How is streaming video created?

Most streaming video is currently encoded as 720p H.264/AVC at 24, 23.976, 25, 29.97 or 30 frames/sec. There is some use of VC-1 as a streaming codec, far less now than there used to be. There are a handful of sources of 1080p (at the same frame rates): VUDU, Xbox Video, Netflix and YouTube that I'm aware of and probably others. I have no idea what color space various source encodes use--I'm fairly certain that there's no standardization. The device receiving it has to render it into its fixed or specified color space at its fixed or specified output frame rate. A BD player has to do the same thing.

I imagine that Roku is outputting what their engineers think is what the great majority of displays can handle. No one, really, is striving to please the AV-o-phile market with streaming video (VUDU and Xbox Video come the closest, with available 9 and 10 Mbps 1080p streaming encodes, twice the bit rate of other sources).

They are all receiving the same stream at the same resolution. When Roku get 720p24, it's the same 720p24 stream that the Oppo is sent. (Actually it's a little more complicated than that; Netflix used to use VC-1 with WMA stereo sound and some older devices are still receiving that instead of AVC w/whatever-stereo-encode-or-DD+-5.1 sound. Netflix bought some technology earlier this year which encodes AVC with the same PQ at lower bit rates and there is evidence that they're transitioning some set of devices to that set of video encodes already). Whatever the codec the frame rate's going to be the same; I'm not sure about the color space.
There is, though not all devices offer it. 2012 Panasonic 3D BD players (DMP-BDT220, -BDT320 and -BDT500) can output all of the streaming services at 24p to devices which support 24p (you have to turn it on in a submenu every time you run the streaming player, unlike BDs, for which it's a permanent setting). Some small set of other devices also have this capability; I think that WD TV Live is one of them.
It's the only one of the three devices that you've tested, out of hundreds of devices which stream Netflix. My television is a 5 y/o 60 Hz 1080p LCD panel; it can't deal with 24 fps output so all of the video devices connected to it have to convert whatever source they're given into what my television can take (though my AVR will turn 24 fps into 60 fps for it); pretty much every kind of video device can do this.

On all recent devices these days Netflix uses a technology call Adaptive Bit-rate Streaming (ABS for short). In this system every title has several encodes at various bit rates. If the player is keeping its buffer full it will ask for a higher-bit-rate/better-picture-quality encode; if it's failing to keep its buffer full, it will ask for a lower-bit-rate/lower-picture-quality encode which it will start filling its buffer with before it runs out of content to display. This avoids the old situation of running out of content and stopping to re-buffer a lower bit rate version, never to return to the better encode. When this ABS algorithm works well, it's very smooth and resembles the focus of a camera lens becoming sharper or softer.

Try playing "Example 8 Hour 23.976", which displays information about the resolution and bit rate of the currently selected video encode in a text overlay on the picture. (Search Netflix for "Example" to find an assortment of such clips at different frame rates, though only this one and "Example Short 23.976" have these info text overlays).

I think you will find most (Netflix and other) content encoded as YCbCr at either 24/60 fps.

I have an oldish BD390 Blu-Ray player which if you set it to output 24 fps will output either 24 fps or 60 fps dependent on the Netflix source frame rate.

Unfortunately my BD390 can only get the the 720P streams while my ROKU 2 can get 1080P streams.

So I have to choose either the BD390 and get 720P24 (on P24 material) with 2.0 sound or 1080P60 with 5.1 on the ROKU.

My 55VT30 can accept P24 sources and display them at 96Hz. So I would love to get 1080P24 with 5.1 sound from Netflix - a WD TV Live may be in my future.

For some discussion of YCbCr and RGB see http://www.audioholics.com/tweaks/calibrate-your-system/hdmi-black-levels-xvycc-rgb

My guess is most (all?) of the 1080P Netflix movies are encoded at YCbCr 24fps.

Your playback device then decides the output format - YCbCr/RGB P24/P60 etc

I'm not aware of any streaming service which encodes at 60 fps. Much of the "filmic" material they're given by content providers has a native rate of 24 fps; some shot to video stuff get 30 fps encodes and a lot of European television gets encoded at 25 fps. For some reason most HDTV gets encoded at 24 fps, though the broadcast encodes are 30 or 60 fps. I think that whatever frame rate it's produced at, it gets committed to BD as 24 fps and that encode is what content providers give the streaming services.

To detect what the frame rate of a Netflix streaming title's encode is, just play it in the PC web player; once it starts running (and before blowing it up fullscreen), left-click the video to give it keyboard focus and type CTRL-SHIFT-ALT-D. This will bring up a diagnostic information overlay; about mid-way down the screen you'll see a line labelled "Frames renders/dropped"--when the rendered part is stable it will indicate the frame rate of the encode. Try an episode of Torchwood as an example of 25 fps, some classic TV like an episode of The Dick Van Dyke Show for an example of 30 fps and almost anything else for 24 fps (I had to hunt a little to find some 30 fps; even some classic TV shows like the original Twilight Zone are encoded at 24 fps).

