Comparing Bit Rates For Video And Storage

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Comparing Bit Rates For Video And Storage

To capture, store, playback and output today's wide variety of video formats we work with in a computer editing system, we first need to determine the bit rates of the video format and compare this to the bit rates that of different storage mediums.

Megabits vs. Megabytes

As we saw in the section Bit Rates, bit rates for video formats tend to be quoted in Megabits per second (Mbps or Mbit/sec). For example, DV has a bit rate of 25 Mbit/sec.

Data rates for hard drives tend to be quoted in Megabytes per second (MBps or MByte/sec).

Since these are using two different measurement methods, its difficult to try and figure out how they correspond to one another. We need a way to compare video formats and hard drive performance using the same measurement scale. To do this, we need to convert Mbit/sec to MByte/sec or the other way around. This is actually pretty simple using the following conversion:

1 Byte = 8 Bits

Comparing Bit Rates In Megabytes Per Second

This would be a good way to figure out how much hard drive bandwidth is needed for a particular video format. To compare bit rates using Megabytes per second, we need to convert the video formats from Mbit/sec to MByte/sec:

Take the video format's bite rate in Mbit/sec and divide by 8. The result is MByte/sec.

Using DV for an example, 25Mbit/sec is a little over 3MByte/sec (its actually closer to 3.5 MByte/sec).

Comparing Bit Rates in Megabits Per Second

On the other hand, if you want to compare video formats and hard drive storage in Megabits per second, then use the following conversion:

Take the hard drive's bit rate in MByte/sec and multiply by 8. The result is Mbit/sec.

For example, let's assume a drive data rate is listed as 100 MByte/sec. This equals 800 Mbit/sec.