1080 and 720 and 576 switch on HD STB...do i change it depending on channel

[Rudyard]

On my LG HD digital set top box there is a button that changes between 1080, 720, 570p and 576i.
My tv is a nec LCD HD tv that when I rang them am told has a native resolution of 1366x768.
Now I understand TV stations broadcast different formats of HD material (im in Sydney, Australia) so am I meant to physically change the set top box each time I change channel to match what the station is broadcasting to pass the correct signal to the tv?? If so how the heck am I meant to know what signal is coming in?

If not what is the switch for? And why would they make a TV that has a native resolution (i am told they look best with a signal that matches the native resolution) that is neither 1080, 720 or 576??? What format is going to output 1366x768? I am a novice but it seems odd to me not to make the display fit the used resolutions.

I ask all this because I have not seen 1 iota of difference on any program ever between HD and SD broadcasts. They look 100% identical (this also happens on 2 different tvs at my inlaws (LG plasma and samsung LCD), cannot see any difference.

So either I dont have these things set up correctly, the tv stations are not actually using HD or there is not really a difference between HD and SD to the average Joe.

*edit: I hook up my HD set top box to my TV via DVI cable and the antenna signal comes via standard coax to the HD STB.

[Krispy Kritter]

If you can't tell a difference, then I expect you are not actually receiving an HD broadcast.

I assume you have a new HD OTA antenna and not a regular SD antenna? There is a very visible difference between SD and HD programming.

You don't need to change resolutions between stations. Just choose whichever resolution (if any) has the better picture, then leave it.

[edDV]

On my LG HD digital set top box there is a button that changes between 1080, 720, 570p and 576i.
My tv is a nec LCD HD tv that when I rang them am told has a native resolution of 1366x768.
Now I understand TV stations broadcast different formats of HD material (im in Sydney, Australia) so am I meant to physically change the set top box each time I change channel to match what the station is broadcasting to pass the correct signal to the tv?? If so how the heck am I meant to know what signal is coming in?

If not what is the switch for? And why would they make a TV that has a native resolution (i am told they look best with a signal that matches the native resolution) that is neither 1080, 720 or 576??? What format is going to output 1366x768? I am a novice but it seems odd to me not to make the display fit the used resolutions.

The 1080i, 720p, 576i, 576p settings define what gets sent over the DVI (or analog component) connector to the HDTV. Best match for your TV is 720p if you want the tuner to do all the processing (e.g. deinterlacing and scaling of 576i or 1080i broadcasts). The HDTV will then convert (upscale) 1280x720p to 1366x768 with a bit of overscan for good measure.

If you think your HDTV can do a better job of deinterlacing and scaling (all of them do it at variable quality), then you would use the 1080i setting. The cable box will then convert 576i and 720p broadcasts to 1080i, then the HDTV deinterlaces and scales down to 1366x768.

Try it both ways and see which deinterlacer you prefer.

576i would be used for standard TV sets. 576p would be used for standard definition progressive TV sets. In these modes, HD broadcasts get downconverted to SD in the tuner.

Over this side of the pond, we usually get two settings. One defines how HD is handled 1080i vs.720p. The other is called SD "override". This defines how 576i (480i here) will be handled.
Choices on the Motorola box are:
- "480i" - 480i 4:3
- "480p" - 480i output as 480p
- "Stretch" - expands normal 480i 4:3 horizontally to 16:9 (people get fat)
- "off" - uses HD settings similar to your box.

I ask all this because I have not seen 1 iota of difference on any program ever between HD and SD broadcasts. They look 100% identical (this also happens on 2 different tvs at my inlaws (LG plasma and samsung LCD), cannot see any difference.

So either I dont have these things set up correctly, the tv stations are not actually using HD or there is not really a difference between HD and SD to the average Joe.

*edit: I hook up my HD set top box to my TV via DVI cable and the antenna signal comes via standard coax to the HD STB.

You need to study the program listings to see which programs are broadcast in HDTV (1080i or 720p). If you still don't see a difference, call the local broadcaster. Maybe they aren't broadcasting in HD.

[Rudyard]

Krispy Kritter wrote:

If you can't tell a difference, then I expect you are not actually receiving an HD broadcast.

I assume you have a new HD OTA antenna and not a regular SD antenna? There is a very visible difference between SD and HD programming.

You don't need to change resolutions between stations. Just choose whichever resolution (if any) has the better picture, then leave it

Ah no, I have the same antenna ive used since before I got digital TV......I recieve the HD channels (e.g. channel 10 has SD 10 and HD 10 the latter which I couldnt recieve until I got a HD STB) and assumed that was the HD signal.

