Guys,
Have any of you looked closely at this? It comes straight from the spec
for a2dp on page 66:
/* Build a 80 values vector U */
for (i = 0; i <= 4; i++) {
for (j = 0; j < 8; j++) {
state->U[ch][i * 16 + j] = state->V[ch][i * 32 + j];
state->U[ch][i * 16 + j + 8] = state->V[ch][i * 32 + j + 24];
}
}
But isn't this code only populating u[ch][0..63] and not through 79 like
the comment suggests? So the u[ch][64..79] terms are always 0 right?
This isn't the only thing that looks wrong in the spec. We also have a
sliding window of v[] values that moves 16 values in each pass. The
vector is 160 elements long even though the code above never accesses
anything beyond the 128th value!
It's amazing this stuff even works as poorly specified as it is :(
BTW, in our code it looks like sbc_synthesize_eight was multiplying
sbc_proto_8_80 by -4 where it should be -8. I changed that in cvs.
Brad
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Peter
> outer loop goes from i=0 up to i=4 -> 5 times * 8 * 2 = 80
Yes, thanks... I missed the <= (working too late).
I also remembered that Henryk was always testing the decoder against sbc
files on the filesystem which simplifies testing. I'm going to have
another whack at the simplification step and then try unrolling things.
Brad
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Hi,
outer loop goes from i=0 up to i=4 -> 5 times * 8 * 2 = 80
Ciao,
Peter
On Sat, 3 Sep 2005, Brad Midgley wrote:
> Guys,
>
> Have any of you looked closely at this? It comes straight from the spec
> for a2dp on page 66:
>
>
> /* Build a 80 values vector U */
> for (i = 0; i <= 4; i++) {
> for (j = 0; j < 8; j++) {
> state->U[ch][i * 16 + j] = state->V[ch][i * 32 + j];
> state->U[ch][i * 16 + j + 8] = state->V[ch][i * 32 + j + 24];
> }
> }
>
> But isn't this code only populating u[ch][0..63] and not through 79 like
> the comment suggests? So the u[ch][64..79] terms are always 0 right?
>
> This isn't the only thing that looks wrong in the spec. We also have a
> sliding window of v[] values that moves 16 values in each pass. The
> vector is 160 elements long even though the code above never accesses
> anything beyond the 128th value!
>
> It's amazing this stuff even works as poorly specified as it is :(
>
> BTW, in our code it looks like sbc_synthesize_eight was multiplying
> sbc_proto_8_80 by -4 where it should be -8. I changed that in cvs.
>
> Brad
>
>
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> SF.Net email is Sponsored by the Better Software Conference & EXPO
> September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices
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> _______________________________________________
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