From b2fe6756e34d1316d0fa799e8a5ace993059c407 Mon Sep 17 00:00:00 2001
From: Justin Ruggles <justin.ruggles@gmail.com>
Date: Wed, 31 Oct 2012 15:40:12 -0400
Subject: lavr: add option for dithering during sample format conversion to s16

---
 libavresample/audio_convert.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

(limited to 'libavresample/audio_convert.c')

diff --git a/libavresample/audio_convert.c b/libavresample/audio_convert.c
index dcf8a39b06..eb3bc1f1de 100644
--- a/libavresample/audio_convert.c
+++ b/libavresample/audio_convert.c
@@ -29,6 +29,8 @@
 #include "libavutil/samplefmt.h"
 #include "audio_convert.h"
 #include "audio_data.h"
+#include "dither.h"
+#include "internal.h"
 
 enum ConvFuncType {
     CONV_FUNC_TYPE_FLAT,
@@ -46,6 +48,7 @@ typedef void (conv_func_deinterleave)(uint8_t **out, const uint8_t *in, int len,
 
 struct AudioConvert {
     AVAudioResampleContext *avr;
+    DitherContext *dc;
     enum AVSampleFormat in_fmt;
     enum AVSampleFormat out_fmt;
     int channels;
@@ -246,10 +249,18 @@ static void set_generic_function(AudioConvert *ac)
     SET_CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, AV_SAMPLE_FMT_DBL)
 }
 
+void ff_audio_convert_free(AudioConvert **ac)
+{
+    if (!*ac)
+        return;
+    ff_dither_free(&(*ac)->dc);
+    av_freep(ac);
+}
+
 AudioConvert *ff_audio_convert_alloc(AVAudioResampleContext *avr,
                                      enum AVSampleFormat out_fmt,
                                      enum AVSampleFormat in_fmt,
-                                     int channels)
+                                     int channels, int sample_rate)
 {
     AudioConvert *ac;
     int in_planar, out_planar;
@@ -263,6 +274,17 @@ AudioConvert *ff_audio_convert_alloc(AVAudioResampleContext *avr,
     ac->in_fmt   = in_fmt;
     ac->channels = channels;
 
+    if (avr->dither_method != AV_RESAMPLE_DITHER_NONE          &&
+        av_get_packed_sample_fmt(out_fmt) == AV_SAMPLE_FMT_S16 &&
+        av_get_bytes_per_sample(in_fmt) > 2) {
+        ac->dc = ff_dither_alloc(avr, out_fmt, in_fmt, channels, sample_rate);
+        if (!ac->dc) {
+            av_free(ac);
+            return NULL;
+        }
+        return ac;
+    }
+
     in_planar  = av_sample_fmt_is_planar(in_fmt);
     out_planar = av_sample_fmt_is_planar(out_fmt);
 
@@ -289,6 +311,15 @@ int ff_audio_convert(AudioConvert *ac, AudioData *out, AudioData *in)
     int use_generic = 1;
     int len         = in->nb_samples;
 
+    if (ac->dc) {
+        /* dithered conversion */
+        av_dlog(ac->avr, "%d samples - audio_convert: %s to %s (dithered)\n",
+                len, av_get_sample_fmt_name(ac->in_fmt),
+                av_get_sample_fmt_name(ac->out_fmt));
+
+        return ff_convert_dither(ac->dc, out, in);
+    }
+
     /* determine whether to use the optimized function based on pointer and
        samples alignment in both the input and output */
     if (ac->has_optimized_func) {
-- 
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