Image Processing Reference
In-Depth Information
Certain codecs are mandated if you decide to present your content on particular
devices. DVDs, for example, mandate MPEG-2. Mobile 3GPP phones require MPEG-4 con-
strained within a particular profile defining the bit rate and picture size.
The kind of material you are compressing may require certain quality-of-service met-
rics that dictate a particular codec. A browsable-quality copy of the video is used as
a proxy in a modern IT-based newsroom to create an edit decision list (EDL) in the pro-
duction workflow. This requires a coding scheme composed entirely of I-frames. The
pixlet codec was designed with this sort of application in mind.
Video Capture
Capturing the video can be done in several ways. If the video was shot on a digital cam-
era or is already in a digital format, then the ingest process is fairly easy. DV cameras can
be accessed with FireWire, as can digital decks.
When ingesting video from an analog source, pre-roll your source material
to avoid syncing issues.
Broadcast equipment may support an Ethernet port that you can access with an FTP
Analog video presents a few more difficulties because it needs to be converted. If it
is possible to transfer to a digital format using broadcast-quality or professional equip-
ment, then that is preferable. Otherwise some kind of bridge or video-input card will be
A bridge is preferable to a video card because it is optimized for transfer and does
not load your CPU as heavily. An AJA Io would be an ideal solution. Video cards such as
those made by Blackmagic Design have built-in video-bridging capability and can convert
from analog to digital as the video is played back.
Low-Quality Domestic Tapes
The quality of what you feed into the input of the compression system will have an enor-
mous effect on the output compression result.
For example, compression of a low-quality VHS recording will always be compro-
mised by the inherent noise that is a “feature” of that format. Old Betamax tapes will fare
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