Digital Video Editing18-04-2004

THE VIDEO BASICS

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THE VIDEO BASICS

Analog signals are made up of continuously varying waveforms. Inother words, the value of the signal, at any given time, can be anywhere in the range between the minimum and maximum allowed.

Digital signals, by contrast, are transmitted only as precise points selected at intervals on the curve.

The type of digital signal that can be used by the computer is binary, describing these points as a series of minimum or maximum values -the minimum value represents zero; the maximum value represents one. These series of zeroes and ones can then be interpreted at the receiving end as the numbers representing the original information.

Video Signals:

THE VIDEO BASICS

PIXELS (Picture Elements) is the minimum screen display element,represented as a point with a specified color and intensity level (RGB or YCC).

Frame Resolution:

FRAME is a single still image in a sequence of images (Video).

PIXELFRAME

320

240

640

480320 X 240

640 X 480

FRAME RESOLUTION is the amount of information (PIXELS) in each frame.

Higher resolution will result in a better quality image and more storage required.

THE VIDEO BASICS

The Frame Aspect Ratio describes the ratio of width to height in the dimensions of a frame. For example, the frame aspect ratio of NTSC video is 4:3, and some motion-picture (Film) frame sizes use the more elongated aspect ratio of 16:9.

Frame Aspect Ratio:

Frame Aspect Ratio

Width

Height

4

3

16

9

4:316:9

THE VIDEO BASICSPixels Aspect Ratio:

Some video formats use a different aspect ratio for the pixels that make up the frame. When a video using square pixels is displayedon a non-square pixel system, or vice versa, shapes and motion appear stretched. For example, circles are distorted into ellipses.

Square Pixels Aspect Taller Pixels Aspect Wider Pixels Aspect

Pixels Aspect Ratio:Square Pixels (1.0),DV NTSC (0.9),DV PAL (1.067),Widescreen 16:9 (1.422) etc.

THE VIDEO BASICSFrame Rate:

FRAME RATE is the number of images (Video Frames) shown within a specified time period; often represented as FPS (Frames Per Second) creates the illusion of motion.

The more frames per second (FPS), the smoother the motion appears and more storage required.

24 FPS

MOTIONPICTURE

(FILM)

25 FPS

PAL/SECAMTV

SCREEN

29.97 FPS

NTSCTV

SCREEN

2 FPS 5 FPS 8 FPS 12 FPS

15 FPS 20 FPS 25 FPS 30 FPS

THE VIDEO BASICSTime Code:

Timecode defines how frames are counted and affects the way to view and specify time throughout a project. Timecode never changes the timebase or frame rate of a clip or project - it only changes how frames are numbered.

Professional videotape decks and camcorders can read and write timecode directly onto the videotape, which lets it synchronize audio, video, and edits, or edit offline using the timecode SMPTE (Society of Motion Picture and Television Engineers).

When using the NTSC-standard timebase of 29.97, the fractional difference between this timebase and 30 fps timecode causes a difference between the displayed duration of the program and itsactual duration. While tiny at first, this difference grows as program length. Drop-frame timecode is a SMPTE standard for 29.97 fps video that eliminates this error, preserving NTSC time accuracy.When using drop-frame timecode, it renumbers the first two frames of every minute except for every tenth minute. For example, the frame after 59:29 is labeled 1:00:02. No frame are lost, becausedrop-frame timecode doesn’t actually drop frames, only frame numbers.

00:00:00:00Hours

MinutesSeconds

Frames

00 23Frame -Film

00 24Frame -PAL

00 29Frame -NTSC

00 59Seconds

00 59Minutes

00 99Hours

RANGETIMEBASE

For example, in a 25 fps timebase, you never see a 25 (00:00:00:25) in the frames part, because the 25th frames is one second (00:00:01:00).

Same for Second, Minute, hour and the NTSC, PAL, Film timebase. The 18962th frame in a NTSC 29.97 fps timebase is 00:10:32:20

The 18962th frame in a PAL 25 fps timebase is 00:12:38:12

The 18962th frame in a Film 24 fps timebase is 00:13:10:0200:00:00:00 Non Drop Frame Time Code

00;00;00;00 Drop Frame Time Code

THE VIDEO BASICSFrame Rate Convert:

For smooth and consistent playback, the timebase, the source frame rate, and the project frame rate should be identical. In general, use 24 fps for editing motion-picture film, 25 fps for editing PAL and SECAM video, 29.97 fps for editing NTSC video, and 30 fps for other video type.

When time system don’t match, the most important value to set is the timebase, which you should choose appropriately for the most critical final medium.

You’ll get the most predictable results if your timebase and frame rate are identical, or are at least even multiples of each other.

A 24 fps frame rate clip (one-half second shown here) display in a 24 fps frame rate project. All frames display as expected.

