HD stream and video conferencing, bw, cpu or gpu bottlenet?

[endervalentine]

I wasn't sure where to post this but figure I would get some pointers here ... the other day i got thinking, there's a big lack of quality in terms of stream HD content, eg netflix movies, video conferencing, etc.

My question is this bottleneck due to the limited bandwidth, or is it limited to the CPU not being able to decode fast enough? I mean woudn't the PS3's cell be able to just crunch through anything real time. If it's bw limited how fast does it have to be?

Or what if I'm interested in streaming with livestream in HD quality without lag and not suffer in the FPS department. Can I get better streaming w/ more bw, better cpu or better gpu?

Prob a stupid question but if anyone can shed some light ... thanks!

 

[bobsmith1492]

It's all bandwidth.

 

[Modelworks]

bandwidth would be the first issue. The other issue is the content provider themselves. People might be surprised to learn that while netflix and similar sites have permission to stream some movies in HD they do not have permission to stream it in full bluray quality. It is the typical slight of hand you get from hollywood where you think you are getting one thing but have to read the fine print. I was told that netflix contracts are limited to 28Mbps for streaming which is just slightly better than half the full bitrate of bluray.

Studios try to appease customers by allowing streaming content but keep it just below bluray enough that if consumers want the full experience they have to buy the disc while at the same time making money off the streaming rights.

Right now there is nothing you can buy that will give you better streaming quality. There is another service startup that is interesting that uses satellite downloads for streaming the content that says it is full bluray quality but I don't know much about it other than the PR stuff.
http://www.xstreamhd.com/

The tricky thing with all the streaming sites is they always say things like full 1080p but do not disclose the bitrate. 1080P is a resolution and frame rate but can look from crap to great depending on the bitrate. All full 1080P means is that the picture is 1920x1080.

 

[sjwaste]

Full bluray bitrates would tax most home connections too. We're talking ~25 MBit, right? Only through a promotion do I have a higher tier of Fios speed, but even that's "only" 25/25 (according to the speed test I just ran).

Realistically, 720p is doable over your average broadband and average recent pc. 1080p would take a lot more bandwidth and decoding power, or basically a really low bit rate (for that res) stream. I'm not 100% sure that the very common Intel integrated graphics chips can decode 1080p blu-ray quality video without a very strong cpu.

Or I could be totally full of shit. That's fine too, someone can call me out if I am.

 

[Murloc]

bandwidth is the main limit imho.

processor power is an issue with atom netbooks and similar, but not for computers with a somewhat modern dedicated gpu.

 

[endervalentine]

thanks for the replies guys, so from what I gather bandwidth is the main limit to full 1080p streaming. Is there some sort of 'back of the envelop' calculation on how fast my pipe have to be for 720p, 420p and anything in between?

also, how come web cam suck so much then? the quality is no where near 1080p and it's still super grainy and slow ... I actually have a Microsoft LifeCam Cinema on both sides which is not your crappy webcam, but the quality is still mediocre.

 

[Murloc]

I think that the service you're using influences that too, if you have to go through msn servers with a webcam they'll compress video to spare bandwidth.

anyway someone has to upload the video stream, and even if he has a 20mbit connection, upload speed will be around 1mbit.
That limits it probably.

 

[Modelworks]

thanks for the replies guys, so from what I gather bandwidth is the main limit to full 1080p streaming. Is there some sort of 'back of the envelop' calculation on how fast my pipe have to be for 720p, 420p and anything in between?

also, how come web cam suck so much then? the quality is no where near 1080p and it's still super grainy and slow ... I actually have a Microsoft LifeCam Cinema on both sides which is not your crappy webcam, but the quality is still mediocre.

Nope you can't use resolution, that is all the 720/1080 numbers are. Terms like 720P just means 1280x720 at 30 frames per second but say nothing about picture quality unless you also specify bitrate. Companies like MS like to make PR about how xbox will have full 1080P streaming, but they don't reveal the bitrate in the PR.

DVD 720x480 30 frames with audio = 10Mbit /sec
Blu-Ray 1920x1080 30 frames with audio = 36Mbit/sec
Broadcast Stations 1920x1080 30 frames with audio = 19Mbit/sec


Anything being streamed less than that has been compressed or altered in some way. Consider netflix streams HD content at 3Mbit/sec and you can see it isn't even up to DVD specs. The most used codecs are below with what they need for high/excellent quality on average.

WMVHD 1280x720 30 frames with audio = 7Mbit/sec
Divx-HD 1280x720 30 frames with audio = 4Mbit/sec
Divx 720x480 30 frames interlaced with audio = 1.6Mbit/sec
H.264 1280x720 25 frames with audio = 2.8Mbit/sec
H.264 1920x1080 25 frames with audio = 3.6Mbit/sec

Remember that when content is encoded with the above it is usually from another already compressed format so it degrades further.

Web cam pictures are poor because people see numbers like 7MP and think the camera has a sensor taking images at 7 million pixels when the sensor is only taking pictures at 1 million pixels and is using software/hardware to increase that = crap picture quality.

Logitech has some true HD webcams out that have true MP sensors but notice they still use the 10MP as a marketing gimmick.

http://www.logitech.com/en-us/webcam-communications/webcams/devices/6816
Full HD 1080p video capture (up to 1920 X 1080 pixels) with recommended system*
Photos: Up to 10 megapixels (software enhanced)

 

[sjwaste]

Nope you can't use resolution, that is all the 720/1080 numbers are. Terms like 720P just means 1280x720 at 30 frames per second but say nothing about picture quality unless you also specify bitrate. Companies like MS like to make PR about how xbox will have full 1080P streaming, but they don't reveal the bitrate in the PR.

DVD 720x480 30 frames with audio = 10Mbit /sec
Blu-Ray 1920x1080 30 frames with audio = 36Mbit/sec
Broadcast Stations 1920x1080 30 frames with audio = 19Mbit/sec

Aren't most blu-ray 1080p movies going to be in 24p though? I'm not saying it detracts from your point (see a few posts up, where I totally agree with you). I'm just asking b/c I don't own blu-ray.

Come to think of it, I have a 720p plasma and a 1080p LCD. I have no idea if the LCD would actually support 1080p/60 input though.

 

[Modelworks]

Aren't most blu-ray 1080p movies going to be in 24p though? I'm not saying it detracts from your point (see a few posts up, where I totally agree with you). I'm just asking b/c I don't own blu-ray.

Come to think of it, I have a 720p plasma and a 1080p LCD. I have no idea if the LCD would actually support 1080p/60 input though.

Most blu-ray will be 24P if they came from film content. It will not change the bitrate much though.

Just giving those for comparison so people can see the different formats and how bitrates can differ. Most LCD will support 1080P/60 for input they just will not display it as 60 frames.