Video quality vs bandwidth

[??]

Hello experts,

We would like to make use of Flash Media Server as our streaming server to
make a live video broadcast on the website. Bit rate 500 kb/sec is the video
quality requirement. Is that mean each session will use up 500kb? We expect
there will be 1000 concurrent sessions to our website to see the live broadcast
online. Is that mean 500kb x 1000 = 500MB bandwidth will be used at that period
of time? We urgently need to know if there is any configuration / settings in
the server to reduce the cost to pay for the internet (we may need to pay for a
1GB broadband which is expensive) without making the video quality poor. Any
idea?

-FATKUEN

[MMLincoln]

Are you going to use On2 VP6 w/ Flash Media Encoder? If you set the video to
500 kbps, then it will roughly stay around that number for the actual
bandwidth. This could be for video only though, so you'll have to make sure
that you figure in audio if you haven't already. An 11 Khz audio rate will use
up around 31-33 kbps. With 1,000 users you will use roughly 500 mbps (megabits
per second). You'll want to have probably at least 768 kbps upload on the
broadcasting connection too.

Are you using a CDN / Streaming service?
How long are you planning on running the event?

[??]

Thanks for your information MMLincoln =)
I am not sure if we are going to use On2 VP6 - i have to confirm with my
technical guy. You have also raise a good point about the bandwidth for audio
which we have never think about. What we are really concern is the
international bandwidth we would like to buy from ISP in order to make sure the
users in other countries can view the video very smoothly. Is 10MB enough for
1000 concurrent users with 768 mbps?

[fmslove]

500kbps x 1000 stream = ~ 500 mbps inevitable;
apart from using On Vp6, you may also want decrease the frame rate a bit <20
fps depending upon motion in your live stream. using these two ways you should
be able to achieve similar video quality with lesser bandwidth consumption per
stream.

[??]

Thanks. But do you think a dedicated 10 MB broadband enough to cater these 1000
concurrent sessions?
It is actually a live racing broadcast channel so I'm not sure if decrease
the frame rate will help. Would you please advice?

[fmslove]

Theoretically 10 Mbps broadband is sufficient for only 20 (19 downstream + 1
up-stream); In practice, this number will go lower due to network fluctuation
(even a fluctuating clients link can make FMSs network usage fluctuate due to
buffer settings). Also, one should to keep some bandwidth spare as initial data
transfer FMS to flash player can be a bit more sure to client buffer settings.

[??]

That's unfortunate - as the money to pay for the international bandwisth is
really expensive. Just wanna think of any approach wich can save bandwidth
without making the quaility poor.

I heard that we can set either unicast or multicast for broadcasting. Is that
a possible way to save the bandwidth?

[MMLincoln]

I would recommend setting up a test system. Just take a recording of a previous
event or a similar racing video and pipe that into your capture card and
through the flash server. Load up Flash Media Encoder (for On2 VP6) and a
viewer and start tweaking the audio/video settings until you find something
that will work for you. It possible that you might be able to get by with
something lower than 500 kbps.