CableWorld CW-4412 MPEG-4 Encoder Duo

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light, there’s also shadow, and in the case of CBR easy calculation comes at the expense of changing video quality. The bit rate requirements of fast camera movements or dynamic video content may easily exceed the pre-set constant bitrate (unless it equals the maximum bit rate, which generally is not the case and would waste valuable resources whenever more static content is transmitted), causing the dreaded block artefacts none of us likes to see. This is where VBR kicks in: Whenever video content does not change much, the required bit rate decreases because only few image details need to be compressed. And when all of a sudden dynamic changes in the video content occur the bit rate increases alongside so that the intended video quality after compression can be maintained. On average, the bit rate with VBR is lower than with CBR. And there’s another benefit with VBR: The chance that several variable bit rates within a single transport stream all peak at the very same time is rather low, which means that the overall bandwidth of a transponder’s transport stream with VBR signals can be smaller, while the video quality of the individual signals is higher. Sounds perfect, right? Yes, in theory. In the real world, however, VBR comes with some strings attached. For example, the encoder has to know the low and high bit rate limits that must not be exceeded. Those limits, however, depend entirely on the average bit rate. This means the encoder must analyse the video signal based Web Frontend 19. ENCODER – VIDEO & AUDIO SETUP: This menu option allows to independently configure the output signal. You can select between a constant bitrate (CBR) or a variable bitrate (VBR). Also, you can change other relevant MPEG-4 parameters. 20. ENCODER – MULTIPLEX SETUP: Here you can select the required PIDs for the output stream. This comes very handy, as you can avoid problems with multiplexers, if you configure the PIDs correctly at this stage. Being able to input the desired service name and service provider name is just perfect. 19 21. IP STREAMER – IP STREAMER SETUP: Next you can configure the IP streaming, again independently for each encoder. Just select the mode (Multicast or Unicast) and specify the relevant IP and port and you are set. 22. SETTINGS – WEB INTERFACE SETTINGS: This option lets you configure the network settings for the web interface. The CW-4412 can be controlled through a browser or by means of free applications provided by CableWorld. Both use independent networking configurations, which is actually very convenient. If you cannot access one network, for whatever reason, you can still communicate with the CW-4412 through the alternative way. 21 20 22 24 TELE-audiovision International — The World‘s Leading Digital TV Industry Publication — 11-12/2014 — www.TELE-audiovision.com
23 24 25 on these parameters and then compress the signal accordingly. This is a hugely complex process, and the fact that it frequently has to happen in real-time doesn’t help either. CableWorld does a great job for easing that situation: For one thing, the CW-4412 does not accept incorrect or impossible parameters in the first place. And for another, it shows the formulae required to calculate meaningful parameters: video bit rate >= max. video bit rate video bit rate >= avg. video bit rate 1.5 x avg. video bit rate = max. video bit rate 0 < min. video bit rate
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CableWorld CW-4412 MPEG-4 Encoder Duo

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