Groundbreaking Video Processor
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Lumagenreprint 4/2/03 10:26 AM Page 22 EQUIPMENT REVIEW Lumagen Vision™ Groundbreaking Video Processor G REG R OGERS Introduction Lumagen is a new video company with an exciting goal and two Visions. It believes that existing video scalers are too expensive and intends to provide high-performance video processors at more affordable prices. The Vision™ ($999) and VisionPro™ ($1,895) are the first entries in the Lumagen product line. Both share the same video processing circuits, but the VisionPro includes addition- al input switching capabilities. The ground- their own proprietary scaling algorithms. horizontal lines of a single field. To avoid breaking Vision is the subject of this review. You might also expect a video scaler wide-area flicker a new field is displayed priced at $999 to be limited to only a single approximately 60 times per second. Product Overview output format. Instead, the Vision provides Inter-line flicker occurs along horizontal more image sizing features and display format edges because the top or bottom edge of The Vision upconverts standard-definition options than scalers many times its price. It an object appears to lie on an odd line in interlaced video to match the native, or opti- also provides YPbPr or RGB output signals, one field and an even line in another. As mal resolution of projectors, flat-panel dis- with a complete selection of sync options. odd and even fields are alternately dis- plays, and high-definition direct-view moni- The Vision does have a few limitations when played, the edge appears to move up and tors. It will produce virtually any progressive compared with far more expensive scalers. down by one line in the picture. Since odd video format from 480p to 1080p, and also It doesn’t have variable adaptive detail fields and even fields are each displayed generates 1080i for the many CRT-based enhancement, and it only upconverts standard- approximately 30 times per second, the rear-projection TVs that accept that format. definition interlaced video formats. Hence, it edge appears to blink on and off, or bob up Video upconverters are usually referred to won’t scale 480p input signals, nor deinterlace and down, at a 30 Hz rate. This is most as scalers in the consumer world, but scal- 1080i signals. But it provides a high-band- commonly called line-twitter. ing is only part of the upconversion process. width pass-through input to connect 480p or Line twitter is not limited to the edges of Analog interlaced signals must first be digi- high-definition signal sources to the display. objects. It can appear wherever there are tized and converted to a progressive format high-contrast horizontal lines in an inter- by a deinterlacing process. Then the pro- Why Deinterlace Or laced image. The addition of slow vertical gressive format is scaled to a display format Scale? motion increases the twittering as horizontal with more scan lines per frame, and finally edges move across field lines. converted back to analog component video The purpose of deinterlacing and scaling Inverse-telecine deinterlacing can eliminate to drive a high-resolution projector or monitor. is to eliminate interlaced video artifacts, and line twitter from interlaced film-sources, and When 1080i signals are required, an addi- reduce the visibility of scan lines on CRT motion-adaptive deinterlacing can reduce line tional progressive-to-interlaced step occurs projectors, or match the native resolution of twitter from original interlaced-video sources. prior to the digital-to-analog conversion. fixed-pixel displays. The larger the screen the But to reduce line twitter on interlaced dis- Every step in the upconversion process is more visible artifacts become. The most objec- plays, vertical filtering is applied in video critical to the ultimate picture quality, and tionable interlace artifacts are inter-line flicker cameras and film-to-video DVD transfers to you might expect a product at this price to (line twitter), jagged edges, and motion comb- soften horizontal edges. For that reason, cut some corners in its signal processing. ing. I’ll briefly discuss each of these artifacts. deinterlacing 480i video can never produce But that isn’t the case. The Vision uses 10- Interlaced video is composed of a the full vertical resolution that would otherwise bit oversampled analog-to-digital and digi- sequence of fields, where each field con- be possible from an unfiltered 480p source. tal-to-analog converters to maximize signal tains only the odd or the even horizontal Jagged edges (jaggies) along diagonal linearity and minimize noise. Inverse- lines of picture information. In the 480i-inter- lines are an unavoidable consequence of a telecine deinterlacing with 3-2 field pull- laced format, each field