page_title: Hanover bars
section_title: Suppression of Hanover bars
hierarchical_section_title: Hanover bars / Suppression of Hanover bars
caption_attribution_description: English: A simulation of severe phase errors in PAL color decoding shown applied to a PM5544 test pattern. In this example the chroma delay line is enabled, cancelling out the phase errors and suppressing Hanover bars. The outermost columns of the test pattern contain color signals that do not alternate phase between lines unlike a normal PAL signal; if the phase is correct those signals will have complementary color from line to line, and cancel out if a delay line is present. In this case, they reveal the phase error through discoloration.
context_page_description: Hanover bars, in one of the PAL television video formats, are an undesirable visual artifact in the reception of a television image. The name Hanover refers to the city in which the PAL system developer Telefunken Fernseh und Rundfunk GmbH was located.
  Two signals, B-Y and R-Y (V) are used in the PAL system to carry the color information for a picture, with the phase of the V signal reversed on alternate lines. This is done to cancel minor phase errors in the reception process. However, if gross errors occur, complementary errors from the V signal carry into the U signal, and thus visible stripes occur.
  Later PAL systems introduced alterations to ensure that Hanover bars do not occur, introducing a "swinging burst" to the color synchronization. Other PAL systems may handle this problem differently.
context_section_description: To suppress Hanover bars, PAL color decoders use a delay line which repeats the chroma information from each previous line, and blends it with the current line. This causes phase errors to cancel out, at the cost of vertical color resolution, and in early designs, also a loss of color saturation proportional to the phase error.
caption: Cancellation of Hanover bars through a chroma delay line
exif: {}