Closing File '2006' and Opening File '2007'
Last month we concluded our series that described how an NLE like Avid Liquid can handle both multiple video formats and multiple audio formats. By the last installment, I had created a 720p30 HDV sequence that had both stereo and 5.1 soundtracks. My goal was multiple HD and SD exports:
- 720p30 HDV with MP2 stereo, sent to an HDV camcorder
- 720p30 HDV with PCM stereo, to D-VHS deck at 25Mbps
- Widescreen DV with a PCM stereo, sent to a DV camcorder
- Widescreen NTSC DVD with an AC-3 5.1 soundtrack
- Letterboxed PAL DVD with a PCM stereo soundtrack
- High-definition DVD with an AC-3 5.1 soundtrack
These targets were easy to create. I simply created Sequences of the appropriate types and then dragged the 16:9, 1280x720, 30p Master Sequence into each empty Sequence. From here it was only a matter of enabling the desired soundtrack and disabling the unwanted soundtrack — followed by the desired export to tape or file.
In a later installment, we will look at how the export to a high-definition DVD was done. In fact, we will explore how high-definition DVDs can be created without buying a new DVD burner. In this installment, however, we''ll look at “Full HD.” You may already have encountered the “Full HD” logo.
Full HD means the display panel has 1920x1080 elements that are presented at 60p. (There is, of course, nothing new about 60p: every flat-panel TVs refreshes all pixels at 60Hz.) The point about Full HD is that these HDTVs have the pixels necessary to display all the pixels carried in a 1080i broadcast or stored on a Blu-ray or HD-DVD disc. As we shall see, the Full HD marketing program has several implications. Obviously, its primary impact is in the display arena.
For HD producers, Full HD will impact camcorder specifications. Beginning next year, the Full HD logo will appear on certain prosumer HD camcorders. And yes, it means these camcorders record 1920x1080 video. More about this in February.
In my “What is 1080i?” article, I described a test Gary Merson performed on 54 HDTVs. Merson reported that almost half of the models tested failed to properly de-interlace a 1080i high-definition signal — resulting in a loss of picture resolution. Both he and I commented that we expected far more 2006 models to pass. Moreover, with the advent of Full HD marketing programs, one would certainly hope that all Full HD units would pass. Unfortunately, as Merson reports in the October 2006 issue of Home Theater, the failure rate in his second test was greater.
For both tests, Merson used a 1080i SMPTE 133 test pattern. In the corners and to the right of the middle of the pattern are boxes with alternating horizontal black and white lines a single pixel high. The HDTV sends the white lines to the first field and the black lines to the second field. To add a motion to the image, a clockwise rotating white line is positioned on the left side of the pattern.
If a given display properly processes all lines, the pattern's alternating horizontal lines should remain intact. If, however, the display only shows single 540-line fields (all odd- or all even-numbered lines) and upconverts to the HDTV's vertical resolution, the box will strobe all black and then all white. Strobing signals a failure.
Many folks have responded to Merson''s tests by commenting there is “no way they would not notice such a resolution loss.” This response is valid — and also invalid. Unless you use one of the new “Full HD” HDTVs, you have never had a chance to see 1080-line video. (Many, if not most, CRTs cannot display a full 1080 raster.)
The author, however, has overstated the seriousness of the situation by creating the concept of “failing” HDTVs. The reality is that TVs vary in the degree that they provide a viewer with all the information that's possible. Which raises the obvious question — how much vertical information is possible? We know the maximum in a 1080i signal is 540 lines per field.
A very high-quality CRT will, over a frame time of 1/30 second, present 1080 raster lines. Our eyes integrate two 540-line fields into a single 1080-line frame. Flat-panel displays with 1080 rows of pixels function very differently. Each 1/60 second, they present 1080 rows to the eye. Those testing displays assume a field carries 540 lines of information. Doesn''t this value define the maximum possible information that can be presented during each field time?
Not exactly. It turns out that depending on the nature of an HDTV''s de-interlacer, more information can be presented. In fact, it is possible to present 1080 lines of video information every 1/60 second by using a de-interlacing technique called “weave.” Weave combines even and odd lines into a single 1080-line frame. A second-stage, isotropic filter blends pixels at the edges of moving objects in order to reduce combing. Each frame is sent to the panel twice during a frame time. With 1080 TV lines as the benchmark, an HDTV that presents only 540 lines is deemed by Merson to “fail.” Those that failed used “bob” de-interlacing. In my earlier article, I described incorrectly its operation. In the next issue, I will provide the correct description of bob de-interlacing as well as several other de-interlacing methods.
Editor's note: The day this article published, as reported by Camcorderinfo.com, JVC announced at CES its new GZ-HD7 camcorder, the first consumer camcorder to capture a full 1920x1080 image, which it does via three 1/5in. CCDs using pixel-offset technology.