Note
Access to this page requires authorization. You can try signing in or changing directories.
Access to this page requires authorization. You can try changing directories.
There are two types of stream layout SEI messages. They differ by the presence of the Layer Description field.
Full stream layout.
The P field MUST be "1". There MUST be at least one Layer Description field. For each bit of value "1" in the layer presence bytes, there MUST be a Layer Description field with PRID as the layer index.
Update stream layout.
The P field MUST be "0". The LDSize and Layer Description fields are not present.
A full stream layout defines the complete stream layout information of simulcast streams. It specifies how many layers are contained in the simulcast streams and the information about each layer. There MUST be one full stream layout PACSI inserted prior to any other NAL unit. More full stream layout PACSIs MAY be inserted as needed. The PACSI NAL unit of the base layer of the first simulcast stream of an IDR access unit MUST carry a full stream layout. The PACSI NAL units of the base layers of other simulcast streams of the same IDR access unit MAY also carry full stream layout optionally to reduce the impact of network packet loss.
An update stream layout defines an update to a previous full stream layout or update stream layout. An update stream layout does not contain any detailed Layer Description field, so it MUST only be used to indicate the adding or removing of layers from the simulcast streams through changing the bit values of the layer presence bytes. A layer presence bit MUST NOT be set to "1" if the value of the same bit is "0" in the most recent full stream layout. This means that an update stream layout MUST NOT contain a new layer that is not defined in the previous full stream layout.