From afcf0795c44260f54e74ec854297de439e7562c3 Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Sun, 22 Dec 2013 17:39:26 +0100 Subject: [PATCH] pcm/Volume: improved dithering Instead of just adding a rectangular random value before shifting back to the normal scale, use the existing PcmDither library. --- NEWS | 2 ++ src/pcm/PcmDither.cxx | 13 +++++++++++ src/pcm/PcmDither.hxx | 12 ++++++++++ src/pcm/Volume.cxx | 47 +++++++++++++++++++++++----------------- src/pcm/Volume.hxx | 2 ++ test/test_pcm_volume.cxx | 5 +++-- 6 files changed, 59 insertions(+), 22 deletions(-) diff --git a/NEWS b/NEWS index 387a1a597..bd7ed3e91 100644 --- a/NEWS +++ b/NEWS @@ -3,6 +3,8 @@ ver 0.19 (not yet released) - new commands "addtagid", "cleartagid" * input - alsa: new input plugin +* filter + - volume: improved software volume dithering * new resampler option using libsoxr ver 0.18.6 (2013/12/24) diff --git a/src/pcm/PcmDither.cxx b/src/pcm/PcmDither.cxx index f07d0b343..d9d4d28ca 100644 --- a/src/pcm/PcmDither.cxx +++ b/src/pcm/PcmDither.cxx @@ -62,6 +62,19 @@ PcmDither::Dither(T sample) return output >> scale_bits; } +template +inline ST +PcmDither::DitherShift(ST sample) +{ + static_assert(sizeof(ST) * 8 > SBITS, "Source type too small"); + static_assert(SBITS > DBITS, "Non-positive scale_bits"); + + static constexpr ST MIN = -(ST(1) << (SBITS - 1)); + static constexpr ST MAX = (ST(1) << (SBITS - 1)) - 1; + + return Dither(sample); +} + template inline typename DT::value_type PcmDither::DitherConvert(typename ST::value_type sample) diff --git a/src/pcm/PcmDither.hxx b/src/pcm/PcmDither.hxx index fdcdb1f6a..473a45ac3 100644 --- a/src/pcm/PcmDither.hxx +++ b/src/pcm/PcmDither.hxx @@ -32,6 +32,18 @@ public: constexpr PcmDither() :error{0, 0, 0}, random(0) {} + /** + * Shift the given sample by #SBITS-#DBITS to the right, and + * apply dithering. + * + * @param ST the input sample type + * @param SBITS the input bit width + * @param DBITS the output bit width + * @param sample the input sample value + */ + template + ST DitherShift(ST sample); + void Dither24To16(int16_t *dest, const int32_t *src, const int32_t *src_end); diff --git a/src/pcm/Volume.cxx b/src/pcm/Volume.cxx index 0ccfe03b5..6347657c6 100644 --- a/src/pcm/Volume.cxx +++ b/src/pcm/Volume.cxx @@ -25,62 +25,69 @@ #include "util/ConstBuffer.hxx" #include "util/Error.hxx" +#include "PcmDither.cxx" // including the .cxx file to get inlined templates + #include #include template> static inline typename Traits::value_type -pcm_volume_sample(typename Traits::value_type _sample, +pcm_volume_sample(PcmDither &dither, + typename Traits::value_type _sample, int volume) { typename Traits::long_type sample(_sample); - sample = (sample * volume + pcm_volume_dither() + - PCM_VOLUME_1S / 2) - >> PCM_VOLUME_BITS; - - return PcmClamp(sample); + return dither.DitherShift(sample * volume); } template> static void -pcm_volume_change(typename Traits::pointer_type dest, +pcm_volume_change(PcmDither &dither, + typename Traits::pointer_type dest, typename Traits::const_pointer_type src, typename Traits::const_pointer_type end, int volume) { while (src < end) { const auto sample = *src++; - *dest++ = pcm_volume_sample(sample, volume); + *dest++ = pcm_volume_sample(dither, sample, volume); } } static void -pcm_volume_change_8(int8_t *dest, const int8_t *src, const int8_t *end, +pcm_volume_change_8(PcmDither &dither, + int8_t *dest, const int8_t *src, const int8_t *end, int volume) { - pcm_volume_change(dest, src, end, volume); + pcm_volume_change(dither, dest, src, end, volume); } static void -pcm_volume_change_16(int16_t *dest, const int16_t *src, const int16_t *end, +pcm_volume_change_16(PcmDither &dither, + int16_t *dest, const int16_t *src, const int16_t *end, int volume) { - pcm_volume_change(dest, src, end, volume); + pcm_volume_change(dither, dest, src, end, volume); } static void -pcm_volume_change_24(int32_t *dest, const int32_t *src, const int32_t *end, +pcm_volume_change_24(PcmDither &dither, + int32_t *dest, const int32_t *src, const int32_t *end, int volume) { - pcm_volume_change(dest, src, end, volume); + pcm_volume_change(dither, dest, src, end, + volume); } static void -pcm_volume_change_32(int32_t *dest, const int32_t *src, const int32_t *end, +pcm_volume_change_32(PcmDither &dither, + int32_t *dest, const int32_t *src, const int32_t *end, int volume) { - pcm_volume_change(dest, src, end, volume); + pcm_volume_change(dither, dest, src, end, volume); } static void @@ -143,28 +150,28 @@ PcmVolume::Apply(ConstBuffer src) gcc_unreachable(); case SampleFormat::S8: - pcm_volume_change_8((int8_t *)data, + pcm_volume_change_8(dither, (int8_t *)data, (const int8_t *)src.data, (const int8_t *)end, volume); break; case SampleFormat::S16: - pcm_volume_change_16((int16_t *)data, + pcm_volume_change_16(dither, (int16_t *)data, (const int16_t *)src.data, (const int16_t *)end, volume); break; case SampleFormat::S24_P32: - pcm_volume_change_24((int32_t *)data, + pcm_volume_change_24(dither, (int32_t *)data, (const int32_t *)src.data, (const int32_t *)end, volume); break; case SampleFormat::S32: - pcm_volume_change_32((int32_t *)data, + pcm_volume_change_32(dither, (int32_t *)data, (const int32_t *)src.data, (const int32_t *)end, volume); diff --git a/src/pcm/Volume.hxx b/src/pcm/Volume.hxx index c31aafb6e..50742225f 100644 --- a/src/pcm/Volume.hxx +++ b/src/pcm/Volume.hxx @@ -23,6 +23,7 @@ #include "PcmPrng.hxx" #include "AudioFormat.hxx" #include "PcmBuffer.hxx" +#include "PcmDither.hxx" #include #include @@ -87,6 +88,7 @@ class PcmVolume { unsigned volume; PcmBuffer buffer; + PcmDither dither; public: PcmVolume() diff --git a/test/test_pcm_volume.cxx b/test/test_pcm_volume.cxx index bba5d3bbf..c3a261f7a 100644 --- a/test/test_pcm_volume.cxx +++ b/test/test_pcm_volume.cxx @@ -60,8 +60,9 @@ TestVolume(G g=G()) const auto _dest = ConstBuffer::FromVoid(dest); for (unsigned i = 0; i < N; ++i) { - CPPUNIT_ASSERT(_dest.data[i] >= (_src[i] - 1) / 2); - CPPUNIT_ASSERT(_dest.data[i] <= _src[i] / 2 + 1); + const auto expected = (_src[i] + 1) / 2; + CPPUNIT_ASSERT(_dest.data[i] >= expected - 4); + CPPUNIT_ASSERT(_dest.data[i] <= expected + 4); } pv.Close();