Filter and Other Operations#
The filtering unit performs an operation on a series of unsigned integers, resulting in an output stream of integers. The bit-width of these integers can vary between 1-32 bits.
Some operations process a single data stream, which comes from the
normal input fields in the job structure. Some of them operate on two
data streams. For these operations, the second data stream is specified
using the qpl_job.next_src2_ptr and
qpl_job.available_src2 fields. This will be referred
to as source-2, whereas the main input stream will be referred to as
source-1.
By default, the source-1 data is read directly from the specified input
buffer. If the QPL_FLAG_DECOMPRESS_ENABLE flag is given, then the data
from the input buffer is firstly decompressed, and then the decompressed
data is sent to the filter unit.
Each filtering job is independent. Filtering job does not support processing a large stream as a series of smaller jobs, as compression and decompression jobs do. Thus, each filtering job is considered implicitly both a FIRST and a LAST job. That is, for a filtering operation, it is as if the flags specified both FIRST and LAST.
If the bit-width of an array is 1, then the array will be referred to as a bit-vector. That is, a bit-vector is just an array whose width happens to be 1. If the bit-width is more than 1, it is called an array.
The output can be written as a packed little-endian array or as a packed big-endian array.
In some cases, for example, for small bit-widths, the number of input
elements is ambiguous. To account for this, the number of input elements
must be specified in qpl_job.num_input_elements.
Processing will stop when these input elements are processed.
If the input ends before these input elements are processed, then the actual number of elements processed is implementation specific, and an error status will be returned.
In most cases, qpl_job.num_input_elements reflects the number
of elements in source-1. The exception is that for the expand operation,
it reflects the number of elements in source-2.