# Dirac - A Video Codec

Created by the British Broadcasting Corporation.

Classes | Typedefs | Enumerations | Functions
dirac_encoder.h File Reference

C interface to Dirac Encoder. More...

`#include <libdirac_common/dirac_inttypes.h>`
`#include <libdirac_common/dirac_types.h>`

Go to the source code of this file.

## Classes
struct | dirac_encparams_t
struct | dirac_encoder_context_t
struct | dirac_enc_data_t
struct | dirac_enc_picstats_t
struct | dirac_enc_seqstats_t
struct | dirac_mv_t
struct | dirac_mv_cost_t
struct | dirac_instr_t
struct | dirac_encoder_t

## Typedefs
typedef PrefilterType | dirac_prefilter_t
typedef VideoFormat | dirac_encoder_presets_t
typedef MVPrecisionType | dirac_mvprecision_t

## Enumerations
enum | dirac_encoder_state_t { ENC_STATE_INVALID = -1, ENC_STATE_BUFFER, ENC_STATE_AVAIL, ENC_STATE_EOS }

## Functions
DllExport void | dirac_encoder_context_init (dirac_encoder_context_t *enc_ctx, dirac_encoder_presets_t preset)
DllExport dirac_encoder_t * | dirac_encoder_init (const dirac_encoder_context_t *enc_ctx, int verbose)
DllExport int | dirac_encoder_load (dirac_encoder_t *encoder, unsigned char *uncdata, int uncdata_size)
DllExport dirac_encoder_state_t | dirac_encoder_output (dirac_encoder_t *encoder)
DllExport void | dirac_encoder_end_sequence (dirac_encoder_t *encoder)
DllExport void | dirac_encoder_close (dirac_encoder_t *encoder)

## Detailed Description

A set of 'C' functions that define the public interface to the Dirac encoder. Refer to the the reference encoder source code, encoder/encmain.cpp for an example of how to use the "C" interface. The pseudocode below gives a brief description of the "C" interface usage.

     #include <libdirac_decoder/dirac_encoder.h>

     #define ENCBUF_SIZE 1024*1024;
     unsigned char *buffer, enc_buf[ENC_BUFSIZE];
     int buffer_size;
     dirac_encoder_t *encoder;
     dirac_encoder_context_t enc_ctx;

     // Initialse the encoder context with the presets for SD576 - Standard
     // Definition Digital
     dirac_encoder_context_init (&enc_ctx, VIDEO_FORMAT_SD576I50);

     // Override parameters if required
     // interlace : 1 - interlaced; 0 - progressive
     enc_ctx.seq_params.interlace = 0;
     enc_ctx.seq_params.topfieldfirst = 0;
     enc_ctx.enc_params.qf = 7.5;
     // disable instrumentation flag
     enc_ctx.instr_flag = 0;
     // return locally decoded output
     enc_ctx.decode_flag = 1;

     // Initialise the encoder with the encoder context.
     // Setting verbose output to false
     encoder= dirac_encoder_init(&enc_ctx, false);

     // Set the buffer size. For SD576 4:2:0 chroma
     buffer_size = (720*576*3)/2;
     buffer = (unsigned char *)malloc (buffer_size);

     // Output buffer

     dirac_encoder_state_t state;
     int go = 1;
     do
     {
        read uncompressed frame data into buffer
        if (end of file)
        {
            // push end of sequence
            dirac_encoder_end_sequence(encoder);
        }
        // load one frame of data into encoder
         if (dirac_encoder_load(encoder, buffer, buffer_size) == 0)
        {
            // Retrieve encoded frames from encoder
            do
            {
                encoder->enc_buf.buffer = enc_buf;
                encoder->enc_buf.size = ENCBUF_SIZE;
                state = dirac_encoder_output (encoder);
                switch (state)
                {
                case ENC_STATE_AVAIL:
                     // Encoded frame available in encoder->enc_buf
                     // Encoded frame params available in enccoder->enc_fparams
                     // Encoded frame stats available in enccoder->enc_fstats
                     break;
                case ENC_STATE_BUFFER:
                    break;
                case ENC_STATE_EOS:
                    // Reached end of sequence
                    // End of sequence information is available in encoder->enc_buf
                    // Sequence statistics available in encoder->enc_seqstats;
                    go = 0; // exit from the encoding loop
                    break;
                case ENC_STATE_INVALID:
                default:
                    // Unrecoverable error encountered. Exit;
                    exit (exit code);
                }
                if (encoder->decoded_frame_avail)
                {
                    //locally decoded frame is available in
                    //encoder->dec_buf
                    //locally decoded frame parameters available
                    //in encoder->dec_fparams
                }
                if (encoder->instr_data_avail)
                {
                    //Instrumentation data (motion vectors etc.)
                    //available in encoder->instr
                }
            } while (state == ENC_STATE_AVAIL)
        }
     } while (go == 1);

