# Dirac - A Video Codec

Created by the British Broadcasting Corporation.

Classes | Typedefs | Functions
dirac_parser.h File Reference

C interface to Dirac decoder. More...

`#include <libdirac_common/dirac_types.h>`
`#include <libdirac_decoder/decoder_types.h>`

Go to the source code of this file.

## Classes
struct | dirac_decoder_t

## Typedefs
typedef DecoderState | dirac_decoder_state_t

## Functions
DllExport dirac_decoder_t * | dirac_decoder_init (int verbose)
DllExport void | dirac_decoder_close (dirac_decoder_t *decoder)
DllExport dirac_decoder_state_t | dirac_parse (dirac_decoder_t *decoder)
DllExport void | dirac_buffer (dirac_decoder_t *decoder, unsigned char *start, unsigned char *end)
DllExport void | dirac_set_buf (dirac_decoder_t *decoder, unsigned char *buf[3], void *id)

## Detailed Description

A set of 'C' functions that define the public interface to the Dirac decoder. Refer to the the reference decoder source code, decoder/decmain.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_parser.h>\n
     Initialise the decoder

     dirac_decoder_t *decoder_handle = dirac_decoder_init();
     do
     {
         dirac_decoder_state_t state = dirac_parse (decoder_handle);
         switch (state)
         {
         case STATE_BUFFER:
             read more data.
             Pass data to the decoder.
             dirac_buffer (decoder_handle, data_start, data_end)
             break;

         case STATE_SEQUENCE:
             handle start of sequence.
             The decoder returns the sequence parameters in the
             seq_params member of the decoder handle.
             Allocate space for the frame data buffers and pass
             this to the decoder.
             dirac_set_buf (decoder_handle, buf, NULL);
             break;

         case STATE_SEQUENCE_END:
             Deallocate frame data buffers
             break;

         case STATE_PICTURE_AVAIL:
             Handle picture data.
             The decoder sets the fbuf member in the decoder
             handle to the frame decoded.
             break;

         case STATE_INVALID:
             Unrecoverable error. Stop all processing
             break;
         }
     } while (data available && decoder state != STATE_INVALID

     Free the decoder resources
     dirac_decoder_close(decoder_handle)

## Typedef Documentation

typedef DecoderState dirac_decoder_state_t

## Function Documentation

DllExport void dirac_buffer | ( | dirac_decoder_t * | decoder,
|  | unsigned char * | start,
|  | unsigned char * | end
| ) |  |

Copy data into internal buffer

Parameters:

  decoder | Decoder object
  start | Start of data
  end | End of data

DllExport void dirac_decoder_close | ( | dirac_decoder_t * | decoder | ) |

Release the decoder resources

Parameters:

  decoder | Decoder object

DllExport dirac_decoder_t* dirac_decoder_init | ( | int | verbose | ) |

Decoder Init Initialise the decoder.

Parameters:

  verbose | boolean flag to set verbose output

Returns:
  decoder handle

DllExport dirac_decoder_state_t dirac_parse | ( | dirac_decoder_t * | decoder | ) |

Parses the data in the input buffer. This function returns the following values.
STATE_BUFFER: Not enough data in internal buffer to process
STATE_SEQUENCE: Start of sequence detected. The seq_params member in the decoder object is set to the details of the next sequence to be processed.
STATE_PICTURE_START: Start of picture detected. The frame_params member of the decoder object is set to the details of the next frame to be processed.
STATE_PICTURE_AVAIL: Decoded picture available. The frame_aprams member of the decoder object is set the the details of the decoded frame available. The fbuf member of the decoder object has the luma and chroma data of the decompressed frame.
STATE_SEQUENCE_END: End of sequence detected.
STATE_INVALID: Invalid stream. Stop further processing.

Parameters:

  decoder | Decoder object

Returns:
  Decoder state

DllExport void dirac_set_buf | ( | dirac_decoder_t * | decoder,
|  | unsigned char * | buf[3],
|  | void * | id
| ) |  |

Set the output buffer into which the decoder copies the decoded data

Parameters:

  decoder | Decoder object
  buf | Array of char buffers to hold luma and chroma data
  id | User data

© 2004 British Broadcasting Corporation. Dirac code licensed under the Mozilla Public License (MPL) Version 1.1.
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