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1Preset Options
2--------------
3
4Presets
5=======
6
7.. _preset-tune-ref:
8
9x265 has a number of predefined :option:`--preset` options that make
10trade-offs between encode speed (encoded frames per second) and
11compression efficiency (quality per bit in the bitstream). The default
12preset is medium, it does a reasonably good job of finding the best
13possible quality without spending enormous CPU cycles looking for the
14absolute most efficient way to achieve that quality. As you go higher
15than medium, the encoder takes shortcuts to improve performance at the
16expense of quality and compression efficiency. As you go lower than
17medium, the encoder tries harder and harder to achieve the best quailty
18per bit compression ratio.
19
20The presets adjust encoder parameters to affect these trade-offs.
21
22+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
23| | ultrafast | superfast | veryfast | faster | fast | medium | slow | slower | veryslow | placebo |
24+==============+===========+===========+==========+========+======+========+======+========+==========+=========+
25| ctu | 32 | 32 | 32 | 64 | 64 | 64 | 64 | 64 | 64 | 64 |
26+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
27| bframes | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 8 | 8 | 8 |
28+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
29| b-adapt | 0 | 0 | 0 | 0 | 2 | 2 | 2 | 2 | 2 | 2 |
30+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
31| rc-lookahead | 10 | 10 | 15 | 15 | 15 | 20 | 25 | 30 | 40 | 60 |
32+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
33| scenecut | 0 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 40 |
34+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
35| refs | 1 | 1 | 1 | 1 | 3 | 3 | 3 | 3 | 5 | 5 |
36+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
37| me | dia | hex | hex | hex | hex | hex | star | star | star | star |
38+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
39| merange | 25 | 44 | 57 | 57 | 57 | 57 | 57 | 57 | 57 | 92 |
40+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
41| subme | 0 | 1 | 1 | 2 | 2 | 2 | 3 | 3 | 4 | 5 |
42+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
43| rect | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 |
44+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
45| amp | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
46+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
47| max-merge | 2 | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 4 | 5 |
48+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
49| early-skip | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |
50+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
51| fast-intra | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 |
52+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
53| b-intra | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
54+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
55| sao | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
56+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
57| signhide | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
58+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
59| weightp | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
60+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
61| weightb | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 |
62+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
63| aq-mode | 0 | 0 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 2 |
64+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
65| cuTree | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 |
66+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
67| rdLevel | 2 | 2 | 2 | 2 | 2 | 3 | 4 | 6 | 6 | 6 |
68+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
69| lft | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
70+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
71| tu-intra | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 3 | 4 |
72+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
73| tu-inter | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 3 | 4 |
74+--------------+-----------+-----------+----------+--------+------+--------+------+--------+----------+---------+
75
76Placebo mode enables transform-skip prediction evaluation.
77
78Tuning
79======
80
81There are a few :option:`--tune` options available, which are applied
82after the preset.
83
84.. Note::
85
86 The *psnr* and *ssim* tune options disable all optimizations that
87 sacrafice metric scores for perceived visual quality (also known as
88 psycho-visual optimizations). By default x265 always tunes for
89 highest perceived visual quality but if one intends to measure an
90 encode using PSNR or SSIM for the purpose of benchmarking, we highly
91 recommend you configure x265 to tune for that particular metric.
92
93+--------------+-----------------------------------------------------+
94| --tune | effect |
95+==============+=====================================================+
96| psnr | disables adaptive quant, psy-rd, and cutree |
97+--------------+-----------------------------------------------------+
98| ssim | enables adaptive quant auto-mode, disables psy-rd |
99+--------------+-----------------------------------------------------+
100| fastdecode | no loop filters, no weighted pred, no intra in B |
101+--------------+-----------------------------------------------------+
102| zerolatency | no lookahead, no B frames, no cutree |
103+--------------+-----------------------------------------------------+