Editing MPEG-4 Part 3 (section)

=== Why AAC-SSR was introduced ===
The idea behind AAC-SSR was not only the advantage listed above, but also the possibility of reducing the data rate by removing 1, 2 or 3 of the upper PQF bands. A very simple bitstream splitter can remove these bands and thus reduce the bitrate and sample rate.

Example:
* 4 subbands: bitrate = 128&nbsp;kbit/s, sample rate = 48&nbsp;kHz, f_lowpass = 20&nbsp;kHz
* 3 subbands: bitrate ~ 120&nbsp;kbit/s, sample rate = 48&nbsp;kHz, f_lowpass = 18&nbsp;kHz
* 2 subbands: bitrate ~ 100&nbsp;kbit/s, sample rate = 24&nbsp;kHz, f_lowpass = 12&nbsp;kHz
* 1 subband: bitrate ~  65&nbsp;kbit/s, sample rate = 12&nbsp;kHz, f_lowpass = 6&nbsp;kHz

'''Note:''' although possible, the resulting quality is much worse than typical
for this bitrate. So for normal 64&nbsp;kbit/s AAC LC a bandwidth of 14–16&nbsp;kHz is
achieved by using intensity stereo and reduced NMRs. This degrades audible quality
less than transmitting 6&nbsp;kHz bandwidth with perfect quality.