Need help with x264 settings (high motion scenes issue)

[simps]

I did some low bitrate encodes (2pass 320kb/s) with x264, and found out some issues, mainly on high motion scenes. I suspect the answer for this 3 questions is "yes", but I am really not 100% sure.

1) High motion scenes are hurt too much.
Question 1: Can --qcomp 0.7 (instead of default 0.6), help the high motion scenes?

2) Encoded video is "too soft". (I know at this low bitrate it will be due to deblock, but still...)
Question 2: I am using --psy-rd 1.02:0.4 --deblock 0:0. Will I get sharper frames with more details on it, with --deblock -1:-1?

3) I do see some blocks on dark areas and high motion scenes.
Question 3: I am using the default --aq-strength 1, will --aq-strength 1.05 be a good reasonable number to go?

Thanks,
Simps

[Chengbin]

You're expecting good quality with 320Kbps???

Your expectation does not go with your bitrate.

No settings can change the sharpness because your bitrate is way too low.

[JohannesL]

--qcomp 1 and exact same settings for both passes.

[Dark Shikari]

Originally Posted by Chengbin

You're expecting good quality with 320Kbps???

I didn't see any mention of resolution in his post that would justify such a response.

If you have something worthwhile to add, don't post.

[Adub]

@simps
You got some good ideas there. Unfortunately, without a sample of your source, we can't tell you how good your ideas are.

You can try increasing the qcomp like JohannesL stated. I don't know if I would go with 1, but anywhere between .7 and .9 should be okay depending on your source.

As for deblock, negative numbers actually aim to produce a sharper picture instead of a softer one, so you have the right idea, but you risk increasing the blocking factor. You may try decreasing your values, with a max drop of -3 for both. Bumping up PSY-RD past 1 is okay, but if you want it even sharper you may want to go ahead and try something like 1.1 instead of 1.02.

Same for AQ. 1.0 and 1.05 are not hugely different. Usually when tuning these settings I go in increments of .1 not .01. You will see a bigger difference that way.

[CruNcher]

you could try --no-fast-pskip and see if you like that visual result more, especially @ low bitrate and high motion it is a interesting difference motion quality vs detail preservation also b-frames tend to go hi wire @ to low bitrates create strange visual artifacting in high motion scenes so maybe disabling b-frames would be also a option (though im not sure if this is still the case for current x264 development state) (the b-frame problems for example where not that obvious with Atemes Encoder back then maybe --b-adapt 2 fixes this now) i used the close up fight scene from 300 @ 720p and bitrates as low as 120 kbps (there x264 actually ended it wasn't possible to go lower Ateme was able to go down to like 50 kbps) some very interesting visual result differences between all the Encoder (motion/detail/artifacting). Also you could try --direct temporal if you keep b-frames it can help motion --direct auto is good but still @ very low bitrates --direct temporal seems better motions wise (the effect can be very nicely seen in Paramounts Intro when the stars move in and the camera pans).

[simps]

I opened the thread below for this discussion.
http://forum.doom9.org/showthread.ph...76#post1289176

Adub, CruNcher,

Thanks for the tips. I think I found the sweet spot, at least for this material.
I did change my settings, with --qcomp 0.7, --deblock -1:-1, --aq-strength 1.05 and some tweaks, and I managed to produce very good results at 320kb/s (2pass). High motion scenes are better now, and blocks are gone.
I am now doing some tests at --bitrate 240, and I would like to share my results with you guys. I hope this can help someone too.
Resolution is 640x352. I know, it is too much for 240kb/s (it wasn't for 320kb/s with my settings, it looked very good)



Here we go, this is my settings, and why I used it.

1) Default x264 settings will give a too much soft looking picture at low bitrates.
--trellis 2 and --psy-rd 1.02:0.4 (this is the optimal for me, closest to the source) adjust from 1.0:0.2 to 1.08:0.5
--deblock -1:-1 (this will give sharper picture with more details, but might give blocks too) adjust from -1:-1 to -2:-2
--aq-strength 1.05 (this is the correction I use to prevent blocks, from using --deblock -1:-1) adjust from 1.02 to 1.08

2) High motion scenes are hurt too much with default settings at low bitrates.
--qcomp 0.7 (this is provide more quality to high motion frames) adjust from 0.7 to 0.85
--no-fast-pskip (this helps a bit too) use it

3) b-frames tweak
--b-adapt 2 (this is the best for quality) use it
--bframes 8 (Overkill??? Well, from my tests arround 20% of my bframes were 5, 6, 7 consecutive) adjust from 8 - 10
--b-pyramid (this is good stuff) use it
--weightb (this is good stuff) use it

4) --direct
I am using "auto" here. Since I asked and DS said "auto" would be best, since the encoder is smart enough to handle it properly.

5) Other settings
--ref 16
--partitions all
--me umh
--merange 16
--subme 9
--mixed-refs
--8x8dct

6) --no-dct-decimate
I found this was bad for low bitrates. It increases the file size, and hurt compression / quality. It can preserve more detail under massive bitrates, and I would use it there, but under low bitrates, it is best not to use it.



Results at 640x352 with 2pass 240kb/s:
I was impressed, remember this is with --qcomp 0.7, I bet with --qcomp 0.8-0.85, the high motion scenes would look much better, without decreasing too much the rest of the video. I might give it a try, and post back results.

Static scene 1:
Source

x264 - 2pass 240kb/s




Static scene 2:
Source

x264 - 2pass 240kb/s




Low motion scene 1:
Source

x264 - 2pass 240kb/s




Low motion scene 2:
Source

x264 - 2pass 240kb/s




High motion scene 1:
Source

x264 - 2pass 240kb/s




High motion scene 2:
Source

x264 - 2pass 240kb/s




I might post the video file (.264) if anyone is interested.

I opened the thread below for this discussion.
http://forum.doom9.org/showthread.ph...76#post1289176

Thanks,
Simps

[Dark Shikari]

Please don't crosspost.