A 24 fps frame rate clip (one-half second shown here) display in a 30 fps frame rate project. Some of the frames are repeated.

A 24 fps frame rate clip (one-half second shown here) display in a 15 fps frame rate project. Some of the frames are omitted.

If the source frame rate and the project frame rate don’t match, the system will convert the source frame rate to the project frame rate by repeat or omit some of the source frames. The effect may be distracting or imperceptible depending on the differences between the timebase and the frame rates in the project.

THE VIDEO BASICSInterlaced & Non-Interlaced Video:

A picture on a television or computer monitor consists of horizontal lines. There is more than one way to display those lines. Most personal computers display using Progressive Scan (Non-Interlaced) display, in which all lines in a frame are display in one pass from top to bottom before the next frame appears. Television standards such as NTSC, PAL, and SECAM standards are interlaced, where each frame is divided into Two Fields. Each field contains every other horizontal line in the frame. A TV display the first field of alternating lines over the entire screen, and then display the second field to fill in the alternating gaps left by the first field.

Interlaced video describes a frame withtwo passes of alternating scan lines.

Progressive-scan video describes a frame withone pass of sequential scan lines.

1 Frame = 2 Fields

NTSC: 29.97 frames per second; about 60 fields per second

PAL: 25 frames per second50 fields per second

SECAM: 25 frames per second50 fields per second

TV PAL Upper Field FirstTV NTSC Lower Field First

Computer Monitor

THE VIDEO BASICSVideo Color:

RGB: Computer monitor typically transmit color with 8 bits of information for each of the Red, Green, and Blue components. With these 24 bits of information, over a million different variations of color can be represented for each pixel (that is 2 raised to the 24th power). This type of representation is known as 24-bit RGB color.RED

GREEN

BLUE

YCC: The TV screen uses the YCC color to represents the image.

The “Y” was the luminance signal that was used by black and white televisions, while the “C’s” stood for the color components. The two color components would determine the hue of a pixel, while the luminance signal would determine its brightness.

RGB

THE VIDEO BASICSOverscan and Safe Zones:

Frame size can be misleading if it’s preparing video for television. Most NTSC consumer television sets enlarge the picture; however,this pushes the outer edges of the picture off the screen. This process is called Overscan. Because the amount of overscan is not consistent across all televisions, it should keep action and titles inside two safe areas - Action-Safe Area and Title-Safe Area. The action-safe zone is a margin, about the width of a typical amount of overscan, around all sides of a frame. The title-safe zone is a margin that extends further into the frame than the action-safe zone. The title-safe zone helps ensure that text and important graphics are completely displayed, and avoids the distortion of text and graphics which can occur toward the edges of many television. Always anticipate overscan by using safe zones, keeping important action and text within them, and testing the video on an actual television monitor.

Televisionmonitor

Computermonitor

Computer monitor canshow 100% of the frame

Television monitor can onlyshow center part of the frame

THE VIDEO BASICSAnalog Video Formats & Their Typical Connections:

Because of the noise, in analog video, the type of connection between devices is extremely important. There are three basic types of analog video connections.Composite: The simplest type of analog connection is the composite cable. This cable uses a single wire to transmit the video signal. The luminance and color signal are composited together and transmitted simultaneously. This is the lowest quality connection because of the merging of the two signals.S-Video: The next higher quality analog connection is called S-Video. This cable separates the luminance signal onto one wire and the combined color signals onto another wire. The separate wires areencased in a single cable.Component: The best type of analog connection is the component video system, where each of the YCC signals is given its own cable.

Typically, the higher the quality of the recording format, the better the quality of the connection type.

Industrial Video, BroadcastBestComponentBetaSP

Prosumer, Industrial VideoBetterS-VideoS-VHS, Hi-8

Home VideoGoodCompositeVideo-8, VHS

APPROPRIATE APPLICATIONSQUALITYVIDEO FORMATTAPE FORMAT

Composite With Audio

S-Video With Audio

Component

THE VIDEO BASICSDigital Video Formats & Their Typical Connections:

DV25: A prosumer-targeted variation on the theme is called MiniDV and Digital8. They offer the same data rate and color sampling as DV25. Sampling is 4:1:1.DVCAM and DVPRO: The basic DV format was designed for the consumer marketplace. Sony has introduced a professional variant known as DVCAM, which uses the same compression and tape as DV, but records less video on each tape. Recording is accomplished by magnetizing very small sections of videotape with differing polarities. Both the DVCAM and DVCPRO systems are designed with the professional in mind and each offers distinct benefits for a particular customer type.DV50 and DV100: In addition to the DV25 standard, there are also emerging standards known as DV50 and DV100. Since DV25 indicates 25 Mbits/sec of video, DV50 indicates 50 Mbits/sec and DV100 represents 100 Mbits/sec. The DV50 standard uses 4:2:2 color sampling and a lower compression of 3:3:1. The video quality of this standard is extremely high, and is suitable for the most demanding professional broadcast purposes. The DV100 format will be used for HDTV (High Definition Television) recording.Digital Betacam: Also known as DigiBeta, Digital Betacam is the high-end broadcast professional's choice. It provides superior image quality, and the high-end equipment required to work in this format is commensurately costly. Analog Betacam SP tapes can also be played back in DigiBeta decks.

