Anti Multi Path plugin

BPP_AMPPlugin is designed to reduce the distortion introduced by the antenna in multipath reception. The plugin may be useful to both the users of individual or collective antennas and those who have cable TV.

Distortions arising from multipath reception, as a rule, are a consequence of insufficient selectivity of the receiving TV antenna, which in addition to the main signal of the transmitter receives the signals reflected from other objects. Due to the difference in the distance, the reflected beam falls on the receiving antenna with a time delay, summed with the main signal. On the TV or tuner, it looks as double or triple ghosting. Depending on the width of the antenna pattern, number, size, structure and location of objects (facades, roofs, etc.) that can reflect the signal of the transmitter, the pattern of distortion can be very different, but fairly constant over time.

In cable networks, such distortions can occur when the signal reflects due to the mismatch between cable impedances in pathways.

Depending on the phase the reflected signal came, direct or opposite, it is added or subtracted from the main signal, thereby increasing or decreasing the brightness of the main image. On the screen it will look as outlines of high or low brightness, up to a negative.

BPP_AMPPlugin models the reverse process – weakening, shift («time delay») and subtraction or addition of resultant picture with original one.

Usually there are several reflected beams. Depending of performance of PC with the help of plugin you may suppress up to eight reflected images.

Because distortions have individual character for each channel, every channel must have their own group of settings. Low frequency VHS and S-VHS inputs are not an exclusion.

To start plugin setup select a proper picture in which the distortions are most evident. For this whait until you see a needed picture and press "Freeze" in plugin settings dialog window.

Plugin processe picture step-bu-step. With each step you supress one reflected beam and for each step you need to set it's own values of shift (delay) and level (suppression) of signal. The process of setting these values is rather intuitive. First you need to choose the most strong reflected signal (most bright outline) and try to suppress them. For this set the arbitrary non-zero value for level of signal and shift picture for several pixels. After that you'll see, positive or negative value of signal level you should enter. Then you need to match two outlines together and finally select the level so that they'll compensate each other. After that you may start to compensate other beams.

To comprehend the work of plugin more clearly you may simulate multipath reception of signal.

1. Select channel.
2. Open plugin settings window and turn on picture processing.
3. First simulate multipath reception by setting the level to –30% and shift by 5% to the right. Every picture element will have a negative ghost. That's the multipath reception.
4. Set the second step of plugin to compensate the introduced distortion. It will be natural to assume that compensating level will be the opposite to that we chosen at first step, i.e. level +30%, shifted by 5% to the right.
5. After these manipulations there still will be traces of multipath reception and you may try to compensate them too.

On supression of distortions the level of resulting picture may result in fall out of signal range, that will be seen as saturation of white and black areas of picture. To avoid this plugin allows to adjust brightness and contrast of source picture yet before applying the main settings. Brightness and contrast settings of plugin duplicate the same settings of Behold TV application, so if you turn them off and will use the main program settings, you may save a few percents of CPU resources.

Turning processing (plugin) on and off, in freeze mode or in live video you may control the process of plugin setting.

Here are the samples of properly sat plugin (click picture to view in original size):

Without plugin	With plugin

List of changes

• First release.

• Shift value now set in percents of frame width, that allows to get rid of settings import to other resolutions;
• Added automatic settings saving for each user profile.

• Added settings saving under Windows 7.

• Added support of Behold TV instances.

• Added english interface.

Link to the plugin: BPP_AMPPlugin_v250.zip (43.9 kb)

14.03.16