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What to use: 1080i or 720p?

beemer_man
04-03-2005, 05:14 PM
My TV will accomodate 1080i, which is what I have it set on. But some of the shows I watch do not broadcast that high (720p, for instance). My question is, when I am watching something in 720p, should I switch my TV to 720p, or it is okay to just leave it on 1080i?

borromini
04-03-2005, 06:29 PM
You haven't told us what your TV make and model is or what your HD STB resolution setting is, but normally your TV will be set to it's native resolution and that's the best resolution to view it at. If you know what is the physical resolution of your TV's screen, set it to that resolution. For instance, if your TV is a CRT tube that is 1080i natively, then set your STB to pass the HD signal thru to the TV, thereby letting the TV scale up anything that's 720p up to 1080i. If your TV is an LCD or DLP that has a 720p native resolution then let those channels that have 1080i pass thru and be down-converted by the TV.

beemer_man
04-03-2005, 09:29 PM
It's a Sony Trinitron Wega KD-34XS955. Since it's a tube tv, it has 1080i. But, at any rate, I take it that I should just leave it on 1080i and let it convert the 720p signals to 1080i? Is that how I will get the best picture with a 720p signal?

RSawdey
04-03-2005, 09:47 PM
You can NOT change your TV's resolution. You CAN change the image format that your video sources are delivered in... setting to deliver anything except the native 1080i will cause multiple conversions of 1080i & degradation of PQ, once in the STB, then again in the TV. IF you want the TV to do all the format conversion, set your STB to 'pass thru' the formats as they are sent. For the STB to do all conversions, set your output to the native res of the TV, 1080i.

Blue Goose
04-04-2005, 05:27 AM
You can NOT change your TV's resolution. You CAN change the image format that your video sources are delivered in... setting to deliver anything except the native 1080i will cause multiple conversions of 1080i & degradation of PQ, once in the STB, then again in the TV. IF you want the TV to do all the format conversion, set your STB to 'pass thru' the formats as they are sent. For the STB to do all conversions, set your output to the native res of the TV, 1080i.

Ok I'm glad this question came up as I have the same TV and have not been 100% happy with the PQ. The settings on my SA8300 are fixed, passthrough, upconvert 1, upconvert 2 and HDMI. Right now I am using HDMI. By looking at the display on the 8300 it will say that ESPNHD is being broadcast in 720P...if I change the channel to INHD it will snow out a bit and say 1080i.

If I leave it on passthrough it will do the same conversion but without any of the snow etc. I'm not sure which is which but up 1 and up 2 will force all the HD to be either 720p or 1080i(again based on what the SA8300 display is telling me)

What setting should I be at for the best PQ?

borromini
04-04-2005, 11:29 AM
Let everything passthrough the STB and let your TV take the incoming signal and do the conversion to 1080i.

Blue Goose
04-04-2005, 12:03 PM
Let everything passthrough the STB and let your TV take the incoming signal and do the conversion to 1080i.

Will do, thanks! :D

RSawdey
04-04-2005, 12:27 PM
Alternatively, if the above doesn't work well set the STB to 'fixed' 1080i.

timh
04-04-2005, 02:41 PM
My SA8300 has Passport software installed and
therefore does not offer passthrough mode. But
you can go into setup and pick the output format.
Right now I think I only have 720p selected. Question
is should I also enable 1080i and 480i so that the box
outputs this to a Sammy DLP????

Thanks for the help

RSawdey
04-04-2005, 05:21 PM
No, you're setup right for your DLP... output everything as 720p. Assuming the STB does a decent job on the format conversion...

maicaw
04-10-2005, 03:23 AM
I looked through the forum for an answer to this specific question - it seems it should be lurking in this thread.
Since this is the direct view (CRT) part of the forum I hope the 1080i format setting is the correct output for the STB even though the Sony 34XBR will accept HD at 480p and 720p too- If I am using the 1024x768 projector I would suppose that would be another situation - with more variables. - all this is about OTA network DT signals-- to Sony 34XBR via component video cables.
My question is the older Zenith HDV420 I still use doesn't have a pass through setting that I know of and the format must be changed on the front panel - not with the remote. I have noticed that the SD digital subchannel(s) look better using 480p than 1080i I assume because the native signal is 480i. Also if the 480p is temporarily used for HD signals it allows aspect ratio changes in the STB for HD signals wheras the 720p and 1080i doesn't -but if the STB is set for 1080i the aspect ratio works only on the SD subchannel signal - the manual only mentions the display format setting in connection with go/no-go troubleshooting. I normally use the 1080i and component output, It doesn't have DVI - Should I be using 720p for Fox and ABC or does the STB upscale without creating vertical artifacts - I assume the horizontal resolution is unaffected by the vertical reformatting in the STB - Frankly I don't see the interlace artifacts on anything but PBS but they seem to be using some sort of bandwidth/bitrate challenged hard drive as a source that is far from a benchmark signal.

