Page 4 of 8: x264 Options: B-Frames

x264 Options: B-Frames



Direct Mode:

Description: This option when selected can improve compression efficiency. Disabled by default, Auto seems to be the most common value, with Spatial being used occasionally.
Available Options:
None
Spatial
Temporal: least used (at least in Sharktooth's profiles)
Auto: most common
Command Line: --direct x
(where 'x' is 'none', 'spatial', 'temporal' or 'auto')


Bias:

Description: Sets how much bias x264 should give the usage of B-frames (higher means more use of B-frames). Setting this to 100 is the equivalent of not selecting the "Adaptive" option (see below). A default value of 0 works well. Option only available when at least 1 B-frame has been set.
Command Line: --b-bias n
(where 'n' is the bias value)


Adaptive:

Description: Turns on adaptive B-frames, which allows x264 to determine the number of B-frames to use (within the set B-frames limit in the previous section). A default value of On works well. Option only available when at least 1 B-frame has been set.
Command Line: --no-b-adapt
(disables adaptive B-frames)


Pyramid:

Description: Turns on B-frame Pyramid option, which allows B-frames to be used as references for other B-frames in prediction. A default value of On (when available) works well. Option only available when at least 2 B-frame has been set.
Command Line: --b-pyramid
(enables adaptive B-frames)


RDO:

Description: Turns on/off RDO for B-Frames. Turning it On will improve quality at the expense of encoding speed, but it is almost always worth it. Must have at least 1 B-frame and must have a "Subpixel Motion Estimation" (see "Analysis options" section) of 6 or 7.
Command Line: --b-rdo
(enables RD based mode decision for B-frames)


Weighted Prediction:

Description: Turns on weighted prediction for B-frames, which results in improved accuracy and therefore a more efficient encoding. Set it to On in most cases. Option only available when at least 1 B-frame has been set.
Command Line: --weightb
(enables weighted prediction)


Bidirectional M.E.:

Description: Turns on bidirectional M.E, which allows predictions based on motion both before and after the B-frames. Set it to On in most cases.
Command Line: --bime
(enables bidirectional M.E.)

 

 


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