Data Rates and Storage Devices
The data rate of the video you capture depends on the format of the source video and
the codec you use for capture. If you are capturing low data rate video, chances are you
can use more inexpensive storage devices. If you need to capture extremely high data
rate video, you may need a faster hard disk. Here are some examples of data rates for
common capture formats:
Whatever disk drive technology you decide to use, your storage disk’s sustained
transfer speed must be fast enough to keep up with the data rate. Depending on the
data rate of the video you’re capturing, a single drive may or may not be enough.
For example, if you plan to capture uncompressed SD video at 24 megabytes per
second (MB/sec.), it’s unlikely that a single hard disk will be able to record the data fast
enough. Even if you somehow successfully get the data on disk, Final Cut Pro may drop
frames during playback or output.
Typical data rate
OfflineRT (using Photo JPEG)
Varies between 300 and 500 KB/sec.
25:1 Motion JPEG (M-JPEG)
DVCPRO HD (1080i60)
DVCPRO HD 720p60)
DVCPRO HD (720p24)
2:1 Motion JPEG (M-JPEG)
Uncompressed SD video
1080 29.97i HD video
1080 29.97i HD video
Determining Your Hard Disk Storage Options
If your hard disk or its connection to your computer does not support the data rate of
your video format, you need to consider three factors:
Â Sustained transfer speed is a measurement of how fast data can be written to a disk in
MB/sec. When you use a video interface that utilizes M-JPEG compression, the
sustained transfer speed of your hard disk determines the maximum quality of the
video you can capture. Disks with a higher sustained transfer speed allow you to
capture video media files with a higher data rate, which results in higher visual quality.
Â Seek time is a measurement of how quickly data stored on the disk can be accessed
in milliseconds (ms). Low seek times are important when playing back an edited
sequence of clips, because the disk must spend a lot of time searching for the next
clip to play.
Â A faster spindle speed increases a disk’s sustained transfer rate (typical multimedia
disks run at 7200 revolutions per minute, or rpm). However, the faster a hard disk
runs the more it heats up, so ventilation is important when you install disks internally
or in external enclosures.
Note: Removable media drives such as Jaz, Zip, and CD-RW drives are not suitable for
video capture and playback because of their low data transfer rates.