Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion. Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules. |
3rd December 2017, 20:52 | #1 | Link |
Registered User
Join Date: Jan 2010
Location: France
Posts: 851
|
x265 and preset influence with CRF ?
Hi,
I would like to encode some Blu ray to x265 and I read some informations on Google about presets but never the same result. So does preset with CRF have an influence on the quality or only on the bitrate ? Medium seems to be a good choice but if slow gives a better quality I may use it. Thank you ! |
3rd December 2017, 21:39 | #2 | Link |
Registered User
Join Date: Dec 2002
Posts: 5,565
|
Preset has influence on both speed and quality. But you can have same quality with medium as with e.g. slow - you just need more bitrate.
Step 1: choose preset according to speed you are willing to accept Step 2: adjust CRF until you have quality/bitrate you are willing to accept (strictly speaking CRF also has some impact on speed so you may need to repeat the process) |
3rd December 2017, 22:15 | #3 | Link |
Registered User
Join Date: Jan 2010
Location: France
Posts: 851
|
Thank you !
Medium's speed is good for me, slow is a little bit "slow" and slower is too slow. What is the vein approximatively between preset and CRF ? For example is Medium / CRF18 similar to Slow / CRF20 or more ? I know it's related to my choice but I would like to know a base to start. |
5th December 2017, 19:55 | #4 | Link | |
Registered User
Join Date: Jan 2010
Location: France
Posts: 851
|
I have found this on the FFMPEG website (https://trac.ffmpeg.org/wiki/Encode/H.265) :
Quote:
|
|
5th December 2017, 21:31 | #5 | Link |
Registered User
Join Date: Jun 2017
Posts: 89
|
This does not apply to x265. It did not even really apply to x264.
However, in x265 the files do not even get bigger with faster presets, they mostly get smaller. Generally speaking, results with medium look good, fast is still ok, but you should not go faster than that. Make a few comparisons, you will see why. The speed drops significantly if you go to slow, yes - but it is worth it. Slow (and the slower presets) keep(s) considerably more detail. In my humble opinion, slow is the sweetspot for quality/speed. Others see slower as that sweetspot, I think because it makes pretty much full use of x265's efficiency potential. I linked my personal table here, maybe it helps you too: https://forum.doom9.org/showthread.p...10#post1820010 Essentially, you can't really go wrong with slow, a CRF below 20 and --no-sao. But again, this is just my opinion based on my personal findings and some good advice here. |
6th December 2017, 04:24 | #7 | Link |
Registered User
Join Date: Feb 2002
Location: San Jose, California
Posts: 4,407
|
It is less significant with x265 but 10bit encoding is more efficient.
http://x264.nl/x264/10bit_02-ateme-w..._bandwidth.pdf
__________________
madVR options explained |
7th December 2017, 00:16 | #9 | Link | |
Moderator
Join Date: Jan 2006
Location: Portland, OR
Posts: 4,770
|
Quote:
10-bit is also somewhat more memory and power intensive to decode. |
|
7th December 2017, 11:11 | #11 | Link |
Registered User
Join Date: Jun 2017
Posts: 89
|
I would never encode to x265 in 8bit.
Some months back, I made a few 8bit vs. 10bit encoding comparisons - same CRF and settings. I admit, that was still using x265 2.3 and things might have improved a bit since. However, gradations were much, much better with 10bit encoding. I always saw ugly banding in 8bit, even down to CRF13 and even with --tune grain. I did only compare with the medium preset though - things might be better for 8bit with slow, slower, veryslow... |
7th December 2017, 15:25 | #12 | Link | |
Moderator
Join Date: Jan 2006
Location: Portland, OR
Posts: 4,770
|
Quote:
I'd suggest using 10-bit when its known all target devices support it. But that's not a safe assumption outside of Smart TVs. |
|
11th December 2017, 22:31 | #13 | Link |
Registered User
Join Date: Jan 2010
Location: France
Posts: 851
|
Thank you, I'll try both.
I've used a simple commandline : x265-8b.exe Video.avs --preset medium --keyint 240 --crf 20 --output Video.hevc I get an error message : x265 [error]: yuv: width, height, and FPS must be specified The same commandline with x264.exe works very well : x264.exe Video.avs --preset slow --keyint 240 --crf 22 --output Video.264 x265 doesn't include a decoder ? How can I use Avisynth script as input ? Thank you ! |
12th December 2017, 00:26 | #18 | Link |
Registered User
Join Date: Jan 2010
Location: France
Posts: 851
|
A last question : is it possible to use 2pass encoding with CRF ? If yes, is it a good choice to do a slow-firstpass then a second pass ? Or is it better to increase the preset (from medium to slow) ?
Thank you. |
12th December 2017, 09:23 | #20 | Link |
Registered User
Join Date: Jun 2017
Posts: 89
|
I did not know that is possible.
However, what would be the benefit? Isn't one of the reasons to use a CRF instead of a bitrate target to be freed from any bitrate constraints? I thought CRF uses whatever bitrate necessary for each moment to achieve a certain degree of quality... If CRF uses whatever is needed - what difference would a 2pass encode even make? |
|
|