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Diffstat (limited to 'gpr/source/lib/vc5_common/companding.c')
| -rwxr-xr-x | gpr/source/lib/vc5_common/companding.c | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/gpr/source/lib/vc5_common/companding.c b/gpr/source/lib/vc5_common/companding.c new file mode 100755 index 0000000..00b0fb5 --- /dev/null +++ b/gpr/source/lib/vc5_common/companding.c @@ -0,0 +1,259 @@ +/*! @file companding.c + * + * @brief Implementation of the routines for computing the companding curves + * that is applied to the quantized coefficient magnitudes. + * + * @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" + +//TODO: Change the companding parameter into a global constant + +#ifndef COMPANDING +#define COMPANDING 1 +#define COMPANDING_MORE (54) // Zero means no companding (54 is a good value) +#endif + + +/*! + @brief Maximum coefficient magnitude in the codebook + + @todo Need to calculate the maximum value from the codebook +*/ +const int maximum_codebook_value = 255; + + +/*! + @brief Apply the default companding curve to the specified value + + Note that this companding curve has been superceeded by the cubic curve. +*/ +int32_t CompandedValue(int32_t value) +{ + const int midpoint_rounding = 2; + + int32_t magnitude = absolute(value); + +#if COMPANDING + if (magnitude >= 40) + { + magnitude -= 40; + magnitude += midpoint_rounding; + magnitude >>= 2; + magnitude += 40; + + #if COMPANDING_MORE + if (magnitude >= COMPANDING_MORE) + { + magnitude -= COMPANDING_MORE; + magnitude += midpoint_rounding; + magnitude >>= 2; + magnitude += COMPANDING_MORE; + } +#endif + } +#endif + + // Restore the sign to the companded value + return ((value >= 0) ? magnitude : neg(magnitude)); +} + +/*! + @brief Return the parameter that controls the companding curve + + This parameter does not apply if the cubic companding curve is used. +*/ +uint32_t CompandingParameter() +{ + return COMPANDING_MORE; +} + +/*! + @brief Compute a table of values for the cubic companding curve + + The companding curve is f(x) = x + (x ^ 3 / (255 ^ 3)) * 768 + so the range of coefficient magnitudes from 0 to 255 becomess 0 to 1023. +*/ +CODEC_ERROR ComputeCubicTable(int16_t cubic_table[], int cubic_table_length, int16_t maximum_value) +{ + size_t cubic_table_size = cubic_table_length * sizeof(cubic_table[0]); + int last_cubic_table_index = cubic_table_length - 2; + int16_t last_magnitude; + int16_t index; + + // Clear the cubic table + memset(cubic_table, 0, cubic_table_size); + + for (index = 1; index <= maximum_value; index++) + { + double cubic = index; + + int magnitude = index; + + cubic *= index; + cubic *= index; + cubic *= 768; + //cubic /= 256*256*256; + cubic /= 255*255*255; + + magnitude += (int)cubic; + + //if (mag > 1023) mag = 1023; + if (magnitude > last_cubic_table_index) { + magnitude = last_cubic_table_index; + } + + cubic_table[magnitude] = index; + } + + // Fill unused entries in the cubic table + last_magnitude = 0; + for (index = 0; index < cubic_table_length; index++) + { + if (cubic_table[index]) + { + last_magnitude = cubic_table[index]; + } + else + { + cubic_table[index] = last_magnitude; + } + } + + return CODEC_ERROR_OKAY; +} + +/*! + @brief Invert the companding curve applied during encoding +*/ +int32_t UncompandedValue(int32_t value) +{ +#if 1 //CUBIC_COMPANDING + double cubic; + int32_t magnitude = absolute(value); + + cubic = magnitude; + cubic *= magnitude; + cubic *= magnitude; + cubic *= 768; + //cubic /= 256*256*256; + cubic /= 255*255*255; + + magnitude += (int32_t)cubic; + + // Restore the sign + value = ((value < 0) ? neg(magnitude) : magnitude); +#else + if (40 <= value && value < 264) + { +#if COMPANDING_MORE + if (value >= COMPANDING_MORE) + { + value -= COMPANDING_MORE; + value <<= 2; + value += COMPANDING_MORE; + } +#endif + value -= 40; + value <<= 2; + value += 40; + } + else if (value <= -40) + { + // Apply the inverse companding formula to the absolute value + value = -value; + +#if COMPANDING_MORE + if (value >= COMPANDING_MORE) + { + value -= COMPANDING_MORE; + value <<= 2; + value += COMPANDING_MORE; + } +#endif + value -= 40; + value <<= 2; + value += 40; + + // Restore the sign + value = -value; + } +#endif + + return value; +} + +/*! + @brief Invert the companding curve applied to a pixel +*/ +PIXEL UncompandedPixel(PIXEL value) +{ +#if 1 //CUBIC_COMPANDING + double cubic; + int32_t magnitude = absolute(value); + + cubic = magnitude; + cubic *= magnitude; + cubic *= magnitude; + cubic *= 768; + //cubic /= 256*256*256; + cubic /= 255*255*255; + + magnitude += (int32_t)cubic; + + // Restore the sign + value = ClampPixel((value < 0) ? neg(magnitude) : magnitude); +#else + if (40 <= value && value < 264) + { +#if COMPANDING_MORE + if (value >= COMPANDING_MORE) + { + value -= COMPANDING_MORE; + value <<= 2; + value += COMPANDING_MORE; + } +#endif + value -= 40; + value <<= 2; + value += 40; + } + else if (value <= -40) + { + // Apply the inverse companding formula to the absolute value + value = neg(value); + +#if COMPANDING_MORE + if (value >= COMPANDING_MORE) + { + value -= COMPANDING_MORE; + value <<= 2; + value += COMPANDING_MORE; + } +#endif + value -= 40; + value <<= 2; + value += 40; + + // Restore the sign + value = neg(value); + } +#endif + + return value; +} + |