Interlaced vs. Progressive

[MrEbert]

This is not really a problem as much as it is a curiosity. I'm curious why, in the 1080i rips of Top Gear episodes, all the scenes that take place in the studio are interlaced (it's very noticeable) and the rest of the episode is progressive (looks crystal clear). Is this something the BBC does or is it something to do with the .ts file format?

 

[ESPNSTI]

I don't know the answer, but if it's very noticeable, you're probably not using a deinterlacer or you're not using a very good one.
I'm using Media Player Classic HC with ffdshow's deinterlacer and I can't tell on a 55" 1080p HDTV that it's interlaced (not that I'm an expert).
Now if you have a fairly new graphics card you could have it take care of the deinterlacing (DXVA) as opposed to having a codec do it.
For me that wasn't an option since my graphics card is a bit older and doesn't use a very good deinterlacing method, plus ffdshow doesn't pass on the interlaced flag to the rendered for some reason.

FYI, there is some interlacing talk in this thread:
http://forums.finalgear.com/the-site-itself/720p-vs-1080i-rips-40573/

 

[MrEbert]

Alright. I'm using VLC to play everything so I'll look and see if I can fix the interlacing within that.

 

[narf]

In VLC you can just select video -> deinterlace -> yadif from the menu

 

[MrEbert]

Yeah, I really shouldn't have missed that option.

 

[MrEbert]

But my curiosity remains. Why are the studio segments interlaced and the other parts aren't?

 

[narf]

I'd say they used different cameras (or settings) for the different segments. A studio segment apparently was shot with TV-style cameras recording 50 distinct fields per second. A nonstudio segment apparently was shot with film-style cameras recording 25 distinct frames per second. The former can cause interlacing artifacts on computer screens because the two fields of a frame are recorded at different instances in time, while the latter puts one frame into two fields recorded at the same instance in time. When the computer screen is displaying both fields at the same time the former method causes interlacing artifacts.

 

[Leetpro]

Im not 100% but it might be the broadcaster ?
I know in South-Africa we have a HD channel but sometimes the video is more compressed than other times...

But my curiosity remains. Why are the studio segments interlaced and the other parts aren't?

 

[essentialatom]

I'd say they used different cameras (or settings) for the different segments. A studio segment apparently was shot with TV-style cameras recording 50 distinct fields per second. A nonstudio segment apparently was shot with film-style cameras recording 25 distinct frames per second. The former can cause interlacing artifacts on computer screens because the two fields of a frame are recorded at different instances in time, while the latter puts one frame into two fields recorded at the same instance in time. When the computer screen is displaying both fields at the same time the former method causes interlacing artifacts.

This is basically it, it's to do with the settings. In the TV segments there's generally not a lot of artifact-causing high motion so you can reap the benefits of the higher frame rate (although I suppose it's technically a higher field rate) - the overall result is higher smoothness is perceived. As they're expecting high motion in the film segments, they don't want the inevitable artifacts caused so they go for the progressive option as it eliminates these at the cost of producing less smooth motion. I also think it's a deliberate stylistic decision - the idiosyncratically 'digital' smoothness to the TV pictures gives them a feeling of rawness that is associated with liveness, something they're looking to emphasise in those segments (also with the use of a the studio audience). The slightly choppier motion in the film segments gives them a more cinematic feel, to me at least, which again, is the effect I think they're looking to achieve.

 

[93Flareside]

Interlacing is supposedly a much clearer, but the artifacts are what makes it a drag. It's good for public speaker our news report stuff. Stuff with little motion.