H.264码流SPS,PPS,IDR

H.264码流第一个 NALU 是 SPS（序列参数集Sequence Parameter Set）

对应H264标准文档 7.3.2.1 序列参数集的语法进行解析

SPS参数解析// fill sps with content of pview plainint InterpretSPS (VideoParameters *p_Vid, DataPartition *p, seq_parameter_set_rbsp_t *sps)
{
unsigned i;
unsigned n_ScalingList;
int reserved_zero;
Bitstream *s = p->bitstream;

assert (p != NULL);
assert (p->bitstream != NULL);
assert (p->bitstream->streamBuffer != 0);
assert (sps != NULL);

p_Dec->UsedBits = 0;

sps->profile_idc                            = u_v  (8, "SPS: profile_idc"                           , s);

if ((sps->profile_idc!=BASELINE       ) &&
(sps->profile_idc!=MAIN           ) &&
(sps->profile_idc!=EXTENDED       ) &&
(sps->profile_idc!=FREXT_HP       ) &&
(sps->profile_idc!=FREXT_Hi10P    ) &&
(sps->profile_idc!=FREXT_Hi422    ) &&
(sps->profile_idc!=FREXT_Hi444    ) &&
(sps->profile_idc!=FREXT_CAVLC444 )
#if (MVC_EXTENSION_ENABLE)
&& (sps->profile_idc!=MVC_HIGH)
&& (sps->profile_idc!=STEREO_HIGH)
#endif
)
{
printf("Invalid Profile IDC (%d) encountered. /n", sps->profile_idc);
return p_Dec->UsedBits;
}

sps->constrained_set0_flag                  = u_1  (   "SPS: constrained_set0_flag"                 , s);
sps->constrained_set1_flag                  = u_1  (   "SPS: constrained_set1_flag"                 , s);
sps->constrained_set2_flag                  = u_1  (   "SPS: constrained_set2_flag"                 , s);
sps->constrained_set3_flag                  = u_1  (   "SPS: constrained_set3_flag"                 , s);
#if (MVC_EXTENSION_ENABLE)
sps->constrained_set4_flag                  = u_1  (   "SPS: constrained_set4_flag"                 , s);
reserved_zero                               = u_v  (3, "SPS: reserved_zero_3bits"                   , s);
#else
reserved_zero                               = u_v  (4, "SPS: reserved_zero_4bits"                   , s);
#endif
assert (reserved_zero==0);

sps->level_idc                              = u_v  (8, "SPS: level_idc"                             , s);

sps->seq_parameter_set_id                   = ue_v ("SPS: seq_parameter_set_id"                     , s);

// Fidelity Range Extensions stuff
sps->chroma_format_idc = 1;
sps->bit_depth_luma_minus8   = 0;
sps->bit_depth_chroma_minus8 = 0;
p_Vid->lossless_qpprime_flag   = 0;
sps->separate_colour_plane_flag = 0;

if((sps->profile_idc==FREXT_HP   ) ||
(sps->profile_idc==FREXT_Hi10P) ||
(sps->profile_idc==FREXT_Hi422) ||
(sps->profile_idc==FREXT_Hi444) ||
(sps->profile_idc==FREXT_CAVLC444)
#if (MVC_EXTENSION_ENABLE)
|| (sps->profile_idc==MVC_HIGH)
|| (sps->profile_idc==STEREO_HIGH)
#endif
)
{
sps->chroma_format_idc                      = ue_v ("SPS: chroma_format_idc"                       , s);

if(sps->chroma_format_idc == YUV444)
{
sps->separate_colour_plane_flag           = u_1  ("SPS: separate_colour_plane_flag"              , s);
}

sps->bit_depth_luma_minus8                  = ue_v ("SPS: bit_depth_luma_minus8"                   , s);
sps->bit_depth_chroma_minus8                = ue_v ("SPS: bit_depth_chroma_minus8"                 , s);
//checking;
if((sps->bit_depth_luma_minus8+8 > sizeof(imgpel)*8) || (sps->bit_depth_chroma_minus8+8> sizeof(imgpel)*8))
error ("Source picture has higher bit depth than imgpel data type. /nPlease recompile with larger data type for imgpel.", 500);

