Video quality vs bandwidth

Forum|Forum|18 years ago
February 12, 2008
3 replies
785 views

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

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A

Anonymous

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 due to client buffer settings.

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肥權84_2Author

Known Participant

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?

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MMLincoln

Known Participant

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.

A

Anonymous

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.

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肥權84_2Author

Known Participant

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?

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MMLincoln

Known Participant

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?

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肥權84_2Author

Known Participant

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?

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