When is a webcam not a webcam? When it’s actually a DSLR!
Around here we are strong believers in DSLRs. Our first DSLR was an Olympus E-10, but these days we have a couple of Canon Rebel XSi’s. Released in Q1-2009 these are not the latest and greatest by any stretch, but they’re nice cameras. We also have a small selection of lenses.
As DSLRs have come to shoot video it would make some sense that they could also be used the more sedate role of webcam. Our Rebel XSi’s don’t shoot video, but they do make nice 12 mega-pixel pictures.
It happens that many Canon cameras, including the XSi, have a feature called “Live View” that’s intended to stream the image to the LCD viewfinder or even across a USB connection.
In the last installment in this series I examined the role of USB 2.0 as the primary means of connecting a webcam to a host computer, and the inherent limitations involved. But USB 2.0 is just so 20th-century…what about the newer, SuperSpeed USB 3.0? Doesn’t this lightning-fast (5 Gbps!) bus promise to allow real 1080p or even 4K webcams? Cheap-as-chips!
The answer to that question is a definite maybe (many thanks to Ray Davies.) However, as a practical matter, USB 3.0 webcams basically don’t exist. Even so, it’s worth having a look a the relatively brief existence of USB 3.0.
Have you ever noticed that basically all webcams are connected to the host computer using the USB 2.0 bus? The ubiquitous USB 2.0 bus is cheap and convenient for such purposes. Providing 480 Mbps it’s no slouch, but it’s not exactly state-of-the-art either. This has implications when webcams are reaching for HD resolutions at decent frame rates.
Until quite recently webcams always provided an uncompressed image stream to the host computer. USB 2.0 is a serial connection standard supporting up to 480 Mbps. That’s about one third of the data rate of the production HD-SDI standard, SMPTE-292M, which is 1.485 Gbps.
Let’s do a little math corresponding to a 720p video stream as related to uncompressed HDTV.
8 bit/pixel @ 1280 x 720 @ 59.94fps = 105 MB per/sec, or 370 GB per/hr.
105 MB/s = 840 mbps
…but a lot of video conferencing gear actually uses 30 frames/second instead of 59.94 or 60 frames/second…so half that value…
720p30 = 420 mbps!
There you have it! The mathematics supports the assertion that 720p30 uncompressed “HD” video stream can be passed across the USB 2.0 serial bus. This explains how Skype, Google, ooVoo, VSee and others have been able to offer HD video using common USB 2.0 connected webcams. Understanding the limit of the USB 2.0 connection also informs us why 1080-capable webcams have not become similarly commonplace.
The first post in this series on webcams was historical. This one is as well, but it highlights the performance offered by the very first HD-capable webcam that was recommended for use in UC/video conference solutions.
There was a time when I was pursuing the ability to deploy HDVoice for my home office. If this were possible then it would improve not only my working life, but also that of my US co-workers.
While I might have the lovely Polycom hardware there was no way that I could convince my employer to replace our existing IP phones en masse. At the time they had around a dozen older SoundPoint models in service.
However, some of our staff also used soft phones on Windows laptops. I saw this as a way to sneak HDVoice into the operation for minimal cost. The trick was to find a good, G.722-capable soft phone for a reasonable price.
In the post-roll after last week’s VUC call I was able to invite Andy to join me in trying Talky a relatively new WebRTC– based video calling service from &Yet. The service is very interesting as is the company itself. I heartily recommend their blog.
Andy and I had a good, lengthy chat using Talky. We came to the conclusion that it was the best experience with WebRTC that either of us has encountered. Admittedly, neither of us are WebRTC experts.
Talky supports screen sharing from within Chrome, given that a configuration change is made prior to starting the session. What it lacks is any kind of text chat.
A couple of weeks ago Stella’s beloved Nexus 4 had an unfortunate meeting with asphalt. It fell from an outside pocket of her purse as she was getting out of the family vehicle. The upshot of the event was a broken front glass and loss of touch functionality. Everything about the phone worked, but she could not even answer a call without touch capability.
Happily, her phone was still covered by insurance, which I had more than once thought to cancel. The insurance would not replace the Nexus 4 with the same model as just days before they had become unavailable. In the run-up to the October launch of the Nexus 5 Google has let inventory lapse so replacements were not to be found.
The insurance company offered a refurbished Samsung Galaxy S3 in white. While this might have been acceptable to most people it presented Stella with a certain problem. Her company-issued cell phone is a Samsung Galaxy S3 and she’s not especially happy with it. She prefers her Nexus 4.
A quick look online revealed that there are some places that could repair the broken Nexus 4. Gophermods was once such service, quoting $170 for the job. At the present time they report “out of stock” on the screen replacement. I wonder if parts will start becoming hard to get as the phone fades from the front line?