I am seeing something in all my renders and it bugs the heck out of me. I have a new Sony HDR-CX550v. It records at 30i in 1920x1080. When I finish trans-coding multiple clips from AVCHD to DNxHD 1920x1080 30i, and edit them to my liking, and render to format (VOB or MPEG2 for a DVD), I see what appears to be some kind of interlacing(I'm not sure thats what to call it). The video looks like someone has offset a frame a pixel or so, and rolled it threw the video. Like when one is watching CRT monitor footage on progressive display(flat panel) except it is very fast. Cant really follow it, it just flickers threw. It only occurs when a object or the camera is moving quickly. What is it? Is it my camera? Should I try to deinterlace the image? Any advice or explanation would be greatly appreciated.

There isn't actually any 30i format. Most cameras support 30p and 60i, but I think the Sony only has 60i, which is 60 fields per second interleaved and stored in 30 frames.

If you're not careful, when you transcode the clips without either de-interlacing them or preserving the interlacing through your workflow, you can end up with 30p footage but with interlace artifacts. When you then downsize to DVD resolution, the interlace artifacts will appear randomly depending on how the pixels are weighted and averaged during the downscaling. That's probably why it looks random or "rolling".

As you guessed, one solution (possibly the simpler) is to de-interlace when you're transcoding and work with a progressive workflow (1080p). I don't use kdenlive for transcoding, so I don't know if any of its transcoding profiles can deinterlace. If they can't, you can probably create one that can.

Since the end result is a DVD, you could also preserve the interlacing through your project by using a 1080i project setting, but then you need to be careful to preserve the interlaced format through the transcoding stage, and I don't know if kdenlive's transcoding profiles are setup to do that.

Generally, deinterlacing causes some loss of resolution, but since your source material is much higher resolution than your rendered format, you won't really loose much quality from de-interlacing.

Thank you for the explanation. I am going to set the project up as 1080i and transcode all the AVCHD to DNxHD 1920x1080 30i. When I render the VOB or MPEG-2 it should stay interlaced. Ill keep you posted on the out come.

Ok... I did as I mentioned above and forced interlacing in the render dialogue. The interlacing artifacts are still present. This is horrible. Its like the first time someone pointed out the color wheel effect in a DLP TV. That flicker will always kill the experience for me.

Maybe this has to do with the field order or something?

First of all, I think I see where the 30i confusion comes from. I looked at kdenlive's transcode profiles, and the transcode profile for interlaced dnxhd is labeled "DNxHD 1920x1080 30i 220Mb/s". It should really say 60i, not 30i.

So theoretically, if you preserved interlace all through to your output, the video *should* still be interlaced. There are a few places where something might be going wrong:

You could be viewing the rendered output on a progressive monitor. You will generally see interlace artifacts if you are. The best way to test your VOB is to create a DVD and watch it on an old fashioned interlaced CRT TV. If it doesn't look OK there, then there may be a problem somewhere in the workflow.

One possible problem could be in the scaling. I don't know if the scaling that occurs when rendering is interlace-aware. Perhaps someone who knows can answer that.

Dave

The scaler is not interlace-aware, but the framework will force deinterlace if vertical scaling is involved. But of course, if it thinks the clips are progressive, then it does not deinterlace.

Some kdenlive versions' DNxHD transcode presets did not have a -top option in them. That caused the output images to be interlaced but not indicated as such in the file. So, the deinterlacer would think they are progressive and not do anything. Do your transcode presets have -top in them? If you are using the force progressive option in advanced clip properties, you need to force them to be 0 to indicate they are interlaced.

Sorry, in haste, I gave you some wrong information. -top affects the indicated field order in the output, not interlaced vs. deinterlaced. "-flags +ilme+ildct" in the transcode preset indicates interlaced encoding and signaling.
Kdenlive version 0.7.7 added interlace flags and separate progressive presets.
version 0.7.8 added the -top option for field order detection.
So, you could be seeing the results of deinterlacing on incorrect field order.

I am using this profile:

-s 1920x1080 -r ntsc -top -1 -flags +ilme+ildct -b 220000k -threads 2 -vcodec dnxhd -acodec copy %1.mov;High quality encoding

I am going to try all the options: "top=1/bottom=0/auto=-1 field first"


I noticed the bit rate is set to 220000k.

My Sony instructions say "Movies are recorded with AVCHD 1920 1080/60i format when the FX or FH mode of the high definition image quality (HD) is selected. You can select the following high definition image quality (HD) recording mode. “24M” of [HD FX] is the maximum bit-rate, and the value other than of [HD FX], such as “17M,” is an average bit-rate.
[HD FX] (AVC HD 24M (FX))
[HD FH] (AVC HD 17M (FH))"

That sounds like the video can peak at 24 Mbps. Maybe the video is going crazy when the video is above the set 22 Mbps? When I try to change FFMPEG to 240000k it fails. Could this be causing it the interlaced artifacts?

I have tried all the field options and I get the same result. I used a 1080i profile for the project. When I rendered the VOB I forced interlace. I think I have kept the whole process interlaced, from source to transcode, time-line to render (force interlace). Here is a upload of the clip I have been working with. Its just stock footage of my dogs playing "who's yard is it"? Please forgive the marketing of the territory.

http://www.youtube.com/watch?v=viL2bGVKywg

Sorry now check it out.

http://www.youtube.com/watch?v=viL2bGVKywg

About the bitrate, the transcode preset is the bitrate of the output DNxHD, which is intentionally high bitrate and is completely unrelated to the bitrate of the input.

With Kdenlive, you can not retain interlace when resizing from 1080i to 480i. It does not have a field-aware scaler. As long as your clip is properly identified as interlace, then it will deinterlace prior to scaling. My attachment shows what it looks like when you vertically scale interlaced video (without a field-aware scaler, of course).

Your YouTube video looks good. Did that turnout as you expected?

ddennedy, yes it did. I think the video was improved when I switched the field order. I have produced the same effect as you showed above by accident. I am beginning to think the occasional artifact has to do with the quality of the camera. It has a hard time keeping up with fast moment. I reviewed some Youtube clips like this one.



If you watch the black and white wheel spinning you can see this horizontal artifact. I apologizes if this thread was due to the camera and not some ffmpeg setting. On the other hand, if that is the case, I sure know what to look for in my next camera purchase.

I love Kdenlive
B