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CharlesJamieson
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Photobridge & HD quality over a network

Sat Apr 08, 2006 6:46 am

I was wondering whether anyone might be able to help.

I'm re-wiring my house for ethernet network anyway and am debating CAT 5e or CAT 6.

I saw that the photobridge will only support 10/100 Mbps

How can it deliver true HD TV via a network when HD TV signals need 1600Mbps transfer rate.

Sorry if this seems stupid but the maths doesnt add up to me

Any help would be much appreciated
 
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TheEndless
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Re: Photobridge & HD quality over a network

Sat Apr 08, 2006 8:13 am

CharlesJamieson wrote:
How can it deliver true HD TV via a network when HD TV signals need 1600Mbps transfer rate.

Where did you get that number? If I'm not mistaken, average broadcast HDTV is around 19Mbps, with an absolute top end of somewhere around 40Mbps. So 10/100 should be more than enough.

As for wiring your house. If you're planning on staying there for awhile, I'd go ahead and run CAT 6, if for no other reason than "future-proofness" (is that a word? :P)...

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CharlesJamieson
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Sat Apr 08, 2006 10:05 am

Thanks for that.
 
andy
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Re: Photobridge & HD quality over a network

Sun Apr 09, 2006 10:38 am

CharlesJamieson wrote:
I'm re-wiring my house for ethernet network anyway and am debating CAT 5e or CAT 6.

I used CAT 5e when I ran cables in my house. It is working fine with a gigabit switch. If you just have one PB you can use a 10/100 switch instead. I have put details of my recommendataions here:

http://frequal.com:8080/pmn/TopComponents.html

What is the price differential between Cat5e and Cat6 nowadays? It may be safer long-term to use Cat6, just as TheEndless said.

CharlesJamieson wrote:
I saw that the photobridge will only support 10/100 Mbps

How can it deliver true HD TV via a network when HD TV signals need 1600Mbps transfer rate.

The PB needs only stream the 19-20Mbps compressed MPEG2 Transport Stream (TS) file from your server. I do this every day and can assure you that it works well with a Cat 5E network.

I think the raw HD signal would require around 1440 Mbps, if it was a 1080p signal. 2 megapixels * 24 bits / pixel * 30 frames / second = 1440 megabits per second (Mbps).

For the 1080i max supported by the PB the raw rate is half that, or 720Mbps. Fortunately the MPEG2 compression brings it down to 19-20Mbps without too much perceptible loss.
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dgburns
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Re: Photobridge & HD quality over a network

Sun Apr 09, 2006 10:44 pm

andy wrote:
I think the raw HD signal would require around 1440 Mbps, if it was a 1080p signal. 2 megapixels * 24 bits / pixel * 30 frames / second = 1440 megabits per second (Mbps).

err...1080p is progessive, i.e. 60fps, not 30....
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MP3 Mike
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Mon Apr 10, 2006 9:48 am

I didn't think the difference between interlaced and progresive was the frame rate... I thought it was the field data. In interlaced you only get hald of the field data in each frame. (So 1080i is exactly half the bandwidth as 1080p, but they are both 30fps.)
 
jimre

Mon Apr 10, 2006 4:57 pm

There's both 1080p30 and 1080p60. And 1080p24 for that matter (which I believe will be the "native" format of movies stored on Blue-Ray or HD-DVD).

As to the original poster's question - do you also think your local HDTV station transmits 1.6 Gbit/sec over the airwaves to your TV antenna? Of course not - that's like 150 times faster than Wi-fi.

HDTV source material is never transmitted or distributed in raw, uncompressed format. It's always encoded in a highly-compressed format, usually MPEG2. This results in a bitrate of around 19.2 Mbit/sec for broadcast HDTV, slightly more or less for other HD sources like cable or satellite. This is easily handled by 100 Mbit/sec ethernet.

These ultra-high bandwidth speeds (1.4 Gbit/sec or more) we're talking about are only used for transmitting raw, uncompressed digital HD video over short distances - between a decoder device and a digital display, usually via DVI or HDMI cables. That high bandwidth requirement is one reason why DVI/HDMI cables are expensive and limited in length.
 
dgburns
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Tue Apr 11, 2006 3:18 pm

jimre wrote:
There's both 1080p30 and 1080p60. And 1080p24 for that matter (which I believe will be the "native" format of movies stored on Blue-Ray or HD-DVD).


There's no 1080p60 in the ATSC spec's:
Table 5.1 Digital Television Standard Video Formats
Vertical Lines Pixels Aspect Ratio Picture Rates
1080 1920 16:9 60I, 30P, 24P
720 1280 16:9 60P, 30P, 24P
480 704 16:9 and 4:3 60P, 60I, 30P, 24P
480 640 4:3 60P, 60I, 30P, 24P

(from http://www.atsc.org/standards/a53.html)
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jimre

Tue Apr 11, 2006 9:40 pm

dgburns wrote:
[There's no 1080p60 in the ATSC spec's:...
That doesn't mean it doesn't exist. It just means it's not broadcast over the airwaves in the US. As I understand it, 1080p60 will be the native capture format used by the next generation of professional HD cameras.
 
sansp00
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Tue Apr 11, 2006 11:03 pm

While on the subject of house wiring ...
My house is currently being built. Before they close the walls, I was thinking of wiring my HT room for audio and the rest of the house ( 3 bedrooms, HT room, living room ) with RJ-45.
I currently use a Netgear 4 port wireless router WGR614v4 hooked up to my high speed ISP modem. Since I was thinking of using more than 4 wired ports, and that I am not too fond of using wireless, how can I expand the setup ? Could I hook up a basic a multiport switch to to my router ? How will my IP addressing will look like ? I am not too familiar with multi device networking ...

