Add u8 format to FormatConverter

This is compatible with some tools like welle.io that take
u8 input

4 files changed, 37 insertions, 12 deletions

diff --git a/doc/example.ini b/doc/example.ini
index f8cec36..56adcb2 100644
--- a/doc/example.ini
+++ b/doc/example.ini
@@ -156,6 +156,9 @@ output=uhd
 ; effectively mapping the gainmode VAR range of -50000 -- 50000
 ; to -128 -- 128. For other gainmodes, use the digital_gain setting
 ; to make sure you don't create clipping.
+;
+; The format u8 is the same as s8, except that the values are mapped
+; between 0 and 255.
 ;format=s8
 
 ; The output file:
diff --git a/src/DabMod.cpp b/src/DabMod.cpp
index 4e4cdab..88c7524 100644
--- a/src/DabMod.cpp
+++ b/src/DabMod.cpp
@@ -197,8 +197,11 @@ static shared_ptr<ModOutput> prepare_output(
                 s.normalise = 1.0 / normalise_factor_file_var;
             output = make_shared<OutputFile>(s.outputName);
         }
-        else if (s.fileOutputFormat == "s8") {
+        else if (s.fileOutputFormat == "s8" or
+                s.fileOutputFormat == "u8") {
             // We must normalise the samples to the interval [-127.0; 127.0]
+            // The formatconverter will add 127 for u8 so that it ends up in
+            // [0; 255]
             s.normalise = 127.0f / normalise_factor;
 
             output = make_shared<OutputFile>(s.outputName);
@@ -284,8 +287,10 @@ int launch_modulator(int argc, char* argv[])
     modulator_data m;
 
     shared_ptr<FormatConverter> format_converter;
-    if (mod_settings.useFileOutput and mod_settings.fileOutputFormat == "s8") {
-        format_converter = make_shared<FormatConverter>();
+    if (mod_settings.useFileOutput and
+            (mod_settings.fileOutputFormat == "s8" or
+             mod_settings.fileOutputFormat == "u8")) {
+        format_converter = make_shared<FormatConverter>(mod_settings.fileOutputFormat);
     }
 
     auto output = prepare_output(mod_settings);
diff --git a/src/FormatConverter.cpp b/src/FormatConverter.cpp
index 89b3274..6826972 100644
--- a/src/FormatConverter.cpp
+++ b/src/FormatConverter.cpp
@@ -2,7 +2,7 @@
    Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
    the Queen in Right of Canada (Communications Research Center Canada)
 
-   Copyright (C) 2014
+   Copyright (C) 2017
    Matthias P. Braendli, matthias.braendli@mpb.li
 
     http://opendigitalradio.org
@@ -39,8 +39,10 @@
 #  include <xmmintrin.h>
 #endif
 
-FormatConverter::FormatConverter(void) :
-    ModCodec() { }
+FormatConverter::FormatConverter(const std::string& format) :
+    ModCodec(),
+    m_offset_by_127(format == "u8")
+{ }
 
 /* Expect the input samples to be in the range [-255.0, 255.0] */
 int FormatConverter::process(Buffer* const dataIn, Buffer* dataOut)
@@ -54,6 +56,8 @@ int FormatConverter::process(Buffer* const dataIn, Buffer* dataOut)
     float* in = reinterpret_cast<float*>(dataIn->getData());
 
 #if 0
+#error "TODO: SSE FormatConvert does not support u8 yet"
+
     // Disabled because subscripting a __m64 doesn't seem to work
     // on all platforms.
 
@@ -84,11 +88,20 @@ int FormatConverter::process(Buffer* const dataIn, Buffer* dataOut)
         out[j+3]  = b4[0];
     }
 #else
-    int8_t* out = reinterpret_cast<int8_t*>(dataOut->getData());
-
     // Slow implementation that uses _ftol()
-    for (size_t i = 0; i < sizeIn; i++) {
-        out[i] = in[i];
+    if (m_offset_by_127) {
+        uint8_t* out = reinterpret_cast<uint8_t*>(dataOut->getData());
+
+        for (size_t i = 0; i < sizeIn; i++) {
+            out[i] = in[i] + 128;
+        }
+    }
+    else {
+        int8_t* out = reinterpret_cast<int8_t*>(dataOut->getData());
+
+        for (size_t i = 0; i < sizeIn; i++) {
+            out[i] = in[i];
+        }
     }
 #endif
 
diff --git a/src/FormatConverter.h b/src/FormatConverter.h
index 86ce347..ce848b6 100644
--- a/src/FormatConverter.h
+++ b/src/FormatConverter.h
@@ -2,7 +2,7 @@
    Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Her Majesty
    the Queen in Right of Canada (Communications Research Center Canada)
 
-   Copyright (C) 2014
+   Copyright (C) 2017
    Matthias P. Braendli, matthias.braendli@mpb.li
 
     http://opendigitalradio.org
@@ -35,6 +35,7 @@
 #include "porting.h"
 #include "ModPlugin.h"
 #include <complex>
+#include <string>
 #include <stdint.h>
 
 typedef std::complex<float> complexf;
@@ -42,10 +43,13 @@ typedef std::complex<float> complexf;
 class FormatConverter : public ModCodec
 {
     public:
-        FormatConverter(void);
+        FormatConverter(const std::string& format);
 
         int process(Buffer* const dataIn, Buffer* dataOut);
         const char* name();
+
+    private:
+        bool m_offset_by_127 = false;
 };