H.264 reference frame List Management Analysis -- Analysis of related functions in JM (medium)

This article describes several functions related to reference frame re-sorting.

[Cpp]
/*!
**************************************** ********************************
* \ Brief
* Reordering process for short-term reference pictures short-term reference frame Reordering
*
**************************************** ********************************
*/
Static void reorder_short_term (StorablePicture ** RefPicListX, int num_ref_idx_lX_active_minus1, int picNumLX, int * refIdxLX)
{
Int cIdx, nIdx;
 
StorablePicture * picLX;
 
PicLX = get_short_term_pic (picNumLX );//! <Obtain the corresponding short-term reference frame based on the given picNumLX
 
For (cIdx = num_ref_idx_lX_active_minus1 + 1; cIdx> * refIdxLX; cIdx --)
RefPicListX [cIdx] = RefPicListX [cIdx-1]; //! <Move the reference frames after refIdxLX in sequence

RefPicListX [(* refIdxLX) ++] = picLX ;//! <Save the specified picNumLX short-term reference frame to the refIdxLX position
 
NIdx = * refIdxLX;
 
For (cIdx = * refIdxLX; cIdx <= num_ref_idx_lX_active_minus1 + 1; cIdx ++)
If (RefPicListX [cIdx]) www.2cto.com
If (RefPicListX [cIdx]-> is_long_term) | (RefPicListX [cIdx]-> pic_num! = PicNumLX ))//! <This operation overwrites the reference frame whose serial number is picNumLX in the reference frame list.
RefPicListX [nIdx ++] = RefPicListX [cIdx];
 
}
 

[Cpp]
/*!
**************************************** ********************************
* \ Brief
* Returns short term pic with given picNum Returns the short-term reference frame of the given picNum number
*
**************************************** ********************************
*/
Static StorablePicture * get_short_term_pic (int picNum)
{
Unsigned I;
 
For (I = 0; I <dpb. ref_frames_in_buffer; I ++ )//! <Traverse reference frames in dpb
{
If (img-> structure = FRAME )//! <Frame mode
{
If (dpb. fs_ref [I]-> is_reference = 3)
If ((! Dpb. fs_ref [I]-> frame-> is_long_term) & (dpb. fs_ref [I]-> frame-> pic_num = picNum ))
Return dpb. fs_ref [I]-> frame ;//! <Find the short-term reference frame with pic_num equal to picNum and not a long-term reference frame, and return
}
Else //! <Field mode (omitted)
{
If (dpb. fs_ref [I]-> is_reference & 1)
If ((! Dpb. fs_ref [I]-> top_field-> is_long_term) & (dpb. fs_ref [I]-> top_field-> pic_num = picNum ))
Return dpb. fs_ref [I]-> top_field;
If (dpb. fs_ref [I]-> is_reference & 2)
If ((! Dpb. fs_ref [I]-> bottom_field-> is_long_term) & (dpb. fs_ref [I]-> bottom_field-> pic_num = picNum ))
Return dpb. fs_ref [I]-> bottom_field;
}
}
// Return NULL;
Return no_reference_picture;
}

 

[Cpp]
/*!
**************************************** ********************************
* \ Brief
* Reordering process for long-term reference pictures
*
**************************************** ********************************
*/
Static void reorder_long_term (StorablePicture ** RefPicListX, int num_ref_idx_lX_active_minus1, int LongTermPicNum, int * refIdxLX)
{
Int cIdx, nIdx;
 
StorablePicture * picLX;
 
PicLX = get_long_term_pic (LongTermPicNum );//! <Obtain the corresponding long-term reference frame of the given LongTermPicNum
 
For (cIdx = num_ref_idx_lX_active_minus1 + 1; cIdx> * refIdxLX; cIdx --)
RefPicListX [cIdx] = RefPicListX [cIdx-1]; //! <Shift the reference frames after refIdxLX to the right in sequence

RefPicListX [(* refIdxLX) ++] = picLX ;//! <Save LongTermPicNum's long-term reference frame to the refIdxLX position
 
NIdx = * refIdxLX;
 
For (cIdx = * refIdxLX; cIdx <= num_ref_idx_lX_active_minus1 + 1; cIdx ++)
If (RefPicListX [cIdx])
If ((! RefPicListX [cIdx]-> is_long_term) | (RefPicListX [cIdx]-> long_term_pic_num! = LongTermPicNum ))//! <Duplicate reference frames with the serial number LongTermPicNum can be overwritten.
RefPicListX [nIdx ++] = RefPicListX [cIdx];
}
[Cpp]
<Pre class = "cpp" name = "code"> /*!
**************************************** ********************************
* \ Brief
* Returns long term pic with given LongtermPicNum
*
**************************************** ********************************
*/
Static StorablePicture * get_long_term_pic (int LongtermPicNum)
{
Unsigned I;
 
For (I = 0; I <dpb. ltref_frames_in_buffer; I ++ )//! <Traverse all long-term reference frames in dpb
{
If (img-> structure = FRAME )//! <Frame mode
{
If (dpb. fs_ltref [I]-> is_reference = 3)
If (dpb. fs_ltref [I]-> frame-> is_long_term) & (dpb. fs_ltref [I]-> frame-> long_term_pic_num = LongtermPicNum ))
Return dpb. fs_ltref [I]-> frame ;//! <Find the long-term reference frame with long_term_pic_num equal to LongtermPicNum and return
}
Else //! <Field mode (omitted)
{
If (dpb. fs_ltref [I]-> is_reference & 1)
If (dpb. fs_ltref [I]-> top_field-> is_long_term) & (dpb. fs_ltref [I]-> top_field-> long_term_pic_num = LongtermPicNum ))
Return dpb. fs_ltref [I]-> top_field;
If (dpb. fs_ltref [I]-> is_reference & 2)
If (dpb. fs_ltref [I]-> bottom_field-> is_long_term) & (dpb. fs_ltref [I]-> bottom_field-> long_term_pic_num = LongtermPicNum ))
Return dpb. fs_ltref [I]-> bottom_field;
}
}
Return NULL;
} </Pre> <pre class = "cpp" name = "code"> </pre>
<Pre> </pre>