2.3.1.1 microsoft_format_change_capability
The microsoft_format_change_capability parameter specifies whether the Wi-Fi Display Sink supports dynamic changes to the video resolution and video refresh rate.
The ABNF syntax is as follows:
-
microsoft-format-change-capability = "microsoft_format_change_capability:" SP format-change-caps CRLF format-change-caps = "supported" / "none"
If the format-change-caps parameter equals the value "supported", it means that the Wi-Fi Display Sink monitors the sequence parameter set/picture parameter set (SPS/PPS) in the H.264 stream for changes to the video resolution or video frame rate. And it adapts to such changes without displaying any visible changes such as flicker or a black screen.
The H.264 video bit stream that is sent by a Wi-Fi Display Source MUST include an instantaneous decoder refresh (IDR) frame as the first video frame after changing either the video resolution or the video frame rate. The bit stream MUST also include the SPS/PPS with the new resolution and frame rate. The new video resolution MUST belong to the set of video resolutions included in the Wi-Fi Display Sink’s M3 message response. The video frame rate MUST be less than or equal to the maximum frame rate that the Wi-Fi Display Sink claims support for at that resolution.
For details about how the Wi-Fi Display Sink specifies which video resolutions and video frame rates it supports, see [WF-DTS2.1] section 6.1.3.
If the format-change-caps parameter has the value "none", the frame rate and video resolution of the H.264 bit stream cannot be changed unless the Wi-Fi Display Source sends an M4 message ([WF-DTS2.1] section 6.4.4).