borromini
04-10-2005, 06:47 AM
Your Sony is 1080i natively for all HD displays so there's no advantage to setting your STB to 720p unless it makes the image look better on those channels.

RSawdey
04-13-2005, 02:22 PM
Your STB will crossconvert 720p to 1080i.

maicaw
04-13-2005, 02:36 PM
Crossconvert? --Please elaborate - That word is not in the glossary and it appears to have only been used once before in any thread -only by you -
If the bitstream is 720p and I set the STB to 720p and the TV accepts 720p - sure there is going to be a lot of stuff going on in the TV - and I trust the XBR - but what I don't want is a lot of stuff going on before it gets to the TV- The STB puts out whatever I tell it to - not what the incoming bitstream is formatted to. - The question was- what has happened to the analog signal if the analog signal is not the same as the Digital format

RSawdey
04-13-2005, 06:20 PM
Crossconversion is format conversion of 720p to 1080i... it's not really up or down conversion, since both formats are about 60 Mpixels/sec... 720p trades off spatial res for doubled temporal res (framerate).

Although your TV accepts all formats, it only produces 1080i & 480p. Handing it a 720p signal just means the TV will convert it to 1080i (or maybe 540p) for display.

What happens to an analog cable channel? It's digitized & scaled & possibly deinterlaced into the STB's image memory for output.

If you are not going to use 'pass thru mode' you should just leave it set to 1080i for both HD modes.

maicaw
04-13-2005, 11:32 PM
What happens to an analog cable channel? It's digitized & scaled & possibly deinterlaced into the STB's image memory for output.

I think my question clearly stated I was talking about HD not SD -
HD is analog on the consumer version of a component video interface
(The Original Component Video interface years ago was digital -and may still be -but by the time it became a consumer interface it morphed to analog) --
At the highest quality of OTA HDTV --The 1081i signal is 1920 pixels wide officially whereas the 720p signal is 1280 pixels wide officially - If a 720p signal is converted to a 1080i the number of pixels per second can be about the same but the mapping is certainly not. In the most simplistic explanation there would have to be some odd dropping and stuffing to get the proper number of lines 1080/720 or 720/1080 in each frame.
I suggest the following link to a more detailed discussion: http://www.sonyhdvinfo.com/article.php?filename=1080i-vs.-720p

RSawdey
04-14-2005, 08:44 AM
I misunderstood your question " what has happened to the analog signal if the analog signal is not the same as the Digital format "... what has happened is called a D/A conversion (digital to analog).

The old 'component video interface' is RGBHV, same signals as on a VGA connector... and both are analog.

When you are comparing the two HD formats, you are forgetting to consider the framerate, temporal resolution... 1080i is only 30 frames per second, while 720p is 60 fps. If you want to compare the pixels per 1/60 of a second, it's 1920 x 540 vs 1280 x 720.

maicaw
04-14-2005, 08:44 PM
I misunderstood your question " what has happened to the analog signal if the analog signal is not the same as the Digital format "... what has happened is called a D/A conversion (digital to analog).

The old 'component video interface' is RGBHV, same signals as on a VGA connector... and both are analog.

When you are comparing the two HD formats, you are forgetting to consider the framerate, temporal resolution... 1080i is only 30 frames per second, while 720p is 60 fps. If you want to compare the pixels per 1/60 of a second, it's 1920 x 540 vs 1280 x 720.
Ok "Mr Wizard" if that's your understanding of my question so be it. Maybe I shouldn't be on this thread.

maicaw
05-07-2005, 11:59 PM
....The old 'component video interface' is RGBHV, same signals as on a VGA connector... and both are analog.....
Actually "Component Video" is properly called "Analog Component Video" and the signals sometime improperly use the same designations as the older digital component video signals -Y,Cb,Cr --which are the 8 bit digital equivalent to analog signals Y,PB,Pr :D if they are properly labelled.