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TOPIC: Image overlay on interlaced footage

Image overlay on interlaced footage 2 weeks, 2 days ago #168929

  • andrixnet
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I got some footage from a Panasonic FHD camera, MTS format, 1920x1080i 25fps, accepted natively by LWKS.
The image is interlaced.
I have an image to overlay (placed on separate track, using 2D DVE to move it around). The image is a still, of course, progressive.
(see my borders leaking post, same scenario)
Project settings is 1080i.

Exporting to 720p has the following results:
- interlaced video footage is downscaled, interlacing artifacts look awful. But this was expected, as LWKS does not deinterlace.
- overlayed image's motion is clearly progressive.

This looks to me like export is done according to the setting first, that is all video tracks are rescaled and treated as progressive before rendering.
I would have expected rendering to take place according to project settings, the blended image's motion to be broken into fields as well, resulting in a full interlaced output at project setting resolution and only then scaled down to export setting.

Please clarify if this is intended behaviour, or is there something else I've missed?

Thank you.

Re: Image overlay on interlaced footage 2 weeks, 2 days ago #168937

  • hugly
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Intended, I suspect.

Lightworks does not apply de-interlacing. Footage recorded truly interlaced (separated fields) is treated as interlaced, progressive footage as progressive. There is a user effect which can be applied to de-interlace, as far as I can remember, but I don't know how this will work when scaling footage on export or applying DVE.

Consequently, you can't use interlaced footage with Lightworks Free without combing artifacts in exported files. Deinterlacing prior to import is needed. Beyond that, downscaling (truly) interlaced footage on export (e.g. HD/UHD to 720p or less) will reduce visible combing artifacts significantly.

The way to combine interlaced and progressive material with best possible results is exporting to an interlaced format. That's a Pro feature only, and creates interlaced media which isn't always a desired format for delivery .
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Last Edit: 2 weeks, 1 day ago by hugly.

Re: Image overlay on interlaced footage 2 weeks, 2 days ago #168940

  • hugly
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Just to avoid possible misunderstandings, this meets professional needs in most cases.

In the past, the broadcast people had strictly interlaced workflows, the film people strictly progressive. De-interlacing wasn't needed. The telecine process incorporated converting frame-based material to field based material. The opposite wasn't so frequently needed and de-interlacing reduces quality visibly, anyway.

Nowadays where everybody can create broadcast content with whatever device, things have become more difficult.
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Last Edit: 2 weeks, 1 day ago by hugly.

Re: Image overlay on interlaced footage 2 weeks, 1 day ago #169007

  • andrixnet
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Thank you, though these still do not clarify if transcoding to DVCPRO 100 results in deinterlaced footage is a bug or a feature.

If it is a bug, it should be fixed.
If it is a feature, then transcoding to DVCPRO 100 should be recommended in this forum in all deinterlacing topics as a native LWKS shortcut, without the need of processing with external tools before importing.

Re: Image overlay on interlaced footage 2 weeks, 1 day ago #169009

  • hugly
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I believe to remember that you started already another topic about DVCPro100.

I'm not a DV specialist, but in my view DVCPro100 (DVCPro HD) is a legacy format. I've used it only for temporary timeline rendering (it's fast). The format is limited in terms of frame rates and supported resolutions (more or less to the historic broadcast standards) and it's anamorphic by default which decreases quality of non-anamorphic formats when used as intermediate.

I can't explain your findings in the other thread. I don't believe that DVCPro HD is usable to replace de-interlacing in general for truly interlaced footage (separated fields). It might help for progressive footage incorrectly detected as interlaced (the MPEG2-hack in AVI container), but that's more a feeling rather than understanding.
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Last Edit: 2 weeks, 1 day ago by hugly.

Re: Image overlay on interlaced footage 2 weeks ago #169061

  • jwrl
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I've worked with DVCpro 100 quite a lot in the past. I still have a Panasonic camera in my junk room that shoots it. I believe that hugly is right on the money. The format won't and can't automatically deinterlace, but will reliably support PsF media correctly. And it is also an anamorphic format. Panasonic themselves describe it as 1920x1080, but in reality it is either 1280x1080 or 1440x1080 depending on the frame rate.

It isn't a good codec to work with if you care about quality. When I had to use it I used to transcode to a square pixel intermediate codec and do all my post that way to minimise quality loss. My recommendation: don't use it unless you're absolutely forced to.

Re: Image overlay on interlaced footage 2 weeks ago #169074

  • andrixnet
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Understood. Do not use unless really necessary for certain technical reasons.

Still doesn't explain why the end result was deinterlaced, though.

Re: Image overlay on interlaced footage 2 weeks ago #169075

  • hugly
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To say it more dramatically: No codec on this planet incorporates de-interlacing.

The question is, what makes you think that your footage is truly interlaced? I'd suggest adding the question to your list: Could it be that the visible artifacts in preview have another cause?

I'm referring to this thread: www.lwks.com/index.php?option=com_kunena&func=view&catid=23&id=168928&Itemid=81#168928
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Last Edit: 2 weeks ago by hugly.

Re: Image overlay on interlaced footage 2 weeks ago #169076

  • hugly
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One question: Does the camera in this picture move and if so, in which direction?

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Re: Image overlay on interlaced footage 2 weeks ago #169084

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Although I tested several things using the same footage and the same project, I will continue exclusively on topic.

Camera motion is horizontal, from left to right, then from right to left.

All exports below are 720p.