p_Vid->lossless_qpprime_flag                  = u_1  ("SPS: lossless_qpprime_y_zero_flag"            , s);

sps->seq_scaling_matrix_present_flag        = u_1  (   "SPS: seq_scaling_matrix_present_flag"       , s);

if(sps->seq_scaling_matrix_present_flag)
{
n_ScalingList = (sps->chroma_format_idc != YUV444) ? 8 : 12;
for(i=0; iseq_scaling_list_present_flag[i]   = u_1  (   "SPS: seq_scaling_list_present_flag"         , s);
if(sps->seq_scaling_list_present_flag[i])
{
if(i<6) scaling_list="">ScalingList4x4[i], 16, &sps->UseDefaultScalingMatrix4x4Flag[i], s);
else
Scaling_List(sps->ScalingList8x8[i-6], 64, &sps->UseDefaultScalingMatrix8x8Flag[i-6], s);
}
}
}
}

sps->log2_max_frame_num_minus4              = ue_v ("SPS: log2_max_frame_num_minus4"                , s);
sps->pic_order_cnt_type                     = ue_v ("SPS: pic_order_cnt_type"                       , s);

if (sps->pic_order_cnt_type == 0)
sps->log2_max_pic_order_cnt_lsb_minus4 = ue_v ("SPS: log2_max_pic_order_cnt_lsb_minus4"           , s);
else if (sps->pic_order_cnt_type == 1)
{
sps->delta_pic_order_always_zero_flag      = u_1  ("SPS: delta_pic_order_always_zero_flag"       , s);
sps->offset_for_non_ref_pic                = se_v ("SPS: offset_for_non_ref_pic"                 , s);
sps->offset_for_top_to_bottom_field        = se_v ("SPS: offset_for_top_to_bottom_field"         , s);
sps->num_ref_frames_in_pic_order_cnt_cycle = ue_v ("SPS: num_ref_frames_in_pic_order_cnt_cycle"  , s);
for(i=0; inum_ref_frames_in_pic_order_cnt_cycle; i++)
sps->offset_for_ref_frame[i]               = se_v ("SPS: offset_for_ref_frame[i]"              , s);
}
sps->num_ref_frames                        = ue_v ("SPS: num_ref_frames"                         , s);
sps->gaps_in_frame_num_value_allowed_flag  = u_1  ("SPS: gaps_in_frame_num_value_allowed_flag"   , s);
sps->pic_width_in_mbs_minus1               = ue_v ("SPS: pic_width_in_mbs_minus1"                , s);
sps->pic_height_in_map_units_minus1        = ue_v ("SPS: pic_height_in_map_units_minus1"         , s);
sps->frame_mbs_only_flag                   = u_1  ("SPS: frame_mbs_only_flag"                    , s);
if (!sps->frame_mbs_only_flag)
{
sps->mb_adaptive_frame_field_flag        = u_1  ("SPS: mb_adaptive_frame_field_flag"           , s);
}
sps->direct_8x8_inference_flag             = u_1  ("SPS: direct_8x8_inference_flag"              , s);
sps->frame_cropping_flag                   = u_1  ("SPS: frame_cropping_flag"                    , s);

if (sps->frame_cropping_flag)
{
sps->frame_cropping_rect_left_offset      = ue_v ("SPS: frame_cropping_rect_left_offset"           , s);
sps->frame_cropping_rect_right_offset     = ue_v ("SPS: frame_cropping_rect_right_offset"          , s);
sps->frame_cropping_rect_top_offset       = ue_v ("SPS: frame_cropping_rect_top_offset"            , s);
sps->frame_cropping_rect_bottom_offset    = ue_v ("SPS: frame_cropping_rect_bottom_offset"         , s);
}
sps->vui_parameters_present_flag           = (Boolean) u_1  ("SPS: vui_parameters_present_flag"      , s);

