| AOMedia AV1 Codec

Scalable Video Coding
Encoder Algorithm

## Data Structures
struct | LAYER_CONTEXT
| The stucture of quantities related to each spatial and temporal layer. More...
struct | SVC
| The stucture of SVC. More...

## Typedefs
typedef struct SVC | SVC
| The stucture of SVC.

## Functions
void | av1_init_layer_context (struct AV1_COMP *const cpi)
| Initialize layer context data from init_config().
bool | av1_alloc_layer_context (struct AV1_COMP *cpi, int num_layers)
| Allocate layer context data.
void | av1_update_layer_context_change_config (struct AV1_COMP *const cpi, const int64_t target_bandwidth)
| Update the layer context from a change_config() call.
void | av1_update_temporal_layer_framerate (struct AV1_COMP *const cpi)
| Prior to encoding the frame, update framerate-related quantities for the current temporal layer.
bool | av1_check_ref_is_low_spatial_res_super_frame (struct AV1_COMP *const cpi, int ref_frame)
| Prior to check if reference is lower spatial layer at the same timestamp/superframe.
void | av1_restore_layer_context (struct AV1_COMP *const cpi)
| Prior to encoding the frame, set the layer context, for the current layer to be encoded, to the cpi struct.
void | av1_save_layer_context (struct AV1_COMP *const cpi)
| Save the layer context after encoding the frame.
void | av1_free_svc_cyclic_refresh (struct AV1_COMP *const cpi)
| Free the memory used for cyclic refresh in layer context.
void | av1_svc_reset_temporal_layers (struct AV1_COMP *const cpi, int is_key)
| Reset on key frame: reset counters, references and buffer updates.
void | av1_one_pass_cbr_svc_start_layer (struct AV1_COMP *const cpi)
| Before encoding, set resolutions and allocate compressor data.
int | av1_svc_primary_ref_frame (const struct AV1_COMP *const cpi)
| Get primary reference frame for current layer.
void | av1_get_layer_resolution (const int width_org, const int height_org, const int num, const int den, int *width_out, int *height_out)
| Get resolution for current layer.

## Detailed Description

This module describes scalable video coding algorithm in AV1. More details will be added.

## Function Documentation

## ◆ av1_init_layer_context()

void av1_init_layer_context | ( | struct AV1_COMP *const | cpi | ) |

Initialize layer context data from init_config().

Parameters

  [in] | cpi | Top level encoder structure

Remarks
  Nothing returned. Set cpi->svc.

References LAYER_CONTEXT::actual_num_seg1_blocks, LAYER_CONTEXT::actual_num_seg2_blocks, PRIMARY_RATE_CONTROL::avg_frame_qindex, PRIMARY_RATE_CONTROL::avg_q, RATE_CONTROL::best_quality, PRIMARY_RATE_CONTROL::bits_off_target, PRIMARY_RATE_CONTROL::buffer_level, AV1_COMP::common, LAYER_CONTEXT::counter_encode_maxq_scene_change, SVC::downsample_filter_phase, SVC::downsample_filter_type, SVC::drop_spatial_layer, SVC::force_zero_mode_spatial_ref, SVC::has_lower_quality_layer, SVC::last_layer_dropped, PRIMARY_RATE_CONTROL::last_q, SVC::layer_context, LAYER_CONTEXT::map, CommonModeInfoParams::mi_cols, AV1Common::mi_params, CommonModeInfoParams::mi_rows, AV1_COMP::oxcf, PRIMARY_RATE_CONTROL::rate_correction_factors, AV1EncoderConfig::rc_cfg, LAYER_CONTEXT::sb_index, RateControlCfg::starting_buffer_level_ms, AV1_COMP::svc, PRIMARY_RATE_CONTROL::total_actual_bits, RateControlCfg::worst_allowed_q, and RATE_CONTROL::worst_quality.

## ◆ av1_alloc_layer_context()

bool av1_alloc_layer_context | ( | struct AV1_COMP * | cpi,
|  | int | num_layers )

Allocate layer context data.

Parameters

  [in] | cpi | Top level encoder structure
  [in] | num_layers | Number of layers to be allocated

Remarks
  Allocates memory for cpi->svc.layer_context.

