[FFmpeg-soc] decoding 7_pt_1.eac3

[Bartlomiej Wolowiec]

On niedziela, 6 kwietnia 2008, Michael Niedermayer wrote:
> On Sat, Apr 05, 2008 at 11:18:55PM +0200, Bartlomiej Wolowiec wrote:
> > Hi,
> > while decoding information from 7_pt_1.eac3 I got unsatisfactory
> > results... I mean that I don't know how is channel_map related to
> > channels in the frame:
> >
> > [ac3 @ 0x8444bb0]channel_mode=7 lfe=1 (channels = 6)
> > [ac3 @ 0x8444bb0]channel_mode=5 lfe=0 (channels = 4)
> >
> > [ac3 @ 0x8444bb0]channel_map = 00001101000000000
>
> channel_map has 16 bits, what you print here has 17 digits
>
> > (set bits: 9 - Lsd/Rsd pair, 11 - Lvh/Rvh pair, 12 - Cvh)
>
> to me this looks like bits 3,4 and 6
>
> [...]

When it reads while using get_bits it gets 0x1a00 value...
Description of bites is strange, because in remaining part of documentation 
there is "normal" order.
So, what is better?
-to read and reverse order of bits. I haven't seen such possibility, so should 
something like this be done:
        ret = (ret & 0x00FF) << 8 | (ret & 0xFF00) >> 8;
        ret = (ret & 0x0F0F) << 4 | (ret & 0xF0F0) >> 4;
        ret = (ret & 0x3333) << 2 | (ret & 0xCCCC) >> 2;
        ret = (ret & 0x5555) << 1 | (ret & 0xAAAA) >> 1;
-write the whole code differently than in eac3 documentation (reverse bits)

-- 
Bartlomiej Wolowiec