Industrial Video, DVD, BroadcastBestDV50, DV100,DigiBeta

Prosumer, Industrial Video, DVDBetterDVCAM, DVPRO

Home/Prosumer Video, Web, CD-ROM, DVDGoodDV25 (MiniDV)

APPROPRIATE APPLICATIONSQUALITYDV FORMAT

IEEE 1394 is also know as “FireWire”(Apple Computer) and “i. LINK” (Sony Corporation)

THE VIDEO BASICSBroadcast Standards:

There are three television standards in use around the world. These are known by the acronyms NTSC, PAL, and SECAM.

If you begin producing content for international consumption, or if you wish to incorporate foreign content into your production. You can translate between the various standards, but quality can be an issue because of differences in frame rate and resolution. The multiple video standards exist for both technical and political reasons.

France, Middle East, Much of Africa etc.1.06725 fps625 LinesSECAM

Australia, China, Most of Europe, South

America etc.1.06725 fps625 LinesPAL

USA, Canada, Japan, Korea, Mexico etc.0.929.97 fps525 LinesNTSC

COUNTRIESPIXELS ASPECTFRAME RATEHORIZONTAL LINESBROADCAST FORMAT

The SECAM format is only used for broadcasting. In countries employing the SECAM standard, PAL format cameras and decks are used.

NTSC: National Television Systems Committee

PAL: Phase-Alternating Line

SECAM: Sequential Couleur Avec Memoire

THE VIDEO BASICSGetting Video Into Your Computer:

IEEE 1394 Cards

The simplest kind of card available is the IEEE 1394 interface card. This card does not support any analog video I/O, compression, orspecial processing. In fact, it does not really “capture” video, it merely enables the “transfer” of digital video into your computer. The IEEE 1394 interface can be used for many other connections as well, such as hard drives, scanners, and networking.

Analog Capture Cards

Analog capture cards actually perform the task of converting analog video to and from digital video. There are many different sources of analog video, including VHS tapes, Hi-8 cameras, Beta-SP tapes, etc. These cards vary in price depending upon the type of analog interface supported.

Real-Time Editing Cards

When you do editing a video, a special effect like a transition would make you wait while it calculated the effect, whereas the high-end system included specialized hardware to create it instantly. Sometimes the calculation of the effect (Called Rendering) on the desktop system could take minutes or even hours, which would slow production to a crawl. This productivity barrier between the high-end and the desktop has now been shattered by a variety of newly introduced Real-Time editing cards. These boards have specialized processors to handle the enormous number of calculations required for video effects.

IEEE 1394 Card

Analog Capture Card

Real-Time Editing Card

THE VIDEO BASICSFile Formats:

Graphic:

Vector or Bitmap still picture.

Color Depth - 8, 16, 24 and 32 bits.

Image Resolution - 320x240, 640x480 and 720x576 etc.

PSD, AI, JPG, BMP, GIF, PNG, TGA, TIF and EPS etc.

Audio:

Sample Rate - 11025, 22050, 32000, 44100, 48000, 96000 Hz.

Sample Type - 8, 16, 24, 32 bits.

Channels - Mono, Stereo and 5.1 Surround Sound.

Audio CD - 44100Hz, 16bits and Stereo.

AIF, MP3, Wav, RA, MOV, ASF and AVI etc.

Video:

Color Depth - 8, 16, 24 and 32 bits.

Frame Size - 320x240, 640x480 and 720x576 etc.

Frame Rate - 5, 8, 12, 15, 24, 25, 29.97 and 30 fps etc.

Pixel Aspect Ratio - Square Pixels (1.0), DV NTSC (0.9), DV PAL (1.067), Widescreen16:9 (1.422) etc.

AVI, MOV, WMV, MPEG, etc

Mono

Stereo 5.1

THE VIDEO BASICSVideo Compression:

The goal of data compression is to represent the same content (Quality) using the less data (Storage). Using the Codec (Compressor/Decompressor) to manage the compression.

Spatial Compression

Spatial compression uses a method to delete information that is common to the entire frame by looking for pattern and repetition among of pixels. It looks for redundant information, but instead of specifying each pixel in an area, it defines that area using coordinates.

