For a movie, such as Avengers (2012), source is the untouched Blu-ray video
Re-encoding it at 1920x1080 or 1280x720 resolutions
I have a few questions, Subme 9 is RD of course, subme 10 is Quantisized Psychovisual Rate Distortion in all frames, 11 is "Full RD"
Does subme 11 really do anything? I heard it was for a newer trellis, How does subme 9 10 11 differ in visual quality and compression? How do they work?
Merange 16 vs merange 32 vs 64, etc. I found merange 32 isnt much slower than 16, but whats the compression and quality benefit, is it worth it?
I encode 1080p or 720p versions of my bluray movies to fit on DVD5/DVD9 discs (BD5/BD9 Discs) using FULLY compatible options, I don't even enable weighted p-frames, to ensure compatibility with all players, EVEN THOUGH my player can play any AVC video, any resolution, any buffsize, any level, etc.
I use 4 ref frames for 1080p, 6 for 720p (max)
3 b frames
no weighted p frames
Pyramidal B-frames Strict
Adaptive B-frames Optimal
Adaptive direct mode Automatic
Uneven Multi Hexagon
subme 10 QPRD in all frames
Motion estimation range 32
Adaptive Quantization Strength 1.00
Psy Rd 1.00
Psychovisual Trellis 0.15
Deblock -3,-3 or -1,-1 or 0,0 (most often -1,-1)
2 pass, turbo first pass
Max bitrate 14.0 Mbps, bufsize 15.0 Mbps
RC lookahead 0, no mbtree, keyint 48, keyint min 1, qpmin 10, qpmax 51
cabac=1 / ref=6 / deblock=1:-1:-1 / analyse=0x3:0x133 / me=umh / subme=10 / psy=1 / psy_rd=1.00:0.15 / mixed_ref=1 / me_range=32 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-3 / threads=3 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=1 / constrained_intra=0 / bframes=3 / b_pyramid=1 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=1 / weightp=0 / keyint=48 / keyint_min=1 / scenecut=40 / intra_refresh=0 / rc_lookahead=0 / rc=2pass / mbtree=0 / bitrate=3400 / ratetol=1.0 / qcomp=0.50 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=14000 / vbv_bufsize=15000 / nal_hrd=vbr / ip_ratio=1.10 / pb_ratio=1.10 / aq=1:1.00
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Last edited by DrDeceit; 18th Nov 2012 at 11:01.
Generally it's not worth it, except in some cases like very low bitrate encodes .
Subme - Quantitatively , there is a tiny fractional benfit in SSIM for subme 11 vs. 10 vs. 9 when testing on a variety of sources . Qualitatively, sometimes I've seen cases where the quality is actually slightly worse
Merange - anything over 24 is overkill. Even "placebo" has merange at 24.
I spent some time recently playing around with MSU's Video Quality Measurement Tool with x264 and have found that settings such as "me_range", "subme" and "me" have very little effect on the visual quality.
The temptation of course is to set them to "full", but IMHO the loss of encoding speed compared to the negligable gain in quality is just not worth it.
Below is what I got when I compared two files (720x576 DVD source) with the following settings:
--me esa --subme 10 --merange 24 --crf 20 --- Speed - 19.5 fps --me hex --subme 7 --merange 14 --crf 20 --- Speed - 57.5 fps
Not much difference there, certainly nothing I could notice with the naked eye.
If we compare the same high quality settings with medium settings with a small hike in --crf.
--me umh --subme 7 --merange 20 --crf 19.5 --- Speed - 48.0 fps --me esa --subme 10 --merange 24 --crf 20 --- Speed - 19.5 fps
This seems to suggest that --crf has much more of an effect on quality than anything else.
Of course the lower the --crf, the bigger the file size, but the 2.5x speed increase seems like a good trade-off.
Last edited by mh2360; 29th Nov 2012 at 10:23.
mh2360 - can you add the resulting filesizes ? You can't compare "quality" at different bitrates . You either have to do multiple incremental CRF encodes or 2pass bitrate . So at a given bitrate, higher --merange and --subme will yield slightly better quality
They do make minor differences, but the effect is larger and noticable on very low bitrate encodes . For "typical" scenarios, it's usually not worth it, and especially if you are using CRF (because usually you don't pay as much attention to the filesize or bitrate)
A larger value for merange can make a bigger difference on HD encodes with lots of action compared to a SD source (but overall it's still very tiny difference)
Of course you are correct in saying that you can't compare quality at different bitrates, so I compared another file (The World War Z trailer downscaled to 720x576 if anyone is interested), at a much lower bitrate using 2 passes.
The settings used for both samples are below.
--me hex --subme 6 --merange 14 --bitrate 1400 --trellis 0 --me esa --subme 10 --merange 24 --bitrate 1400 --trellis 2
1400kbps is below what I would use for a DVD conversion, but there's still very little difference, both visually and according to the chart.
It could be that I'm using SD sources, and that using higher settings might be more helpful with HD material at lower bitrates.
Last edited by mh2360; 29th Nov 2012 at 12:49.
There is definitely a visible quality difference in the lower bitrate range with the lower subme values vs. higher subme values, when viewing still frames.
At "normal" or higher bitrates, or normal viewing - it won't be very noticible
Difference between subme 7 vs. something like 9 or 10 is minimal . The OP was considering 9-11 and the difference between these is negligible (only visible through metrics, or the odd frame). But difference between something like 2-3 vs. 9-10 is definitely noticeable and reproducable on almost all sources in the low bitrate range. b-frames specifically suffer the effects, they are noticably worse . I've done many, many , many tests that show this. I can dig up some old examples - there should be some posted either here or doom9
Also - Be careful about using SSIM or PSNR to measure "quality" . This has been discussed many times before
What I think goes through peoples' mind when they set up the x264 encoder is that they see how much slower the encoder runs when everything is set to "full", and naturally they assume that all that extra processing must mean that it's making a huge difference quality-wise.
What I attempted to show is that just because x264 is running 2.5x slower with certain settings, the quality isn't going to be 2.5x better (or even 0.01x better). For most jobs the default settings are just as good as the HQ ones, if not better since the encoder will run much faster.
It is a tradeoff and to most people and "normal" usage scenarios - the slower settings aren't worth it
For pixel peepers, there is a noticable difference as you go into slower settings in low bitrate scenarios. "low bitrate" meaning relative to content complexity. It's almost never noticable in motion, but on frame-by frame examination it will be noticable. Higher bitrates alleviate everything and make differences difficult to visualize. The differences are very clear in the lower bitrate ranges, but almost imperceptible if you use low quantizers/low crf or high bitrates
The OP was considering merange 64 . Well "placebo" has it set at 24.... so that tells you something. Only on a 4k action packed movie might you have a chance to catch a pixel that might have been missed at a lower value. It's exceedingly rare and the cost/benefit ratio is very very very low . For SD resolutions, don't even think about it