InitVUI(sps);
ReadVUI(p, sps);

sps->Valid = TRUE;
return p_Dec->UsedBits;
}

H.264码流第二个 NALU 是 PPS（图像参数集Picture Parameter Set）

对应H264标准文档 7.3.2.2 序列参数集的语法进行解析

PPS参数解析

view plainint InterpretPPS (VideoParameters *p_Vid, DataPartition *p, pic_parameter_set_rbsp_t *pps)
{
unsigned i;
unsigned n_ScalingList;
int chroma_format_idc;
int NumberBitsPerSliceGroupId;
Bitstream *s = p->bitstream;

assert (p != NULL);
assert (p->bitstream != NULL);
assert (p->bitstream->streamBuffer != 0);
assert (pps != NULL);

p_Dec->UsedBits = 0;

pps->pic_parameter_set_id                  = ue_v ("PPS: pic_parameter_set_id"                   , s);
pps->seq_parameter_set_id                  = ue_v ("PPS: seq_parameter_set_id"                   , s);
pps->entropy_coding_mode_flag              = u_1  ("PPS: entropy_coding_mode_flag"               , s);

//! Note: as per JVT-F078 the following bit is unconditional.  If F078 is not accepted, then
//! one has to fetch the correct SPS to check whether the bit is present (hopefully there is
//! no consistency problem :-(
//! The current encoder code handles this in the same way.  When you change this, don't forget
//! the encoder!  StW, 12/8/02
pps->bottom_field_pic_order_in_frame_present_flag                = u_1  ("PPS: bottom_field_pic_order_in_frame_present_flag"                 , s);

pps->num_slice_groups_minus1               = ue_v ("PPS: num_slice_groups_minus1"                , s);

// FMO stuff begins here
if (pps->num_slice_groups_minus1 > 0)
{
pps->slice_group_map_type               = ue_v ("PPS: slice_group_map_type"                , s);
if (pps->slice_group_map_type == 0)
{
for (i=0; i<=pps->num_slice_groups_minus1; i++)
pps->run_length_minus1 [i]                  = ue_v ("PPS: run_length_minus1 [i]"              , s);
}
else if (pps->slice_group_map_type == 2)
{
for (i=0; inum_slice_groups_minus1; i++)
{
//! JVT-F078: avoid reference of SPS by using ue(v) instead of u(v)
pps->top_left [i]                          = ue_v ("PPS: top_left [i]"                        , s);
pps->bottom_right [i]                      = ue_v ("PPS: bottom_right [i]"                    , s);
}
}
else if (pps->slice_group_map_type == 3 ||
pps->slice_group_map_type == 4 ||
pps->slice_group_map_type == 5)
{
pps->slice_group_change_direction_flag     = u_1  ("PPS: slice_group_change_direction_flag"      , s);
pps->slice_group_change_rate_minus1        = ue_v ("PPS: slice_group_change_rate_minus1"         , s);
}
else if (pps->slice_group_map_type == 6)
{
if (pps->num_slice_groups_minus1+1 >4)
NumberBitsPerSliceGroupId = 3;
else if (pps->num_slice_groups_minus1+1 > 2)
NumberBitsPerSliceGroupId = 2;
else
NumberBitsPerSliceGroupId = 1;
pps->pic_size_in_map_units_minus1      = ue_v ("PPS: pic_size_in_map_units_minus1"               , s);
if ((pps->slice_group_id = calloc (pps->pic_size_in_map_units_minus1+1, 1)) == NULL)
no_mem_exit ("InterpretPPS: slice_group_id");
for (i=0; i<=pps->pic_size_in_map_units_minus1; i++)
pps->slice_group_id[i] = (byte) u_v (NumberBitsPerSliceGroupId, "slice_group_id[i]", s);
}
}

