Freeview HD The Truth

grahamlthompson · 22-11-2009, 4:45 PM

The inexplicable closure of a recent thread has left some highly inaccurate and misleading information without a response

Namely You can get 1080p50 on Freeview HD without extra bandwidth.

This is pure rubbish. You might be able to get 1080p in the same bandwidth as 1080i by changimg from mpeg2 to mpeg4 compression. Freeview HD already uses mpeg4 (h264) compression and in addition will use DVB-T2 transmission which increases the bits you can transmit by around 30-40% over DVB-T. Using both these techniques you can just about squeeze four HD channels into a single mux with a likely effect on quality that encoder improvements might (or might not) recover. It's not even certain that you will get 4 1080i channels they may have to be 720p. Increasing the frame rate to 50 full frames/second will double the data requirement and in any case the equipment spec precludes the use of 1080p50.

The next one is the assertion that the use of 1080p24 causes additional motion artefacts, the reverse is the case. Bluray and movie transmissions are derived from a 24 frame/second film master. Transmitting this at 25fps required the addition of extra frames to pad the video using a technique known as pull down. This causes the jerkiness that a TV which can sychronise at the original 24 frame/second eliminates. Hence the number of TV's now that can handle 24, 25 and 29.97 fps.

**Gavtech** · 22-11-2009, 5:29 PM

Quote:

Originally Posted by grahamlthompson

The inexplicable closure of a recent thread has left some highly inaccurate and misleading information ...

Hi Graham

That was part of the reason for the closure.

Fuller reasons will emerge later - time permitting.

G.

petet66 · 22-11-2009, 5:40 PM

Quote:

Originally Posted by grahamlthompson

Bluray and movie transmissions are derived from a 24 frame/second film master. Transmitting this at 25fps required the addition of extra frames to pad the video using a technique known as pull down. This causes the jerkiness that a TV which can sychronise at the original 24 frame/second eliminates.

That's not true for the UK where movies are simply transferred to PAL video at 25 fps, i.e.: running the film slightly faster than it would have been shown in the cinema. The extra frames issue did arise in the USA where NTSC video runs at 29.97 fps and the addition of extra frames (3:2 pull down) did cause jerkiness on pans and tilts etc.

grahamlthompson · 22-11-2009, 5:49 PM

Quote:

Originally Posted by Gavtech

Hi Graham

That was part of the reason for the closure.

Fuller reasons will emerge later - time permitting.

G.

Now i am intrigued

petet66 · 22-11-2009, 6:13 PM

And now the original thread is back open. I've just read it from start to finish and couldn't see anything different from the content of many other threads. There was a debate about the definition of launch but take a look at any plasma V LVD threads... (btw plasma IS better

)

grahamlthompson · 23-11-2009, 9:18 AM

Quote:

Originally Posted by petet66

That's not true for the UK where movies are simply transferred to PAL video at 25 fps, i.e.: running the film slightly faster than it would have been shown in the cinema. The extra frames issue did aise in the USA where NTSC video runs at 29.97 fps and the addition of extra frames (3:2 pull down) did cause jerkiness on pans and tilts etc.

This method shortens the playing time and increases the sound pitch. Pretty sure both techniques are used. In any case playing a bluray to a non 24p TV uses pulldown to get to 25fps.

pdoherty76 · 23-11-2009, 12:25 PM

Quote:

Originally Posted by petet66

And now the original thread is back open. I've just read it from start to finish and couldn't see anything different from the content of many other threads. There was a debate about the definition of launch but take a look at any plasma V LVD threads... (btw plama IS better

)

I can't for the life of me understand the closure of that thread.

I was the one involved in the "launch" discussion and it was a perfectly civil debate.

The thread was closed at the point where I had just provided the evidence that the BBC had called it a launch. Most strange that it should close then.