Digital Signal Processing Reference
In-Depth Information
second. In practice there is timing information associated with
each frame of video which we shall ignore for now.
If this video has to be processed in real-time
which means
e
without buffering
then the pixels have to be processed at
e
124.4 MHz.
Any operation that needs to be done on the bits of one pixel
must be done so fast that the same operation can be done on
124.4 million pixels in the space of one second. In other words the
frequency is 124.4 Mhz. In reality this is around 148 Mhz since we
must account for the timing information in each video frame.
This frequency is important because whatever processing
platform you choose must be able to work at this frequency. Also
remember that each pixel is comprised of color planes and each
color plane is represented by a certain number of bits. A color
plane refers to the bits associated with each color R, G or B, for
example. Let's say 8 bits for each color plane and let's assume
simple RGB color planes. Going back to the processing speed,
each pixel's 24 bits have to be manipulated at a frequency of
148 Mhz. With an FPGA this is relatively easy since a wide, 24-bit
hardware processing chain can be laid out. If you use an 8-bit
DSP, which can manipulate 8 bits, then you have to run this DSP
at 3
148 Mhz to keep up with the pixels coming in. In practice
HD video manipulation would normally be done on a 32-bit DSP
or processor.
