What deinterlacing method to choose?

[FlyingAces]

Hello, guys!

Recently I got Bref. Blu-ray.
BDInfo (whole series):

Codec                   Bitrate             Description     
-----                   -------             -----------     
MPEG-4 AVC Video        18452 kbps          1080i / 25 fps / 16:9 / High Profile 4.1

MediaInfo (episode 1):

Video
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4.1
Format settings                          : CABAC / 4 Ref Frames
Format settings, CABAC                   : Yes
Format settings, Reference frames        : 4 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 1 min 49 s
Bit rate mode                            : Variable
Bit rate                                 : 18.7 Mb/s
Maximum bit rate                         : 22.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 50.000 FPS
Original frame rate                      : 25.000 FPS
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Interlaced
Scan type, store method                  : Separated fields
Scan order                               : Top Field First
Bits/(Pixel*Frame)                       : 0.181
Stream size                              : 245 MiB (91%)
Language                                 : French
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709

MeGUI's AVS script creator after analysing says it's progressive.
ffmpeg, using advice from SO:

ffmpeg -filter:v idet -frames:v 5490 -an -f rawvideo -y NUL -i bref.s01e01.mkv
------
[Parsed_idet_0 @ 000001da3eb27200] Repeated Fields: Neither: 2729 Top: 4 Bottom: 12
[Parsed_idet_0 @ 000001da3eb27200] Single frame detection: TFF: 49 BFF: 70 Progressive: 2399 Undetermined: 227
[Parsed_idet_0 @ 000001da3eb27200] Multi frame detection: TFF: 0 BFF: 27 Progressive: 2694 Undetermined: 24

I want to rip it and store on my hdd. But the problem is that I don't know the right way to deinterlace it.

Fisrt, I followed the advice from this forum post:

For the record, if you select "Interlaced" and "Yadif with Bob" as the de-interlacing method in the script creator, that'll give you double frame rate output as QTGMC does by default (50fps for PAL). If you select "yadif with bob" and use the preview, and when you step through the frames one at a time it just looks like every frame is repeated (as it does for your sample) it's a fair indication it's not really interlaced. If each frame is different, then it probably is.
Of course there's always the possibility that some parts will be interlaced and other parts progressive (hence MeGUI's partially interlaced option), but generally for movies they're either one or the other.

Yes, every frame looks like it's repeated, but with some small differences in artifacts.

However on this screenshot there're lines visible, especially noticable on the garland (blue lights):


Here is a sample of the original video (BDRemux):
sample.mkv

Can someone help me, please?

P.S. Thank you for reading

[manono]

Can someone help me, please?

You'll have to provide an untouched video sample. 10 seconds or so that shows the problem. All those words and pictures are pretty much useless.

[jagabo]

(yadif bob) Yes, every frame looks like it's repeated, but with some small differences in artifacts.

Then you don't want to deinterlace at all. Try TFM() field matching.

The crap in your second image has nothing to do with deinterlacing. It's errors decoding the source video -- common with ffvideosource(). Try using LSmash's LWlibavVideoSource() instead.

And yes, an non-reencoded sample would help the analysis. One with moderate motion and a sharp picture (relatively free of motion blur), like a medium speed panning shot.

[lordsmurf]

All those words and pictures are pretty much useless.

Blunt, yet succinct and accurate. Sample required.

[LigH.de]

In general, deinterlacing filters only help if the content is continuously linearly interlaced. But there are so many other possible reasons for combing; NTSC world has telecine, and the results of norm conversions may have blended versions. They need different treatments...

[FlyingAces]

Thank you for all your responses.
I updated my post and added a sample video.

The crap in your second image has nothing to do with deinterlacing. It's errors decoding the source video -- common with ffvideosource(). Try using LSmash's LWlibavVideoSource() instead.

Yep, thanks for that. I was using ffvideosource only in AvsPmod to make screenshots with overlay text. And LSmash's plugin to index in MeGUI.

[jagabo]

Sample.mkv is encoded interlaced but the frames are all progressive. There's no need to deinterlace of field match, just treat it as progressive.

[LigH.de]

However on this screenshot there're lines visible, especially noticable on the garland (blue lights):

This kind of aliasing is probably not caused by interlacing (this scene doesn't look like heavy horizontal motion), but rather by YUV 4:2:0 chroma subsampling artifacts. Rather highly saturated red and blue has only half the resolution, compared to average brightness.

[FlyingAces]

Alright, it's a progressive video then. Thank you.

This kind of aliasing is probably not caused by interlacing (this scene doesn't look like heavy horizontal motion), but rather by YUV 4:2:0 chroma subsampling artifacts. Rather highly saturated red and blue has only half the resolution, compared to average brightness.

How can I deal with it? If I encode to 720p it looks good without any of these lines, they just blend in (is it correct terminology?). However in 1080p they look almost like in the source (depending on x264 settings).

[jagabo]

The problem around the blue lights is because of the interlaced encoding. You can get rid of it with:

MergeChroma(vInverse())

[FlyingAces]

MergeChroma(vInverse())

http://avisynth.nl/index.php/Vinverse - this one, right?

The problem around the blue lights is because of the interlaced encoding.