This is the result, when project settings is 1080i 25fps:
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This is the result, when project settings is 1080sf 25fps:
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This is the result, when project settings is 1080p 50fps:
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This is the overlayed image:
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Removed the video track and left only the image animation:
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I can't do more tests because I don't have 720i or 1080i export ability.
As a parallel, Premiere Pro CC renders the motion of the still image as interlaced, but I can't make a 100% parallel because at 720p export it also does an automatic deinterlace I couldn't disable)
1080i export with premiere.
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720p export with premiere.
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If LWKS does no deinterlacing (and I'm fine with that), my question is:
if project is 1080i, shouldn't the image's motion be rendered as interlaced?
The output being 720p with no deinterlacing, then I should see interlacing artifacts for both the video footage and the image animation, same as premiere_test.mp4 viewed downscaled to 1280x720 without deinterlacing?
Last Edit: 2 weeks ago by andrixnet.

Re: Image overlay on interlaced footage 2 weeks ago #169086

  • andrixnet
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So, referring to image overlay on incerlaced footage:

I will try to add more details. This is a fragment of the original file, as it came out of the camera. As stated, 1080i 25fps.


General
ID                             : 1 (0x1)
Complete name                  : E:\send\00000.mts
Format                         : BDAV
Format/Info                    : Blu-ray Video
File size                      : 5.00 MiB
Duration                       : 2s 690ms
Overall bit rate mode          : Variable
Overall bit rate               : 15.5 Mbps
Maximum Overall bit rate       : 18.0 Mbps

Video
ID                             : 4113 (0x1011)
Menu ID                        : 1 (0x1)
Format                         : AVC
Format/Info                    : Advanced Video Codec
Format profile                 : High@L4
Format settings, CABAC         : Yes
Format settings, ReFrames      : 4 frames
Format settings, GOP           : M=3, N=12
Codec ID                       : 27
Duration                       : 2s 680ms
Bit rate mode                  : Variable
Bit rate                       : 14.6 Mbps
Maximum bit rate               : 16.8 Mbps
Width                          : 1 920 pixels
Height                         : 1 080 pixels
Display aspect ratio           : 16:9
Frame rate                     : 25.000 fps
Color space                    : YUV
Chroma subsampling             : 4:2:0
Bit depth                      : 8 bits
Scan type                      : Interlaced
Scan order                     : Top Field First
Bits/(Pixel*Frame)             : 0.283
Stream size                    : 4.68 MiB (94%)

Audio
ID                             : 4352 (0x1100)
Menu ID                        : 1 (0x1)
Format                         : AC-3
Format/Info                    : Audio Coding 3
Mode extension                 : CM (complete main)
Format settings, Endianness    : Big
Codec ID                       : 129
Duration                       : 2s 432ms
Bit rate mode                  : Constant
Bit rate                       : 256 Kbps
Channel(s)                     : 2 channels
Channel positions              : Front: L R
Sampling rate                  : 48.0 KHz
Bit depth                      : 16 bits
Compression mode               : Lossy
Delay relative to video        : -80ms
Stream size                    : 76.0 KiB (1%)

Text
ID                             : 4608 (0x1200)
Menu ID                        : 1 (0x1)
Format                         : PGS
Codec ID                       : 144
Duration                       : 2s 336ms
Delay relative to video        : -80ms




Apparently .MTS attachments are not supported.
See here the original file: 00000.mts
Last Edit: 2 weeks ago by andrixnet.

Re: Image overlay on interlaced footage 2 weeks ago #169089

  • hugly
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andrixnet,

Thanks for providing the source and the samples.

The footage is interlaced.

Is it possible that you haven't changed the scan type to interlaced before importing the video?

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Last Edit: 2 weeks ago by hugly.

Re: Image overlay on interlaced footage 1 week, 6 days ago #169136

  • andrixnet
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Upon further investigation, I have found more puzzling results.

Based upon your question, I recreated a new project, as follows:
- new project, "auto".
- before importing, I checked project settings, it says 1080p (sf) 23.98fps.
footage says 1080i 25fps, AVCHD.
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- after import, I checked the project settings again, it says 1080i 25fps.
footage says HD 1080i.
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I used the same 00000.MTS as source.

Surprisingly, all player windows in LWKS no longer show interlacing artifacts.

I quickly exported a few seconds as 720p, the result is a good progressive image. See here:
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I redid the image animation over it. Exported as 720p and the result is a good progressive image. See here:
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Re: Image overlay on interlaced footage 1 week, 6 days ago #169137

  • andrixnet
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So, LWKS does or doesn't do deinterlacing?

I remember creating the initial project (when first reported this) as "mixed" because I had 25 and 50 fps test files.
So let's do another test:

- new project, mixed
- project setting defaulted to 1080p (sf) 23.98fps. footage is 1080i 25 fps.
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- after import, project setting remains unchanged. Footage is seen as HD 1080i.
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All player windows now show interlaced rescaling artifacts. Output is rescaled interlaced, so very bad.

So, if I create a mixed project (leaving defaults before importing), everything is imported at the default project setting.
Changing project setting later has no effect.

IMO changing project setting should have changed the way footage is handled in the same way as it was handled in my previous post.

-----------------------------------------------------------

Furthermore, I've done another test:
- new project, mixed
- change project settings to 1080i 25fps BEFORE importing anything
- import 1080i 25fps footage.

The result is the same, that the interlaced is handled as progressive.

-----------------------------------------------------------

One more test:
- new project, 25fps
- initial project setting shows 1080p (sf) 25fps, leave unchanged, or change to 1080i before importing, the end result is the same.
- import 1080i 25fps footage

The result is the same as the project "auto" in my previous post, that is video image is progressive.

Re: Image overlay on interlaced footage 1 week, 6 days ago #169138

  • andrixnet
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So the final questions are:

1. does or does not LWKS deinterlace?

2. why project setting changes have no effect when changing between i and p?

3. what is wrong with the "mixed" type project? The setting refers to frame rate, right?
Am I to understand that "mixed" handles only pure progressive sources properly?

Thank you.
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