  We address the task of advertisement detection in broadcast television
content. While typically approached from a video-only or audio-visual
perspective, we present an audio-only method. Our approach centres on the
detection of short silences which exist at the boundaries between programming
and advertising, as well as between the advertisements themselves. To identify
advertising regions we first locate all points within the broadcast content
with very low signal energy. Next, we use a multiple linear regression model to
reject non-boundary silences based on features extracted from the local context
immediately surrounding the silence. Finally, we determine the advertising
regions based on the long-term grouping of detected boundary silences. When
evaluated over a 26 hour annotated database covering national and commercial
Portuguese television channels we obtain a Matthews correlation coefficient in
excess of 0.87 and outperform a freely available audio-visual approach.
