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Unformatted text preview: ncoding is applied on the run-length coded stream to
obtain the JPEG compressed stream.
The lossless mode of JPEG compression uses a different method than the lossy
method shown in Figure 19.10. Fundamentally, the image pixels are handled
separately (i.e., the 8 x 8 block structure is not used), and each pixel is predicted
based on three adjacent pixels using one of eight possible predictor modes. The
basic steps of lossless JPEG compression (shown in Figure 19.11) are as follows
(the decoder performs the inverse operations):
A simple predictive coding scheme is first applied to the image to be
compressed. For this, each pixel of the image is handled separately.
A variable-length encoder is then used to encode the predicted pixels
losslessly to obtain the JPEG compressed bit stream.
MPEG (Motion Pictures Experts Group) is a multimedia standard with
specifications for coding, compression, and transmission of audio, video, and data
streams in a series of synchronized, mixed packets. MPEG video standard is a
subset of the MPEG standard. It is divised for compression of a wide range of
video and motion pictures. It defines the structure of coded video bit streams
transmitted to the decoder and the decoder architecture, but leaves the encoder
architecture undefined, so that some encoders may produce higher quality
compression, some may be real-time, and some may require manual intervention.
MPEG compression is lossy and asymmetric, with the encoding process requiring
more time than the decoding process.
Digital video compression may either apply intraframe compression to each
individual frame of the video or combine both intraframe and interframe compression. The former scheme yields a lower compression ratio than the latter
because it does not exploit temporal redundancy. Differential encoding is one
approach to remove temporal redundancy. It encodes and sends the differences in
the adjacent frames. Motion compensation is another technique for interframe
compression. It compa...
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- Spring '14