swresample: add exact_rational option

give high quality resampling
as good as with linear_interp=on
as fast as without linear_interp=on
tested visually with ffplay
ffplay -f lavfi "aevalsrc='sin(10000*t*t)', aresample=osr=48000, showcqt=gamma=5"
ffplay -f lavfi "aevalsrc='sin(10000*t*t)', aresample=osr=48000:linear_interp=on, showcqt=gamma=5"
ffplay -f lavfi "aevalsrc='sin(10000*t*t)', aresample=osr=48000:exact_rational=on, showcqt=gamma=5"

slightly speed improvement
for fair comparison with -cpuflags 0
audio.wav is ~ 1 hour 44100 stereo 16bit wav file
ffmpeg -i audio.wav -af aresample=osr=48000 -f null -
        old         new
real    13.498s     13.121s
user    13.364s     12.987s
sys      0.131s      0.129s

linear_interp=on
        old         new
real    23.035s     23.050s
user    22.907s     22.917s
sys      0.119s     0.125s

exact_rational=on
real    12.418s
user    12.298s
sys      0.114s

possibility to decrease memory usage if soft compensation is ignored

Signed-off-by: Muhammad Faiz <mfcc64@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/libswresample/swresample_internal.h b/libswresample/swresample_internal.h
index 5d61de47af..3828b722cc 100644
--- a/libswresample/swresample_internal.h
+++ b/libswresample/swresample_internal.h
@@ -69,7 +69,7 @@ struct DitherContext {
 };
 
 typedef struct ResampleContext * (* resample_init_func)(struct ResampleContext *c, int out_rate, int in_rate, int filter_size, int phase_shift, int linear,
-                                    double cutoff, enum AVSampleFormat format, enum SwrFilterType filter_type, double kaiser_beta, double precision, int cheby);
+                                    double cutoff, enum AVSampleFormat format, enum SwrFilterType filter_type, double kaiser_beta, double precision, int cheby, int exact_rational);
 typedef void    (* resample_free_func)(struct ResampleContext **c);
 typedef int     (* multiple_resample_func)(struct ResampleContext *c, AudioData *dst, int dst_size, AudioData *src, int src_size, int *consumed);
 typedef int     (* resample_flush_func)(struct SwrContext *c);
@@ -126,6 +126,7 @@ struct SwrContext {
     int filter_size;                                /**< length of each FIR filter in the resampling filterbank relative to the cutoff frequency */
     int phase_shift;                                /**< log2 of the number of entries in the resampling polyphase filterbank */
     int linear_interp;                              /**< if 1 then the resampling FIR filter will be linearly interpolated */
+    int exact_rational;                             /**< if 1 then enable non power of 2 phase_count */
     double cutoff;                                  /**< resampling cutoff frequency (swr: 6dB point; soxr: 0dB point). 1.0 corresponds to half the output sample rate */
     int filter_type;                                /**< swr resampling filter type */
     double kaiser_beta;                                /**< swr beta value for Kaiser window (only applicable if filter_type == AV_FILTER_TYPE_KAISER) */