GPUJPEG
  JPEG encoder and decoder library and console application for NVIDIA GPUs.

AUTHOR:
  Martin Srom, CESNET z.s.p.o
  Jan Brothánek
  Martin Jirman
  Jiri Matela
  Martin Pulec
  Petr Holub

DESCRIPTION:
  The first test implementation of the JPEG image compression standard for 
NVIDIA GPUs used for real-time transmission of high-definition video.

OVERVIEW:
-It uses NVIDIA CUDA platform.
-Not optimized yet (it is only the first test implementation).
-Encoder and decoder use Huffman coder for entropy encoding/decoding.
-Encoder produces by default baseline JPEG codestream which consists of proper codestream
 headers and one scan for each color component without subsampling and it uses
 restart flags that allows fast parallel encoding. The quality of encoded 
 images can be specified by value 0-100.
-Optionally encoder can produce interleaved stream (all components in one scan) or/and
 subsampled stream.
-Decoder can decompress only JPEG codestreams that can be generated by encoder. If scan 
 contains restart flags, decoder can use parallelism for fast decoding.
-Encoding/Decoding of JPEG codestream is divided into following phases:
   Encoding:                       Decoding
   1) Input data loading           1) Input data loading
   2) Preprocessing                2) Parsing codestream 
   3) Forward DCT                  3) Huffman decoder
   4) Huffman encoder              4) Inverse DCT
   5) Formatting codestream        5) Postprocessing
 and they are implemented on CPU or/and GPU as follows:
   -CPU: 
      -Input data loading
      -Parsing codestream
      -Huffman encoder/decoder (when restart flags are disabled)
      -Output data formatting
   -GPU: 
      -Preprocessing/Postprocessing (color component parsing, 
       color transformation RGB <-> YCbCr)
      -Forward/Inverse DCT (discrete cosine transform)
      -Huffman encoder/decoder (when restart flags are enabled)  

PERFORMANCE:
  Following tables summarizes encoding/decoding performance using NVIDIA 
GTX 580 for non-interleaved and non-subsampled stream with different quality 
settings (time, PSNR and encoded size values are averages of encoding several 
images, each of them multiple times):

Encoding:
         |           4k (4096x2160)         |         HD (1920x1080)
 --------+----------------------------------+---------------------------------
 quality | duration |     psnr |       size | duration |     psnr |       size
 --------+----------+----------+------------+---------------------------------
      10 | 26.79 ms | 29.33 dB |  539.30 kB |  6.71 ms | 27.41 dB |  145.90 kB
      20 | 26.91 ms | 32.70 dB |  697.20 kB |  6.74 ms | 30.32 dB |  198.30 kB
      30 | 27.17 ms | 34.63 dB |  850.60 kB |  6.84 ms | 31.92 dB |  243.60 kB
      40 | 27.19 ms | 35.97 dB |  958.90 kB |  6.89 ms | 32.99 dB |  282.20 kB
      50 | 27.29 ms | 36.94 dB | 1073.30 kB |  6.92 ms | 33.82 dB |  319.10 kB
      60 | 27.39 ms | 37.96 dB | 1217.10 kB |  6.95 ms | 34.65 dB |  360.00 kB
      70 | 27.51 ms | 39.22 dB | 1399.20 kB |  7.04 ms | 35.71 dB |  422.10 kB
      80 | 27.76 ms | 40.67 dB | 1710.00 kB |  7.13 ms | 37.15 dB |  526.70 kB
      90 | 28.36 ms | 42.83 dB | 2441.40 kB |  7.32 ms | 39.84 dB |  768.40 kB
     100 | 35.47 ms | 47.09 dB | 7798.70 kB |  9.31 ms | 47.21 dB | 2499.60 kB

