Same but I converted to Opus, because I was trying to squeeze it into as little bandwidth as possible. It was mostly speech content and Opus auto detects and optimizes for speech at low nitrates.
You can download the Opus directly with -f 249 / 250 / 251 (~48kbps / ~80kbps / ~128 kbps respectively, but youtube don't always make them all available, where are -f 140 for the ~128kbps AAC (.m4a) is always available, and often the format code 139 (~48kbps) - the lower bitrates being adequate for most speech based content.
