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xhe-aac: allow lower bit rates (mono 6 kbit/s, stereo 12 kbit/s) - #185
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The open-source build only has the DASH configuration table, which starts at 12 kbit/s mono and 16 kbit/s stereo. The same tools encode and decode lower (tested with Dream's xHE-AAC receive path, tone test; perceptual quality at the low rates has not been assessed): mono 6, 8 and 10 kbit/s, stereo 12 kbit/s. Stereo 8 and 10 kbit/s cannot be opened by the encoder. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
At 48 kHz output (SBR 4:1, 12 kHz core) the mono SBR tuning table of the quad rate mode starts at 6 kbit/s, so Open failed with an internal error (SBR configuration) below that. Open the first row down to 2 kbit/s and the configuration table row down to 4 kbit/s: mono 4 kbit/s now encodes and the stream decodes (tested through a DRM chain at 4.5 kHz, tones and music; perceptual quality at 4 kbit/s has not been assessed). 2 kbit/s is still rejected. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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The open-source xHE-AAC encoder only carries the DASH configuration table, which starts at 12 kbit/s mono and 16 kbit/s stereo. This lowers the table minimums (two lines in
main_aot_42_dash_oss.c).Tested with the encoder and decoder round trip and with Dream's xHE-AAC receive path (tone test): mono 6, 8 and 10 kbit/s, stereo 12 kbit/s. Stereo 8 and 10 kbit/s cannot be opened by the encoder. Perceptual quality at the low rates has not been assessed.
Replaces #184, which was opened from a branch that also carried unrelated packaging commits.
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