Decoding:
         |           4k (4096x2160)         |         HD (1920x1080)
 --------+----------------------------------+---------------------------------
 quality | duration |     psnr |       size | duration |     psnr |       size
 --------+----------+----------+------------+---------------------------------	
      10 | 10.28 ms | 29.33 dB |  539.30 kB |  3.13 ms | 27.41 dB |  145.90 kB
      20 | 11.31 ms | 32.70 dB |  697.20 kB |  3.59 ms | 30.32 dB |  198.30 kB
      30 | 12.36 ms | 34.63 dB |  850.60 kB |  3.97 ms | 31.92 dB |  243.60 kB
      40 | 12.90 ms | 35.97 dB |  958.90 kB |  4.28 ms | 32.99 dB |  282.20 kB
      50 | 13.45 ms | 36.94 dB | 1073.30 kB |  4.56 ms | 33.82 dB |  319.10 kB
      60 | 14.71 ms | 37.96 dB | 1217.10 kB |  4.81 ms | 34.65 dB |  360.00 kB
      70 | 15.03 ms | 39.22 dB | 1399.20 kB |  5.24 ms | 35.71 dB |  422.10 kB
      80 | 16.64 ms | 40.67 dB | 1710.00 kB |  5.89 ms | 37.15 dB |  526.70 kB
      90 | 19.99 ms | 42.83 dB | 2441.40 kB |  7.48 ms | 39.84 dB |  768.40 kB
     100 | 46.45 ms | 47.09 dB | 7798.70 kB | 16.42 ms | 47.21 dB | 2499.60 kB
     
USAGE:
  1) LIBGPUJPEG LIBRARY:
      To build libgpujpeg library check REQUIREMENTS and go to 
    gpujpeg/libgpujpeg/ directory and run 'make' command. The shared library 
    object ./libgpujpeg.so will be build.
      To use library in your project you have to include library to your 
    sources and linked shared library object to your executable:
      
      #include "libgpujpeg/gpujpeg.h"
      
    ENCODING:
      For encoding by libgpujpeg library you have to declare two structures
    and set proper values to them. The first is definition of encoding/decoding 
    parameters, and the second is structure with parameters of input image:
      
      struct gpujpeg_parameters param;
      gpujpeg_set_default_parameters(&param);   
      param.quality = 80; 
      // (default value is 75)
      param.restart_interval = 16; 
      // (default value is 8)
      param.interleaved = 1;
      // (default value is 0)
      
      struct gpujpeg_image_parameters param_image;
      gpujpeg_image_set_default_parameters(&param_image);
      param_image->width = 1920;
      param_image->height = 1080;
      param_image->comp_count = 3;
      // (for now, it must be 3)
      param_image->color_space = GPUJPEG_RGB; 
      // or GPUJPEG_YCBCR_ITU_R or GPUJPEG_YCBCR_JPEG
      // (default value is GPUJPEG_RGB)
      param_image.sampling_factor = GPUJPEG_4_4_4;
      // or GPUJPEG_4_2_2
      // (default value is GPUJPEG_4_4_4)
      
    If you want to use subsampling in JPEG format call following function,
    that will set default sampling factors (2x2 for Y, 1x1 for Cb and Cr):
    
      // Use default sampling factors
      gpujpeg_parameters_chroma_subsampling(&param);
      
    Or define sampling factors by hand:
    
      // User custom sampling factors
      param.sampling_factor[0].horizontal = 4;
      param.sampling_factor[0].vertical = 4;
      param.sampling_factor[1].horizontal = 1;
      param.sampling_factor[1].vertical = 2;
      param.sampling_factor[2].horizontal = 2;
      param.sampling_factor[2].vertical = 1;
        
    Next you have to initialize CUDA device by calling:
      
      if ( gpujpeg_init_device(device_id, 0) )
          return -1;
        
    where first parameters is CUDA device (e.g. device_id = 0) id and second 
    parameter is flag if verbose output should be used (0 or GPUJPEG_VERBOSE). 
    Next step is to create encoder:
    
      struct gpujpeg_encoder* encoder = gpujpeg_encoder_create(&param, 
          &param_image);
      if ( encoder == NULL )
          return -1;
        
    When creating encoder, library allocates all device buffers which will be 
    needed for image encoding and when you encode concrete image, they are 
    already allocated and encoder will used them for every image. Now we need 
    raw image data that we can encode by encoder, for example we can load it 
    from file:
    
      int image_size = 0;
      uint8_t* image = NULL;
      if ( gpujpeg_image_load_from_file("input_image.rgb", &image, 
               &image_size) != 0 )
          return -1;
            
