Recording 103
ALEXA can internally record on Sony SXS PRO cards. These cards have an
ExpressCard34 form factor and are currently available with 8, 16 or 32 GB
storage space.
Card file format
SxS PRO cards have to be formatted in the camera before they can be used
for recording. ALEXA uses an UDF file system. This file system is read-only
for computers, which means data can be copied from the card to another
device, but the data cannot be manipulated on the card itself.
Card preparation
The typical usage cycle of a card is: Format - Record - Copy - Backup -
Verification - Format
Format Before recording, cards have to be formatted in the
camera. The camera always performs a blank format,
which means that the cards contain no meta data and
are not assigned a reel number prior to recording the
first clip. The camera auto-detects cards with a
wrong file system and asks the user to format the
card. ALEXA uses an UDF file system. This file
system is read-only for computer systems, which
minimizes the risk of data corruption.
Record When pressing the REC button, the camera starts to
write a clip to the card. With the first clip, the card is a
assigned a reel number. More information on file
naming later in this chapter.
Copy After recording to the card is finished, either because
it is full, or for any other reason, the data should be
copied to another device to minimize the risk of data
loss. Also, the data should be verified after copying
through checksums to ensure that no error has
occured during the copy process.
Backup The data should actually be copied to two physically
separate destinations, with the first copy being the
"working copy", and the second copy being the
"Backup". These two copy processes can be done in
parallel, as long as the result are two independent
devices containing the verified data.
Format Only when the data has been copied and verified to
two independent devices, the card should be
formatted to remove all data from it. It is also
recommended that the card is formatted by the
person that has verified the copy and backup, so that
the camera crew only receives empty cards. This
fuctions as a security check, so that the crew is
alerted if they receive a card with valid data on it,
which might not have been copied and backed up.
The card can be formatted with any file system, as it
has to be reformatted by the camera anyway.
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