Returns
  True on success, false on allocation failure.

References SVC::layer_context, SVC::num_allocated_layers, and AV1_COMP::svc.

## ◆ av1_update_layer_context_change_config()

void av1_update_layer_context_change_config | ( | struct AV1_COMP *const | cpi,
|  | const int64_t | target_bandwidth )

Update the layer context from a change_config() call.

Parameters

  [in] | cpi | Top level encoder structure
  [in] | target_bandwidth | Total target bandwidth

Remarks
  Nothing returned. Buffer level for each layer is set.

References LAYER_CONTEXT::actual_num_seg1_blocks, LAYER_CONTEXT::actual_num_seg2_blocks, RATE_CONTROL::best_quality, PRIMARY_RATE_CONTROL::bits_off_target, PRIMARY_RATE_CONTROL::buffer_level, AV1_COMP::common, LAYER_CONTEXT::counter_encode_maxq_scene_change, AV1_COMP::framerate, SVC::layer_context, LAYER_CONTEXT::map, PRIMARY_RATE_CONTROL::maximum_buffer_size, CommonModeInfoParams::mi_cols, AV1Common::mi_params, CommonModeInfoParams::mi_rows, PRIMARY_RATE_CONTROL::optimal_buffer_level, AV1_PRIMARY::p_rc, AV1_COMP::ppi, AV1_COMP::rc, LAYER_CONTEXT::sb_index, PRIMARY_RATE_CONTROL::starting_buffer_level, AV1_COMP::svc, and RATE_CONTROL::worst_quality.

## ◆ av1_update_temporal_layer_framerate()

void av1_update_temporal_layer_framerate | ( | struct AV1_COMP *const | cpi | ) |

Prior to encoding the frame, update framerate-related quantities for the current temporal layer.

Parameters

  [in] | cpi | Top level encoder structure

Remarks
  Nothing returned. Frame related quantities for current temporal layer are updated.

References AV1_COMP::framerate, get_layer_context(), SVC::layer_context, AV1_COMP::rc, and AV1_COMP::svc.

Referenced by av1_svc_reset_temporal_layers().

## ◆ av1_check_ref_is_low_spatial_res_super_frame()

bool av1_check_ref_is_low_spatial_res_super_frame | ( | struct AV1_COMP *const | cpi,
|  | int | ref_frame )

Prior to check if reference is lower spatial layer at the same timestamp/superframe.

Parameters

  [in] | cpi | Top level encoder structure
  [in] | ref_frame | Reference frame

Returns
  True if the ref_frame if lower spatial layer, otherwise false.

References AV1_COMP::ppi, AV1_PRIMARY::rtc_ref, and AV1_COMP::svc.

Referenced by av1_restore_layer_context().

## ◆ av1_restore_layer_context()

void av1_restore_layer_context | ( | struct AV1_COMP *const | cpi | ) |

Prior to encoding the frame, set the layer context, for the current layer to be encoded, to the cpi struct.

Parameters

  [in] | cpi | Top level encoder structure

Remarks
  Nothing returned. Layer context for current layer is set.

References CYCLIC_REFRESH::actual_num_seg1_blocks, LAYER_CONTEXT::actual_num_seg1_blocks, CYCLIC_REFRESH::actual_num_seg2_blocks, LAYER_CONTEXT::actual_num_seg2_blocks, av1_check_ref_is_low_spatial_res_super_frame(), AV1_COMP::common, LAYER_CONTEXT::counter_encode_maxq_scene_change, AV1_COMP::cyclic_refresh, SVC::force_zero_mode_spatial_ref, RATE_CONTROL::frames_to_key, get_layer_context(), AV1_COMP::gf_frame_index, AV1Common::height, CYCLIC_REFRESH::map, LAYER_CONTEXT::map, LAYER_CONTEXT::max_mv_magnitude, MotionVectorSearchParams::max_mv_magnitude, AV1_COMP::mv_search_params, AV1_COMP::oxcf, AV1_PRIMARY::p_rc, AV1_COMP::ppi, AV1_COMP::rc, AV1EncoderConfig::rc_cfg, SPEED_FEATURES::rt_sf, AV1_PRIMARY::rtc_ref, CYCLIC_REFRESH::sb_index, LAYER_CONTEXT::sb_index, AV1_COMP::sf, AV1_COMP::svc, RateControlCfg::target_bandwidth, and AV1Common::width.