By "interlaced encoding" you mean because video of this BD was just flagged "interlaced" when encoded?

[LigH.de]

Yes, to be Blu-ray compliant, video in specific framerate/resolution combinations need to be encoded in interlaced mode even if the content is progressive. Hardware encoders will use PAFF interlacing which is not most efficient in this case, and the disadvantage is that colors are shared based on fields, skipping a line each. In contrast, x264 has a "fake-interlaced" mode which supports MBAFF; it may use interlaced mode for every macroblock but will always use progressive mode in reality.

[FlyingAces]

LigH.de thank you for the explanation. Can you, please, give me a link where I can start learning about that in more detail?

MergeChroma(vInverse())

Fixed these lines. Does that mean I have to use this function on every BD video that was encoded as interlaced while being progressive?

And also there're some blocks (sorry, I don't know the proper terminology) on the edges of the blue lights between pink and blue. Should I do something to get rid of them or it's normal with this source?


I encoded it with the following params:

cabac=1 / ref=4 / deblock=1:-2:-2 / analyse=0x3:0x113 / me=umh / subme=10 / psy=1 / psy_rd=1.05:0.00 / mixed_ref=1 / me_range=48 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-3 / threads=12 / lookahead_threads=3 / sliced_threads=0 / nr=0 / decimate=0 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=16 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc=2pass / mbtree=0 / bitrate=12900 / ratetol=1.0 / qcomp=0.70 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=2:0.80

[jagabo]

Can you, please, give me a link where I can start learning about that

Note that the comb-like artifacts are a consequence of interlaced encoding of 4:2:0 chroma subsampled video. You can find a very detailed explanation here:

https://hometheaterhifi.com/technical/technical-reviews/the-chroma-upsampling-error-an...hroma-problem/

See the section entitled "4:2:0 Interlaced: Fundamentally Broken". The problem here isn't the upsampling error but you need to understand now the chroma subsampling works in order to understand how the problem arises even when done properly. Some more explanation and samples here:

https://en.wikipedia.org/wiki/Chroma_subsampling#4:2:0

You can also fix the artifacts with:

MergeChroma(Blur(0,0, 1.0))

That is essentially what the earlier fix does though vInverse() only does the fix where it sees combing. To restore some of the sharpness you can follow with a little sharpening:

MergeChroma(Blur(0,0, 1.0).Sharpen(0.0, 0.6))

Does that mean I have to use this function on every BD video that was encoded as interlaced

If the video has sharp chroma edges and 4:2:0 subsampling it will have those artifacts. It's up to you if you want to "fix" it or not.

[FlyingAces]

Well, it will be very interesting to read that.

You can also fix the artifacts with:

They're the same picture.
Jokes aside, I was able to see some minor differences only zooming it, but blur+sharpening produced a better picture to my liking.

though vInverse() only does the fix where it sees combing

So it's better to use vInverse() in order not to blur/sharpen other parts of the video?

Note that the comb-like artifacts are a consequence of interlaced encoding of 4:2:0 chroma subsampled video.

And the last question. How do I know if it's 4:2:0 chroma subsampled video?

[poisondeathray]

How do I know if it's 4:2:0 chroma subsampled video?

Blu-ray is 4:2:0

99.9999% of commonly distributed video is 4:2:0

[jagabo]

Well, it will be very interesting to read that.

You can also fix the artifacts with:

They're the same picture.
Jokes aside, I was able to see some minor differences only zooming it, but blur+sharpening produced a better picture to my liking.

though vInverse() only does the fix where it sees combing

So it's better to use vInverse() in order not to blur/sharpen other parts of the video?

It's a judgment call. And may depend on the particular video. vInverse() may be safest. Blur.Sharpen more thorough.

Note that the comb-like artifacts are a consequence of interlaced encoding of 4:2:0 chroma subsampled video.

And the last question. How do I know if it's 4:2:0 chroma subsampled video?

MediaInfo is pretty reliable for interlaced encoding and 4:2:0 subsampling.

[FlyingAces]

Ok, understood.

Thank you very much, guys, for your help!

[Takashi]

Sample.mkv is encoded interlaced but the frames are all progressive. There's no need to deinterlace of field match, just treat it as progressive.

1 - how can I know when the frames are progressive if mediaInfo says that Sample.mkv is interlaced type TFF?

2 - using mediaInfo how can I know when to use TFF and BFF or none in MeGUI "interlaced mode"?

3 - besides mediaInfo is there any other software I should use?

I am new and I have learned many things about encoding in this forum such as that it is progressive or interlaced and how interlaced FTT and BFF work but I cannot understand when I can apply this when encoding a video

[jagabo]

1 - how can I know when the frames are progressive if mediaInfo says that Sample.mkv is interlaced type TFF?

Open the video in an editor that you know won't automatically deinterlace the preview (many deinterlace because the combing freaks people out). I use VirtualDub2.

2 - using mediaInfo how can I know when to use TFF and BFF or none in MeGUI "interlaced mode"?

In VirtualDub2 apply the Bob Doubler filter (Video -> Filters -> Add -> Bob Doubler). Step frame-by-frame through a section with motion. If you see motion that moves back and forth you have the wrong field order (Bob Doubler defaults to BFF).