JM8.6编解码器中trace_enc.txt和trace_dec.txt文件的功能

        前面博文已经说过，在JM8.6编码端如何开启trace_enc.txt功能以及如何利用trace_enc.txt文件的信息来分析码流，在此，不再赘述.下面来看看在解码端如何开启trace_dec.txt. 在JM8.6解码端的define.h文件中有：

#if defined _DEBUG#define TRACE           0                   //!< 0:Trace off 1:Trace on#else#define TRACE           0                   //!< 0:Trace off 1:Trace on#endif

        只需要把代码改为下面的即可开启trace_dec.txt的功能：

#if defined _DEBUG#define TRACE           1                   //!< 0:Trace off 1:Trace on#else#define TRACE           0                   //!< 0:Trace off 1:Trace on#endif

        这里面实际上用到了C语言中的条件编译, 如果把控制trace的开关放在配置文件中，其实也是可以的，但是，程序中就多了很多要编译的代码，这样不好，影响性能. 所以，还是用条件编译比较好.

 

        生成的trace_dec.txt文件的部分内容为：

 

Annex B NALU w/ long startcode, len 8, forbidden_bit 0, nal_reference_idc 3, nal_unit_type 7

@0      SPS: profile_idc                                      01000010  ( 66)
@8      SPS: constrained_set0_flag                                   0  (  0)
@9      SPS: constrained_set1_flag                                   0  (  0)
@10     SPS: constrained_set2_flag                                   0  (  0)
@11     SPS: reserved_zero_5bits                                 00000  (  0)
@16     SPS: level_idc                                        00011110  ( 30)
@24     SPS: seq_parameter_set_id                                    1  (  0)
@25     SPS: log2_max_frame_num_minus4                               1  (  0)
@26     SPS: pic_order_cnt_type                                      1  (  0)
@27     SPS: log2_max_pic_order_cnt_lsb_minus4                       1  (  0)
@28     SPS: num_ref_frames                                    0001011  ( 10)
@35     SPS: gaps_in_frame_num_value_allowed_flag                    0  (  0)
@36     SPS: pic_width_in_mbs_minus1                           0001011  ( 10)
@43     SPS: pic_height_in_map_units_minus1                    0001001  (  8)
@50     SPS: frame_mbs_only_flag                                     1  (  1)
@51     SPS: direct_8x8_inference_flag                               0  (  0)
@52     SPS: frame_cropping_flag                                     0  (  0)
@53     SPS: vui_parameters_present_flag                             0  (  0)

Annex B NALU w/ long startcode, len 5, forbidden_bit 0, nal_reference_idc 3, nal_unit_type 8

@54     PPS: pic_parameter_set_id                                    1  (  0)
@55     PPS: seq_parameter_set_id                                    1  (  0)
@56     PPS: entropy_coding_mode_flag                                0  (  0)
@57     PPS: pic_order_present_flag                                  0  (  0)
@58     PPS: num_slice_groups_minus1                                 1  (  0)
@59     PPS: num_ref_idx_l0_active_minus1                      0001010  (  9)
@66     PPS: num_ref_idx_l1_active_minus1                      0001010  (  9)
@73     PPS: weighted prediction flag                                0  (  0)
@74     PPS: weighted_bipred_idc                                    00  (  0)
@76     PPS: pic_init_qp_minus26                                     1  (  0)
@77     PPS: pic_init_qs_minus26                                     1  (  0)
@78     PPS: chroma_qp_index_offset                                  1  (  0)
@79     PPS: deblocking_filter_control_present_flag                  0  (  0)
@80     PPS: constrained_intra_pred_flag                             0  (  0)
@81     PPS: redundant_pic_cnt_present_flag                          0  (  0)

Last NALU in File

Annex B NALU w/ long startcode, len 2741, forbidden_bit 0, nal_reference_idc 3, nal_unit_type 5

@82     SH: first_mb_in_slice                                        1  (  0)
@83     SH: slice_type                                         0001000  (  7)
@90     SH: pic_parameter_set_id                                     1  (  0)
@91     SH: frame_num                                             0000  (  0)
@95     SH: idr_pic_id                                               1  (  0)
@96     SH: pic_order_cnt_lsb                                     0000  (  0)
@100    SH: no_output_of_prior_pics_flag                             0  (  0)
@101    SH: long_term_reference_flag                                 0  (  0)
@102    SH: slice_qp_delta                                       00100  (  2)

*********** POC: 0 (I/P) MB: 0 Slice: 0 Type 2 **********
@107    mb_type                                                      1  (  0)
@108    intra4x4_pred_mode                                           1  ( -1)
@109    intra4x4_pred_mode                                        0001  (  1)
@113    intra4x4_pred_mode                                           1  ( -1)
@114    intra4x4_pred_mode                                        0110  (  6)
@118    intra4x4_pred_mode                                        0001  (  1)
@122    intra4x4_pred_mode                                        0111  (  7)
@126    intra4x4_pred_mode                                           1  ( -1)
@127    intra4x4_pred_mode                                           1  ( -1)
@128    intra4x4_pred_mode                                        0000  (  0)

......

  

      根据上述内容，可以辅助分析JM8.6解码端是如何对码流进行解析的（即如何解析一个NALU）.