[FFmpeg-devel] indeo4/indeo5 inverse quantization

Maxim max_pole
Sat May 29 02:04:25 CEST 2010

Hi crews,

due the fact that quantization schemes of indeo4/indeo5 are quite
different I & Kostya elaborated an unified version. According to that
the base quant tables of the existing indeo5 decoder must be upscaled by
the factor of 2. This let us calculate dequantization factor in the
common way for both codecs using the following equation:

q = (base_tab[scan_pos] * scale_tab[q_level]) >> 9;

Indeo4 doesn't require any scale table so a dummy one is used that
statisfies the following condition:

dummy_scale_tab[q_level] = q_level;

Indeo4 quant tables can be found in the attached "indeo4data.h". Note
that it's for reference only!

It would be very appreciated if someone had an idea how that stuff can
be further optimized/improved. If not - I'll commit it after some time...

Best regards
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