diff options
| -rw-r--r-- | libavcodec/flacenc.c | 23 |
1 files changed, 11 insertions, 12 deletions
diff --git a/libavcodec/flacenc.c b/libavcodec/flacenc.c index e997bca129..3b01a3ba1a 100644 --- a/libavcodec/flacenc.c +++ b/libavcodec/flacenc.c @@ -447,20 +447,19 @@ static void copy_samples(FlacEncodeContext *s, int16_t *samples) #define rice_encode_count(sum, n, k) (((n)*((k)+1))+((sum-(n>>1))>>(k))) +/** + * Solve for d/dk(rice_encode_count) = n-((sum-(n>>1))>>(k+1)) = 0 + */ static int find_optimal_param(uint32_t sum, int n) { - int k, k_opt; - uint32_t nbits[MAX_RICE_PARAM+1]; - - k_opt = 0; - nbits[0] = UINT32_MAX; - for(k=0; k<=MAX_RICE_PARAM; k++) { - nbits[k] = rice_encode_count(sum, n, k); - if(nbits[k] < nbits[k_opt]) { - k_opt = k; - } - } - return k_opt; + int k; + uint32_t sum2; + + if(sum <= n>>1) + return 0; + sum2 = sum-(n>>1); + k = av_log2(n<256 ? FASTDIV(sum2,n) : sum2/n); + return FFMIN(k, MAX_RICE_PARAM); } static uint32_t calc_optimal_rice_params(RiceContext *rc, int porder, |