Streaming HD with FMLE?

Question

I am using FMLE (for mac) with watershed ustream service and they claim that you can output HD to the web using FMLE. I am fairly new to the world of video streaming and don't entirely understand all of the codecs and what not, but is there somewhere where I can learn a little more about streaming this in High Definition?
My camera that I will be using is an HD (production quality) camera so that camera is not an issue.
I am also going from camera to camtwist then FMLE then the server
I'm using CamTwist because its free and allows me to switch between desktop view and live video camera easily.

Answer 1

That test happened to be with a Tricaster switcher with FMLE inside of it.  The 4-5Mbps was average which means spikes would be higher but in later analysis of the archive files from the Tricaster we see that it was 720p60 and that COULD explain why the average was so high.  What I would expect to see from FMLE is an average around 2 to 3Mbps but spikes up to 5Mbps.  We are running further tests on native FMLE (not in the Tricaster switcher) now that it has Blackmagic capture card support and you are free to contact me for those results once we finish our analysis ([email protected]).  Also, I do not want to diss FMLE or Adobe because FMLE does provide a very valuable low cost component in the ecosystem that Adobe has built around Flash Media Server and that ecosystem is what makes the Flash video platform viable for all of us to use - both customers and vendors like Kulabyte.
Regarding the content, it was typical content we use for testing with both easy and difficult to encode video.  Regarding the FMLE settings, they were the standard settings for FMLE in the Tricaster switcher.  We no longer have the switcher, but even so it wouldn't be right to distribute that data as it belongs to Newtek.
I want to get back to the question about whether the bitrate was average or spikes, however, because this is the most critical issue for live streaming.   The point I will make below is that for live streaming, constant-bitrate (CBR) encoding is an absolute must and FMLE does not do constant-bitrate; it only does variable bitrate (VBR).  The way we know this is from observation and also knowing that FMLE uses MainConcept's H.264 Standard codec which does not support CBR.  Kulabyte's XStream Live 2, on the otherhand, uses MainConcept's H.264 Professional codec which does support CBR.  See http://www.mainconcept.com/products/sdks/video/h264avc.html for more details.
Now, consider the variation in internet connections among all of the people watching your stream.  First, everyone in your audience will not have the same download bandwidth on their internet connection.  Some may have 1.5Mbps, others will have 10Mbps on fiber, and most in the U.S. will fall in the 2Mbps to 5Mbps range.  For this reason, to insure the best possible user experience with a broad audience such as this, you really need to have multiple streams available to the viewer including maybe a 2Mb stream, a 1.2Mb stream, a 750Kb stream, and a 200-300Kb stream for mobile and and then you should use dynamic or adaptive streaming supported by FMS 3.5 with the major CDN's so that the player will negotiate with the FMS server and choose the best stream for that viewer's download bandwidth.
Next, consider the path the stream must go from the encoder to the player computer.  First from the encoder to the FMS entry point, then from the entry point to an edge server, and then from the edge server to the audience members player.  With a good CDN, the bandwidth between the entry point FMS server and edge FMS server is huge so we can ignore that piece of the path.
Before diving into the upload bandwidth from the encoder and download bandwidth to the player computer, let's estimate how much bandwidth is needed.  For sake of argument, let's assume that FMLE has a 50% swing in bitrate from the average.  Kulabyte's XStream Live's actual bitrate swing is typically about 5-8%, but well assume 10% to be generous.  Next, let's assume (I think this is pretty safe) FMLE's average bitrate is about 50% higher than XStream Live 2's average bitrate for the same video quality (due to other differences between the MainConcept codec and other optimizations done by Kulabyte).  Now let's calculate the bandwidth needed for the streams I mentioned above.
XStream Live 2
                  Average         Peak
720p              2Mbps          2.2Mbps
480p              1.2Mbps        1.32Mbps
360p              750Kbps        825Kbps
Total                            4.3Mbps
(I'm leaving off the 4th stream for mobile because FMLE can only do 3 output streams, XStream Live 2 can do 4 plus more if you really want to)
FMLE
                  Average         Peak
720p              3Mbps          4.5Mbps
480p              1.8Mbps        2.7Mbps
360p              1.1Mbps        1.6Mbps
Total                            8.8Mbps
Now back to the path the stream takes.  If you are streaming from a fixed location where you can get fiber and a solid 10Mbps uplink, then you will be able to send the three streams noted above from your encoder to the FMS entry point.  However, if you can only get a solid 5Mbps uplink (like business class cable modem), what you will see with the FMLE encoder is that every time the video is a bit challenging and it swings to the high side of its bitrate, your video is not going to get to the FMS entry point and everyone down the line will see buffering.  If your viewers didn't pay for what their watching, then maybe that's OK but for professional streaming with paid subscribers, this would be unacceptable.  If it's not as good as TV, then you will not retain viewers.  And, what we find with our streaming customers is that more often than not, getting good uplink bandwidth is very challenging.
Now consider the path from the edge FMS server to the audience member's player on their laptop.  With dynamic streaming enabled, the viewer should see the stream most appropriate for their download bandwidth, but at 4.5Mbps for the 720p stream, how many people are going to be able to see that with their home internet connection.  Many will only be able to see the 480p at 2.7Mbps and many others will only be able to see the 1.6Mbps stream.  I think I mentioned this very early in the thread, but research done by Akamai shows that you will get much better audience retention with 720p versus 480p and, of course, you can not have the video stop for buffering ever.  Thus, not having a good constant bitrate stream can bite you both on the uplink side from your encoder, unless you are fortunate enough to be streaming from a location with fiber, and this affects all viewers (i.e. buffering) and it can bite you on the downlink side for your audience because they will not see the quality of video they could see if you had a good constant bitrate and lower average bitrate stream.
Tim