On Tue, Apr 29, 2014 at 12:12:09AM -0400, Thomas Tsou wrote:
Hi,
> Add a separate, faster convolution decoding implementation for rates
> up to N=4 and constraint lengths of K=5 and K=7, which covers the
> most GSM code uses. The decoding algorithm exploits the symmetric
> structure of the Viterbi add-compare-select (ACS) operation - commonly
> known as the ACS butterfly. This shift-register optimization can be
> found in the well-known text by Dave Forney.
I am not knowledgable enough to comment on the actual viterbi things
so I will focus on the things around it.
> +/* Aligned Memory Allocator
> + * SSE requires 16-byte memory alignment. We store relevant trellis
> values
> + * (accumulated sums, outputs, and path decisions) as 16 bit signed
> integers
> + * so the allocated memory is casted as such.
> + */
> +#define SSE_ALIGN 16
> +
> +static int16_t *vdec_malloc(size_t n)
> +{
> +#ifdef HAVE_SSE3
> + return (int16_t *) memalign(SSE_ALIGN, sizeof(int16_t) * n);
> +#else
> + return (int16_t *) malloc(sizeof(int16_t) * n);
> +#endif
> +}
argh, it would be nice if you could use talloc here but then we would
need to play games and align pointers ourselves. Maybe change the API
to at least have a 'ctx' similar to other talloc API?
> +static void free_trellis(struct vtrellis *trellis)
> +{
> + if (!trellis)
> + return;
> +
> + free(trellis->vals);
> + free(trellis->outputs);
> + free(trellis->sums);
> + free(trellis);
Can you use talloc here?
> + _traceback_rec(dec, state, out, len);
_ is reserved for the system. We might want to avoid using that.
cheers
holger
