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T351 - Summer Week 5 Agenda / Reality check
Lecture & lab today:
Readings:
Final Projects: review criteria All of your written materials (except for storyboards) should be typed. The amount of detail along with the appearance and presentation of your materials & packet affects your grade.
Video & Multimedia Video from a non-linear editor often needs to be converted for uses other than television. Other uses include:
Each of these applications use different codecs. It's important to understand the difference between multimedia systems or architecture (the container) and codecs, which are specific file types. Codecs are designed for specific purposes. Some are optimized for delivery, some are best suited for editing. Two popular mutlimedia systems include Windows Media and Apple Quicktime. Both of these systems support a number of different codecs. The Internet supports many competing architectures: Windows, Quicktime & Real. Websites often offer video at vaying bandwidths depending on your connection speed, but often use just one of the three architectures. You've discoveed this if you've ever found that you couldn't play video from a website untll installing the right plug-in for your browser Examples:
Software such as Apple Compressor, Adobe Media Encoder, Sorenson Squeeze, or Flip4Mac can take a movie and output it in a variety of formats and resolutions. Most allow for batch processing. You could use it to make three different versions of a movie, each for a different purpose (web, SD DVD & BluRay). In many cases you can export your video directly from your editing software into the appropriate codec. Sometimes you need specialized or proprietary hardware or software in order to make the codec in a different multimedia architexcture. Exporting for mass consumption: DVD & web. 2 popular codecs:
If you are exporting movies for non-broadcast uses (E.g. for DVD or YouTube), always add at least a half second of black at the beginning before the program fades up from black. This gives a chance for the player to lock onto the audio. If your audio starts instantaneously, the first few milliseconds of audio will likely be cut off. Fade to black at the end and add at least a few more seconds of black. This way your DVD won't immediately jump back to the menu. It gives just a moment to conclude the ending. In your sequence/timeline, set an in-point at the beginning and an out-point a few seconds after the fade out at the end. From the "File" menu, choose "Export -> Using Quicktime Conversion" For the web:
Video Codecs - Interframe verses Intraframe Only the highest end video is uncompressed. Almost all video (especially HD) uses some sort of compression. When looking at the characteristics of various video recording gear, it's important to understand the basic differences between two general types of compression. Most standard definition production tv codecs use some type of intraframe compression. This is where we take each individual frame and squeeze it so it all fits onto tape or disk. Examples of intraframe codecs include:
The nice thing about most intraframe recording is that it can be compressed and played back in real-time using inexpensive hardware. However many new HD recording formats use interframe or Group of Pictures (GOP) compression. The important thing to understand about interframe compression is that it compresses over time as well as space. In intraframe compression we divide the picture into smaller rectangles called macroblocks. These macroblocks are compressed and tracked over time and placed into a GOP (Group of Pictures) Examples of interframe codecs include:
MPEG-2 is a popular interframe codec. It is a very efficient in that it can squeeze a high definition video image into the same amount of space that a standard DV stream can occupy. (That's why we can record HDV onto a miniDV tape.) The other interesting thing about MPEG-2 is that it's scalable- we can make the frame dimensions varying sizes (720 x 480, 1440 x 1080 etc.). The down side is that GOPS can be difficult to edit. Deconstructing the GOPs during the edit process tasks the computers to a greater degree than intraframe codecs. 4:4:4 vs. 4:2:2 vs. 4:1:1 Today’s digital technology provides us with several ways to digitize video, mainly 4:2:2 and 4:1:1. What do they refer to? Quite simply, they refer to the ratio of the number of luminance (Y) samples to the samples of each of the two color difference signals. In the video signal, the most important component is the luminance as it gives us all the detail absolutely necessary in the picture. As a result, we must sample luminance at a very high rate, 13.5 Megahertz (million times per second). Given that the luminance portion is sampled at 13.5 MHz. Let's apply the before mentioned ratios: 4:2:2 and 4:1:1. In a 4:1:1 component digital sample, the color information is sampled at 1/4 the luminance rate: 3.375MHz. In a 4:2:2 system, the color is sampled at 1/2 the rate of the luminance or 6.75MHz. What about 4:2:0? The 4:2:0 is used in MPEG-2 sampling. The two color difference signals are sampled on alternating lines. What does this mean? Quite simply, the color depth of a 4:2:2 component digital signal is twice that of a 4:1:1 signal and, from the standpoint of color bandwidth, is twice that of today’s popular component analog formats. This means better color performance, particularly in areas such as special effects, chromakeying, alpha keying (transparencies) and computer generated graphics. Format Conversion Editors will have to deal with a number of different media formats and need to understand the physical distinction between them. Some of the different formats include film, standard definition and high definition versions of NTSC, PAL, 16 x 9 and 4 x 3. NTSC (National Television Systems Committee) definition of standard definition TV broadcast, (used in North America, some of South America, Japan, etc) uses a frame rate close to 30 (actually 29.97) frames per second. There are 525 scan lines; approximately 480 of these are visible.