There are a plethora of inexpensive video chipsets which convert from one frame rate to another for output; every bottom-of-the-line BD player can do it.

24 fps takes less data. Even if the file is reported at 29.97 or 59.x there are often flags in the file saying it is really 24 fps. When recording NBC HD shows they actually had the flag while CBS didn't. Some of the encoders like Dr. Divx might actually find the flag. Otherwise it starts creating extra frames that don't exist. Of course film is 24 fps and that option is also available on HD cameras and even recently on consumer HD cameras. You can put a longer video on that SD card at 24 fps than at 30.

Motion pictures are still shot and produced at 24 fps even on HDCAMs and projected in theaters at 24 fps. There is a movement to adopt 48 fps--they're trying it out for the The Hobbit: An Unexpected Journey which hits theaters in a month (only some will be projecting at 48 fps). I've read that preview audiences did not like it, especially in close up scenes (here's a blog post about it). In any case 48 fps can obviously be reduced to 24 so business as usual for streaming.

I commented on that a few posts above this.

I have no idea. Inasmuch as the 2012 Panasonic 3D BD players can do it, it is surprising that the much more expensive Oppo BD players can't. Someone above stated that his Oppo can't get the 1080p Netflix streams because they couldn't satisfy Netflix's security requirements which is also surprising; I have 2 BD players, a PS3, TiVo Premiere and Roku 2, all of which can play 1080p Netflix.

DMP-BDT220. I also have the previous year's equivalent model, the DMP-BDT110, which has closed captions/subtitle and DD+ 5.1 surround support in Netflix, but which is restricted to 720p, or at least it was. The BDT110 is no longer getting the same set of encodes as most of my other devices; I suspect that they've been generating same-PQ-at-lower-bit-rate video encode sets via the new encoder tech that they obtained from eyeIO (see this) and that they're testing that set of encodes out on a limited group of platforms including the BDT110. eyeIO claims that their H.264/AVC encoder can deliver the same PQ in half the bandwidth.

If you're buying a BD player with an eye towards streaming, the weakness of the Panasonics (for me) is their Amazon player, which lacks 5.1 sound support.

Sorry I should have said 'most ......... content (is) encoded as YCbCr at either 24/30 fps.

It does seem strange Oppo Blu-Ray players can't do 'native' streaming.

My ancient (3 year old) LG BD390 will do Native streaming - albeit limited to 720P encodes for Netflix. It will do native VUDU HDX streaming - outputing 1080P24 when getting a 24 fps stream - same as Blu-Ray.

If the ROKU 2 would do native Netflix and Vudu 'streaming' it would become my default player for streaming.

It comes down to "what looks good", really. What I find is an occasional movie on Netflix that some idiot has encoded to 30 fps and that makes it judder due to the extra pseudo frames. Ever since DVD, players have been able to handle 24 fps. It's all built into the chipsets. The studios early on realized they could get more video on DVD at a higher bit rate if they stuck to 24 fps. In fact you should only need one master file for both NTSC and PAL standard discs and just mux them differently.

Netflix encodes at 30 fps if the source they're given is 30 fps. It's usually shot-to-video-tape stuff; old television series or made-for-TV movies. Famously the stuff they used to get from Starz Play before they ditched it was fairly recent theatrical release titles in SD 30 fps with horrible judder. I haven't encountered any 30 fps high def stuff as yet. Have you?

Michael, how do you know some of the streams don't have embedded telecine flags and are really 24 fps even though they say 30 fps? Broadcast transport streams with 24 fps content will still read 30 fps even with the telecine flags. We had a lot of discussion on this over on the HTPC section years ago.

I don't. The only 30 fps stuff I've run across is old television and the occasional low rent movie.

No, it is not because of that, it is 24fps because all the movies from DVD/BR are shot first on film. Even some TV series are shot on film, to look beter. That film has 24 fps since 1920's till today.
When shown on TV, sure, the player has to add extra frames (by repetition) to make 30p/60i, but is no reason to add those repeated frames on the optical support, it is done in the player hardware.

Well we all know that movies were shot at 24 fps every since Academy Ratio was made the standard back then. But given that studios are cheapskates they would have opted to put 30 fps (29.97) on DVD. And we know that some did. Somewhere during the development of DVD engineers figured they could easily supply the interpolation needed for 24->30 fps. I do seem to recall reading somewhere that studios liked the idea. And if you have ever encoded a DVD you would know you can get more data into the stream at 24 fps. You also would get the side benefit of one encoding for both NTSC an PAL and as I mention just remux for the two formats. Back in the 1950s the conversion from 24fps to 30 for television was done with 5 blade projectors. Do the simple math to see how that worked.

I can throw all kinds of frame rates at my BD player in files that I've encoded and it can handle them. In a decoder you find in the header where the frame rate is (and sometimes it's given as microseconds per frame) and you know how long to hold each frame before displaying the next one. My Android phone does HD videos at really weird frame rates.