"H.264 / AVC Video Code Technology Detailed" video tutorial has been on "CSDN", which details the background, standard protocol and implementation of H.264, and through a practical engineering form to H.264 Standard analysis and implementation, welcome to watch!
"The paper is very shallow, perceived this matter", only the standard document is operated in the form of code, in order to have a sufficient understanding and understanding of the video compression coding standards!
Link address: H.264 / AVC video codec technology detailed
GitHub code address: Click here
In the video stream encoded in the H.264 format, the macroblock structure inevitably contains the prediction structure (except I_PCM mode), which contains information such as pixel block prediction mode. For macroblocks of different prediction modes, their prediction structures are different. From the upper macroblock structure, it can be seen that for partial mode, the prediction information is saved in the MB_PRED () structure, and the SUB_MB_PRED () structure is used for another part mode.
In our version of the H.264 Analyzer SimpleH264Analyzer project, the first macroblock of the first IDR frame we analyzed, and its MB_TYPE is i_nxn. In fact, for all INTRA macroblocks other than I_PCM modes, the prediction structure uses the MB_PRED () structure.
In the standard document, the definition of MB_PRED () is as shown in the following table (just in Intra mode):
As can be seen from the table, the structure of the Intra prediction mode mainly has two groups, indicating 4 × 4 and 8 × 8 mode, respectively, each group contains two elements, respectively represents the prediction mode identification bit and prediction mode value, and the last Chromaticity component prediction mode.
prev_intra4x4_pred_mode_flag and prev_intra8x8_pred_mode_flag: Indicates the intra prediction mode predictive identifier. If the identification bit is 1, the predicted value indicating the intra prediction mode is the actual mode, otherwise it is necessary to transfer the actual intra prediction mode. Prev_intra4x4_pred_mode_flag and prev_intra8x8_pred_mode_flag: Indicates an additional actual intra prediction mode. INTRA_CHROMA_PRED_MODE: indicates the prediction mode of the chroma component, the value ranges [0, 3], represents DC, horizontal, vertical and planar mode, respectively.
EtOAc EtOAc EtOAc Code Different:
IF (M_MB_TYPE == 25)
{
// to do: i-pcm mode ...
}
ELSE IF (m_MB_type == 0)
{
// intra_nxn mode ...
IF (M_PPS_ACTIVE->GET_TRANSFORM_8X8_MODE_FLAG ())
{
M_Transform_Size_8x8_flag = get_bit_at_position (m_psoDB, m_bypeoffset, m_bitoffset);
}
// Get Prediction-block Num ...
IF (m_transform_size_8x8_flag)
{
// using intra_8x8
m_pred_struct = new intrapredstruct [4];
For (int lauma8x8blkidx = 0; luma8x8blkidx < 4; luma8x8blkidx ++)
{
m_pred_struct [luma8x8blkidx] .block_mode = 1;
M_PRED_STRUCT [LUMA8X8BLKIDX] .prev_intra_pred_mode_flag = get_bit_at_position (m_psoDB, m_bypeoffset, m_bitoffset);
IF (! m_pred_struct [luma8x8blkidx] .prev_intra_pred_mode_flag)
{
M_PRED_STRUCT [LUMA8X8BLKIDX] .REM_INTRA_PRED_MODE = GET_UINT_CODE_NUM (m_psoDB, m_bypeoffset, m_bitoffset, 3);
}
}
}
Else
{
// using intra_4x4
m_pred_struct = new intrapredstruct [16];
For (int LUMA4X4BLKIDX = 0; luma4x4blkidx < 16; luma4x4blkidx ++)
{
m_pred_struct [luma4x4blkidx] .block_mode = 0;
M_PRED_STRUCT [LUMA4X4BLKIDX] .prev_intra_pred_mode_flag = get_bit_at_position (m_psoDB, m_bypeoffset, m_bitoffset);
IF (! m_pred_struct [luma4x4blkidx] .prev_intra_pred_mode_flag)
{
M_PRED_STRUCT [LUMA4X4BLKIDX] .REM_INTRA_PRED_MODE = GET_UINT_CODE_NUM (m_psoDB, m_bypeoffset, m_bitoffset, 3);
}
}
}
// intra_chroma_pred_mode
M_Intra_chroma_pred_mode = get_uev_code_num (m_psoDB, m_bypeoffset, m_bitoffset);
}
Else
{
// to do: intra_16x16 mode
}
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More detailed information can be downloaded to Github Download the full project: https://github.com/yinwenjie/simpleh264analyzer
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