Hello everyone! As most of you know, television networks do not currently broadcast in 1080p. The only high-definition formats that they currently broadcast in are 720p and 1080i. I have Comcast Digital Cable and am renting a high-definition converter from them. The converter has an option that allows me to set the output resolution to either 480i, 480p, 720p, or 1080i. If I have a 1080p television, should I set the output resolution to 720p or 1080i? I know a 1080p television is progressive, but can't it just de-interlace the 1080i source and convert it to 1080p? Correct me if I'm wrong: Standard NTSC-based progressive video content displays a frame every 1/30th of a second. Standard NTSC-based interlaced video content displays a "field" every 1/60th of a second, the first field being every odd horizontal line of resolution and the second field being every even horizontal line of resolution. Since both fields of 1080i content are displayed in the same time that one frame of 1080p content is display, can't the television simply "combine" both fields (the one field with every odd line of resolution and the other field with every even line of resolution) of the 1080i content to convert it to 1080p? Thanks!

I'd opt for "Native" if available, odds are your tv will do a better job of handling the various broadcasts vs. a crappy cable box. ABC and ESPN are all 720p as are other networks and your tv can decide on how to process it best.

+1. To expand a bit further, if the cable box can't do 1080p, the native resolution of your TV, then the TV is going to process the signal it gets regardless. So... telling the cable box NOT to process it (if possible) will minimize the amount of processing done on the signal. Hopefully that will increase quality.
If you can't go this route, you'll have to choose which channels get higher quality: if you tell the cable box to output 1080i, 1080i programming will simply be deinterlaced in the TV, if the TV does a good job it'll be fine. 720p programming will be interlaced and upscaled in the STB (not necessarily in that order) and the TV will de-interlace it. That's 3 conversions. If you tell the cable box to output 720p, 720p programming will simply be upscaled in the TV, but 1080i programming will be de-interlaced and downscaled in the STB (not necessarily in that order), and then upscaled in the TV... so you'll have to decide which is mode is more important to maintain integrity for you, partially based on the capabilities of the TV and the STB...

you can look up reviews of your TV (and cbale box IF you're lucky) and see if there's one particular conversion or the other (upscaling vs de-interlacing) that it's better or worse at, compare the two, and hopefully be able to optimize the conversions.

There's a lot more to de-interlacing a signal (properly) than just combining the two fields. Since the fields were taken at different points in time, if you just combined them you would get artifacts visible at any edges of any not-slow-enough moving objects, for one. Imagine a ball moving across the screen horizontally, now imagine every other scan line of that ball being horizontally offset from the others...

So if one is generally accepted to have a much better de-interlacer than the other, let that one do the de-interlacing and the other do the scaling.

Thank you both very much for your help. Unfortunately, there is not a "native" option or an option that tells the converter not to process the signal. Like I said, my only options are literally 480i, 480p, 720p, and 1080i.

There's a lot more to de-interlacing a signal (properly) than just combining the two fields. Since the fields were taken at different points in time, if you just combined them you would get artifacts visible at any edges of any not-slow-enough moving objects, for one. Imagine a ball moving across the screen horizontally, now imagine every other scan line of that ball being horizontally offset from the others...
I did not realize that the fields were taken at different points in time. When progressive video content is converted to interlaced, is the same frame simply split into two separate fields?

The previous posters are entirely correct about the "native" setting. I know this to be true because I am also a Comcast customer. The newer model Motorola DCX3400 incorporates the "native" option and it makes quite a difference. You might have to hound Comcast to get one though :). . .

I fix my cable box to 1080i -- speeds up changing channels and the pic looks the same regardless.

My Directtv dvr has 1080p setting.Once i get a 1080p i'm assuming i would set the dvr to 1080p.What happens then with the different programing resolutions?Will be getting a 1080p set soon.

I did not realize that the fields were taken at different points in time. When progressive video content is converted to interlaced, is the same frame simply split into two separate fields?
This of course applies to video shot with an original intent to produce interlaced video. Shooting with an intention for progressive video (or film) that is then interlaced should go through an algrorithm to avoid the same artifacts. Whether or not it does is another story.
My Directtv dvr has 1080p setting.Once i get a 1080p i'm assuming i would set the dvr to 1080p.What happens then with the different programing resolutions?Will be getting a 1080p set soon.

