Transmission/Technical Information

Why do the aspect ratio's change when I am watching certain programmes?

Channel 4 originated transmissions provide for three aspect ratios: 4:3, 16:9 that is safe for 14:9 viewing and 16:9. Using a 4:3 TV to view a 4:3 aspect ratio transmission is straight forward. When a 4:3 TV is used to view 16:9 safe for 14:9, what should happen is that the freeview box will zoom in a little to provide thin black bands top and bottom and cut a little of the sides of the picture off. This facility is intended to provide a reasonable compromise for viewers with 4:3 TVs. (14:9 is often used for analogue transmissions for the same reason).Note that some freeview boxes do not support this option and will produce a 16:9 letterbox display in this mode with thick black lines top and bottom, but the correct aspect ratio.A few types of box may become confused and not produce satisfactory pictures. When a 4:3 TV is used to view 16:9 programmes the pictures may be presented in one of two ways depending on the chosen option in the freeview box. Either in letterbox with thick black lines top and bottom or in centre cut out. Centre cut out enlarges the centre of the 16:9 image to fill the 4:3 screen and in so doing cuts off the sides of the picture. Note that some shows which are a mixture of 16:9 and 4:3 have to present the 4:3 with an area of black each side of the screen. If this is being watched in letterbox on a 4:3 TV, this will result in an area of black all around the image. E4 is transmitted with a different resolution setting from E4+1.Some boxes can give unexpected results as a result of this. If you are able to compare results/settings with friends and neighbours it may be helpful.

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