What are the common format for video files? What are the difference between VCD and DVD? How can we produce video files to fit our needs?

Activity --- Video Editing

5.1 Different Video Attributes Video Standards Different countries use different video standards for broadcasting Video standard Full name Countries PAL Phase Alternate Line The United Kingdom, most countries in Europe, Hong Kong, China, Singapore, Australia NTSC National Television Standards Committee The United States, Japan, Taiwan SECAM Sequential Colour And Memory France, Russia TV display standards in different countries

5.1 Different Video Attributes Frames Digitized video consists of a sequence of frames Slightly different frames are displayed successively at high speed → continuous motion Frame 1 Frame 2 Frame 3 Frame 4 Frame 5 Frame 6 Frame 7 Frame 8 Frame 9 Frame 10 Frame 11 Frame 12 Frame 13 Frame 14 Frame 15 Frame 16 A video actually consists of individual frames

5.1 Different Video Attributes Frame Size The width and height of individual frames Larger frame size → higher video quality → larger file size Aspect ratio the ratio of the video width to its height What are the common aspect ratio used? 4:3 16:9

5.1 Different Video Attributes Frame size Aspect ratio Application 720 × 576 5 : 4 PAL DVD 480 × 576 5 : 6 PAL SVCD 352 × 288 11 : 9 PAL VCD 240 × 180 4 : 3 Web video 160 × 120 Web video or video mail What are the frame size of TVs? Traditional TV: 500 x 375 LCD/Plasma TV (32”): 1366 x 768 HD TV: 1920 x 1080(i./p)

5.1 Different Video Attributes Colour Depth Each video frame is composed of pixels arranged in a rectangular grid The colour depth of each pixel specifies the number of bits used to store colour information Most video has 24-bit colour depth

5.1 Different Video Attributes Frame Rate The number of video frames displayed on the screen in one second Measured in frames per second (fps) Higher frame rate (above 24 fps) → smoother motion Frame rate (fps) Multimedia system 30 NTSC TV 25 PAL TV 24 Movie films 15 Computer video or animation (such as Flash movies) 12

5.1 Different Video Attributes Effect of frame rate

5.1 Different Video Attributes Bit Rate (Encoding bit rate) Determines the number of bits used to store one-second video Can also be regarded as the number of bits passing through a particular point in a video stream Measured in bits per second (bps) The idea of video bit rate. The bit rate of video stream B is double of that of stream A.

5.1 Different Video Attributes Bit Rate (encoding bit rate) Increasing bit rate → higher quality → larger file size Choice of bit rate depends on user’s network connection speed Low bit rate causes substantial quality loss Bit rate: 20 kbps File size: 56 KB Bit rate: 50 kbps File size: 127 KB Bit rate: 100 kbps File size: 274 KB Bit rate: 450 kbps File size: 1,113 KB increasing bit rate increasing quality Increasing file size

5.1 Different Video Attributes The following videos have different bit rate, can you see the different? 80 kbps 700 kbps

5.1 Different Video Attributes Video File Size (uncompressed) Can be estimated by the formula, Video file size Frame size Colour depth Frame rate Duration × = Consider a ten-second DVD frame size video clip (without audio), the uncompressed file size is: (720 × 576) pixels/frame × 24 bits/pixel × 25 frames/second × 10 seconds = 2,488,320,000 bits = 311,040,000 bytes = 296.6 MB

5.1 Different Video Attributes Codec (Compressor and Decompressor) The software used to compress and decompress video files Compression reduces the storage space and the video access time Original video Compression Compressed video Decompression Storage Decompressed video (playback) This step requires the appropriate codec installed on user’s computer

5.1 Different Video Attributes Codec (Compressor and Decompressor) Most codecs are lossy Final file size governed by a quality factor and encoding bit rate Some common codecs MPEG-1, MPEG-2, MPEG-4 Windows Media Video DivX RealVideo Intel Indeo®Video Cinepak Codec by Radius

5.3 Common Video File Formats Audio Video Interleave (AVI) Native Windows video format developed by Microsoft Data storage Video data and audio data are stored in an interleaved manner Improves the synchronization of audio and video playing The structure of an AVI file

5.3 Common Video File Formats Audio Video Interleave (AVI) Large file size in uncompressed format Supports many codecs The same 15-second AVI video in 3 formats AVI (MPEG-4 codec) File size: 3.28 MB AVI (Cinepak Codec by Radius) File size: 13.1 MB AVI (uncompressed) File size: 111 MB

5.3 Common Video File Formats Motion Picture Experts Group (MPEG, MPG) A lossy compression file format Preserves video quality yet supports high compression ratio Stores only changes between successive frames, not all the image information of every individual frame → high compression 1 2

5.3 Common Video File Formats Motion Picture Experts Group (MPEG, MPG) A family of compression standards Standard Maximum resolution Encoding bit rate Application MPEG-1 (1992) 352 × 288 (PAL) 352 × 240 (NTSC) 1.5 Mbps Video CDs, interactive CD-ROMs and MPEG-1 Audio Layer-3 music MPEG-2 (1994) 720 × 576 (PAL) 720 × 480 (NTSC) Varying up to 4 Mbps DVDs and digital TV broadcast MPEG-4 (1998) - From 64 kbps up to 4 Mbps Video in digital camera mobile phone, iPod and QuickTime MPEG-4 can be as good as MPEG-2, but an MPEG-4 video is of a smaller file size and at a lower bit rate

5.3 Common Video File Formats Windows Media Video (WMV, ASF) A streaming compressed video format developed by Microsoft Can be played by Windows Media Player Can be created with Windows Movie Maker Windows Media Player Windows Movie Maker

5.3 Common Video File Formats RealVideo (RV, RM) A proprietary compressed streaming audio format developed by RealNetworks Can be played by RealPlayer RealProducer can encode video in other file formats with various bit rate. Example 1 Example 2

5.3 Common Video File Formats RealVideo support video streaming a user does not have to wait to download the whole video file before watching it Without streaming With streaming

5.3 Common Video File Formats QuickTime (MOV) A streaming compressed multimedia file format on Macintosh computers Can store text, still images and animation Can be played with QuickTime Player QuickTime Player QuickTime pro

5.3 Common Video File Formats QuickTime VR support virtual reality (VR) format can display 360º panoramas of scenic Example 1 Example 2 Example 3 QuickTime VR

Video capturing device 5.2 Capture Digital Video Concept To capture digital video, it is necessary to have A capturing device (a camcorder) A storage medium Video encoding hardware and software Video capturing device Storage medium Video encoding hardware and software

5.2 Capture Digital Video Examples Video capturing devices DV camcorder (or Handycam) Digital camera Webcam Video encoding hardware Video capture card An external video capturing device DVD-recorder IEEE 1394 (firewire/i-link) Video capturing and editing software is usually bundled with the hardware product

5.2 Capture Digital Video Examples A video capture card (top left) and an external video capturing device (bottom left) from Pinnacle. Moviestar, the video capturing and editing software, is bundled with the capturing hardware (right).

5.4 Simple Video Editing Common video editing techniques trimming (cutting) video clips adding titles adding filters adding transitions importing still images adding background music

END