ARRIS DCX3600 User Guide - Manual (Page 21)

Product Overview
Set-Top Entertainment Hub DCX3600-M • User Guide 14
365-095-25659 x.1
Transcoding
With the rising popularity of handheld video playback devices such as smartphones, tablets, and
portable game consoles, consumers are no longer required to sit down in front of their
televisions to enjoy their favorite broadcast programs. However, traditional television
programming is not broadcast in formats that are ideally suited for playback on these types of
handheld devices.
The DCX3600-M is equipped with an integrated dual session transcoder that allows it to convert
broadcast television content into audio and video formats that are more ideally suited for
playback on handheld video devices such as tablets and smartphones. The DCX3600-M can
transcode up to two broadcast television programs simultaneously, converting them from
formats intended to be viewed on a television (with a cable set-top box such as the DCX3600-M)
into formats that can be easily streamed across the in-home wireless (WiFi) network for playback
on two handheld devices in or around the home
7
The Basics of Transcoding
.
The majority of digital television programs broadcast on the cable system make use of two
primary digital encoding formats: MPEG-2 for video and Dolby Digital for audio. The DCX3600-M,
like all cable set-top box units, is specifically designed to receive and decode video and audio
transmitted in these formats. However, many of today’s handheld video devices have limited
capability to decode MPEG-2 video or Dolby Digital audio. In addition, MPEG-2 video (especially
High Definition video) requires a great deal of bandwidth to transmit within the home. Wireless
networks, particularly those using 2.4 GHz 802.11b/g/n connections, can have difficulty
streaming MPEG-2 high definition video services reliably due to their high sustained bandwidth
requirements.
The integrated transcoder in the DCX3600-M converts broadcast television services into formats
that are more likely to be supported by modern handheld playback devices and also require
much less bandwidth to stream across the in-home wireless network. The transcoder decodes
the MPEG-2 video of broadcast television services and re-encodes using the much more
efficient MPEG-4 (Advanced Video Coding) format. Video which is encoded using the AVC format
requires approximately half the transmission bandwidth of video encoded using the MPEG-2
format for roughly the same picture quality. This 50% (or greater) reduction in bandwidth means
that the in-home wireless network can more easily stream the video service to handheld
playback devices with much fewer interruptions and rebuffering attempts.
The transcoder also converts the broadcast television audio soundtrack from the Dolby Digital
format to the AAC (Advanced Audio Coding) format. While the bandwidth savings can also be as
high as 50% in performing this conversion, it is fairly inconsequential since the bandwidth to
7 Note that the amount of data that can be streamed over a wireless network is directly related to signal quality
(strength) between the wireless access point and the wireless station (such as a laptop computer, smartphone,
tablet, etc.). The further a station “roams” from the access point, the weaker the received wireless signal strength. If
a station is too far from the access point, the signal quality may be reduced to a point where the station cannot
properly receive and display television programming that is being transcoded and streamed by the DCX3600-M.