Image Processing Reference
so that the content is mapped in a logical manner, then a failed encoder can be swapped
out with a minimum of fuss. The video input is rerouted to another encoder and the con-
figuration file of the stream server is changed to point at a different encoded stream. This
adds to the resilience of the stream.
For high-end operations where you intend to stream hundreds of different programs
simultaneously, there are large encoding systems available from a variety of manufactur-
ers. Sun Microsystems builds massively distributed systems that might be good candi-
dates, or you may want to rack mount hundreds of Linux-based encoders and run them
with some centralized administration. If you are looking for low latency and high quality
at high bit rates then a hardware solution is optimal, but it will be expensive. Over the next
couple of years, as the H.264 codec implementations become more efficient when imple-
mented in software, the hardware solutions may only be used for top-end TV broadcast
distribution or high definition. This applies to D-cinema applications as well, because they
operate at a similar resolution.
Eliminating Problems with Live-Encoded Output
The time that you are most likely to encounter problems is when you are encoding live-
video sources. Some of these issues you may be able to avoid and others you may have to
put up with or deal with in a remedial way. When evaluating your alternative encoder
suppliers, be sure to run some tests with real-world services to observe what happens to
the encoded output.
Summary: What I've Learned About Live Encoding
Live encoding is not very different from offline encoding. The main difference is that it
cannot afford to slow down or stop, even momentarily. Latency is important to be mind-
ful of because any delay leads to buffering issues.
Now that we've looked at bit streams in the previous chapter and live encoding in
this one, let's move on and see how this compressed video might be stored in files.