Switcher using shared decompression processors for processing both broadband and compressed video data

A switcher using shared processors has an input matrix with a plurality of inputs to which a corresponding plurality of sources may be coupled. One or more of the sources may provide compressed data. The input matrix routes selected ones of the sources to a plurality of outputs which is less in number than the number of inputs, the routing being determined by a tally output. A pool of processors, such as compression decoders, color correctors or the like, are coupled to the outputs of the input matrix as needed for processing those sources that require such processing to provide processed data. The outputs of the processors provide processed data to a conventional switcher that combines the selected processed data to provide a program output. The conventional switcher also provides the tally output. For sources that provide inter-frame compressed data, the conventional switcher provides a preview output and a preview tally output so that the necessary time delay for decompressing such data is anticipated to minimize delay in switching the preview output to the program output. A resource management module keeps track of which processors are committed to which sources.

BACKGROUND OF THE INVENTION 
The present invention relates to the switching of signals, and more 
particularly to a switcher that uses shared processors, such as 
compression decoders, color correctors or the like. 
It is projected that, particularly in an HDTV (High Definition TeleVision) 
plant, most of the disk and storage devices in a television plant will use 
compression. It is desirable to interconnect these devices in their native 
compressed formats. One problem with this approach is that production 
switchers, master control switchers and digital effects systems, all of 
which operate in a non-compressed format, require de-compression functions 
on their inputs. For a large switcher with a great number of inputs this 
could result in a significant economic burden due to the large number of 
de-compression functions required, i.e., one for each input. Other 
functions also are desired in a switcher, such as color correctors. But 
again having a color corrector for each input is expensive in cost and 
hardware. 
Although a switcher has a large number of inputs, only a small number of 
them are actually active at the output of the switcher. For the majority 
of the time there may actually only be one input routed to the output of 
the switcher. The switcher typically includes a tally function that 
indicates all of the inputs which are actively used to generate a program 
output at any particular time. Typically where two videos are combined, 
one a foreground video and another a background video like a weather man 
in front of a weather map, and characters are overlaid on top, three input 
sources are being used to create the program output, and the tally 
function causes switcher lights to illuminate, indicating the three inputs 
being used. 
What is desired is a switcher with multiple inputs that minimizes the 
number of processing functions required at the input to produce a program 
output. 
BRIEF SUMMARY OF THE INVENTION 
Accordingly the present invention provides a switcher with multiple inputs 
using shared processors that has an input stage architecture which allows 
automated assignment from a small number of processor functions based on 
the output requirements of the switcher rather than requiring a large 
number of processor functions based on the input size of the switcher. The 
sources are input to an input matrix for routing to a pool of processors 
that perform a specified processing function, such as compression 
decoding, color correcting or the like. The number of processors is 
determined by the maximum number of sources that can be combined into 
outputs of the switcher. A tally output from the switcher is fed back to 
the input matrix to initiate a change in the routing, such as during the 
vertical interval of the program output for a video signal. A resource 
manager is coupled to the input matrix, the video processors and the 
switcher to keep track of which processors are committed to which 
resources. For processing of multiple frame groups of pictures in a 
compressed environment, a preview output and a preview tally output also 
are provided by the switcher, with the preview tally output being fed back 
to the input matrix. 
The objects, advantages and other novel features of the present invention 
are apparent from the following detailed description when read in 
conjunction with the appended claims and attached drawing.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1 a switcher 10 has a plurality of input sources 11, 
one or more of which may contain compressed data or data that needs to be 
otherwise processed prior to being produced at a program output. The input 
sources 11 are coupled to the inputs of an input matrix 12. The number of 
outputs from the input matrix 12 is less than the number of inputs, but 
provides enough outputs to accommodate the maximum number of outputs 
required by the switcher 10. Further where the input sources are mixed 
between compressed and uncompressed data sources, the input matrix 12 
includes means for detecting whether the input source is compressed or 
uncompressed. A plurality of processors 14, such as compression decoders, 
color correctors or the like, are switchably coupled to the outputs of the 
input matrix 12, with data to be processed being routed through one of the 
processors. The unprocessed data directly from the outputs of the input 
matrix 12 or the processed data from the processors 14 are input in an 
appropriate format to a conventional switcher 16 which provides at a 
minimum a program output and a program tally output. The program tally 
output also is provided as an input to the input matrix 12 to select the 
routing of the data from the input sources 11 through the input matrix 12, 
making the routing changes during the vertical interval for a video 
signal, to create the desired program output. A resource management module 
18, which may be independent or part of either the input matrix 12 or the 
conventional switcher 16, communicates with the input matrix, the 
processors 14 and the conventional switcher 16 to automatically assign one 
or more of the processors as needed at the outputs of the input matrix 12. 
