VCR system skips recorded
System detects TV ads during recording and fast-forwards
through them on playback
Mark A. Gottschalk, Western Technical
Santa Clarita, CA--Regardless of what advertisers and
broadcasters say, nobody likes to watch television commercials. Viewers
frequently head to the kitchen for a snack during these unwanted and boring
interruptions, or, with the advent of the VCR, fast-forward through them during
playback. Yet even the best remote-control jockeys often overshoot a program,
rewind, and then shuttle back and forth a few times to get to where they want to
Like the rest of us, inventor Jerry Iggulden experienced these problems. The difference is, he decided to do something about it. That "something" is called Commercial AdvanceTM, the first successful product to automatically identify and fast-forward through television ads during the playback of a taped program.
It works by recognizing those familiar, silent, black screens that precede every commercial. During recording, the system saves the precise time location of these events in a small "scratchpad" memory. It also marks the location of the event on tape by changing the trailing portion of the tape's control-track square wave into a special "sync mark." At this point, the system only identifies the events and does not determine they signify a commercial. "This is the key to the invention and where other people failed," says Iggulden, "You can't do it in real time."
His approach is to identify commercials after they've been recorded by applying several assumptions (or rules) about the frequency, timing, and spacing of TV advertising. The first: Commercials are sold in increments that always add to 30 or 60 seconds. The second: A brief identifying event precedes each commercial. Lastly, it's assumed that commercials are sold in clusters.
At the end of the recording, the system applies the rules to the time stamps saved in memory. It throws out single, unpaired events, along with those not spaced 30 or 60 seconds apart. Clusters of commercials with definite beginnings and ends remain.
The VCR then rewinds the tape, fast-forwards to the first sync mark corresponding to the beginning of a commercial group, and records a special "A" mark on the control track. At the end of the group it records a different "B" mark. This tape-marking process takes up about three minutes for a 60-minute recording.
During playback, the VCR functions normally until it encounters an "A" mark. It then mutes the audio, puts up a blue screen, and fast forwards to the "B" mark, where normal play resumes.
The fast-forward process takes about eight to ten seconds for a three-minute commercial cluster. It takes less time than the usual forward-scan speed because the VCR does not need to keep the picture synchronized while the blue screen appears. For commercials longer than three minutes, the VCR will disengage the play head and use the high-speed fast-forward.
A big challenge involved making the system compatible with broadcast standards throughout the world. In Japan, for instance, commercials occur in 15 second increments preceded by a precise cut--not a black screen. And in much of Europe, uniform-color flat fields precede commercials. Engineers tackled both of these problems by developing a sophisticated detection algorithm.
Flat fields are simply a special case of the black frame. To spot them, "we analyze every line of every frame of the recording and assign a luminance value to each," says Iggulden. The system subtracts the highest value from the lowest value and looks for a small difference--somewhere between 5 and 10 on a scale of 256. This indicates a flat field, no matter the color.
For Japan, the algorithm breaks the screen into groups of scan lines. It averages the luminance of each group and compares the averages to the same group in the next frame. Drastic changes in luminance from frame to frame indicate a cut and a possible commercial.
Parental program-screening system
Accuracy is quite good. The system detects programs 99% of the time and commercials 97.4% of the time. "That's on a variety of unusual, mixed programming--including things like Australian Football," says Iggulden. "On prime-time programming it's even more accurate."
As with any design, Commercial Advance evolved over several years. Early on, Iggulden looked at just using a precise counter to track events. He also considered a system that would save all the commercial information--even for hundreds of tapes--in onboard memory, and not mark the tape at all.
But the final design won out because it's reliable and easy to use. And for the VCR manufacturer, "it's entirely software-driven and therefore very cheap to implement," he says.
Additional details…Contact Invention Management Associates, 21600 Cleardale St., Newhall, CA 91321, (805) 287-9118, or Circle No. 502.
Commercial Advance algorithm rules
Interval between events is a commercial if:
Less than or equal to 34.99 seconds, or
|Between 43.00 seconds and 49.99 seconds, or
Between 58.00 seconds and 64.99 seconds.
Commercial group is defined as two or more consecutive commercial intervals totaling more than 55.99 seconds
Interval between events is a commercial if it is 15 or 30 seconds ±10 frames
Commercial group is defined as two or more consecutive commercial intervals totaling more than 59 seconds
Live-loaded seat slashes valve-operating torque
Three-way valve delivers leak-free flow
at high volumes and pressures
Terrence Lynch, Contributing Editor
Cresskill, NJ--Sometimes the solution to an engineering problem is to turn the conventional solution on its head. Witness the new 1/2-inch high-pressure three-way ball valve from Hoke Inc. By reversing the conventional relationship of ball and seat, the unit eliminates the leakage and drastically lowers the operating torque that hobbled earlier attempts to manufacture ball valves of this size.
The impetus for the new valve (Model 760651GBY) came from the compressed-natural-gas industry, which needed higher flow in a more compact package. Standard valves used a floating ball forced against rigid seats by line pressure for sealing. Scaling up such designs caused problems--the torque needed to operate them rose beyond practical limits for a manually operated valve. Gangs of smaller valves proved an inefficient, cumbersome alternative.
Vadim Seltser, a Hoke project engineer, says that his three-man team initially considered a pressure-assisted seal for the 1/2-inch-size, 0.375-inch-orifice valve the gas industry wanted, but couldn't get away from the resulting high operating torque. "We were familiar with live-loaded stem seals," explains Seltser, so the team considered that alternative. "In effect, we reversed the roles of the conventional ball and seat," he says.
Space constraints eliminated the possibility of a typical floating-seal design backed by stacks of Belleville springs, but experience with elastomers suggested an alternative. During three months of design work and prototype fabrication, the team developed a live-loaded valve seat of ArlonTM 1330 backed by a elastomeric washer made of nitrile rubber. Because the TeflonTM-filled PEEK seal maintains a calibrated load against the rigidly suspended ball independent of line pressure, at 6,000 psi the new design cut operating torque to just 20 lb-inches, a fifth of conventional designs. Starting or break-away torque was just 22 lb-inches.
Where floating-ball three-way valves were prone to leak when pressure was applied to a side port, the new valve proved exceptionally leak-free regardless of where pressure originated. "Our customer wanted a 6,000-psi valve with an operating range of -40 to 300F," says Seltser. "Even after 100,000 cycles across that range, we had no leakage." Initial compression on the elastomeric washer provided adequate sealing despite wear experienced by the ball.
Seat design aside, good general valve design contributed to the valve's success. The flowpath yields a relatively high valve-flow coefficient (Cv) of 2.44. Hoke's blowout-proof stem and valve-body design gives a four-to-one safety margin: The valve's burst pressure is rated at 24,000 psi. Its proof pressure, i.e., the overpressure at which the valve will operate once and recover to operate at normal conditions, is 12,000 psi.
Additional details…Contact Sergio Radossi, Hoke Inc., One Tenakill Park, Cresskill, NJ 07626, (201) 568-9100, or Circle No. 503.