Referenced by av1_svc_reset_temporal_layers().

## ◆ av1_save_layer_context()

void av1_save_layer_context | ( | struct AV1_COMP *const | cpi | ) |

Save the layer context after encoding the frame.

Parameters

  [in] | cpi | Top level encoder structure

References CYCLIC_REFRESH::actual_num_seg1_blocks, LAYER_CONTEXT::actual_num_seg1_blocks, CYCLIC_REFRESH::actual_num_seg2_blocks, LAYER_CONTEXT::actual_num_seg2_blocks, AV1_COMP::common, LAYER_CONTEXT::counter_encode_maxq_scene_change, AV1Common::current_frame, AV1_COMP::cyclic_refresh, SVC::drop_spatial_layer, AV1_COMP::framerate, get_layer_context(), AV1_COMP::gf_frame_index, LAYER_CONTEXT::group_index, AV1_COMP::is_dropped_frame, CYCLIC_REFRESH::map, LAYER_CONTEXT::map, LAYER_CONTEXT::max_mv_magnitude, MotionVectorSearchParams::max_mv_magnitude, AV1_COMP::mv_search_params, AV1_COMP::oxcf, AV1_PRIMARY::p_rc, AV1_COMP::ppi, AV1_COMP::rc, AV1EncoderConfig::rc_cfg, CYCLIC_REFRESH::sb_index, LAYER_CONTEXT::sb_index, AV1_COMP::svc, and RateControlCfg::target_bandwidth.

## ◆ av1_free_svc_cyclic_refresh()

void av1_free_svc_cyclic_refresh | ( | struct AV1_COMP *const | cpi | ) |

Free the memory used for cyclic refresh in layer context.

Parameters

  [in] | cpi | Top level encoder structure

References SVC::layer_context, LAYER_CONTEXT::map, and AV1_COMP::svc.

## ◆ av1_svc_reset_temporal_layers()

void av1_svc_reset_temporal_layers | ( | struct AV1_COMP *const | cpi,
|  | int | is_key )

Reset on key frame: reset counters, references and buffer updates.

Parameters

  [in] | cpi | Top level encoder structure
  [in] | is_key | Whether current layer is key frame

References av1_restore_layer_context(), av1_update_temporal_layer_framerate(), SVC::layer_context, and AV1_COMP::svc.

## ◆ av1_one_pass_cbr_svc_start_layer()

void av1_one_pass_cbr_svc_start_layer | ( | struct AV1_COMP *const | cpi | ) |

Before encoding, set resolutions and allocate compressor data.

Parameters

  [in] | cpi | Top level encoder structure

References av1_get_layer_resolution(), AV1_COMP::common, SVC::downsample_filter_type, SVC::has_lower_quality_layer, AV1Common::height, SVC::layer_context, CommonModeInfoParams::mi_cols, AV1Common::mi_params, CommonModeInfoParams::mi_rows, AV1_COMP::oxcf, AV1_COMP::svc, and AV1Common::width.

Referenced by av1_get_compressed_data().

## ◆ av1_svc_primary_ref_frame()

int av1_svc_primary_ref_frame | ( | const struct AV1_COMP *const | cpi | ) |

Get primary reference frame for current layer.

Parameters

  [in] | cpi | Top level encoder structure

Returns
  The primary reference frame for current layer.

## ◆ av1_get_layer_resolution()

void av1_get_layer_resolution | ( | const int | width_org,
|  | const int | height_org,
|  | const int | num,
|  | const int | den,
|  | int * | width_out,
|  | int * | height_out )

Get resolution for current layer.

Parameters

  [in] | width_org | Original width, unscaled
  [in] | height_org | Original height, unscaled
  [in] | num | Numerator for the scale ratio
  [in] | den | Denominator for the scale ratio
  [in] | width_out | Output width, scaled for current layer
  [in] | height_out | Output height, scaled for current layer

Remarks
  Nothing is returned. Instead the scaled width and height are set.

Referenced by av1_one_pass_cbr_svc_start_layer().