Upconversion questions

[DBENE]

I don't really understand these posts about some of the VOOM channels being upconverted. My TV does not transmit in 720p it is only 480i, 480p, or 1080i.

So, are some of the HD channels on VOOM not broadcasted in 1080i? If not how can they call that High Definition.

Anyways, if you guys don't mind how about a little "HD upconversion for Dummies" lesson for me.

 

[squicken]

720p and 1080i are both HDTV.

 

[DBENE]

yeah, but how does this upconversion actually work. I mean, can you only upconvert 720p to 1080i or is there a way to upconvert 480i pictures into 1080i?

Also, does unconverted signals look anywhere as good as original 1080i broadcasts.

 

[andrzej]

yeah, but how does this upconversion actually work. I mean, can you only upconvert 720p to 1080i or is there a way to upconvert 480i pictures into 1080i?

Also, does unconverted signals look anywhere as good as original 1080i broadcasts.

You can upconvert anything you want to anything you want (roughly speaking). No, upconverted signal cannot possibly look as good as original 1080i. Regarding 720p --> 1080i; well, some would call it downconversion

 

[JWK]

You can upconvert anything you want to anything you want (roughly speaking). No, upconverted signal cannot possibly look as good as original 1080i. Regarding 720p --> 1080i; well, some would call it downconversion

Yeah, which is the weird thing to me. I'd always understood 720p to be a higher resolution than 1080i, but then I read somewhere (think it was in a string here on these boards) that 1080i is somehow a larger data stream.

It was all a bit over my head. But, yeah, they're both HD -- so you'd think they'd both be pretty close when converted to one another.

 

[occammd]

the argument is that 720p is better for sports because the entire frame is redrawn each scan. 1080i works like todays TV in that it does every odd line, then every even line, interlaced, but at a much higher resolution than todays TV and roughly 2x the resolution of 720p. But 1080i will still give you combing and artifacts during fast moving scenes.

 

[squicken]

1080i is a larger data stream. I'm not saying it's better, but it is more data.

 

[babyj]

well when 1080p gets here.....wow..ahah

 

[andrzej]

I am pretty positive that the glory days of interlaced signals are over. The coming higher resolution formats will all be progressive...

 

[squicken]

I'm going from 1080i to 720p pretty soon myself. But I think 1080p will create even more confusion in the marketplace. I want it to happen, but differing standards keep the layman away from technology.

 

[CraziFuzzy]

1080i is a larger data stream mostly due to the horizontal resolution.
480i -> 720 x 480 x 30fps = 10,368,000 pixels/sec
480p -> 720 x 480 x 60fps = 20,736,000 pixels/sec
720p -> 1280 x 720 x 60fps = 55,296,000 pixels/sec
1080i -> 1920 x 1080 x 30fps = 62,208,000 pixels/sec

Also what compounds this is the fact that interlaced signals are usually a little harder to compress, so when compressed, the difference in bitrates is exaggerated.

However, to actually answer the original question, upconversion on HD channels is usually refering to originally SD content scaled up to HD resolution. This does not really make the picture quality much better, and is similar to what a progressive scan DVD player produces. The real purpose of this is so that the broadcast mode of the station is always the same, I.E., it is not switching formats when a commercial break comes up. As for 720p and 1080i, it is about an even mix on VOOM, some channels are in 720p, and some in 1080i. If you don't have a 720 capable set, then the box should be set on 1080i only output, in which the box converts every signal, 480i, 480p, 1080i, OR 720p to 1080i for display on your screen. This usually will not produce many artifacts, as it is harder to convert 1080i signals to 720p artifact free than the other way around.