Description

The D3D12DDI_VIDEO_ENCODER_SEQUENCE_CONTROL_DESC_0082_0 structure contains the sequence-level parameters for the input of a video encoding operation.

Members

Flags

A D3D12DDI_VIDEO_ENCODER_SEQUENCE_CONTROL_FLAGS_0082_0 value that indicates the sequence control descriptor flags for the current encode frame operation.

IntraRefreshConfig

A D3D12DDI_VIDEO_ENCODER_INTRA_REFRESH_0080 structure that specifies the parameters for the intra-refresh mode that should be used when triggering intra-refresh sessions. See Remarks for details about the use of intra-fresh.

RateControl

A D3D12DDI_VIDEO_ENCODER_RATE_CONTROL_0080_2 structure that specifies the rate control configuration.

Check the D3D12_VIDEO_ENCODER_SUPPORT_FLAG_0083_0_RATE_CONTROL_RECONFIGURATION_AVAILABLE flag to determine whether dynamic reconfiguration of rate control is supported:

• If supported, a modified RateControl causes the rate control algorithm to restart, with the new configuration starting from the execution of the associated EncodeFrame command.
• If not supported, RateControl should be set at the beginning of the encoding session and not changed during the session.

PictureTargetResolution

A D3D12DDI_VIDEO_ENCODER_PICTURE_RESOLUTION_DESC_0080 structure that describes the resolution to use when encoding this frame. The target resolution must be set based on the list of resolutions specified when the associated encoder heap for this operation was created.

Check the D3D12_VIDEO_ENCODER_SUPPORT_FLAG_0083_0_RESOLUTION_RECONFIGURATION_AVAILABLE flag to determine whether dynamic reconfiguration for resolution is supported:

• If supported, PictureTargetResolution indicates the resolution to use for the associated EncodeFrame command. In some codecs, a change in resolution in the middle of the encoding session might require a GOP to be reset with a potential force IDR/Key frame request, also resetting the decoded picture buffer (DPB) buffer and frame management algorithms.
• If not supported, PictureTargetResolution indicates the target resolution for the entire encoding session and must not be changed during the session.

SelectedLayoutMode

A D3D12DDI_VIDEO_ENCODER_FRAME_SUBREGION_LAYOUT_MODE_0080 value that indicates which layout mode is being used, and hence which union members to use in FrameSubregionsLayoutData.

Check the D3D12_VIDEO_ENCODER_SUPPORT_FLAG_0083_0_SUBREGION_LAYOUT_RECONFIGURATION_AVAILABLE flag to determine whether subregion dynamic reconfiguration is supported:

• If supported, SelectedLayoutMode indicates the subregion partitioning mode used for the associated EncodeFrame command.
• If not supported, *SelectedLayoutMode indicates the target subregion mode of the full encoding session and must not be changed during the encoding session.

FrameSubregionsLayoutData

A D3D12DDI_VIDEO_ENCODER_PICTURE_CONTROL_SUBREGIONS_LAYOUT_DATA_0080_2 structure that contains picture subregions layout optional codec-specific data. If SelectedLayoutMode indicates that there are no subregions, this member must be NULL.

CodecGopSequence

A D3D12DDI_VIDEO_ENCODER_SEQUENCE_GOP_STRUCTURE_0082_0 structure that specifies the current GOP used in the video sequence, in display order. Calls to EncodeFrame must follow this GOP but in sequence order after B-Frames reordering.

Check the D3D12_VIDEO_ENCODER_SUPPORT_FLAG__0083_0_SEQUENCE_GOP_RECONFIGURATION_AVAILABLE flag to determine whether GOP dynamic reconfiguration is supported:

• If supported, CodecGopSequence indicates the new GOP subregion mode used starting at the associated EncodeFrame command.
• If not supported, CodecGopSequence indicates the target GOP pattern (in display order) of the full encoding session and must not be changed during the encoding session.

Remarks

See D3D12 video encoding for general information.

Using intra-refresh

The use of bidirectional reference frames (B Frames) is mutually exclusive with intra-refresh. The caller should check that CodecGopSequence's structure does not contain B frames if intra-refresh modes are active. When querying for D3D12DDICAPS_VIDEO_ENCODER_SUPPORT_DATA with an intra-refresh mode other than D3D12_VIDEO_ENCODER_INTRA_REFRESH_MODE_NONE, the CodecGopSequence set must not contain B frames, or the query will return no support.

The use of infinite intra-refresh is possible by periodically requesting a new wave of intra-refresh after each of intra-refresh finishes.

When starting an intra-refresh of N frames of duration, the host does the following:

• Sets the corresponding picture control flag to start intra-refresh;
• Controls the frame index between [0..N) in the picture control structure to hint to the driver about the progress of the intra refresh session.

The expected behavior when explicitly requesting an intra-refresh wave with duration N frames follows:

• If the request for intra-refresh happens at the beginning of a GOP, the intra-refresh occurs for N frames and then a new GOP is started with an I frame.

• If the request for intra-refresh happens in the middle of a GOP, the group of pictures will be ended until the last submitted EncodeFrame command and restarted after the intra-refresh session with a new GOP starting with an I frame. For example, when the GOP is IPPPP...IPPPP..., if the intra-refresh start is requested at the "IPP" partial submission of the GOP, the last two P frames of that GOP will be ignored, the intra-refresh session will be issued for the N next frames, and then a new key-frame that restarts the GOP structure is expected.

For row-based intra-refresh:

• The configured GOP structure will have to be reconfigured to Infinite IPPP...P... GOP (GOPLength = 0u and PPicturePeriod = 1u) for the duration of the intra-refresh session. It can then be reconfigured again after the intra-refresh wave finished.

• The configured subregion partitioning mode will be reconfigured to correspond with N uniform slices partitioning per frame for a duration of N EncodeFrame commands. This is particularly important when the subregion partitioning is set to an incompatible mode with intra-refresh requirements, for example when the row of intra coded units in a slice will disrupt the limitation set to bytes per slice. The expectation for row based intra-refresh is that the resulting frame contains N slices, all P slices, except the current intra-refresh row slice, which has to be an I slice.

See also

D3D12DDI_VIDEO_ENCODER_ENCODEFRAME_INPUT_STREAM_ARGUMENTS_0082_0

D3D12DDI_VIDEO_ENCODER_SUPPORT_FLAGS_0083_0

PFND3D12DDI_VIDEO_ENCODE_FRAME_0082_0

PFND3D12DDI_CREATEVIDEOENCODERHEAP_0080_2