// End of FMO stuff

pps->num_ref_idx_l0_active_minus1          = ue_v ("PPS: num_ref_idx_l0_active_minus1"           , s);
pps->num_ref_idx_l1_active_minus1          = ue_v ("PPS: num_ref_idx_l1_active_minus1"           , s);
pps->weighted_pred_flag                    = u_1  ("PPS: weighted_pred_flag"                     , s);
pps->weighted_bipred_idc                   = u_v  ( 2, "PPS: weighted_bipred_idc"                , s);
pps->pic_init_qp_minus26                   = se_v ("PPS: pic_init_qp_minus26"                    , s);
pps->pic_init_qs_minus26                   = se_v ("PPS: pic_init_qs_minus26"                    , s);

pps->chroma_qp_index_offset                = se_v ("PPS: chroma_qp_index_offset"                 , s);

pps->deblocking_filter_control_present_flag = u_1 ("PPS: deblocking_filter_control_present_flag" , s);
pps->constrained_intra_pred_flag           = u_1  ("PPS: constrained_intra_pred_flag"            , s);
pps->redundant_pic_cnt_present_flag        = u_1  ("PPS: redundant_pic_cnt_present_flag"         , s);

if(more_rbsp_data(s->streamBuffer, s->frame_bitoffset,s->bitstream_length)) // more_data_in_rbsp()
{
//Fidelity Range Extensions Stuff
pps->transform_8x8_mode_flag           = u_1  ("PPS: transform_8x8_mode_flag"                , s);
pps->pic_scaling_matrix_present_flag   =  u_1  ("PPS: pic_scaling_matrix_present_flag"        , s);

if(pps->pic_scaling_matrix_present_flag)
{
chroma_format_idc = p_Vid->SeqParSet[pps->seq_parameter_set_id].chroma_format_idc;
n_ScalingList = 6 + ((chroma_format_idc != YUV444) ? 2 : 6) * pps->transform_8x8_mode_flag;
for(i=0; ipic_scaling_list_present_flag[i]= u_1  ("PPS: pic_scaling_list_present_flag"          , s);

if(pps->pic_scaling_list_present_flag[i])
{
if(i<6) scaling_list="">ScalingList4x4[i], 16, &pps->UseDefaultScalingMatrix4x4Flag[i], s);
else
Scaling_List(pps->ScalingList8x8[i-6], 64, &pps->UseDefaultScalingMatrix8x8Flag[i-6], s);
}
}
}
pps->second_chroma_qp_index_offset      = se_v ("PPS: second_chroma_qp_index_offset"          , s);
}
else
{
pps->second_chroma_qp_index_offset      = pps->chroma_qp_index_offset;
}

pps->Valid = TRUE;
return p_Dec->UsedBits;
}

H.264码流第三个 NALU 是 IDR（即时解码器刷新）

对应H264标准文档 7.3.3 序列参数集的语法进行解析

IDR参数解析

view plaincase NALU_TYPE_IDR:
img->idr_flag = (nalu->nal_unit_type == NALU_TYPE_IDR);
img->nal_reference_idc = nalu->nal_reference_idc;
img->disposable_flag = (nalu->nal_reference_idc == NALU_PRIORITY_DISPOSABLE);
currSlice->dp_mode = PAR_DP_1;   //++ dp_mode：数据分割模式；PAR_DP_1=0：没有数据分割
currSlice->max_part_nr = 1;
currSlice->ei_flag = 0;  //++ 该处赋值直接影响decode_slice()函数中对decode_one_slice()函数的调用
//++ 该值不为0，表明当前片出错，解码程序将忽略当前片的解码过程，而使用错误隐藏
currStream = currSlice->partArr[0].bitstream;
currStream->ei_flag = 0; //++ 此处的赋值为最终赋值，以后不再改变。该值将对每个宏块的ei_flag产生影响
//++ 参见macroblock.c文件read_one_macroblock()函数的如下语句：
//++        :if(!dP->bitstream->ei_flag)      :currMB->ei_flag = 0;
//++ 该值还在macroblock.c文件if(IS_INTRA (currMB) && dP->bitstream->ei_flag && img->number)中用到
currStream->frame_bitoffset = currStream->read_len = 0;
memcpy (currStream->streamBuffer, &nalu->buf[1], nalu->len-1);
currStream->code_len = currStream->bitstream_length = RBSPtoSODB(currStream->streamBuffer, nalu->len-1);

