Video On Demand (vod)

[sajal]

hello all.

i was just wonderin what would be the bandwidth required to stream a PAL quality video to be viewed on regular TV.

the source of the video would be a satelite tv receiver..

the video may be compressed, but the quality of the video MUST be the same as if it were viewed by connecting the TV directly to the receiver.

in other words, i want to implement some IP based technology to enable someone else on the net(or LAN) to view a particular channel i can view on my TV.

no queries regarding the hardware....

i just need to know the bitrate required and the codec recomended for this purpose.

PS: im not into cable piracy or anything. this query if for legit purpose relating to a business venture im currently cooking up in head...

[mouse]

cooking up in head...

I get the same problem when the temps soar as they have the last few days.

[monty]

VCD quality would need around 1.6Mbps (200kBps)

dvd quality requires between 6Mbps and 10Mbps

I guess UBS quality would need around 3Mbps

The codec would be Mpeg2, you can play with the bitrate to find a suitable quality/bandwidth ratio.

No problem on a wired LAN, if you want to wireless you'll need at least 802.11g speeds...

[shaunoro]

Most broadcasters now use Mpeg3 systems as this has suppased Mpeg2 which now "old technology".

It is 1995. You are sitting watching rugby on TV and, being an Engineer, you have placed yourself directly in front of the screen at the ideal viewing distance of 4 x picture height. The game is rather dull and you go to sleep for ten years. Wakening in 2005 you find that someone has kindly replaced your old TV with a brand new 16x9 widescreen model that just happens to have the same vertical picture height. That's good, because you don't have to move your seat. You're still at the ideal viewing distance. Best of all, a game of rugby is just about to start.

At least, it looks like a game of rugby. Certainly that's a rugby ball and the players look like rugby players, but they seem intent on playing football instead. Slowly it dawns on you that you're watching a football match stretched horizontally to fit the widescreen format. You do some mental arithmetic:

The source material is 4:3

It has been stretched to 16:9

Therefore, stretch factor = 4:3

To fix it, compress by 3:4 = 0.75

The easiest way to achieve this without compromising the ideal viewing distance is to move your seat through an arc of 41.4 degrees. This gives the requisite horizontal foreshortening to restore the 4:3 aspect ratio. And because you can go clockwise or anticlockwise, there are now two ideal viewing positions instead of one. Progress.

A couple of things still trouble you though. You are now nearer one end of the screen than the other, and this is putting some strain on your eyes' accommodation faculty. Also you are becoming aware of a rather extreme trapezoidal distortion of the image. You take stock:

You do not want to compromise your hard won 41.4 degree viewing angle.

The trapezoidal distortion is a bigger issue than the ideal viewing distance.

The solution is obvious. Staying on the 41.4 radius, you move away from the screen until the trapezoidal distortion is reduced to the standard 1% that you used to apply in the days of converging monitors. A little calculation shows that this occurs at a viewing distance of 87 x picture height, which in your case is about 50 metres. At this point you bless your foresight in having chosen to live inside a disused linear particle accelerator. Not everyone has such a big lounge.

Two difficulties remain. The geometry is now acceptable but the picture seems small and distant. And the sound has acquired lip-sync and echo problems. While pondering the first of these, you fix the second by rigging a powered speaker by your seat. Finally, inspiration strikes. You fetch a pair of 10x50 binoculars . . .

[sajal]

thanks a lot monty....

im not sure what u ment by UBS quality (did u mean quality of the cable operator UBC?).

802.11b gives 11mbps....so i guess that should sufice even for DVD quality??

any idea whats the bitrate of the free to air streamed directly onto digital satelite receivers?

[sajal]

Most broadcasters now use Mpeg3 systems as this has suppased Mpeg2 which now "old technology".

It is 1995. You are sitting watching rugby on TV and, being an Engineer, you have placed yourself directly in front of the screen at the ideal viewing distance of 4 x picture height. The game is rather dull and you go to sleep for ten years. Wakening in 2005 you find that someone has kindly replaced your old TV with a brand new 16x9 widescreen model that just happens to have the same vertical picture height. That's good, because you don't have to move your seat. You're still at the ideal viewing distance. Best of all, a game of rugby is just about to start.

At least, it looks like a game of rugby. Certainly that's a rugby ball and the players look like rugby players, but they seem intent on playing football instead. Slowly it dawns on you that you're watching a football match stretched horizontally to fit the widescreen format. You do some mental arithmetic:

The source material is 4:3

It has been stretched to 16:9

Therefore, stretch factor = 4:3

To fix it, compress by 3:4 = 0.75

The easiest way to achieve this without compromising the ideal viewing distance is to move your seat through an arc of 41.4 degrees. This gives the requisite horizontal foreshortening to restore the 4:3 aspect ratio. And because you can go clockwise or anticlockwise, there are now two ideal viewing positions instead of one. Progress.

A couple of things still trouble you though. You are now nearer one end of the screen than the other, and this is putting some strain on your eyes' accommodation faculty. Also you are becoming aware of a rather extreme trapezoidal distortion of the image. You take stock:

You do not want to compromise your hard won 41.4 degree viewing angle.

The trapezoidal distortion is a bigger issue than the ideal viewing distance.

The solution is obvious. Staying on the 41.4 radius, you move away from the screen until the trapezoidal distortion is reduced to the standard 1% that you used to apply in the days of converging monitors. A little calculation shows that this occurs at a viewing distance of 87 x picture height, which in your case is about 50 metres. At this point you bless your foresight in having chosen to live inside a disused linear particle accelerator. Not everyone has such a big lounge.

Two difficulties remain. The geometry is now acceptable but the picture seems small and distant. And the sound has acquired lip-sync and echo problems. While pondering the first of these, you fix the second by rigging a powered speaker by your seat. Finally, inspiration strikes. You fetch a pair of 10x50 binoculars . . .

<{POST_SNAPBACK}>

or you could adjust the settings in the TV to compress only the width by 75%...

agreed you are good at maths(or maybe u copied n pasted) ...similar while watching DVD movies in 4:3 screens when u get black patches on top and bottom to adjust the 16:9 feed to the 4:3 display....

i simply didnt get the message u r tryin to convey...that is in case there was one hidden....

Edited April 1, 2005 by devil_dog

[monty]

Sorry,

Typo... I did mean UBC quality

The theoretical speed of 802.11b is 11Mbps. I've never seen it go over 6Mbps in the best case, with the accesspoint right next to the client... The total amount transmitted may be as high as 11Mbps but around 6Mbps is actually data, the rest is error correction and overhead... Anyway, most stuff on the market nowadays is 802.11g...

[sajal]

Sorry,

Typo... I did mean UBC quality 

The theoretical speed of 802.11b is 11Mbps. I've never seen it go over 6Mbps in the best case, with the accesspoint right next to the client... The total amount transmitted may be as high as 11Mbps but around 6Mbps is actually data, the rest is error correction and overhead... Anyway, most stuff on the market nowadays is 802.11g...

<{POST_SNAPBACK}>

tx monty, just the clarification i needed...

one more thing...is ubc video on demand or is it broadcast type?

im actually considering 802.16a...theory says 26mbps as max...

Edited April 1, 2005 by devil_dog

[monty]

UBC is broadcast. For digital sattelite rather low quality since they cram a lot of channels in. No problem for regular TV but on a big projection screen you clearly see the compression artefacts.

Where are you located? Haven't seen any Wimax equipment over here yet... Anyway i tought this was equipment for the big boys to use as a last mile solution. Normally speeds of up to 75Mbps, long range non-line-of sight operation etc...