Thanks
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dgburns
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Wed Apr 12, 2006 6:42 am

sansp00 wrote:
how can I expand the setup ? Could I hook up a basic a multiport switch to to my router ? How will my IP addressing will look like ? I am not too familiar with multi device networking ...

Yes. Just plug a multi-port switch (make SURE you get a switch, NOT a hub) into one of the 4 ports on the router, and you'll have that many more ports. I do this now, I have a switch to which my Roku, PS/2, etc. in my media romm are all connected and 1 cable goes to the router. Unless you go hog wild and buy an expensive managed switch, no impact to the IP addressing, your network will still just big a (now bigger) flat network.
HD-1500 RevB #1 (media room)

Mitsubishi WD-62528 62" LCD RPTV

Kenwood VR-407 receiver w/PSB Alpha's

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M1000 (upstairs)

HD-1000 RevB #2 (bedroom)

Visco 32" LCD

AR 2.1 audio system

PS/2
 
chackett
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Wed Apr 12, 2006 9:31 am

dgburns wrote:
sansp00 wrote:
how can I expand the setup ? Could I hook up a basic a multiport switch to to my router ? How will my IP addressing will look like ? I am not too familiar with multi device networking ...

Yes. Just plug a multi-port switch (make SURE you get a switch, NOT a hub) into one of the 4 ports on the router, and you'll have that many more ports. I do this now, I have a switch to which my Roku, PS/2, etc. in my media romm are all connected and 1 cable goes to the router. Unless you go hog wild and buy an expensive managed switch, no impact to the IP addressing, your network will still just big a (now bigger) flat network.

I don't know much about networking either, so forgive me if this is a stupid question, but doesn't this limit the bandwidth on the entire switch to the bandwidth available for the router port into which it's plugged? Probably not an issue most of the time, but if you were trying to stream HD to two or more devices off of the same switch it could potentially cause a problem, unless my understanding is incomplete (a distinct possibility, I must admit).
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jor
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Wed Apr 12, 2006 12:33 pm

jimre wrote:
HDTV source material is never transmitted or distributed in raw, uncompressed format. It's always encoded in a highly-compressed format, usually MPEG2. This results in a bitrate of around 19.2 Mbit/sec for broadcast HDTV, slightly more or less for other HD sources like cable or satellite. This is easily handled by 100 Mbit/sec ethernet.


If 100bt were fully utilitized, sure. But smb on the roku barely can handle the load. Going PC to slug, I can use 50% of the bandwidth. These low frequency cpus just can't do it as full bore.

These ultra-high bandwidth speeds (1.4 Gbit/sec or more) we're talking about are only used for transmitting raw, uncompressed digital HD video over short distances - between a decoder device and a digital display, usually via DVI or HDMI cables. That high bandwidth requirement is one reason why DVI/HDMI cables are expensive and limited in length.


That...or merely the ability to overprice new cables every time a new format comes along.
 
jor
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Wed Apr 12, 2006 12:42 pm

chackett wrote:
I don't know much about networking either, so forgive me if this is a stupid question, but doesn't this limit the bandwidth on the entire switch to the bandwidth available for the router port into which it's plugged? Probably not an issue most of the time, but if you were trying to stream HD to two or more devices off of the same switch it could potentially cause a problem, unless my understanding is incomplete (a distinct possibility, I must admit).


If you're thinking of streaming multiple HD feeds, yes, you need to start to think about this. There would be a single pipe to the router at 100Mbit. So you wouldn't want to have too many devices plugged into the router that rely on data to/from devices on the switch. You'd want them all on the same switch (either the router or most likely the higher performance added switch). Mind you, each device on a switch has full speed to every other port. So if you plugged in two sources and two display devices to the same switch, the traffic wouldn't interfere with each other. 2 display devices feeding off one source, otoh, has a different problem. You may find it can't stream simultaneously.

It's probably time to go with gigabit over 100bt for switches, and definitely to go with 8 ports over 5 (where one is already lost to plug to the router). You don't get 10X speed, but it is the device and not the switch that is the limiting factor.
 
dgburns
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Thu Apr 13, 2006 7:48 am

jor wrote:
It's probably time to go with gigabit over 100bt for switches, and definitely to go with 8 ports over 5 (where one is already lost to plug to the router). You don't get 10X speed, but it is the device and not the switch that is the limiting factor.


I'd concur.

What >I'd< really like to find is a cable/dsl/wireless router that had GigE ports instead of just 10/100. I'm due for an upgrade (my router is still only 802.11b but all my devices support g), and I was hoping some "pre-n" routers would have Gig-E, but I haven't seen one yet. I have Cat-6 wiring, so I'm ready for Gig-E, but if I'm gonna do it I want to do all the network components in one shot.
HD-1500 RevB #1 (media room)

Mitsubishi WD-62528 62" LCD RPTV

Kenwood VR-407 receiver w/PSB Alpha's

PS/3 60GB (now 250GB) w/750GB Seagate ext

M1000 (upstairs)

HD-1000 RevB #2 (bedroom)

Visco 32" LCD

AR 2.1 audio system

PS/2

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