contains 240 active discrete line or pixel structure, but interlac- down detection is used to optimally deinter- (visible) lines of picture information. When ing exacerbates jaggies. Segments along a lace film sources, and motion-adaptive the fields are sequentially displayed on a diagonal edge will appear to flicker on and deinterlacing is used for original interlaced CRT monitor, we perceive that the odd and off because they lie in different interlaced video sources. Lumagen has even developed even lines create a picture with twice the fields. If there is slow vertical movement the WIDESCREEN REVIEW • ISSUE 72 Page 1/5 Lumagenreprint 4/2/03 10:27 AM Page 23 EQUIPMENT REVIEW jaggies may appear to strobe or move (run- The remote control includes On and Menu Functions ning jaggies). Standby buttons, but there is no power Interlaced combing occurs when an switch on the processor. The Vision includes The Vision has an exceptionally broad list object is in motion. Our eyes tend to track a small external power module that supplies of features, some of which are accessed the object, particularly on a wide screen. 5-volts DC through a cable to a rear panel with dedicated buttons on the remote con- Since the object appears at different loca- jack. The power module includes a sepa- trol, and others through an on-screen hierar- tions in the odd and even fields, we per- rate power cord to connect to an AC power chical menu structure. ceive the odd and even scan lines sepa- line, and an LED that indicates when the The menu functions are logically rately, rather than integrating them into a full module is receiving power. arranged into four main groups—IN, OUT, picture. Vertical and diagonal edges of MISC, and SAVE. moving objects may appear like the teeth in Inputs And Outputs a comb because each field has only half Input Features the scan lines of the frame. Even when The rear panel includes composite, S- objects aren’t in motion, a small component video, and YPbPr component video inputs The IN group submenus include COLR, of vertical jitter in the picture may cause our for standard-definition interlaced video ADJ, BIAS, NAME, and COPY. The COLR eyes to lock onto the fields and see scan sources. The Vision is compatible with NTSC, submenu provides adjustments for black lines as individual fields rather than frames. PAL, and SECAM signals. The S-video input level, contrast, color saturation, and hue. As This is far more likely on larger screens, accepts a standard 4-pin mini-DIN connec- always, it is critical to calibrate these adjust- where the scan line spacing is greater. tor while the other inputs use RCA jacks. ments for each input source with AVIA: Guide The remedy for interlace artifacts is to There is also a 15-pin D-sub (VGA style) To Home Theater or Video Essentials. The deinterlace the video and display progressive pass-through input with a 300-MHz rated PDSTL item in the ADJ submenu should be set frames. Then by scaling the video to have bandwidth for RGB or YPbPr signals. to match the black level (0 or 7.5 IRE) of the more horizontal lines per frame, the visibility of The Vision outputs RGB or YPbPr signals input signal prior to making these adjustments. the individual lines and jaggies along diago- through a 15-pin D-sub connector. It will The ADJ submenu includes SIZE, CPHASE, nal edges can be reduced or eliminated. produce RGB signals with separate H and V SHARP, PDSTL, ENHNCE, and SYNC. The sync, composite sync, or sync on green. SIZE item provides adjustments to scale and Do You Need A Any combination of H, V, or composite sync position the incoming image with respect to Scaler? polarities are selectable from the remote the output frame. This feature will allow you to control. It will output YPbPr signals with bi- remove an annoying line of vertical blanking CRT front projectors always require dein- level or tri-level sync in any output display interval data at the top of an image, or match terlacing and scaling for standard-definition format, but only 480p, 720p, 1080i, and image positions and widths for several sources. interlaced video signals, and very few of 1080p are standard SMPTE YPbPr formats. The CPHASE adjustment delays the luma them have built-in scalers. CRT projectors The rear panel jacks are a bit too tightly signal relative to the chroma signal by ±7 also have a “sweet spot,” or “golden” dis- packed together. There is little room for fin- steps at 1/4 pixel (about 18.5 nS) per step. play format that maximizes their perform- ger space while inserting or removing The SHARP adjustment provides four set- ance. The Vision has the ability to create a cables, and connectors enter the jacks at a tings. The default setting is 1, but the flat custom display format to match the “sweet slight angle because interference between frequency response setting is 0.