     // Free the encoder resources
     dirac_encoder_close(encoder)
     // Free the uncompressed data buffer
     free (buffer);

## Typedef Documentation

typedef VideoFormat dirac_encoder_presets_t

Enumerated type that defines encoder presets that set the encoder and sequence paramters. More presets may be added in future

typedef MVPrecisionType dirac_mvprecision_t

Enumerated type that defines motion vector precisions supported by the encoder.

typedef PrefilterType dirac_prefilter_t

Enumerated type that defines prefiltering types supported by the encoder.

## Enumeration Type Documentation

enum dirac_encoder_state_t

Enumerated type that defines encoder state

Enumerator:

  ENC_STATE_INVALID |
  ENC_STATE_BUFFER |
  ENC_STATE_AVAIL |
  ENC_STATE_EOS |

## Function Documentation

DllExport void dirac_encoder_close | ( | dirac_encoder_t * | encoder | ) |

Free resources held by encoder

Parameters:

  encoder | Encoder Handle

DllExport void dirac_encoder_context_init | ( | dirac_encoder_context_t * | enc_ctx,
|  | dirac_encoder_presets_t | preset
| ) |  |

Function that creates an encoder context based on a preset value. The values can then be overridden by the user by setting each field separately

Parameters:

  enc_ctx | pointer to Encoder context tp be initialised.
  preset | Preset to be used to initialise the encoder context
          For a full list of video formats presets supported and the default values
          of the source and encoder parameters. refer to Annex C of the Dirac
          ByteStream Specification.

DllExport void dirac_encoder_end_sequence | ( | dirac_encoder_t * | encoder | ) |

Request the encoder to end the sequence.

Parameters:

  encoder | Encoder Handle

DllExport dirac_encoder_t* dirac_encoder_init | ( | const dirac_encoder_context_t * | enc_ctx,
|  | int | verbose
| ) |  |

Initialise encoder. Makes a copy of the enc_ctx passed to it.

Parameters:

  enc_ctx | Parameters to initialise encoder context
  verbose | boolean flag to set verbose output

Returns:
  encoder Handle to encoder if successful or NULL on failure

DllExport int dirac_encoder_load | ( | dirac_encoder_t * | encoder,
|  | unsigned char * | uncdata,
|  | int | uncdata_size
| ) |  |

Load uncompressed data into the encoder. Expects one full frame of data

Parameters:

  encoder | Encoder Handle
  uncdata | Uncompressed data buffer
  uncdata_size | boolean flag to set verbose output

Returns:
  return status. >0 - successful; -1 failed Failure may be due to input data size not matching the required frame size.

DllExport dirac_encoder_state_t dirac_encoder_output | ( | dirac_encoder_t * | encoder | ) |

Retrieve an encoded frame from the encoder. Returns the state of the encoder. The encoder buffer enc_buf in the encodermust be set up with the buffer and buffer_size that will hold the encoded frame

Parameters:

  encoder | Encoder Handle

Returns:
  ENC_STATE_INVALID - unrecoverable error ENC_STATE_BUFFER - load data into encoder ENC_STATE_AVAIL - Encoded frame available ENC_STATE_EOS - End of Sequence info available

© 2004 British Broadcasting Corporation. Dirac code licensed under the Mozilla Public License (MPL) Version 1.1.
HTML documentation generated by Dimitri van Heesch's excellent Doxygen tool.