.. _nvjpeg2kintroduction-label:

Introduction
#############

The nvJPEG2000 library accelerates the decoding of JPEG 2000 images on NVIDIA GPUs. The library is built on the CUDA platform and is 
supported on Pascal+ GPU architectures.

.. note:: Throughout this document, the terms "CPU" and "Host" are used synonymously. Similarly, the terms "GPU" and "Device" are synonymous.


nvJPEG2000 Decoder
^^^^^^^^^^^^^^^^^^

The library utilizes both CPU and GPU for decoding. Tier 2 decode stage(First stage of decode. Refer to the JPEG 2000 specification for details.)
is run on the CPU. All other stages of the decoding process are offloaded to the GPU.

The nvJPEG2000 decoder supports the following subset of JPEG 2000 Part 1:

- Up to 16 bits per component
- No of components (channels): 1 or 3
- Reversible(5-3) and Irreversible(9-7) wavelet transforms
- Multiple tiles per image
- Upto 20 quality layers per image
- Component dimensions within an image should be the same (444 subsampling only)
- All progression orders are supported
- Image and tile start coordinates should be 0
- Tile/Resolution based decoding
- Partial decoding of tiles
- jp2 file format and jpeg2000 codestream are supported


Prerequisites
^^^^^^^^^^^^^^
- CUDA Toolkit version 11.0 and above
- CUDA Driver version r450 and above


Platforms Supported
^^^^^^^^^^^^^^^^^^^^

* **Linux versions:**

+-------------+------------------------------------------------+
|             | Distribution Information                       |
+             +-------------+--------+-------+------+----------+
|Architecture |Name         |Version |Kernel |GCC   |GLIBC     |
+=============+=============+========+=======+======+==========+
| x86_64      |RHEL/CentOS  |7.8     |3.10.0 |4.8.5 |2.17      |
|             |             +--------+-------+------+----------+
|             |             |8.2     |4.18   |8.3.1 |2.28      |
|             +-------------+--------+-------+------+----------+
|             |Ubuntu       |20.04.1 |5.4.0  |9.3.0 |2.32      |
|             |             +--------+-------+------+----------+
|             |             |18.04.5 |4.15.0 |8.2.0 |2.27      |
|             |             +--------+-------+------+----------+
|             |             |16.04.7 |4.5.0  |5.4.0 |2.23      |
|             +-------------+--------+-------+------+----------+
|             |OpenSUSE Leap|15.2    |4.12.14|7.4.0 |2.26-lp151|
|             +-------------+--------+-------+------+----------+
|             |SUSE SLES    |15.2    |4.12.14|7.3.1 |2.26      |
+-------------+-------------+--------+-------+------+----------+

* **Windows versions:**

  * Windows 10 and Windows Server 2019 
  * Support added from version 0.1.0 onwards


Thread Safety
^^^^^^^^^^^^^

Not all nvJPEG2000 types are thread safe. The following should be instantiated separately for each thread: :ref:`nvjpeg2kDecodeState_t<nvjpeg2kdecodestate-label>` and 
:ref:`nvjpeg2kStream_t<nvjpeg2kbitstreamhandle-label>`