PIX 220i, 240i, 220, 240 User Guide and Technical Information
v. 3.01
Features and specifications are subject to change. Visit www.sounddevices.com for the latest documentation.
30
Playing Back Files on a Computer
Video iles recorded with the Apple ProRes codec require Quicktime to be installed. Quicktime can
be downloaded from
htp://www.apple.com/quicktime/download/
. See
htp://sotware.sounddevices.com/
Apple_ProRes_White_Paper_July_2009.pdf
for more detailed information about the ProRes codec.
Video iles recorded with the Avid DNxHD codec require DNxHD drivers to be installed. Visit
htp://
www.avid.com/dnxhd
to download DNxHD drivers and for more detailed information about the
DNxHD codec.
Synchronization and Timecode
This section gives a concise overview of timecode and video synchronization. This information ap-
plies primarily to the PIX 240i and its advanced timecode and synchronization options; however it is
useful information for PIX 220i and PIX 240i users alike. For information about the PIX 220i’s time-
code capabilities
see PIX 220i Timecode Features
Synchronization of video, audio, and associated timecode while recording video and audio has long
been a problematic area. Situations where several cameras are used can complicate issues further.
There may be sync issues between two (or more) cameras and/or between audio recorders because of
a) ofset and b) drit. In a production environment (during recording), ofset and drit are both terms
to describe a timing problem between the timecode signal from two or more audio or video record-
ers. In a post-production environment (a non-linear editor application), ofset and drit are both
terms to describe a timing problem between two or more audio or video iles.
Ofset (matching the beginning or “head” of a take) occurs because the beginning of takes are not
aligned due to the absence or misuse of timecode. Drit (matching the end or “tail” of a take) oc
-
curs because diferent recorders (audio or camera) run at diferent rates - the beginning of iles from
each may have zero ofset, but by the end they drit apart. The PIX recorders were designed with
these problems in mind and include the most comprehensive and powerful synchronization features
available in a portable recorder. These features can be used to alleviate or eliminate ofset and drit
problems in both production and post-production. While the PIX recorder’s design makes seting the
parameters as easy as possible, a good understanding of synchronization is still necessary to prop-
erly operate the PIX recorder and ensure a trouble-free worklow.
In a camera, the shuter, video circuitry, audio sampling, and timecode all run of of one ‘heartbeat’
from its master internal clock. If this master clock is slightly fast, then the shuter, audio sampling,
and timecode will be slightly fast, and if the master clock is a slightly slow, the shuter etc will be a
bit slightly slow also.
When a PIX recorder’s video input is connected via HDMI or SDI to the camera, this heartbeat is
passed through the HDMI or SDI, and the PIX is synchronized to the camera’s internal clock as well.
The PIX video and audio circuitry is clocked of of this incoming video. The PIX recorder writes iles
based on this clock as well - each audio sample and video frame writen out to the ile is synchro
-
nized to the incoming video. This way, the PIX recorder is always completely in sync with the con-
nected camera - there can never be any drit of audio or video between the camera and the PIX.
Drit problems in a worklow can arise when more than one camera is used on a shoot, as each
camera is driven of of its own internal master clock. Since internal master clock speed will always
vary from camera to camera (and vary based on temperature and time), each camera used will run
at a slightly diferent shuter speed, audio sample rate and timecode rate. This is also true when
recording video on a camera and recording audio on a separate recorder, as each device has its own
internal master clock. Particularly problematic are long takes where there may be signiicant drit
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