doc/reST/presets.rst

   1 Preset Options
   2 --------------
   3
   4 .. _presets:
   5
   6 Presets
   7 =======
   8
   9 x265 has a number of predefined :option:`--preset` options that make
  10 trade-offs between encode speed (encoded frames per second) and
  11 compression efficiency (quality per bit in the bitstream).  The default
  12 preset is medium, it does a reasonably good job of finding the best
  13 possible quality without spending enormous CPU cycles looking for the
  14 absolute most efficient way to achieve that quality.  As you go higher
  15 than medium, the encoder takes shortcuts to improve performance at the
  16 expense of quality and compression efficiency.  As you go lower than
  17 medium, the encoder tries harder and harder to achieve the best quailty
  18 per bit compression ratio.
  19
  20 The 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 | deblock      |    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
  76 Placebo mode enables transform-skip prediction evaluation.
  77
  78 .. _tunings:
  79
  80 Tuning
  81 ======
  82
  83 There are a few :option:`--tune` options available, which are applied
  84 after the preset.
  85
  86 .. Note::
  87
  88         The *psnr* and *ssim* tune options disable all optimizations that
  89         sacrafice metric scores for perceived visual quality (also known as
  90         psycho-visual optimizations). By default x265 always tunes for
  91         highest perceived visual quality but if one intends to measure an
  92         encode using PSNR or SSIM for the purpose of benchmarking, we highly
  93         recommend you configure x265 to tune for that particular metric.
  94
  95 +--------------+-----------------------------------------------------+
  96 | --tune       | effect                                              |
  97 +==============+=====================================================+
  98 | psnr         | disables adaptive quant, psy-rd, and cutree         |
  99 +--------------+-----------------------------------------------------+
 100 | ssim         | enables adaptive quant auto-mode, disables psy-rd   |
 101 +--------------+-----------------------------------------------------+
 102 | grain        | improves retention of film grain. more below        |
 103 +--------------+-----------------------------------------------------+
 104 | fastdecode   | no loop filters, no weighted pred, no intra in B    |
 105 +--------------+-----------------------------------------------------+
 106 | zerolatency  | no lookahead, no B frames, no cutree                |
 107 +--------------+-----------------------------------------------------+
 108 | cbr          | --pbratio 1.0 --ratetol 0.5                         |
 109 +--------------+-----------------------------------------------------+
 110
 111
 112 Film Grain Retention
 113 ~~~~~~~~~~~~~~~~~~~~
 114
 115 :option:`--tune` grain tries to improve the retention of film grain in
 116 the reconstructed output. It helps rate distortion optimizations select
 117 modes which preserve high frequency noise:
 118
 119     * :option:`--psy-rd` 0.5
 120     * :option:`--psy-rdoq` 30
 121
 122 .. Note::
 123
 124     --psy-rdoq is only effective when RDOQuant is enabled, which is at
 125     RD levels 4, 5, and 6 (presets slow and below).
 126
 127 It lowers the strength of adaptive quantization, so residual energy can
 128 be more evenly distributed across the (noisy) picture:
 129
 130     * :option:`--aq-mode` 1
 131     * :option:`--aq-strength` 0.3
 132
 133 And it similarly tunes rate control to prevent the slice QP from
 134 swinging too wildly from frame to frame:
 135
 136     * :option:`--ipratio` 1.1
 137     * :option:`--pbratio` 1.1
 138     * :option:`--qcomp` 0.8
 139
 140 And lastly it reduces the strength of deblocking to prevent grain being
 141 blurred on block boundaries:
 142
 143     * :option:`--deblock` -2
 144