If all of the input sources 11 are in the form of compressed data, the 
processors 14 are compression decoders and the resource manager 18 keeps 
track of which of the compression decoders are currently being used. All 
outputs from the input matrix 12 that appear in the program output from 
the conventional switcher 16 are decoded. In this case the compression 
decoders 14 may be hardwired to the outputs from the input matrix 12. 
In the case of intra-frame coding, i.e., where the coding is frame-bound, 
one of the outputs of the input matrix 12 may be assigned to one of the 
input sources 11 in response to the tally signal at a time corresponding 
to the beginning of a first frame of video that is used at the output. The 
resource manager 18 assures that one of the compression decoders 14 is 
coupled to the output to decompress the data. Decoding delays are 
pipelined in the conventional switcher 16 so that the tally signal alone 
is an adequate indicator of the required input sources 11, and together 
with the resource manager 18 defines the compression decoders 14 required. 
In the case of compression coding using a long group of pictures (GOP) 
where the compression is inter-frame, however, the compression decoder 14 
may depend on earlier compressed data to reconstruct any particular output 
frame. Therefore with compression coding of longer GOPs, advance 
assignment of required compression decoders 14 is required. It is common 
to use a preview bus in switchers to allow presetting of input sources 11 
and effects before they are actually used. By combining the tally signal 
from this preview or preset bus with the tally signal from the program 
bus, compression decoders 14 may be assigned to provide a preview output 
before their outputs are actually required to create the program output. 
This allows the compression decoders 14 to be primed with a full GOP or 
more of input data before the program output is required. 
In operation when an operator selects at the conventional switcher 16 
certain input sources 11 to be part of the program output, the input 
matrix 12 indicates to the resource manager 18 whether the desired source 
is compressed or uncompressed. For uncompressed sources the resource 
manager 18 does not switch in any of the compression decoders 14 and the 
data passes directly from the output of the input matrix 12 to the 
conventional switcher 16. However for compressed sources the resource 
manager 18 assigns the next available compression decoder 14 to the 
appropriate output of the input matrix 12 so that the conventional 
switcher 16 receives the data in uncompressed format. The conventional 
switcher 16 combines the provided uncompressed data to produce the desired 
program output. 
For compressed sources using long GOPs the operator indicates not only what 
is desired for the program output, but then also what is desired for a 
preview output, i.e., the next change that will appear in the program 
output. The resource manager 18 interacts with the input matrix, decoders 
14 and switcher 16 together with the preview tally, as indicated above, to 
provide the preview output. The preview output allows the compression 
decoders 14 to process GOPs without appreciable delay, starting with the 
first frame of the next GOP, when a change in the program output is 
desired. 
As another example where the processors 14 are color correctors, assignment 
of the color correctors to the outputs of the input matrix 12 gives the 
apparent indication to the operator that all of the inputs have a color 
corrector associated with them. The operator initially assigns color 
correction parameters for each input source 11, and these parameters are 
stored in the resource manager 18. When a color corrector 14 is assigned 
by the resource manager 18 to an output of the input matrix 12, the 
appropriate parameters also are passed on to the color corrector by the 
resource manager. The various types of processors 14 may be switchably 
cascaded together so that a compressed data signal is decompressed and 
then color corrected, or an uncompressed data signal is color corrected, 
or no processing is done for the particular input source 11, as needed. 
Thus the present invention provides a switcher using shared processors that 
are less in number than the number of inputs to an input matrix for the 
switcher, which processors, including compression decoders, color 
correctors and the like, are assigned to the outputs of the input matrix 
as needed to produce a program output from a conventional switcher.