Image Processing Reference
Chapter 30 and Appendix C describe some more software-based encoding solutions;
Appendix L describes the players and the formats they support.
Sizes of Live-Encoded Pictures
You should check the parameter settings on your live encoder carefully to ensure that you
are correctly encoding the full picture. For performance reasons, some earlier models of
the live-encoding tools will drop one or another of the fields when presented with an inter-
laced input. This yields a reasonably good quality output, but at half the resolution in the
Y-axis. The X-axis will be scaled accordingly. If you are encoding from an analog source
through higher-performance hardware, the encoding process may support full-frame,
The lower-resolution encoding is fine for web-based video services but may not be
what you require for the next generation of IPTV delivery.
Building Reliable Live-Encoder Farms
Live encoding on a small scale is generally easy to set up, since you just install a video-
input card into a reasonably high-performance desktop computer and run one of the live
encoders from Microsoft, Real Networks, Apple, or Sorensen. Envivio makes some very
good and fast hardware-based encoders, but these tend to be out of the reach of small proj-
ects for reasons of cost. Appendix B lists some alternative hardware suppliers if you want
to investigate their products.
Medium-scale solutions may be addressed in the same way by setting up multiple
machines. If you have big powerful server-sized boxes with multiple processors you may
be inclined to run several live-stream encoders on them at once. Running these in a UNIX
framework with the encoder driven by a command line and enclosing that within an end-
less loop restarts the encoder automatically if it crashes. This works just fine for Real
Networks encoders running on a Linux platform.
This puts all your eggs into one rather large basket and if you prefer to offset the
risks, then you could deploy multiple cheaper boxes, each one encoding a single stream.
If some routing mechanism is provided at the input and the output stream files are named