// Some syntax of the Slice Header depends on the parameter set, which depends on
// the parameter set ID of the SLice header.  Hence, read the pic_parameter_set_id
// of the slice header first, then setup the active parameter sets, and then read
// the rest of the slice header
BitsUsedByHeader = FirstPartOfSliceHeader();    //++ 参见标准7.3.3
UseParameterSet (currSlice->pic_parameter_set_id);
BitsUsedByHeader+= RestOfSliceHeader ();    //++ 参见标准7.3.3
//++ BitsUsedByHeader在程序中没有实际用处，而且BitsUsedByHeader+= RestOfSliceHeader ()
//++ 重复计算了FirstPartOfSliceHeader()所用到的比特数。因为在FirstPartOfSliceHeader()
//++ 之后，变量UsedBits值并未被置零就代入RestOfSliceHeader()运算，从而RestOfSliceHeader ()
//++ 在返回时，BitsUsedByHeader+= RestOfSliceHeader()多加了一个BitsUsedByHeader值

FmoInit (active_pps, active_sps);

if(is_new_picture())
{
init_picture(img, input);

current_header = SOP;
//check zero_byte if it is also the first NAL unit in the access unit
CheckZeroByteVCL(nalu, &ret);
}
else
current_header = SOS;

init_lists(img->type, img->currentSlice->structure);
reorder_lists (img->type, img->currentSlice);

if (img->structure==FRAME)
{
init_mbaff_lists();
}

/*        if (img->frame_num==1) // write a reference list
{
count ++;
if (count==1)
for (i=0; i

// From here on, active_sps, active_pps and the slice header are valid
if (img->MbaffFrameFlag)
img->current_mb_nr = currSlice->start_mb_nr << 1="" style="color: #0000ff">else
img->current_mb_nr = currSlice->start_mb_nr;

if (active_pps->entropy_coding_mode_flag)
{
int ByteStartPosition = currStream->frame_bitoffset/8;
if (currStream->frame_bitoffset%8 != 0)
{
ByteStartPosition++;
}
arideco_start_decoding (&currSlice->partArr[0].de_cabac, currStream->streamBuffer, ByteStartPosition, &currStream->read_len, img->type);
}
// printf ("read_new_slice: returning %s/n", current_header == SOP?"SOP":"SOS");
FreeNALU(nalu);
return current_header;
break;
case NALU_TYPE_DPA:
//! The state machine here should follow the same ideas as the old readSliceRTP()
//! basically:
//! work on DPA (as above)
//! read and process all following SEI/SPS/PPS/PD/Filler NALUs
//! if next video NALU is dpB,
//!   then read and check whether it belongs to DPA, if yes, use it
//! else
//!   ;   // nothing
//! read and process all following SEI/SPS/PPS/PD/Filler NALUs
//! if next video NALU is dpC
//!   then read and check whether it belongs to DPA (and DPB, if present), if yes, use it, done
//! else
//!   use the DPA (and the DPB if present)

/*
LC: inserting the code related to DP processing, mainly copying some of the parts
related to NALU_TYPE_SLICE, NALU_TYPE_IDR.
*/

if(expected_slice_type != NALU_TYPE_DPA)
{
/* oops... we found the next slice, go back! */
fseek(bits, ftell_position, SEEK_SET);
FreeNALU(nalu);
return current_header;
}

img->idr_flag          = (nalu->nal_unit_type == NALU_TYPE_IDR);
img->nal_reference_idc = nalu->nal_reference_idc;
img->disposable_flag   = (nalu->nal_reference_idc == NALU_PRIORITY_DISPOSABLE);
currSlice->dp_mode     = PAR_DP_3;
currSlice->max_part_nr = 3;
currSlice->ei_flag     = 0;
currStream             = currSlice->partArr[0].bitstream;
currStream->ei_flag    = 0;
currStream->frame_bitoffset = currStream->read_len = 0;
memcpy (currStream->streamBuffer, &nalu->buf[1], nalu->len-1);
currStream->code_len = currStream->bitstream_length = RBSPtoSODB(currStream->streamBuffer, nalu->len-1);    //++ 剔除停止比特和填充比特

