Sequence Number (Seqno); Tag Times (First, Last); Edus (Elemental Data Units) - Nielsen ID3 User Manual

Sequence Number (Seqno)

The PCM-to-ID3 SDK generates a unique sequence number for each DATA or INFO tag
that it creates. Sequence numbers are consecutive, and INFO tags are numbered in
sequence with DATA tags. A missing sequence number in the detailed tag listing is
usually an indication that the ID3 tag was dropped or delivered out of order sometime
after the PCM-to-ID3 SDK generated it. Out-of-order delivery of INFO tags is acceptable.
DATA tags, however, should appear in the output stream in the same order as the PCM-
to-ID3 SDK generated them.

Tag Times (First, Last)

Each ID3 tag includes a First and Last tag time. These values are derived from the
"current time" setting that your application feeds to the PCM-to-ID3 SDK with each call to
InputAudioData().
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The First tag time identifies the time when the current ID3 tag began to collect
incoming watermarks.
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The Last tag time identifies the time when the ID3 tag was packaged and delivered to
your application.
On average, Nielsen ID3 tags should be 10 seconds long. If the PCM-to-ID3 SDK
receives 10 or more EDUs in less than 10 seconds, however, the tag ends promptly after
the tenth EDU is decoded.
Ideally, the Last tag time of the previous DATA tag equals the First tag time of the current
DATA tag. If there is a gap between tag times, combined with a missing sequence
number, we can be relatively certain that a tag that was generated by the PCM-to-ID3
SDK was dropped. If there is a gap between tag times, but no sequence number is
missing, it is likely that the PCM-to-ID3 SDK was presented a segment of un-
watermarked audio data. In the absence of watermarks, no ID3 tags are generated.

EDUs (Elemental Data Units)

The PCM-to-ID3 SDK receives an audio stream from your application, summarizes the
contents of the watermark by creating an EDU, and stores the EDU in an ID3 tag. This
means that there is a "watermark SID" (the SID in the source watermark) and the EDU is
a representation of that SID. Each ID3 tag may contain up to 10 EDUs.
The following sections give examples and descriptions of some of the typical EDUs.
Fields in blue font in the snippets correspond with blue font in the table that follows each
example.
Release 1.8 Revision F 46
ID3 Tag Validator Application User Manual
Nielsen Confidential