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authorRostislav Pehlivanov <atomnuker@gmail.com>2018-06-30 08:31:31 +0100
committerRostislav Pehlivanov <atomnuker@gmail.com>2018-07-03 20:15:01 +0100
commit755e618399264d57a64a21115e2bf067b73492e7 (patch)
tree2032e665490e50574a3b744c6330c7028c0a16b6 /tests/checkasm/h264pred.c
parent3c4af577aa50a3d90bbb0e04cfa42a9b2bd1ce07 (diff)
downloadffmpeg-755e618399264d57a64a21115e2bf067b73492e7.tar.gz
lavc: implement an ATRAC9 decoder
This commit implements a full ATRAC9 decoder, a simple low-delay codec developed by Sony and used in most PSVita games, some PS3 games and some PS4 games. Its similar to AAC in that it uses Huffman coded scalefactors but instead of vector quantization it just Huffman codes the spectral coefficients (in a way similar to how Opus splits band energy coding into coarse and fine precision). It opts to write rather large Huffman codes by packing several small coefficients into one Huffman coded symbol, though I don't believe this increases efficiency at all. Band extension implements SBC in a simple way, first it mirrors the lower spectrum onto the higher frequencies and then it uses one of 5 filters to shape it. Noise substitution is implemented via 2 of them. Unlike previous ATRAC codecs, there's no QMF, this is a standard MDCT codec. Based off of the reverse engineering work of Alex Barney. Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
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