5.1" surround sound.
HDTV yields a better-quality image than standard television because....?
- It has a greater number of lines of resolution.
- The signal is of a digital nature, it produces neither a snowy nor pale image from a weak signal or signal interface. (NZ analogue TV switch off in the South Island in April 2013)
Disadvantages of HDTV...?
- Best possible HD quality is not usually achieved.
- Main problem is many operators don't follow HDTV specifications fully. They may use slower bitrates or lower resolution to pack more channels within the limited bandwidth.
- Image quality may be lost if the television is not properly connected to the input device or not properly configured for the input's optimal performance.
- You have to buy the appropriate cable for example in most cases an HDMI cable or component cables.
- Digital video responds differently to analogue video when subject to interference.
- As opposed to a lower-quality signal one gets from interference in an analogue tv broadcast, interference in a digital television broadcast will freeze, skip, or display "garbage" info.
- Broadcasters may aggressively compress video to save bandwidth and therefore broadcast more channels - this compression manifests itself as reduced video quality.
- Traditional TV shows and films originally filmed in the standard 4:3 ratio, when displayed correctly on an HDTV monitor, will have empty display areas to the left and right of the image.
HDMI stands for...?
High-definition Multimedia Interface.
HDMI is a ...?
Compact audio/video connector interface for transmitting uncompressed digital streams.
HDMI connects a/v sources such as...?
a set-top box, a blu-ray player, PC, game console to a compatible digital audio device and/or video monitor such as a digital TV.
HDMI represents the...?
DRM alternative to consumer analog standards such as RF (coaxil cable), composite video, VGA, and digital standars such as DVI.
A podcast is a...?
collection of digital media files for playback on PCs, etc so that people can listen to content when and where they please.
To access a podcast feed, you will need podcast software such as...?
iTunes. (not all audio is available via podcast for copyright reasons)
A podcast is distinguished from other digital formats because it can be...?
Subscribed to, and downloaded automatically when the new content is added, using a aggregator or feed reader capable of reading feed formats such as RSS.
RSS is a way of...?
Providing content summaries of web content in a simple format. RSS feed is read by a stand-alone feed reading programme such as Feed demon or via a browser plug-in
An e-book stands for...?
E-book is the...?
digital media equivalent of conventional printed book.
(Such documents are usually read on PCs or dedicated devices known as e-book readers or e-book devices.)