    Next step is to encode uncompressed image data to JPEG compressed data 
    by encoder:
    
      struct gpujpeg_encoder_input encoder_input;
      gpujpeg_encoder_input_set_image(&encoder_input, image);
    
      uint8_t* image_compressed = NULL;
      int image_compressed_size = 0;
      if ( gpujpeg_encoder_encode(encoder, &encoder_input, &image_compressed, 
               &image_compressed_size) != 0 )
          return -1;
            
    Compressed data are placed in internal encoder buffer so we have to save 
    them somewhere else before we start encoding next image, for example we 
    can save them to file:
            
      if ( gpujpeg_image_save_to_file("output_image.jpg", image_compressed, 
               image_compressed_size) != 0 )
          return -1;
            
    Now we can load, encode and save next image or finish and move to clean up
    encoder. Finally we have to clean up so destroy loaded image and destroy 
    the encoder.
    
      gpujpeg_image_destroy(image);
      gpujpeg_encoder_destroy(encoder);
        
    DECODING:
      For decoding we don't need to initialize two structures of parameters. 
    We only have to initialize CUDA device if we haven't initialized it yet and 
    create decoder:
        
      if ( gpujpeg_init_device(device_id, 0) )
          return -1;
        
      struct gpujpeg_decoder* decoder = gpujpeg_decoder_create();
      if ( decoder == NULL )
          return -1;
            
    Now we have two options. The first is to do nothing and decoder will 
    postpone buffer allocations to decoding first image where it determines 
    proper image size and all other parameters. All the following images must 
    have the same parameters. The second option is to provide input image size 
    and optionally other parameters and the decoder will allocate all buffers 
    and it is fully ready when encoding even the first image. 
    
      struct gpujpeg_parameters param;
      gpujpeg_set_default_parameters(&param);
      param.restart_interval = 16; 
      param.interleaved = 1;
      
      struct gpujpeg_image_parameters param_image;
      gpujpeg_image_set_default_parameters(&param_image);
      param_image->width = 1920;
      param_image->height = 1080;
      param_image->comp_count = 3;
    
      // Pre initialize decoder before decoding
      gpujpeg_decoder_init(decoder, &param, &param_image);
      
    If you want to specify output image color space and/or subsampling factor,
    you can use following two parameters. You can specify them though the
    param structure befor passing it to gpujpeg_decoder_init. But if you
    postpone this initialization process to the first image, you have no
    other option than specify them in this way:
    
      decoder->coder.param_image.color_space = GPUJPEG_RGB;
      // or GPUJPEG_YCBCR_ITU_R or GPUJPEG_YCBCR_JPEG
      // (default value is GPUJPEG_RGB)
      decoder->coder.param_image.sampling_factor = GPUJPEG_4_4_4;
      // or GPUJPEG_4_2_2
      // (default value is GPUJPEG_4_4_4)
            
    Next we have to load JPEG image data from file and decoded it to raw 
    image data:
            
      int image_size = 0;
      uint8_t* image = NULL;
      if ( gpujpeg_image_load_from_file("input_image.jpg", &image, 
               &image_size) != 0 )
          return -1;
    
      struct gpujpeg_decoder_output decoder_output;
      gpujpeg_decoder_output_set_default(&decoder_output);
      if ( gpujpeg_decoder_decode(decoder, image, image_size, 
               &decoder_output) != 0 )
          return -1;
            
    Now we can save decoded raw image data to file and perform cleanup:
            
      if ( gpujpeg_image_save_to_file("output_image.rgb", decoder_output.data, 
               decoder_output.data_size) != 0 )
          return -1;
        
      gpujpeg_image_destroy(image);
      gpujpeg_decoder_destroy(decoder);
      
    
  2) GPUJPEG CONSOLE APPLICATION:
      The console application gpujpeg uses libgpujpeg library to demonstrate
    it's functions. To build console application check REQUIREMENTS and go to
    gpujpeg directory (where README and LICENSE files are placed) and run 
    'make' command. It builds libgpugjpeg library in subdirectory 
    ./libgpujpeg/ and it creates executable file ./gpujpeg and run script 
    ./gpujpeg.sh, which runs executable file linked to runtime library 
    libgpujpeg.so (which is placed in ./libgpujpeg/ subdirectory).
      To encode image from raw RGB image file to JPEG image file use following
    command:
      