Temporal Compression

This method of compression looks for information that is not necessary for continuity to the human eye. It looks at the video information on a frame-by-frame basis for changes between frames. The compression algorithm compares the first frame (Key Frame) with the next (Delta Frame) to find anything that changes. After the key frame, it only keeps the information that does change, thus deleting a large portion of the file. It does this for each frame until it reaches the end of the file.

Whole Frame Repeating Pixels Non-Repeating Pixels

WholeSequence Key Frame Delta Frames

Uncompress Video Size

720 X 480 x 3 = Frame Storage

HR VR RGB 1 Frame Size

1 Frame = 1 MB1 Second = 30 MB1 Minute = 1.5 GB

THE CREATIVE PROCESS

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THE CREATIVE PROCESSAn Overview of Movie-Making:

Better making a movie includes Pre-Production, Production and Post Production.

Render and Export the Video to the Web, CD-

Rom, DVD, Video Tape and

Film.

Create Motion Graphics and

Visual Effects in a Composite

system.

Using Non-Linear Editing

system to Assemble and Edit the Video.

Import Graphic, Audio and Video.

Digitize Analog/Digital

Audio and Video.

Shoot Video.Create Text, Graphics and

Audio.

OutlineScript

StoryboardBudget/Finance

Locations

Output and Distribute

Create / CompositeAssemble / EditCapture / ImportCreate / Gather Raw Material

Plan the Project

Post Production

Production

Pre-Production

An Overview of Movie-Making

Pre-Production is the planning stage. Typically, it includes steps to take before beginning “production” (Shooting Film or Video). But this is a flexible process and the non-linear editing methods made possible by the advent of digital video make it even more so. When beginning the project, it may have already shot some or all of the video as need.

Production, Capturing live or animated action and sound on film, videotape, or DV - Shooting or Creating raw footage.

Post-Production, edit and assemble the clips and, perhaps, add visual effects, graphics, titles, and a sound track.

A Movie-Making Process

THE CREATIVE PROCESS

Online and Offline Editing:

Online Editing: Online editing is the practice of doing all editing (Including the Rough Cut) on the same clips that will be used to produce the final cut. Previously, online editing had to be done on costly, high-end workstations designed to meet the quality and data-processing requirements of broadcast video.

When you work with DV source material, all editing is done online. DV compression makes standard DV manageable on many desktop systems.

For online editing using analog source material, you capture clips once at the highest level of quality your computer and peripherals can handle.

Offline Editing: In offline editing, you edit a rough cut of your video using low-quality clips, and then produce the final cut using high-quality clips.

Linear and Non-Linear Editing:

Linear Editing is the standard process used successfully for many years where you copy parts of your video source material from your camcorder to a VCR to build up your final program.

Non-Linear Editing (NLE) makes editing and assembling your production as easy and as flexible as word processing.

Random-access editing of video and audio on a computer, allowing for edits to be processed and re-processed at any point in the timeline, at any time. Traditional videotape editors are linear because they require editing video sequentially, from beginning to end.

Once your raw materials are in your computer, you can edit, alter, adjust, and reconfigure them - over and over again -with a few mouse clicks.

THE DISTRIBUTING OF THE PRODUCTION

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THE DISTRIBUTING OF THE PRODUCTIONRecord and Export the Timeline:

The program edited in the Timeline does not actually contain thematerial from which it was pieced together - rather, it references the source files. Before export, make sure that the timeline is ready to output at the quality require. For example, replace any offline files with high-resolution files suitable for final export. To get the edited program out of the computer in one piece, it can:

• Record the timeline to physical media including videotape or motion picture film, if it has the proper hardware for video or film transfer, or has access to a service provider that offers the appropriate equipment and services.

• Export a video file for viewing from a hard disk, removable cartridge, CD-ROM, DVD, or the Web. It can also output stills or sequences of stills, portions of the timeline as clips, and/or an EDL (Edit Decision List).

Web

Video Tape

CD-ROM, DVD

Timeline

THE CONFIGURATION OF THE SYSTEM

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THE CONFIGURATION OF THE SYSTEMSoftware and Hardware:

Non-Linear Video Editing requites both Software Applications and Hardware Systems to achieve the goal.

DV Camcorder

Software Applications: Adobe Premiere Pro, Pinnacle Liquid Edition, Avid Xpress Pro and Apple Final Cut Pro etc.Hardware Systems: Windows, Macintosh, Linux, IRIX etc.

Extend Storage

Personal Computer With an IEEE 1394 Card1024x768 24-bit Video Adapter at least.

DV CamcorderPersonal Computer With a Real-Time DV Card1280x1024 32-bit Video Adapter at least.

TV Monitor

DV CamcorderPC With a Real-Time Analog/DV Editing System1600x1200 32-bit Dual-Head Video Adapter.

TV Monitor Disk ArrayDV Deck

NOTE: It’s important to check the Software Applications and their Hardware Requirements before invest on an Editing System.

Amateur System

Prosumer System

Professional System

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