Method of filter control for block-based adaptive loop filtering

An apparatus for applying adaptive loop filtering for reconstructed video in a video encoding system or video decoding system, wherein each picture of the reconstructed video is partitioned into image units, the apparatus comprising one or more electronic circuits configured to:

• receive video data associated with a reconstructed current image unit from storage or from a processor;
• and
• apply Implicit Sample-based On/Off adaptive loop filter (ALF) to the video data, wherein said apply Implicit Sample-based On/Off ALF comprises:
• classifying each pixel of the video data associated with the reconstructed current image unit into a first group or a second group based on reconstructed video commonly available to both an encoder side and a decoder side;
• applying adaptive loop filter to the pixels of the video data associated with the reconstructed current image unit belonging to the first group;
• and
• skipping the adaptive loop filter for the pixels of the video data associated with the reconstructed current image unit belonging to the second group;
• and for the video encoding system,
• select an ALF mode for the reconstructed current image unit from a filter mode group consisting of ALF-Off mode, ALF-On mode, and ALF Implicit On/Off mode, wherein said apply Implicit Sample-based On/Off ALF is performed only if the ALF Implicit On/Off mode is selected;
• if the ALF-Off mode is selected, skip the adaptive loop filter for all pixels of the video data associated with the reconstructed current image unit;
• if the ALF-On mode is selected, apply the adaptive loop filter to all samples in the video data associated with the reconstructed current image unit;
• and
• incorporate one or more syntax elements in a coded bitstream to signal the ALF mode selected for the reconstructed current image unit.

A method of adaptive loop filtering for reconstructed video in a video encoding system or video decoding system, wherein each picture of the reconstructed video is partitioned into image units, the method comprising:

• receiving video data associated with a reconstructed current image unit;
• and
• applying Implicit Sample-based On/Off adaptive loop filter (ALF) to the video data, wherein said applying Implicit Sample-based On/Off ALF comprises:
• classifying each pixel of the video data associated with the reconstructed current image unit into a first group or a second group based on reconstructed video commonly available to both an encoder side and a decoder side;
• applying adaptive loop filter to the pixels of the video data associated with the reconstructed current image unit belonging to the first group;
• and
• skipping the adaptive loop filter for the pixels of the video data associated with the reconstructed current image unit belonging to the second group;
• and for the video decoding system,
• parsing an ALF mode for the reconstructed current image unit from a coded bitstream, wherein the ALF mode belongs to a filter mode group consisting of ALF-Off mode, ALF-On mode, and ALF Implicit On/Off mode and said applying Implicit Sample-based On/Off ALF is performed only if the ALF Implicit On/Off mode is selected;
• if the ALF-Off mode is selected, skipping the adaptive loop filter for all pixels of the video data associated with the reconstructed current image unit;
• and
• if the ALF-On mode is selected, applying the adaptive loop filter to all samples in the video data associated with the reconstructed current image unit.