50 Hz or 60Hz

What is your source? DVD player? Computer? Games console?

Most modern panels are multisync, but some older ones were notorious for converting 50Hz to 60Hz, resulting in unpleasant motion judder and blurring. The resolution is fixed on LCD and plasmas. Non-native resolutions must be scaled to the resolution of the panel. It's also common for 1080i/p inputs to be scaled slightly on 1080p screens, but there is often a menu option to enable 1:1 pixel mapping.

I have a DVDO Edge scaler.which allows me to output at different frequencies then it confirms display by me pressing info button on handset (ie i assume TV set is not converting the picture).
TV is a Toshiba 42inch Regza

meltcity · 16-04-2009, 17:05

When you say the picture improved when the scaler was set to 60Hz what was the video source?

Is your TV 1080p native, and can it do 1:1 pixel mapping?

SilverFox2 · 16-04-2009, 18:41

Quote:

Originally Posted by SilverFox2

When you say the picture improved when the scaler was set to 60Hz what was the video source?

Is your TV 1080p native, and can it do 1:1 pixel mapping?

Video source Sky HD STB
Yes 1080p native
Dont know re 1:1 pixel mapping
TV is a Toshiba 42XV505 LCD Regza

Chris Frost · 17-04-2009, 10:58

Hi SilverFox2, what improvements have you seen going from 50 to 60Hz?

meltcity · 17-04-2009, 11:26

Quote:

Video source Sky HD STB
Yes 1080p native
Dont know re 1:1 pixel mapping
TV is a Toshiba 42XV505 LCD Regza

I had a look at the manual for this TV and it can indeed do 1:1 pixel mapping. The option is called EXACT SCAN and can be selected by pressing the aspect ratio button on the remote a few times.

You probably already know this, but to get the best out of your scaler you should set it to reject 576p inputs if possible. When the Sky box is set to AUTO it outputs SD channels in 576p, which means the Sky box is doing the deinterlacing, and not very well. If the scaler refuses 576p the Sky box automatically sends 576i, which allows the scaler to do the deinterlacing.

I'm surprised that converting the Sky box's native 50Hz frame rate to 60Hz gives a better picture. I would expect it to look worse.

Nigel Goodwin · 17-04-2009, 11:44

Quote:

Originally Posted by Nigel Goodwin

I'm surprised that converting the Sky box's native 50Hz frame rate to 60Hz gives a better picture. I would expect it to look worse.

Likewise - having to 'invent' five full frames per second isn't likely to improve things.

SilverFox2 · 17-04-2009, 22:06

Quote:

Likewise - having to 'invent' five full frames per second isn't likely to improve things.

Good point, as you say there are an extra 5 full frames per second generated by the scaler.
Does the TV adjust this back to 50 Hz (convert ) or display the extra frames ?

SilverFox2 · 17-04-2009, 22:08

Quote:

I had a look at the manual for this TV and it can indeed do 1:1 pixel mapping. The option is called EXACT SCAN and can be selected by pressing the aspect ratio button on the remote a few times.

You probably already know this, but to get the best out of your scaler you should set it to reject 576p inputs if possible. When the Sky box is set to AUTO it outputs SD channels in 576p, which means the Sky box is doing the deinterlacing, and not very well. If the scaler refuses 576p the Sky box automatically sends 576i, which allows the scaler to do the deinterlacing.

I'm surprised that converting the Sky box's native 50Hz frame rate to 60Hz gives a better picture. I would expect it to look worse.

What advantage does this 1:1 pixel mapping give me?

SilverFox2 · 17-04-2009, 22:24

Quote:

Hi SilverFox2, what improvements have you seen going from 50 to 60Hz?

Seems sharper, particularly on SD.

Have spoken to various ''experts'' at specialist UK supply houses (usually supplying scalers or high end projecters) and they say this improvement is not unusual.
I'm not an expert but they claim this improvement can have a significant effect on some panels.

Dont think I am imagining the improvement.

Realise my setup (particularly with the Edge deinterlacing the SD properly) is special, but i think i am accurately reporting my observations.

Chris Frost · 17-04-2009, 22:33

1:1 pixel mapping means that the TV is not processing the image. Whatever the scaler is sending then the TV displays it pixel position for pixel position.

I've used VP30's, 50's and 50 Pro's. They all have set up test patterns. I don't know if The Edge does, but if so then scroll through for the "one pixel on / one pixel off" patterns. If Exact Scan is working correctly on the TV then the scaler test pattern will be uniformly grey and you should be able to make out individual black and white dots when viewing the screen up close. If the pattern have light and dark bars then the TV is still scaling the image or the scaler output resolution is no correct for that screen.

figrin_dan · 18-04-2009, 12:53

So what about a 100Hz LCD displaying a Blu ray at 24fps?

