Digital Signal Processing Reference
In-Depth Information
values are entered into the video and audio PES headers at maximum in-
tervals of 700 ms and are called “presentation time stamps” (PTS)
As will be seen later in the section on video coding, the order in which
the compressed picture information is transmitted will differ from the or-
der in which it is recorded. The frame sequence is now scrambled in con-
formity with certain coding rules, a necessary measure in order to save
memory space in the decoder. To recover the original sequence, additional
time stamps must be keyed into the video stream. These are called “decod-
ing time stamps” (DTS) and are also transmitted in the PES header.
An MPEG-2 decoder in a set-top box is then able to decode the video
and audio streams of a program, resulting again in video and audio signals,
either in analog form or in digital form.
max. 4 kbyte
SECTION #0
SECTION #1
SECTION #2
SECTION #3
…
SECTION #n
Fig. 3.20.
Sections and tables
3.3.6 Additional Information in the Transport Stream
(SI/PSI/PSIP)
According to MPEG, the information transmitted in the transport stream is
fairly hardware-oriented, only relating to the absolute minimum require-
ments, as it were. However, this does not make the operation of a set-top
box particularly user-friendly. For example, it makes sense, and is neces-
sary, to transmit program names for identification purposes. It is also de-
sirable to simplify the search for adjacent physical transmission channels.
It is also necessary to transmit electronic program guides (EPG) and time
and date information. In this respect, both the European DVB Project
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