Page 6 of 8: x264 Options: Analysis

x264 Options: Analysis

Mixed References:

Description: This option allows x264 to have greater control over "Reference Frames" (see "Common options" section). Especially needed if the "Reference Frames" is set to a high value.
Command Line: --mixed-refs
(enables mixed references)

No Fast P Skip:

Description: Fast P Skip can improve encoding speed at the expense of a very slight quality drop. Leave this option set to Off (to allow for Fast P Skips) is recommended unless encoding for maximum quality with no regard to encoding time.
Command Line: --no-fast-pskip
(disables fast P skip)

Motion Estimation Method:

Description: This option select the way motion is detected by x264. Motion is what compression codecs are all about, tracking differences between scenes to allocate the various frame types and bitrates.
Available Options (listed from fastest to slowest, encoding speed wise):
Diamond: Only use when maximum encoding speed is required.
Hexagon: A good option for when quality is not the most important factor, but still important.
Multi Hex: Also known as "Uneven Multi-Hexagon". This is the most common setting, as it is a good trade off between speed and quality.
Exhaustive: Slowest and totally unnecessary (it isn't estimation anymore, rather, it's Motion Calculation, pixel by pixel).
Command Line: --me x
(where 'x' is 'dia', 'hex', 'umh' or 'esa')

Subpixel Motion Estimation:

Description: Also known as "Partition Decision". A very important option that determines how x264 makes decisions about motion estimation. The options are available from 1 to 7, with 1 being the fastest (lowest quality) and 7 being the slowest (best quality). A setting of 6 is the most common, with 1 or 7 being used in extreme cases (fastest encoding or best quality). A setting of 6 or 7 enables the B-frames RDO option (see "B-Frames options" section).
Command Line: --subme n
(where 'n' is the estimation value)

Trellis RD Quantization:

Description: This option when turned on is supposed to improve quality, but at a severe slow down of encoding. The quality improvements are also subjective. Leaving it Off is recommended unless you have a fast computer and using multi-pass encoding. Never turn it on in single pass quantizer mode, as it would lead to unexpected results.
Available Options:
Disabled: Use this for 1-pass encoding
Final MB: Use this for typical 2-pass encoding
Always: Use this for maximum quality (slowest speed)
Command Line: --trellis n
(where 'n' is 0 {disabled}, 1 {Final MB} or 2 {Always})



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