Is it 24Hz, 60Hz, 100Hz or 120Hz?

Chris Frost · 18-04-2009, 15:08

Quote:

Originally Posted by SilverFox2

So what about a 100Hz LCD displaying a Blu ray at 24fps?

Is it 24Hz, 60Hz, 100Hz or 120Hz?

The rule of thumb is to go with an exact multiple of the base frame rate. So, 24fps works best when displayed at 48 or 72fps (a.k.a. Hz).

R2 DVD video has a base frame rate of 25 fps - so 50/75/100Hz works best for display synchronisation. NTSC video has a base frame rate of 29.97 fps - so 59.94/89.91/119.88Hz are the correct display refresh rates.

R1 DVD film is recorded at 24fps on the disc and flagged for 2:3 conversion. The signal has certain frames repeated to make up the numbers. Hence from a 24fps source we get a 29.97fps video stream which is then interlaced to create 59.97Hz (referred to as 60Hz) video output that a TV or projector would see. Ideally you want to reverse that process if possible and get back to the original 24fps, but since the scalers that do this function reasonably well cost in excess of £1000 most folk are stuck with the TV's own attempts at converting back.

R1 DVD video is true 23.97fps. 60 or 120Hz will be fine.

R2 DVD film is 24fps speeded up by 4% so that it syncs with the 25fps/50 field interlaced UK video system. So 50 or 100Hz is about right.

Coming back to Blu-ray, assuming you have enabled 24pfs on the player then you should get the most stable image at 48Hz or 72Hz. Anything other than an even multiple of 24 is going to introduce some image artefacts.

Chris Frost · 18-04-2009, 15:15

Quote:

Seems sharper, particularly on SD.

Have spoken to various ''experts'' at specialist UK supply houses (usually supplying scalers or high end projecters) and they say this improvement is not unusual.
I'm not an expert but they claim this improvement can have a significant effect on some panels.

Dont think I am imagining the improvement.

Realise my setup (particularly with the Edge deinterlacing the SD properly) is special, but i think i am accurately reporting my observations.

If your TV will take it try setting the scaler to output PAL SD at 75Hz and see how you go on.

SilverFox2 · 18-04-2009, 16:55

Quote:

If your TV will take it try setting the scaler to output PAL SD at 75Hz and see how you go on.

Thanks Chris,

Tried to set it as your suggestion but as you know Edge is cheaper version of VP 50 with less options.

Originally got it to use the PReP which really improves my SD on Sky HD.
Would have liked opportunity to use VP 50, am really intrigued by different possibilities this could bring.

Can only go to 60 Hz on the templates within Edge.

SilverFox2 · 18-04-2009, 17:06

Quote:

1:1 pixel mapping means that the TV is not processing the image. Whatever the scaler is sending then the TV displays it pixel position for pixel position.

I've used VP30's, 50's and 50 Pro's. They all have set up test patterns. I don't know if The Edge does, but if so then scroll through for the "one pixel on / one pixel off" patterns. If Exact Scan is working correctly on the TV then the scaler test pattern will be uniformly grey and you should be able to make out individual black and white dots when viewing the screen up close. If the pattern have light and dark bars then the TV is still scaling the image or the scaler output resolution is no correct for that screen.

Thanks Chris,

Yes latest version of firmware gives me all the test patterns you refer to and in fact used them during calibration of tv.

Need all the help i can get in coaxing the best out of the Sky HD STB, scaler, TV set up, so appreciate all your constructive comments together with the ones from all other forum members.

figrin_dan · 20-04-2009, 14:55

Quote:

Coming back to Blu-ray, assuming you have enabled 24pfs on the player then you should get the most stable image at 48Hz or 72Hz. Anything other than an even multiple of 24 is going to introduce some image artefacts.

Thanks, how can you check what the TV is doing?

SilverFox2 · 20-04-2009, 21:46

Quote:

Thanks, how can you check what the TV is doing?

Got to assume that if tv has no picture then cannot display the output frequency you send to the TV.
No expert but my answer assumes tv does not convert frequency.

My scaler when i change frequency etc. always asks question on screen whether i can see a picture. If no picture have to assume tv cannot display what i send to it.

Experts will no doubt correct me but thats my thoughts anyway.

Chris Frost · 20-04-2009, 22:18

Quote:

Thanks, how can you check what the TV is doing?

Is your TV 24p compatible?

figrin_dan · 21-04-2009, 10:08

I don't have the TV yet but want to know if it's worth getting a 100Hz TV and how it displays 24p

Chris Frost · 21-04-2009, 15:08

Quote: