Bi-directional Predicted Frames/slices (B-frames/slices)
- Require the prior decoding of other frame(s) to be decoded.
- May contain both image data and motion vector displacements or combinations of the two.
- Include some prediction modes that form a prediction of a motion region (e.g., a macroblock or a smaller area) by averaging the predictions obtained using two different previously decoded reference regions.
- In older standard designs (such as MPEG-2), B-frames are never used as references for the prediction of other pictures. As a result, a lower quality encoding (resulting in the use of fewer bits than would otherwise be the case) can be used for such B-frames because the loss of detail will not harm the prediction quality for subsequent pictures.
- In H.264, may or may not be used as references for the decoding of other pictures (at the discretion of the encoder).
- In older standard designs (such as MPEG-2), use exactly two previously decoded pictures as references during decoding, and require one of those pictures to precede the B-frame in display order and the other one to follow it.
- In H.264, can use one, two, or more than two previously decoded pictures as references during decoding, and can have any arbitrary display-order relationship relative to the picture(s) used for its prediction.
- Typically require fewer bits for encoding than either I or P-frames.
Read more about this topic: Video Compression Picture Types
Famous quotes containing the words predicted, frames and/or slices:
“Is it not the chief disgrace in the world, not to be an unit;Mnot to be reckoned one character;Mnot to yield that peculiar fruit which each man was created to bear, but to be reckoned in the gross, in the hundred, or the thousand, of the party, the section, to which we belong; and our opinion predicted geographically, as the north, or the south?”
—Ralph Waldo Emerson (1803–1882)
“The bird would cease and be as other birds
But that he knows in singing not to sing.
The question that he frames in all but words
Is what to make of a diminished thing.”
—Robert Frost (1874–1963)
“the future is simply nothing at all. Nothing has happened to the present by becoming past except that fresh slices of existence have been added to the total history of the world. The past is thus as real as the present.”
—Charlie Dunbar Broad (1887–1971)