Audio. Video

AUDIOVIDEOFLASH

DIGITAL MEDIA:COMMUNICATION AND DESIGN

24.04.2007

Digital Media: Communication and Design F2007

Comments

Web 2.0 guest lecture Evaluation Intro to scripting (PHP) Intro to Flash Mandatory assignment due to 01.05 at

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Index

Audio Video Flash


Audio

What can audio do for us?


Audio

Audio is analogue

Encoding: we sample the wave and round the value to an allowed value


Sampling rate (Hz)

How many times per second we have a sample

Max frequency and recommended sampling rateVoice: ~ 4000 Hz -> 8000 HzMusic: ~20000 Hz -> 44100 Hz


Bit rate (bits)

How many bits we use to describe the values

8 bits: 256 values 16 bits: 65536 values (CD quality)


Ripping a CD to MP3

Bitrate: how many bits per second Radio: 64 kbps CD: 128 kbps (192)

Sampling rate: CD: 44.1 KHz Radio: 8 KHz

Channels: Mono / stereo / joint stereo


File formats

WAV: Wave file Not compressed NOT for the web

MP3: MPEG 1 Layer 3 Lossy compression (1/10 of WAV)

OGG (Vorbis): Lossy compression Free format

MIDI: Contains information about notes and instruments to play


File formats II

QuickTime: Container for audio, video, images...

RealAudio Pioneer on streaming audio PC World: #2 worst tech products of all time

Windows Media Audio Popular for streaming (.asf files)

AAC (Advanced Audio Coding) Substitute of MP3 (?)

Flash


This is Sparta

44 KHz, 228 KB

22 KHz, 114 KB

11 KHz, 57 KB

8 KHz, 42 KB


Audio

2 methods:Link to fileStreaming


Link to a file

<a href=“audio/sparta.mp3”>Download song (1.5 Mb)</a>

<embed src=“starwars.mid” autostart=“true” hidden=“true”></embed>


Streaming

The file starts playing right away

The file is not downloaded: protect copyright

The server must have a special configuration

Good for broadband connections


Streaming

Typical formats:RealAudioQuickTimeWindows MediaFlash


Audio editing

Audacity (open source, free) Sound Forge Audition (old Cool Edit) Garage Band (Mac)


Index

Audio Video Flash


Video

What can video do for us?


Properties of video

Movie length Frame size

Streaming: 320x240Download: 640x480 (HD: up to 1920x1080)

Frame rate (fps)TV: 25 fps (interlaced, 50Hz)Streaming: 10 fps


Properties of video II

Quality:Degree of compression

Bit depth:Number of colours (usually 24 bits)

Bit rate:Number of bits per second (kbps)Audio + video


Compression

Lossless: no information is lost Lossy: throw away information we cannot

see Spatial:

Every frame, similar to JPEG Temporal:

Areas that don’t change over time


Popular codecs

MPEG-1: VHS, VCD MPEG-2: DVD, Digital TV MPEG-4 Part 10: HD-DVD, Blu-ray, iPod, PSP MPEG-4 Part 2: DivX, Xvid Sorenson 3: QuickTime Theora: OGG video WMV: Similar to MPEG-4


Popular formats

QuickTime (.mov) Can contain audio, video, images... Good for streaming

AVI (Audio Video Interleave) MP4 (.mp4, .m4a, .m4p) ASF (Advanced Systems Format)

Windows Media Real Media (.rm)

Broadcasting Flash


Video


Streaming


Video in an HTML document<a href=“video/holidays.avi”>See the video of my holidays (90 Mb)</a>

<object classid=“clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B” codebase=“http://www.apple.com/qtactivex/qtplugin.cab” width=“480”height=“276”> <param name=“type” value=“video/quicktime” /> <param name=“src” value=“poster.png” /> <param name=“href” value=“sample.mov” /> <param name=“controller” value=“false” /> <param name=“autoplay” value=“true” /> <param name=“target” value=“myself” /> <object type=“video/quicktime” data=“poster.png” width=“480” height=“276” class=“hide”> <param name=“href” value=“sample.mov” /> <param name=“controller” value=“false” /> <param name=“autoplay” value=“true” /> <param name=“target” value=“myself” /> </object></object>

QuickTime: http://www.ceprix.net/examples/qt/example4-1.htmlFlash: http://www.ceprix.net/examples/qt/example4-2.html


Index

Audio Video Flash


Flash

What can Flash do for us?


Questions?

Documents

Audio. Video