Modern TV's and their refresh rates vs video framerates

[TFM]

I've hijacked this topic to discuss the American cpcs here.

OMG!    HiJacking can be dangerous...



Hi Jack! LONGER VERSION - YouTube

[mr_lou]

Well, I've reached this far in my project now, and thought I'd just update this thread with the info I've gathered.

It seems I was right in my suspicion.

Play a 720@50p video on a number of different devices, and it'll display rather jerky. I assume because the TV or monitor stays on 60hz or some other non-50hz "compatible" refresh rate.

Some recordings I made from the CPC via a Framemeister and Hauppauge HD PVR Rocket was jerky on both my own PC and girlfriend's PC and our Sony TV when played back from USB via a Sony Blu-ray player.

BUT: Converting the video to a Blu-ray m2ts file including Blu-ray file-structure (i.e. a proper blu-ray disc) and playing that - all was smooth and awesome. 

So in conclusion regarding the first post in this thread:

Blu-ray players (when playing a Blu-ray disc) send out information about framerate, which the TV then uses to switch to a suitable refresh-rate, resulting in an awesome smooth video playback (provided the TV has a matching refresh-rate).
But when playing mp4 files from USB, the framerate information is NOT sent to the TV, so the refresh-rate on the TV may not match, resulting in a lousy playback.

Good news for me in regards to my project where the goal is to have very accurate CPC videos.

Tested on 3 Blu-ray players and 2 TV sets. Will test more devices later.

[1024MAK]

There are a lot of variations in LCD TVs, but the type sold in Europe normally can do 50Hz with no problems.

A lot are actually multi-standard, but the customer interface does not always make all options available.

The LCD display itself does not use the 50Hz, nor the 60Hz field rate, as the display system is completely different to CRT displays. Also keep in mind that CRT TVs are designed for interlaced video, where each field is half the picture information, it takes two fields (an "odd" and an "even" field) to form one complete frame, so for interlaced video, the real frame rate is 25Hz or 30Hz.

But most retro computers do not produce an interlaced video picture, instead they continuity transmit the same field, so are actually producing an out of specification "progressive" video picture. Analogue CRT TVs and monitors were designed to cope with variations in signal timing, so happily cope with this.

All LCD TVs and monitors process the incoming picture information and store it in a memory buffer. Then they read this information out to the LCD display driver system (which is a type of matrix addressing system).

Here is a picture showing the options on my Sharp Aquos TV
[attachimg=1]
There are two PAL options, one for 50Hz and one for 60Hz. And as you can see various other colour standards.

As LCD TVs and monitors have to decode/convert the incoming video signal, how good they are at processing an out of specification video signal very much depends on how much effort the designers have put in to cope with such a signal.

This does result in unexpected results for us, the customers 

Having said that, most LCD TVs work without any significant problems with retro computers. The main issue is the SCART control signals when using RGB SCART inputs.

There is far more detail about the TV standards if you search the web.

Mark

[gerald]

Some recordings I made from the CPC via a Framemeister and Hauppauge HD PVR Rocket was jerky on both my own PC and girlfriend's PC and our Sony TV when played back from USB via a Sony Blu-ray player.

It is very unlikely that your PCs are using a 50Hz video output rate, and the jerkiness comes from that.
No idea why your TV is not able to play it at the proper rate from USB.

[ivarf]

The 6128 was made for the States and shown initially at the CES in Chicago, but failed at the market as the 464 and 664 before.

Are you saying that the Amstrad CPC 464 and 664 was sold in the USA?

[chinnyhill10]

Are you saying that the Amstrad CPC 464 and 664 was sold in the USA?

I don't believe the 464 or 664 were sold in the States. Amstrad didn't want to sell the CPC there as they knew it would fail but Sears put in a bulk order paid for up front so Amstrad created the 6128. It failed exactly as Alan Sugar said it would but it was no skin off of Amstrad's nose as they were paid in full for a huge order.

[Fessor]

Ah... ok... then it was a wrong conclusion of me...
US-Market was no theme in the German "Schneider"-Magazines, and at the Multiformat-Magazines in general only how hard it was for European Manufacturers to get access to the U.S.-Market.