MF_NALU_LENGTH_INFORMATION attribute

Indicates the lengths of NALUs in the sample. This is a MF BLOB that is set on compressed H.264 or H.265 samples.

Data type

BLOB

Remarks

In order for this attribute to be present on a compressed sample, MF_NALU_LENGTH_SET must be set appropriately for the corresponding encoder or decoder MFT.

Set MF_NALU_LENGTH_INFORMATION as a BLOB on the sample, with one DWORD for each NALU in the sample. For example, if there are AUD (9 bytes), SPS (25 bytes), PPS (10 bytes), IDR slice1 (50 k), IDR slice 2 (60 k), then there should be 5 DWORDs with values 9, 25, 10, 50 k, 60 k in the BLOB.

Here some code that sets the BLOB, where rgdwNALULengthInfo is an array of type DWORD and uiNaluLengthIdx is the valid NALU lengths set to the BLOB.

m_spSample->SetBlob( MF_NALU_LENGTH_INFORMATION, 
                    (UINT8*) m_wpParent->m_pdwNALULengthInfo, 
                    sizeof(DWORD)*uiNaluLengthIdx ), 
                    done );

When MF_NALU_LENGTH_INFORMATION is provided as input to a decoder, the decoder will use the NALU lengths to improve performance and reduce decode latency.

When MF_NALU_LENGTH_INFORMATION is emitted from an encoder, the NALU lengths can be used to improve the performance of a mux operation or subsequent decode.

Requirements

See also

Alphabetical List of Media Foundation Attributes

Media Type Attributes