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Old 11th April 2017, 08:42   #1177  |  Link
r0lZ
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Join Date: Jul 2003
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I don't use the tune (except sometimes PSNR or SSIM, when I want to measure the quality of the encoding). IMO, they are useless and often misleading. But I'm not an expert in encoding. Perhaps some of them are really useful in specific circumstances.

The presets have a big incidence on the quality and file size (and on the time necessary for the encoding). It is not easy to understand exactly what they do, because they change a lot of internal settings, and without knowing what settings are modified and how, and without knowing the specific advantages of each of these settings, selecting a different preset is mainly a blind operation. But it is clear that globally, choosing a slower preset compresses more for a quality approximately equivalent. But with the slower, very slow or placebo presets, I have noticed that my TV has some trouble when it decodes some sequences, and the playback may become somewhat jerky. For that reason, I prefer to use the slow preset. Placebo is also extremely slow, even with a powerful CPU! (If you encode in h265, all presets are also much slower!)

Note also that changing the preset may (and will) modify the level (if you don't force it). My TV doesn't support a level greater than 4.2, and if I use a slow preset, I need also to force the level to 4.1 or 4.2. Of course, if the level is restricted, the settings of the preset are modified and you cannot take advantage of its full power. It's another reason to not use a too slow preset. (Level 4.1 is the level used on the blu-ray discs, and is therefore well supported by the vast majority of the hardware players. Levels 5.0 and greater are for the ultra-HD resolutions and full-SBS or full-T&B. Of course, if you encode in Full-SBS, you will need at least level 5.0, and therefore you can use a very slow preset. But be sure that your hardware supports it!)

You can also specify specific settings in the "additional options" field, to modify the default settings of the selected preset and build your own preset. But that requires much knowledge, and if you are really interested in experimenting with the x264 options, I suggest to join the x264 encoding forum. Personally, I trust the authors of the x264 encoder, and I use the presets without trying to modify them much.
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Last edited by r0lZ; 11th April 2017 at 08:49.
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