User Manual

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KONA LHe Plus Installation & Operation Guide — Understanding Typical
HDV Data rate: 19 MB/second high definition720p, 25 MB/second high definition 1080i—supported
by internal system drive
Quality: Excellent
You can use KONA LHe Plus to convert HDV projects to uncompressed—in real time—for
monitoring and/or output. KONA LHe Plus can capture uncompressed from any input, directly
to HDV media. The KONA LHe Plus advanced scaling engine takes the native frame (long GOP
1440 HD) and outputs it via hardware—in real time. Precision AJA circuitry re-sizes the video to
proper 1920 x 1080, providing quick playback of HDV for monitoring and recording.
HDV captures HD images via MPEG2 compression and allows for recording the signal to a
MiniDV tape. This MPEG2 compression is similar to a DVD (although DVD is a program stream vs.
HDV’s transport stream and HDV uses a constant bit rate whereas DVDs use variable bit rates).
The issue for post production is that the HDV transport stream is based around a long-GOP
structure (group of pictures) which produces images based on information over a section of
time, via I, P and B frames; Intraframes, predicted frames and bi-directional frames. Formats that
do not use this scheme treat frames as individual units, as in the progressive formats where a
frame truly is a frame, or as interlaced frames where two fields create the image. Sometimes we
refer to these form ats in contrast to MPEG formats, as I-frame formats where frames can be
easily defined as individual.
Since the fra
mes of HDV have the long GOP structure to define them, herein lies the problem for
post-production; how can we work with the material if we must know what lies before, after and
during? Luckily, the transport stream MPEG2 can be transmitted over IEEE1394 (aka FireWire).
This means that the compressed HD material can be transferred into systems with the
appropriate hardware and software. While this seems like a simple solution for post-
production, it means that the footage must be brought into the system as a rather heavily
compressed format and that the computer must continue to work with the material as a MPEG2
transport stream, which is incredibly processor intensive for the computer.
How does the AJA KONA LHe Plus card connect to HDV and digitize material to uncompressed
HD files for editing—or at the very least, to a lightly compressed I-Frame HD format? The answer
to this is provided in a feature common to many HDV devices: analog HD output via component
video. The component connectors on JVC cameras and decks, along with Sony cameras and
decks, allows for the output of the long GOP MPEG2 data as a standard HD video format such as
720P in the JVC products—or 1080i in the Sony products.
Since the KONA LHe Plus has the ability to digitize analog HD signals, the analog component
output of the HDV devices can simply be connected to the KONA inputs. Note that HD signal
cannot be transported over composite or S-Video (Y/C) cables, so the HDV device must have an
analog component HD output. The KONA LHe Plus also has the ability to ingest analog audio, so
the analog audio outputs of the HDV devices can be sent to the KONA card as well. (Also note
that these analog audio outputs on the HDV devices are usually unbalanced RCA connections
where the KONA card uses balanced XLR style connection so some sort of audio level correction
device, such as a mixer or a stand alone active interface amplifier, should be used for accurately
attenuated audio.)
Finally, you will want to control your device. Where all of the video, audio and timecode
information moved over the FireWire cable, now you are dividing those tasks. Device control is
the most difficult to configure for HDV devices because so few HDV devices have implemented
any form of device control other than IEEE1394. The one notable exception is the JVC BR-HD50
HDV deck which has a remote serial port for RS422 protocol and device control. Check the KONA
LHe Plus support area on the AJA website for a whitepaper on HDV, which gives details on using
KONA LHe Plus with various HDV equipment.
Note: direct capture into HDV media on the LHe is not possible. Direct capture into the LHe
can only be done using uncompressed, DVCPRO HD, or Pro Res. Regarding ProRes 422,
capturing HD resolution ProRes 422 from an HD source requires a Mac Pro with an Intel
Xeon processor.