• Rostislav Pehlivanov's avatar
    lavc: implement an ATRAC9 decoder · 755e6183
    Rostislav Pehlivanov authored
    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: 's avatarRostislav Pehlivanov <atomnuker@gmail.com>
    755e6183
atrac9dec.c 30.3 KB