Image Processing Reference
In-Depth Information
So you have a set of video-encoding tools available to the encoder for compressing
the content. You don't have to use all of them, and if your encoding application provides
an “expert mode,” you can usually turn them on and off individually.
If you do use all the tools available to the encoder, the compression becomes increas-
ingly efficient as the more sophisticated tools are deployed. The more tools you use in the
coder, the slower the coder runs and the harder it is to achieve real-time compression.
Using a simpler coder setup might deliver the compression ratio you need at the speed
you can afford. This is what drives the need for faster computing systems when using
later-model codecs.
Systems Design Choices
As a general rule of thumb, hardware solutions will be less versatile and will concentrate
on coding one format well. They will be fast and efficient and usually deliver better results
than you can get from software products.
On the other hand, software solutions will support a wide range of alternative cod-
ing formats and they will be very flexible.
There is also a sort of middle ground that has hardware-augmented software or
software-controlled hardware compression. This would offer some of the advantages of
each approach, possibly conferring the flexibility of software onto a piece of hardware or
allowing a software framework to route compression jobs through a piece of very fast
hardware, which it uses as a resource.
In addition to compression tools, there are transcoders such as Telestream Flip
Factory and batch-oriented, server-based tools for enterprise-wide solutions.
Be wary of lock-in to applications caused by your codec choice. If the appli-
cation is killed or withdrawn, your service delivery could be severely com-
promised or, at best, unsupported.
Hardware Versus Software Coders
There are fundamentally two ways to implement a coder, hardware or software. Some
companies build hybrid solutions with a combination of hardware and software.
If you have to encode a lot of video very quickly or you are intending to encode live
video as it arrives, then you must consider hardware encoding solutions. Real-time perform-
ance is only possible with hardware assistance, and even then there is a time lag between the
input and output of the encoder. This is because the encoding process must look forward and
backward in order to do the best possible encoding job. Forward error correction and the rea-
son why pictures are grouped together into sequences are both covered shortly.
Software encoders have the advantage that they are relatively cheap and work on
general-purpose hardware. High-end Intel processors and the Apple G5 are well suited to
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