[FFmpeg-devel] AAC-Main (round 2)

Alex Converse alex.converse
Sat Nov 8 01:20:45 CET 2008


Hi,

Attached are a series of patches that implements AAC Main in FFmpeg. These
are very similar to the first round. The only major change was avoiding
unnecessary type punning.

While AAC-Main is rarely used, faad2 supports it, flash claims to support it
(I haven't tested this), and we claim to support it but do not.

Notes:
1) Frequency domain prediction is described only in ISO/IEC 13818-7 not in
14496-3.
2) The prediction operation uses 16-bit floats, using 32-bit floats does not
give adequate accuracy so emulation routines to round to 16-bit are
included.
3) As only 16-bit floats are required it could be possible to store the
prediction state with half the memory but I'm not sure how to approach that
situation without resorting to IEEE type punning.

Regards,

Alex Converse
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