# Dirac - A Video Codec

Created by the British Broadcasting Corporation.

# dirac::ModeDecider Class Reference

Decides between macroblock and block prediction modes. More...

`#include <me_mode_decn.h>`

Collaboration diagram for dirac::ModeDecider:

[legend]

List of all members.

## Public Member Functions

- ModeDecider (const EncoderParams &encp)
    Constructor.
- ~ModeDecider ()
    Destructor.
- void DoModeDecn (const FrameBuffer &my_buffer, int frame_num, MEData &me_data)
    Does the actual mode decision.

## Private Member Functions

- ModeDecider (const ModeDecider &cpy)
- ModeDecider & operator= (const ModeDecider &rhs)
- void DoMBDecn ()
- void DoLevelDecn (int level)
    Make a mode decision given a particular level of decomposition.
- float DoUnitDecn (const int xpos, const int ypos, const int level)
    Decide on a mode for a given prediction unit (block, sub-MB or MB).
- void DoME (const int xpos, const int ypos, const int level)
    Do motion estimation for a prediction unit at a given level.
- float ModeCost (const int xindex, const int yindex)
    Return a measure of the cost of coding a given mode.
- ValueType GetDCPred (int xblock, int yblock)
    Get a prediction for the dc value of a block.
- float GetDCVar (const ValueType dc_val, const ValueType dc_pred)
    Get a measure of DC value variance.

## Private Attributes

- FrameSort fsort
- const EncoderParams & m_encparams
    A local reference to the encoder params.
- float m_lambda
    The Lagrangian parameter for motion estimation.
- OneDArray< float > m_level_factor
    Correction factor for comparing SAD costs for different MB splittings.
- OneDArray< float > m_mode_factor
    Correction factor for comparing mode costs for different MB splittings.
- OneDArray< MEData * > m_me_data_set
    Motion vector data for each level of splitting.
- const PicArray * m_pic_data
- const PicArray * m_ref1_updata
- const PicArray * m_ref2_updata
- int num_refs
- IntraBlockDiff * m_intradiff
- BiBlockDiff * m_bicheckdiff
- int m_xmb_loc
- int m_ymb_loc

## Detailed Description

Loops over all the macroblocks and decides on the best modes. A macroblock is a square of 16 blocks. There are three possible splitting levels: level 0 means the macroblock is considered as a single block; level 1 means the macroblock is considered as 4 larger blocks, termed sub-macroblocks; level 0 means the macroblock is split right down to blocks.

In deciding which modes to adopt, the ModeDecider object calculates costs for all permutations, doing motion estimation for the level 1 and level 0 modes as these have not been calculated before. The process of decision for each is as follows. For each MB, we loop over the levels, and call DoLevelDecn. DoLevelDecn does motion estimation if it's necessary. Then it assumes that we don't have a common block mode and calls DoUnitDecn which finds the best mode for each unit in the MB at that level, individually. When we've got a best cost for that level we go up to the next one.

## Constructor & Destructor Documentation

dirac::ModeDecider::ModeDecider | ( | const EncoderParams & | encp | ) |

The constructor creates arrays for handling the motion vector data at splitting levels 0 and 1, as motion estimation must be performed for these levels.

dirac::ModeDecider::~ModeDecider | ( |  | ) |

The destructor destroys the classes created in the constructor

dirac::ModeDecider::ModeDecider | ( | const ModeDecider & | cpy | ) | `[private]`

## Member Function Documentation

void dirac::ModeDecider::DoModeDecn | ( | const FrameBuffer & | my_buffer,
|  | int | frame_num,
|  | MEData & | me_data |
| ) |  |  |

Does the mode decision

Parameters:

  | my_buffer | the buffer of all the relevant frames
  | frame_num | the frame number for which motion estimation is being done
  | me_data | the motion vector data into which decisions will be written

ModeDecider& dirac::ModeDecider::operator= | ( | const ModeDecider & | rhs | ) | `[private]`

void dirac::ModeDecider::DoMBDecn | ( |  | ) | `[private]`

void dirac::ModeDecider::DoLevelDecn | ( | int | level | ) | `[private]`

float dirac::ModeDecider::DoUnitDecn | ( | const int | xpos,
|  | const int | ypos,
|  | const int | level |
| ) |  |  | `[private]`

void dirac::ModeDecider::DoME | ( | const int | xpos,
|  | const int | ypos,
|  | const int | level |
| ) |  |  | `[private]`

float dirac::ModeDecider::ModeCost | ( | const int | xindex,
|  | const int | yindex |
| ) |  |  | `[private]`

ValueType dirac::ModeDecider::GetDCPred | ( | int | xblock,
|  | int | yblock |
| ) |  |  | `[private]`

float dirac::ModeDecider::GetDCVar | ( | const ValueType | dc_val,
|  | const ValueType | dc_pred |
| ) |  |  | `[private]`

## Member Data Documentation

FrameSort dirac::ModeDecider::fsort`[private]`

const EncoderParams& dirac::ModeDecider::m_encparams`[private]`

float dirac::ModeDecider::m_lambda`[private]`

OneDArray<float> dirac::ModeDecider::m_level_factor`[private]`

OneDArray<float> dirac::ModeDecider::m_mode_factor`[private]`

OneDArray< MEData* > dirac::ModeDecider::m_me_data_set`[private]`

const PicArray* dirac::ModeDecider::m_pic_data`[private]`

const PicArray* dirac::ModeDecider::m_ref1_updata`[private]`

const PicArray* dirac::ModeDecider::m_ref2_updata`[private]`

int dirac::ModeDecider::num_refs`[private]`

IntraBlockDiff* dirac::ModeDecider::m_intradiff`[private]`

BiBlockDiff* dirac::ModeDecider::m_bicheckdiff`[private]`

int dirac::ModeDecider::m_xmb_loc`[private]`

int dirac::ModeDecider::m_ymb_loc`[private]`

The documentation for this class was generated from the following file:

- me_mode_decn.h

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