PAL (Phase Alternate Line) is used in most of Europe, Australia, & Asia and runs at 25 frames per second using 625 lines. SECAM (Sequential Color and Memory) is used in France and its territories and is similar to SECAM. If possible it’s best to edit in the media’s native format. If you have high-quality PAL footage, it’s best to try to keep it in PAL. If you have 24 fps footage, it’s best to keep it in 24 fps. That way you won’t get conversion artifacts from changing frame rates and generation losses. But while ideal, we can’t always practice this. Often we’ll get a tape from another country, or that contains another type of media that must be integrated into our existing content. Film to Video Conversion (or 24P to 60i) When converting film to video we use a 3:2 Pulldown (or a 2:3 Pulldown) See Film and 24p video runs at 24 frames per second. Since film or 24p video runs at 24 fps and video runs about 30 fps, the two aren't directly interchangeable at least on a frame for frame basis. (To be more precise, 23.976 film frames become 29.97 video frames.) In order to transfer film to 30 fps video, the film frames must be precisely sequenced into a combination of video frames and fields. A telecine is a piece of hardware containing a film projector sequenced with a video capture system. The telecine process is a term used to describe the process of converting film to video, also called a 3 2 pulldown. In the 3-2 pulldown each frame of film gets converted to 2 or 3 fields of video. Note how 4 (24fps) frames are converted to 5 interlaced frames (30 fps).
The problem with converting film frames to fields, is that some video frames have fields from two different film frames. If you think about it you'll see that this can present all types of problems. DTV (Digital TV broadcasting) TV Broadcasters are supposed to broadcast totally in digital by 2007, so the analog spectrum can be reclaimed for other purposes. DTV doesn't necessarily mean high-definition. DTV broadcasts can be either HD (High Definition) or SD (standard definition). You can squeeze 4 SD programs in the same space used to broadcast one HD program. Both use MPEG-2 compression. SD vs. HD SD works in both 4:3 and 16:9. Its video pixel dimensions include: HD is 16:9. Its video pixel dimensions include: Video frame rates: 24p, 30p, 30i, 60p, or 60i. HD has 4 discreet channels of audio. Beside having more pixel resolution, HD can display much more information in terms of color and brightness. HD has a much larger contrast ration than SD. It's not film, but it's getting close. Cybercollege reading: http://www.cybercollege.com/dtv_stans.htm Metadata & Closed Captioning Metadata (data about the data) is embedded text and numeric information about the clip or program. It can include, but is not limited to:
It can be stored and accessed in XMP (stands for Extensible Metadata Platform and is based on XML). While data can be embedded in XMP, some media formats do not allow for this so data is written to a separate sidecar file.
Closed-captioning is one type of metadata that can be displayed on screen for the hearing-impaired. Carried in the vertical blanking interval, the FCC mandates that all stations broadcast programming with closed captioning data. If you watch closed-captionined programming, you'll see a variety of variations in readability, placement and duration. Companies like Soft NI create stand-alone subtitler systems that let you integrate subtitles into a video stream. Adding subtitles involves proper placement on the screen. Softel-USA makes products for subtitling HD programming. Good metadata overview by Philip Hodgetts: http://www.youtube.com/watch?v=GnPzpPvoyLA Adobe has speech search capabilities built into SoundBooth. It analyzes the audio and transcribes it into text (speech analysis): http://www.youtube.com/watch?v=5CLqspcNWw0 Capture One photo metadata editor: http://www.youtube.com/watch?v=DbtfBAliHTw Focus Enhancements, Firestore is capable of setting up and recording custom metadata in the field. http://www.youtube.com/watch?v=FUcAQQyz_Mg Avid makes Metasync, a product which let's editors work with data right in the timeline. It can be used to link to other types of evidence and forensic documentation right in the timeline: http://www.youtube.com/watch?v=NGp0dc6yVWQ
Vocabulary (Know these terms)
Final Test Review Final Exam is worth 70 points! The best way to review for it is to study the class notes and the midterm (expect everything you got wrong on the midterm to be on the final). The final will be true/false, multple choice, and short answer. It will cover the following areas:
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