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On-Demand Playback Data Rate and Usage
Last Updated: Dec 27, 2017 03:32PM EST

This article applies to:  Echo360 Admins

Even though you don’t have to manage the data storage for your Echo360 system, you still have to manage the network bandwidth configuration that will make playback of the media as seamless as possible for users.

The table below shows the data rate and corresponding file size (per hour of recording) for streaming rich media via Echo360’s HTML5 media player. These numbers are based on typical content processing. The higher quality and more source combinations result in larger overall volume per hour of playback. This is important to consider when deciding on scheduling policies for recordings.

The section below the table asks some basic questions and provides an example calculation for overall bandwidth needed for on-demand playback. For information on the kind of bandwidth needed for students to view presentations and participate in Activity slides, see Large Classrooms Viewing Class Media. (Spoiler Alert: The network hit for presentations is relatively small.)

All captures are played back in HD 720 by default, if the capture was recorded in HD. Students can change the playback to standard definition for smoother playback if necessary (click the gear icon at the bottom of the playback screen).

media playback controls showing playback definition selection as described

Audio-Only playback not shown: The numbers below are inclusive of the audio stream at 44 kbps, or 0.02 GB/hr. Use these figures to calculate total rate/volume for audio-only content.

Capture Components Standard Definition (480p)
Data Rate and Vol/hr of recording
High Definition (720p)
Data Rate and Vol/hr of recording
Highest Definition* (1080p)
Data Rate and Vol/hr of recording
Audio+Video+Video (AVV) 264 kbps
0.11 GB/hr
1152 kbps
0.49 GB/hr
2304 kbps
0.98 GB/hr
Audio+Display+Video (ADV) 264 kbps
0.11 GB/hr
720 kbps
0.31 GB/hr
1440 kbps
0.62 GB/hr
Audio+Video (AV) 232 kbps
0.10 GB/hr
576 kbps
0.25 GB/hr
1152 kbps
0.50 GB/hr
Audio+Display+Display (ADD) 164 kbps
0.07 GB/hr
288 kbps
0.12 GB/hr
576 kbps
0.24 GB/hr
Audio+Display (AD)   144 kbps
0.06 GB/hr
288 kbps
0.12 GB/hr

* Before selecting 1080p for captures, review Capturing and Streaming in 1080p.

What the numbers in the table indicate are that in order for a student to view a capture smoothly, the capture needs X number of kbps available. However, like YouTube videos, Echo360 tries to temporarily download the full capture, or at least buffer some portion of it, so that the student is actually viewing it locally rather than as a constant network stream. That's where the volume/hr comes in. An hour long AV capture, viewed in HD, for example, will buffer/download a file approximately 0.25 GB in size.

Technical Details: If you read the Live Streaming Data Rate and Usage topic, you'll note the discussion about the connection being used for the visual input (DVI or Composite) being more important to the size of the capture than the thing being captured (video or display). So why don't we have that here? Because the Echo360 media processor is able to distinguish live-action, high motion content (typically delivered from a video camera) from static content (typically delivered by a monitor or other display device). When the capture (or an uploaded video) is processed, the media processor optimizes the visuals, to generate a high quality capture using the least amount of data possible. What this means, though, is that if your A/D/D capture is actually two HD computer monitors both showing videos, the resulting capture will be more along the lines of an A/V/V capture in its resulting file size and bandwidth requirements.

Calculating overall on-demand usage

There are three aspects you need to consider, in order to determine the data requirements for providing media playback for students:

  • The data rate and volume of the media from Echo360’s cloud server to each student watching the capture. This is what is provided in the table above.
  • The type of captures typically generated (audio/display? audio/display/video?).
  • The number of students watching media, on campus, at any given time.

Provided below is a sample calculation, using this methodology and substituting the institutions own assumptions a figure for the peak expected bandwidth usage can be estimated.

Example Data – substitute as appropriate:

  • 10 sections use Echo360 to capture lectures.
  • Each section generates an A/D/V capture, at HD quality.
  • Each section has an average of 25 students enrolled in the class.

At most, 250 students may try to view a capture at one time. YOUR data suggests that even during finals week, at peak, 10% of the possible views are happening, but not all at the same time, and not all from on-campus.

Using those figures, let’s assume that during this peak usage time, only 5% of the students who could view a capture are viewing it WHILE on campus, at the same time. That’s 12.5 students. Ok, 13. That half-student is going to step it up at the end of the semester.

So the peak data rate calculation would look something like this:

13 Students x 720 kbps = 9360 kbps or 9.3 Mbps

This is the total bandwidth required to smoothly play back an Echo360 capture to all 13 students on campus at the same time. Remember that if more than this is available at any point during the viewing, the capture is downloaded/buffered locally to the students' devices, lessening the "current" data stream need.

By comparison, a 720p YouTube video requires up to 6 Mbps each. So if your students are watching YouTube and not complaining, viewing classroom content should be no problem.

Second Example:

We've recently learned of an institution using Echo360 for almost 50 courses, including approximately 2800 students. Let's do the same calculation with the same assumptions: during peak week, 10% of the possible views happen, and we'll assume half of those possible views happen from on campus, all at the same time (which is unlikely but hey, it's an example).

  • 10% of 2800 = 280
  • 5% of 2800 (on campus) = 140 views happening at once, on campus
  • 140 views x 720 kbps = 100,800 kbps/101 Mbps

That's a lot more than our original example. Comparatively speaking though, that's 140 students viewing classroom media taking up as much bandwidth as 17 students viewing a YouTube video.
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