BitsUsedByHeader     = FirstPartOfSliceHeader();
UseParameterSet (currSlice->pic_parameter_set_id);
BitsUsedByHeader    += RestOfSliceHeader ();

FmoInit (active_pps, active_sps);

if(is_new_picture())
{
init_picture(img, input);
current_header = SOP;
CheckZeroByteVCL(nalu, &ret);
}
else
current_header = SOS;

init_lists(img->type, img->currentSlice->structure);
reorder_lists (img->type, img->currentSlice);

if (img->structure==FRAME)
{
init_mbaff_lists();
}

// From here on, active_sps, active_pps and the slice header are valid
if (img->MbaffFrameFlag)
img->current_mb_nr = currSlice->start_mb_nr << 1="" style="color: #0000ff">else

img->current_mb_nr = currSlice->start_mb_nr;

/*
LC:
Now I need to read the slice ID, which depends on the value of
redundant_pic_cnt_present_flag (pag.49).
*/

slice_id_a  = ue_v("NALU:SLICE_A slice_idr", currStream);
if (active_pps->entropy_coding_mode_flag)
{
int ByteStartPosition = currStream->frame_bitoffset/8;
if (currStream->frame_bitoffset%8 != 0)
{
ByteStartPosition++;
}
arideco_start_decoding (&currSlice->partArr[0].de_cabac, currStream->streamBuffer, ByteStartPosition, &currStream->read_len, img->type);
}
// printf ("read_new_slice: returning %s/n", current_header == SOP?"SOP":"SOS");
break;
case NALU_TYPE_DPB:
/* LC: inserting the code related to DP processing */

currStream             = currSlice->partArr[1].bitstream;
currStream->ei_flag    = 0;
currStream->frame_bitoffset = currStream->read_len = 0;
memcpy (currStream->streamBuffer, &nalu->buf[1], nalu->len-1);
currStream->code_len = currStream->bitstream_length = RBSPtoSODB(currStream->streamBuffer, nalu->len-1);

slice_id_b  = ue_v("NALU:SLICE_B slice_idr", currStream);
if (active_pps->redundant_pic_cnt_present_flag)
redundant_pic_cnt_b = ue_v("NALU:SLICE_B redudand_pic_cnt", currStream);
else
redundant_pic_cnt_b = 0;

/*  LC: Initializing CABAC for the current data stream. */

if (active_pps->entropy_coding_mode_flag)
{
int ByteStartPosition = currStream->frame_bitoffset/8;
if (currStream->frame_bitoffset % 8 != 0)
ByteStartPosition++;

arideco_start_decoding (&currSlice->partArr[1].de_cabac, currStream->streamBuffer,
ByteStartPosition, &currStream->read_len, img->type);

}

/* LC: resilience code to be inserted */
/*         FreeNALU(nalu); */
/*         return current_header; */

break;

IDR参数解析/*!view plain<pre name="code" class="cpp"> ************************************************************************
* /brief
*    read the first part of the header (only the pic_parameter_set_id)
* /return
*    Length of the first part of the slice header (in bits)
************************************************************************
*/
//++ 参见标准7.3.3
int FirstPartOfSliceHeader()
{
Slice *currSlice = img->currentSlice;
int dP_nr = assignSE2partition[currSlice->dp_mode][SE_HEADER];
DataPartition *partition = &(currSlice->partArr[dP_nr]);
Bitstream *currStream = partition->bitstream;
int tmp;

UsedBits= partition->bitstream->frame_bitoffset; // was hardcoded to 31 for previous start-code. This is better.

// Get first_mb_in_slice
currSlice->start_mb_nr = ue_v ("SH: first_mb_in_slice", currStream);

tmp = ue_v ("SH: slice_type", currStream);

if (tmp>4) tmp -=5;

img->type = currSlice->picture_type = (SliceType) tmp;

currSlice->pic_parameter_set_id = ue_v ("SH: pic_parameter_set_id", currStream);

return UsedBits;
}