An encoder and encoding method for inserting logos into a digital
television signal. The logo insertion is performed at the front end of the
encoder (e.g., prior to compression) by sharing the video capture frame
buffer of the encoder, so there is no need for a separate logo inserter
with a separate buffer, and encoding cost are reduced. An alpha blending
function receives logo image and logo alpha map data for blending with
input video data. The input video is retrieved from the frame buffer, and
written back to the frame buffer after blending with the logo data.
Subsequently, the frame buffer contents are provided to a pre-processing
function for filtering and film mode detection. For a film mode frame, a
drop field decision is provided from the pre-processing function to the
frame buffer to drop the redundant field. The pre-processed video data is
then provided for conventional compression processing. In an HDTV
embodiment, several compressors are provided which each receive a panel of
a video frame.