So are you telling me I need a HD antenna to see a quality improvement ver SD? As what am I recieving then when I watch the HD channels now? Is it the same signal, just that my antenna converts it or something back down to SD?

EdDV wrote:

You need to study the program listings to see which programs are broadcast in HDTV (1080i or 720p). If you still don't see a difference, call the local broadcaster. Maybe they aren't broadcasting in HD.

I will double check but I try watching the big programs like lost, prison break, CSI etc on advice from here as they are all apparently in HD in the US. I will try to contact the station and see whats going on. I think I recall somone saying that Channel 7 broadcasts in 576p, which if im not mistaken has no resolution change from SD (576i?) just goes to progressive and in PAL land that doesnt make a difference like it does in NTSC land due to some interlace issues not being there with PAL.

Thank you both for your responses.

[edDV]

If 576p it won't make much difference. It will have a faster frame rate 50Hz vs. 25Hz.

Normal 576i/25 would need deinterlacing to 576p/50 in the tuner box. If the channel broadcasts 576p/50 directly, the quality will be better but not HDTV. We call 480p/59.94 "EDTV" here.

Look for 720p or 1080i broadcasts if you want to see HDTV.

Here Lost is broadcast 720p, CSI 1080i.

The antenna will only affect reception or no reception.


PS: 576p/50 and 720p/50 have a great advantage for live sports but for film source like Lost or CSI, there is little improvement.

[Rudyard]

Ok here is what I have found from:

http://www.dba.org.au/index.asp?sectionID=126

Channel 7 (lost, Desperate housewives, prison break):

The Seven Network broadcasts a range of additional widescreen movies and High Definition one-off programs. When broadcasting High Definition programs, the Seven Network uses 576p High Definition format. Check local guides for broadcast times of Seven's programs.

Channel 9 (CSI, Cricket, Rugby League)

The Nine Network broadcasts a range of additional widescreen sport, movies and High Definition one-off programs. When broadcasting High Definition programs, the Nine Network uses 1080i High Definition format. Check local guides for broadcast times of Nine's programs.

Channel 10 (The simpsons):

Network Ten broadcasts many of its sport and movies in 16:9 widescreen format. When broadcasting High Definition programs, Network Ten uses 1080i High Definition format. Check local guides for broadcast times of Ten's programs.

They are the 3 commercial channels and programs I watch.
It seems Channel 7 is kind of useless to me in a HD way and is actually what I have tested most HD on (as those programs are in HD)

I dont know if the simpsons would be in HD (maybe the new ones but they mix in repeats so much its hard to find the new ones) so channel 10 may be hard to test but channel 9 should definately show CSI in HD and this would be 1080i....as my TV is only up to effectively 720p I will try the methods above from eddv to test if there is an improvement.

But in theory I should definately see a better picture on CSI channel 9 if they are broadcasting in 1080i on a LCD 1366x768 TV?

Also my favourite sports are on 9 but I dont know if they are broadcast in HD, will have to check but what is 1080i live brodcast of sport like (as you mention 576p and 720p are good for live sport)?

[edDV]

...

But in theory I should definately see a better picture on CSI channel 9 if they are broadcasting in 1080i on a LCD 1366x768 TV?

Also my favourite sports are on 9 but I dont know if they are broadcast in HD, will have to check but what is 1080i live brodcast of sport like (as you mention 576p and 720p are good for live sport)?

So it looks like your sources are either 576i/25, 576p/50 or 1080i/25 and your HDTV is 1366x768.

If you select 1080i for the DVI connection, the tuner will upconvert 576i to 1080i, and pass 1080i as is. 576p will be first converted to 576i then upconverted to 1080i. This will eliminate any advantages of 576p. The HDTV will deinterlace all arriving 1080i and down convert to 1366x768 progressive.

If you select 720p for the DVI connection, the tuner will deinterlace 576i and upconvert to 720p. 576p will be upconverted to 720p, 1080i will be deinterlaced and down converted to 720p. The HDTV will then scale all these 720p inputs to 1366x768 progressive.

Try it both ways and see which looks better for 1080i broadcasts. 1366x768 should look much better with 1080i source.

576p or 720p would look best for sport because they have double the frame rate. 1080i will look good for resolution but action will be less crisp.

Here the FOX network is sports oriented. They chose 480p as a first step and then moved to 720p for HD. The action is very clear compared to 1080i but 1080i has more detail when there is little image movement.

Good luck with CSI.


PS: I should have said 1080i is best for Cricket, 720p is best for Rugby

[Rudyard]

Thanks so much for your help edDV, it is appreciated....im looking forward to getting some HD material finally happening!

p.s. for my American friends Rugby League is a different sport to Rugby Union the latter which is commonly known as just 'Rugby'
They look very similar to an untrained eye but to the fans in Australia are very different!