1 files changed, 58 insertions, 0 deletions
diff --git a/gpr/source/lib/vc5_common/logcurve.c b/gpr/source/lib/vc5_common/logcurve.c
new file mode 100755
index 0000000..45aecbf
--- /dev/null
+++ b/gpr/source/lib/vc5_common/logcurve.c
@@ -0,0 +1,58 @@
+/*! @file logcurve.c
+ *
+ *  @brief Implementation of functions used to do log conversion.
+ *
+ *  @version 1.0.0
+ *
+ *  (C) Copyright 2018 GoPro Inc (http://gopro.com/).
+ *
+ *  Licensed under either:
+ *  - Apache License, Version 2.0, http://www.apache.org/licenses/LICENSE-2.0
+ *  - MIT license, http://opensource.org/licenses/MIT
+ *  at your option.
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#include "common.h"
+
+uint16_t EncoderLogCurve[LOG_CURVE_TABLE_LENGTH];
+
+uint16_t DecoderLogCurve[LOG_CURVE_TABLE_LENGTH];
+
+void SetupDecoderLogCurve(void)
+{
+    int i;
+    const int log_table_size = sizeof(DecoderLogCurve) / sizeof(DecoderLogCurve[0]);
+    
+    const int max_16_bit = (1 << 16) - 1;
+    
+    for( i = 0; i < log_table_size; i++ )
+    {
+        //input 12-bit, output 16-bit
+        float input = i;
+        float output = max_16_bit * (pow(113.0, input/4095.0) - 1.0)/112.0;
+        
+        DecoderLogCurve[i]  = minimum( (int)output, max_16_bit );
+    }
+}
+
+void SetupEncoderLogCurve(void)
+{
+    int i;
+    const int max_input_val = LOG_CURVE_TABLE_LENGTH - 1;
+    
+    for( i = 0; i < LOG_CURVE_TABLE_LENGTH; i++ )
+    {
+        //input 16-bit, output 12-bit
+        float input = maximum( 0, i );
+        float output = 4095.0 * (log10(input/max_input_val * 112.0 + 1.0)/log10(113));
+
+        EncoderLogCurve[i]  = ( (uint16_t)output );
+    }
+}
+