      ./gpujpeg.sh --encode --size=WIDTHxHEIGHT --quality=QUALITY \ 
              INPUT_IMAGE.rgb OUTPUT_IMAGE.jpg
      
    You must specify input image size by --size=WIDTHxHEIGHT parameter. 
    Optionally you can specify desired output quality by parameter 
    --quality=QUALITY which accepts values 0-100. Console application accepts 
    a few more parameters and you can list them by folling command:
    
      ./gpujpeg.sh --help
      
    To decode image from JPEG image file to raw RGB image file use following 
    command:
      
      ./gpujpeg.sh --decode OUTPUT_IMAGE.jpg INPUT_IMAGE.rgb
      
    You can also encode and decode image to test the console application:
      
      ./gpujpeg.sh --encode --decode --size=WIDTHxHEIGHT --quality=QUALITY \
              INPUT_IMAGE.rgb OUTPUT_IMAGE.jpg
      
    Decoder will create new decoded file OUTPUT_IMAGE.jpg.decoded.rgb and do 
    not overwrite your INPUT_IMAGE.rgb file.
      Console application is able to load raw RGB image file data from *.rgb 
    files and raw YUV and YUV422 data from *.yuv files. For YUV422 you must 
    specify *.yuv file and use '--sampling-factor=4:2:2' parameter. 
    All supported parameters for console application are following:
      --help
          Prints console application help
      --size=1920x1080
          Input image size in pixels, e.g. 1920x1080
      --sampling-factor=4:4:4
          Input image sampling factor (supported are '4:4:4' and '4:2:2')
      --colorspace=rgb
          Input image colorspace (supported are 'rgb', 'yuv' and 'ycbcr-jpeg', 
          where 'yuv' means YCbCr ITU-R BT.601), when *.yuv file is specified,
          instead of default 'rgb', automatically the colorspace 'yuv' is used
      --quality
          Set output quality level 0-100 (default 75)
      --restart=8
          Set restart interval for encoder, number of MCUs between 
          restart markers
      --subsampled
          Produce chroma subsampled JPEG stream
      --interleaved
          Produce interleaved stream
      --encode
          Encode images
      --decode
          Decode images
      --device=0
          By using this parameter you can specify CUDA device id which will 
          be used for encoding/decoding.
    
    Restart interval is important for parallel huffman encoding and decoding.
    When '--restart=N' is used (default is 8), the coder can process each 
    N MCUs independently, and so he can code each N MCUs in parallel. When 
    '--restart=0' is specified, restart interval is disabled and the coder 
    must use CPU version of huffman coder (because on GPU would run only one 
    thread, which is very slow).
      The console application can encode/decode multiple images by following 
    command:
      
      ./gpujpeg.sh ARGUMENTS INPUT_IMAGE_1.rgb OUTPUT_IMAGE_1.jpg \
              INPUT_IMAGE_2.rgb OUTPUT_IMAGE_2.jpg ...
    
REQUIREMENTS:
    To be able to build and run libgpujpeg library and gpujpeg console 
  application you need:
  1) CUDA Toolkit (http://developer.nvidia.com/cuda-toolkit) installed,
     default installation path is /usr/local/cuda. If you have the CUDA 
     installed somewhere else, you need to specify it by environment variable 
     CUDA_INSTALL_PATH or in Makefiles by CUDA_INSTALL_PATH variable.
  2) NVIDIA developer drivers
  3) CUDA enabled NVIDIA GPU

LICENSE:
  See file LICENSE.
  This software contains source code provided by NVIDIA Corporation.
  This software source code is based on SiGenGPU [3].

REFERENCES:
  [1] http://www.w3.org/Graphics/JPEG/itu-t81.pdf
  [2] http://www.ijg.org/
  [3] https://github.com/silicongenome/SiGenGPU
  [4] http://www.ecma-international.org/publications/files/ECMA-TR/TR-098.pdf