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)
“In frames as large as rooms that face all ways
And block the ends of streets with giant loaves,
Screen graves with custard, cover slums with praise
Of motor-oil and cuts of salmon, shine
Perpetually these sharply-pictured groves
Of how life should be.”
—Philip Larkin (1922–1986)
“I don’t sleep. I hate those little slices of death.”
—Walter Reisch (1903–1963)