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/*! @file codec.c
*
* @brief Implementation of functions that are common to the
* reference decoder and encoder
*
* @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"
/*!
@brief Initialize the codec state to before encoding or decoding the bitstream
Most of the codec state can be deduced from the decoding parameters.
For example, the dimensions of the first wavelet band in the bitstream
can be deduced from the encoded frame dimensions and the structure of
the wavelet tree.
The encoder will not insert parameters into the bitstream if the values
of the parameters are the same as in the codec state. This routine
should initialize the codec state with correct values if those values
can be inferred by the decoder, otherwise the use incorrect or default
values.
Note that the default encoded format is YUV 4:2:2, but this format is not
supported by the baseline profile encoder so the encoded format must be
explicitly written into the bitstream.
@todo Add more default values required to properly initialize the codec state.
*/
CODEC_ERROR PrepareCodecState(CODEC_STATE *codec)
{
// Initialize the channel to channel number zero
codec->channel_number = 0;
// Initialize the subband number to subband zero (the lowpass band)
codec->subband_number = 0;
// The number of subbands per channel is a constant
codec->subband_count = 10;
// The default precision of pixels in the input frame is ten bits
codec->bits_per_component = 12;
// Force the encoder to insert the encoded dimensions into the bitstream
//codec->encoded.width = 0;
//codec->encoded.height = 0;
/*
TODO: Do not have to encode the display dimensions into the bitstream if the decoder
can infer the display dimensions from the encoded dimensions and format, but must
encode the display dimensions if the encoded dimensions include padding.
TODO: Check that this matches the current decoder implementation.
*/
// Set the default precision for encoding lowpass band coefficients
codec->lowpass_precision = 16;
//TODO: Set more default values in the codec state
return CODEC_ERROR_OKAY;
}
/*!
@brief Reformat a segment value into the encoder version
The version of the encoder that created the clip may be encoded into every sample.
@todo Document the encoder version number format
*/
uint32_t EncoderVersion(uint32_t value)
{
return (((value >> 12) & 0x0F) << 16) |
(((value >> 8) & 0x0F) << 8) |
((value) & 0xFF);
}
/*!
@brief Unpack the version tag value into its components
*/
void SetCodecVersion(uint8_t version[3], uint16_t value)
{
version[0] = (uint8_t)((value >> 12) & 0x0F); // Major version
version[1] = (uint8_t)((value >> 8) & 0x0F); // Minor version
version[2] = (uint8_t)(value & 0xFF); // Revision
}
#if VC5_ENABLED_PART(VC5_PART_IMAGE_FORMATS)
/*!
@brief Return true if the image format is valid
*/
bool ValidImageFormat(IMAGE_FORMAT image_format)
{
if (0 < image_format && image_format < IMAGE_FORMAT_COUNT) {
return true;
}
return false;
}
#endif
/*!
@brief Unpack the tag value into the prescale table
The prescale table contains the prescale value for each wavelet in the
transform. The prescale value is a right shift that is applied to the
input data before the wavelet is computed.
The prescale table is used for all transforms and does not depend on the
channel number.
*/
CODEC_ERROR UpdatePrescaleTable(CODEC_STATE *codec, TAGWORD value)
{
int wavelet_index;
for (wavelet_index = 0; wavelet_index < MAX_WAVELET_COUNT; wavelet_index++)
{
// Unpack the prescale value
int prescale_value = (value >> (14 - wavelet_index * 2)) & 0x03;
assert(0 <= prescale_value && prescale_value < UINT8_MAX);
// Store the prescale value in the codec state
codec->prescale_table[wavelet_index] = (uint_fast8_t)prescale_value;
}
return CODEC_ERROR_OKAY;
}
/*!
@brief Update the flags that describe the frame structure
The frame structure includes characteristics such as interlaced versus
progressive and top or bottom field first.
*/
CODEC_ERROR UpdateFrameStructureFlags(CODEC_STATE *codec, TAGWORD value)
{
codec->progressive = !(value & IMAGE_STRUCTURE_INTERLACED);
codec->top_field_first = !(value & IMAGE_STRUCTURE_BOTTOM_FIELD_FIRST);
codec->frame_inverted = (value & IMAGE_STRUCTURE_BOTTOM_ROW_FIRST);
return CODEC_ERROR_OKAY;
}
/*!
@brief Initialize the codec state using the default constructor
This routine is like a default constructor in C++ as it guarantees that
the codec state is initialized to a know starting state with all pointers
set to NULL and all counters set to zero.
The routine @ref PrepareCodecState is used to set default values for the
codec state prior to decoding a sample.
*/
CODEC_ERROR InitCodecState(CODEC_STATE *state)
{
// Clear the codec state
memset(state, 0, sizeof(CODEC_STATE));
return CODEC_ERROR_OKAY;
}
/*!
@brief Set the flags that determine the band coding
There can be up to 15 different codebooks as specified by the lower
four bigs in the band coding flags. Use the default codebook if the
active codebook is zero.
The baseline profile does not allow difference coding or alternative
codebooks.
*/
CODEC_ERROR SetBandCoding(CODEC_STATE *codec, TAGWORD value)
{
(void) codec;
return CODEC_ERROR_OKAY;
}
/*!
@brief Return true if the specified part is enabled at runtime
This predicate is used to test whether a specific part in the VC-5 standard is
enabled at runtime by this codec implementation.
*/
bool IsPartEnabled(ENABLED_PARTS enabled_parts, int part_number)
{
return ((enabled_parts & VC5_PART_MASK(part_number)) != 0);
}
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