Video editing and deinterlacing

ringo747 · 27 Aug 2009 at 22:18

Hi,

Having a play around with some footage from shooting with my new Canon HV40. I keep it in standard HDV mode which I think is 1080i. When I import into iMovie and play back the clips it looks fine. When I export to H.264 it looks all liney. I ticked the box to deinterlace the clips. Is this an iMovie issue or do I have to add another step somewhere?

I am always confused by the i and p things so not sure if I even need to deinterlace or not!

Any help with recommendations for software etc would be welcome. I have a trial version of visualhub here which I think could be useful.

Russinating · 27 Aug 2009 at 22:52

A proper article will be better than any of my explanations so if you do really need to know/want to know the difference between progressive and interlace then just do a quick Google

. But, very basically:

Interlaced = refreshes half the screen lines 1 frame, and the rest the next.
Progressive = refreshes the whole screen every frame.

To reduce the effect of interlacing you should have a variety of options available, although I've never used iMovie. Either way the settings will sit with the render (ie the codec). With the render it'll be Field order: None (progressive), Upper field first or Lower field first. I usually try both lower and upper and see which has the best effect.

Interestingly, Canon acquired the rights to progressive, Sony acquired the rights to interlaced. Last laugh's on Canon though, as Sony now fake their progressive HDV by recording in 50i and scrapping every other frame = 25p.

ringo747 · 27 Aug 2009 at 22:55

Thanks for that. I think with the default settings I must be recording in 1080i so I need to deinterlace that then. Is that the same as 50 frames per second? I will have a play with the imovie export settings and see what i can come up with.

Sirrel Squirrel · 28 Aug 2009 at 10:37

This might get confusing...

Basically when you shoot in 1080i you are shooting at 50 interlaced frames a second, so for every second you have 50 half frames, these are split up into upper and lower fields, upper fields being lines 1,3,5,7,9... lower fields being 2,4,6,8... when they are joined up by the human eye it works out as 25 full frames a second but you will have movement on each field. This is why when viewed on a progressive monitor you see the combing effect, when viewed on a CRT TV you don't see this because a TV refreshes at 50hz or 50i.

When you shoot in 1080P, which is 25P or to be technical 25PsF you will end up with 25 full frames but on the tape they are still encoded as 50i, which means your upper and lower fields are identical so when played back there is no combing effect. You can still play it back on a CRT TV because you still have a 50i/50hz signal.

So if you are editing 50i video for the web you need to deinterlace it, if it's going to DVD you don't need to as the TV can handle it, LCD and Plasma TVs will automatically work it out too and deinterlace for you.

Generally speaking for sport and fast action you are best off shooting in 50i, in low light and for pretty much everything else you are best off shooting in 25P.

ringo747 · 28 Aug 2009 at 10:48

Thanks for the info. Very helpful. I was shooting sports so I think I was ok shooting at 50i. What software would you recommend for deinterlacing on a mac? I take it I should export the clip from imovie as mpeg-4 then deinterlace that using some other software?

Sirrel Squirrel · 28 Aug 2009 at 11:48

Quicktime 7 Pro is a very good tool for doing encodes. Export your movie from imovie totally as is so using the same settings you captured with. Open the exported video with Quicktime and select file, export. Select h264 as your codec option under the video settings and choose the quality or enter a bit rate. Under the video size settings you can choose to deinterlace. Have a play around until you get the file size and quality you want.

edit/ just thought of a good free option called Handbrake.

The_Abyss · 29 Aug 2009 at 07:21

Handbrake was recommended here to me a short while back. It is very good, and fast - supports 4 cores. Shame it doesn't run off the graphics card though.

ringo747 · 19 Oct 2009 at 12:46

Hi guys, still having some issues here with deinterlacing. It seems that imovie 06 doesn't actually work properly. I am trying to export clip from the timeline to H264 quicktime, however, the resulting clip is still all 'liney'.

If I am to export in the same format as source what settings should I use. Do I just select full quality in the imovie options? What format is it captured in anyways? Is it mp4 when captured? Sorry for the newb questions.

ChazHurst · 19 Oct 2009 at 13:50

When I do any edits from my Sony camera I got a similar problem. I found a helpful guide to these sorts of things on some blog... I'll try and dig it out. In the meantime, try this:

1080i lacks some amount of the information to create a 1080p video. I always set my project settings to output in 720p 25fps with de-interlace ticked. These settings are usually accessed by clicking on "properties" in the "file" drop down menu, although I'm not sure of the exact workings of iMovie 06.

This will mean that the program has got all the information it needs to make a good looking 25fps de-interlaced video.

ringo747 · 19 Oct 2009 at 13:58

ChazHurst said:
When I do any edits from my Sony camera I got a similar problem. I found a helpful guide to these sorts of things on some blog... I'll try and dig it out. In the meantime, try this:

1080i lacks some amount of the information to create a 1080p video. I always set my project settings to output in 720p 25fps with de-interlace ticked. These settings are usually accessed by clicking on "properties" in the "file" drop down menu, although I'm not sure of the exact workings of iMovie 06.

This will mean that the program has got all the information it needs to make a good looking 25fps de-interlaced video.

That is exactly what I do but the de-interlace option in imovie 06 doesn't seem to work!