Hmm... DirectTV does have some programming that is claimed to be sent in 1080p (mostly on demand movies) so setting the box that way should ensure none of your equipment screws with the signal... BUT... then your box is upconverting anything that's not in that format, when your TV may do a better job of it... so... just like the OP, you may do better if the box has a "native" or "through" or "direct" mode...

The previous posters are entirely correct about the "native" setting. I know this to be true because I am also a Comcast customer. The newer model Motorola DCX3400 incorporates the "native" option and it makes quite a difference. You might have to hound Comcast to get one though :). . .
Yea, I heard about those newer converter boxes. I currently have the 2nd to the newest converter box (the big silver ones). It looks like I'll be fighting with Comcast in order to replace my older converter box with one of these newer ones. Thank you all for your help!

I have Comcast Digital Cable and am renting a high-definition converter from them. The converter has an option that allows me to set the output resolution to either 480i, 480p, 720p, or 1080i. If I have a 1080p television, should I set the output resolution to 720p or 1080i? I know a 1080p television is progressive, but can't it just de-interlace the 1080i source and convert it to 1080p? Science aside, i have tried all possible cable DVR and HD Tivo setting combinations on my various HDTVs (1080i Tube TV, 768p LCD, 768p Plasma, and two 1080p Plasmas) and in every case, the 720p and 1080i HD channels all look crisper and more detailed when the box is set to output everything at 1080i Fixed. When i set it to 720p Fixed, the same recordings look softer and lacking in detail. Setting it back to 1080i Fixed brings the crispness and detail back. Watch something like Sunrise Earth (which often has long close-ups of grass or rocks etc) and try the 720p Fixed setting and see how soft it is, then quickly change it to 1080i Fixed and notice the detail you can now see which isn't there with the 720p setting. It's quite a big difference on all my TVs. If you have an HD DVR then making the comparison is easier because you can replay the same scenes for a back to back comparison. Try both settings and see which one you like better. I only like the 1080i setting, but my GF agrees that the 720p setting is softer and for some reason she likes it better (something about making her favorite older actresses' wrinkles less noticeable.......).

The SD channels aren't affected much if at all - they will look pretty much the same at either setting, but the HD channels do benefit from using the 1080i Fixed setting.

Science aside, i have tried all possible cable DVR and HD Tivo setting combinations on my various HDTVs (1080i Tube TV, 768p LCD, 768p Plasma, and two 1080p Plasmas) and in every case, the 720p and 1080i HD channels all look crisper and more detailed when the box is set to output everything at 1080i Fixed. When i set it to 720p Fixed, the same recordings look softer and lacking in detail. Setting it back to 1080i Fixed brings the crispness and detail back. Watch something like Sunrise Earth (which often has long close-ups of grass or rocks etc) and try the 720p Fixed setting and see how soft it is, then quickly change it to 1080i Fixed and notice the detail you can now see which isn't there with the 720p setting. It's quite a big difference on all my TVs. If you have an HD DVR then making the comparison is easier because you can replay the same scenes for a back to back comparison. Try both settings and see which one you like better. I only like the 1080i setting, but my GF agrees that the 720p setting is softer and for some reason she likes it better (something about making her favorite older actresses' wrinkles less noticeable.......).

The SD channels aren't affected much if at all - they will look pretty much the same at either setting, but the HD channels do benefit from using the 1080i Fixed setting.

Well, to bring science back into it, it sorta makes sense that programs in 1080i will suffer if converted to 720p...
Then, depending on the respective capabilities of the tv/box, I would not expect 720p programs to look any better with a box interlacing them and the tv deinterlacing... rather than just letting the tv upscale...

I- mean interlaced which is an old throw-back to slow band-width of broadcasters and slow CRTs. It means every other row of data, every other frame. With 1080P sets, the interface board does a "frame buffer" which holds all the rows each frame, so the set actually get all 1080 lines at once.

720 will have to scale up (invent data) to fill out the 1080P screen. 1080I will look right (although mathmatically and theoretically, there are some frames that are behind).