Slashdot Mirror
High-Definition PC Video Conferencing?
dsginter asks: "This year's spring Networld+Interop has ended with little fanfare. However, I noticed that a small nugget slipped between the cracks - HD video-conferencing. Two different manufacturers demonstrated such products which means that we'll probably have interoperability soon. After seeing the massive pricing estimates for such products, I couldn't help but think that I should try my hand at my own HD product (a Mac Mini, some H.264, a pinch of AAC and the glue that is H.323 or SIP). However, I'm missing one piece - a small, 720P camera for video acquisition. I've scoured Google but can't come up with anything suitable. Is there an answer? HD video-conferencing is an important step in complete communication between remote parties. While there will be those that joke about the possibilities, it is important to remember that the bulk of business travel still happens for the sake of face-to-face communication. HD video-conferencing might prove to be a panacea."
Trying to decode an HD stream on a Mac mini is probably not that good of an idea - a single G4 doesn't have quite enough power to manage it.
H.264 is designed to scale down to various processor architectures, so a lower-resolution stream would probably play acceptably, but I rather doubt that you'd get enough horsepower out of a Mac mini to acceptably decode HD content encoded with H.264 in realtime.
For more, see Apple's H.264 FAQ.
An iMac G5 should have the horsepower, however.
The bitrate of the MPEG-2 transport stream of the Sony 1080i camera is 25 Mbps. Hardware real-time MPEG-4 Part 10 (aka H.264, aka AVC) encoders do exist, but they're aimed at commercial broadcasters. As the parent pointed out, software encoding, even on the latest and greatest CPU, is *much* slower than real-time.
The other problem you'll run into is the quality of the lens. On a small webcam, it wouldn't help you much to put a high-res CCD in it. The lens would be the bottleneck.
http://www.macnn.com/articles/05/05/17/sony.hdr.hc 1.handycam/
Umm, sorry to put a slight damper on your sarcasm, but they do. Some of them charge like $2 a minute for that... insane.
--
WHO ATE MY BREAKFAST PANTS?
As an engineer who recently wrapped up a video camera project, here's are the problems we ran into:
- The CCD sensor can easily do full-motion XGA or SXGA video, but:
- The DSP has a very difficult time encoding MPEG video at full-motion frame rates for anything larger than VGA resolutions.
- 100 Mbit ethernet is just barely capable of supporting a VGA or D1 bitstream, and,
- XGA has ~twice the number of pixels as D1; SXGA is even more bandwidth intensive.
Now granted, we do build boards which could probably handle HDTV video conferencing. But the problem is that the 4 processors alone cost more than the average low-end PC. From a technical perspective, HDTV video conferencing is possible, but the hardware required is far more expensive than what the market would tolerate.Are you willing to pay $10k for HDTV versus a few hundred for a QVGA webcam setup?
I'd love to be building HDTV cameras, but the problem is that we can't find customers willing to pay the extra expense for the higher resolution.
The society for a thought-free internet welcomes you.
I'm missing one piece - a small, 720P camera for video acquisition.
The cheapest consumer HD video camera I have seen is made by sony. It costs $3,500. The size is about 1 foot long, 6 wide and 6 high. Not sure if it is 720p or 1080i. Doesn't matter much in this case. Now, if you want something that will give you the 1280x720 resolution, try one of the still digital cameras that can give you just as good a resolution (and sometimes act as a web cam). They generally cost much less. Concord has a camera that should work for this, assuming the webcam picture is full res.
Fly me to the moon Let me sing among those stars Let me see what spring is like On jupiter and mars
I am not aware of a real-time H.264 codec that can encode SD video in real-time, even on a 3.73GHz P4, let alone HD. With the advent of the upcoming dual core CPUs, real-time H.264 encoding of SD content may become a reality soon, but real-time encoding of 720p material on a general purpose processor is probably still a few years away.
There are a few companies working on special HW (i.e., chips) for real-time H.264 encoding, though most of the first generation products are focusing on standard definition. Since video encoding is a parallelizable problem, I wouldn't be surprised to see specialized HW that is capable of real-time H.264 encoding 720p material in a couple of years. Even a more general purpose device like the Sony/IBM Cell chip may find an application in this context. By that time, the density of flash cards or microdrives should have reached the sufficient capacity to be able to hold a reasonable amount of MPEG4/H.264 encoded video material. As with the current gen MPEG4 camcorders, I wouldn't be surprised if the encoded video quality of the initial batch of devices are not that great.
Even though hardware encoders are likely to be initially targeted at the small form factor high definition camcorder market, we are likely to see a batch of hardware HD MPEG4/H.264 encoder cards (similar to the current SD MPEG2/MPEG4 cards) as soon as such chips are commercially available.
Of course, the other requirement for HD video conferencing would be an increase of average broadband access rate to 6-10Mb/s range. Even with H.264 encoding, a somewhat static 720p stream can easily burn 2-3Mb/s of net bandwidth.
Peace
Hah... if they're only charging $2.00 a minute then grab it! We (name not supplied due to modesty) charge anything between $2.99 and $6.99 a minute and we certainly aren't the most expensive in the business.
He states "H.264 is designed to scale down to various processor architectures, so a lower-resolution stream would probably play acceptably"
Yes a Mac mini can do H.264, no it cannot do it at HD rates.
I'm sorry but you did not got 640x480@60fps using a TV Wonder. You have 640x480@59.94fps interlaced. That translates to either 640x240@59.94fps or 640x480@29.97fps.
-matt