ttom_fieldspecify the location of chroma samples for the top field and the bottom field, respectively, as shown in Figure E-1. Otherwise (chroma_format_idc is not equal to 1), the values of the syntax elements chroma_sample_loc_type_top_fiele and chroma_sample_loc_type_bottom_field shall be ignored. When chroma format idc is equal to 2 (4:2:2 chroma format) or (4:4:4 chroma format), the location of chroma samples is specified in clause 6.2. When chroma_format_idc is equal to 0, there is no chroma sample array. The value of chroma_sample_loc_type_top_field and chroma_sample_loc_type_bottom_field shall be in the range of 0 to 5, inclusive. When the chroma_sample_loc_type_top_field and chroma_sample_loc_type_bottom_field are not present, the values of chroma_sample_loc_type_top_field and chroma_sample_loc_type_bottom_field shall be inferred to be equal to 0. NOTE 6 - When coding progressive source material, chroma_sample_loc_type_top_fiele hroma_sample_loc_type_bottom_field should have the same value. Rec. ITU-T H.264 (01/2012) H.264(09)_FE-1 Interpretation of symbols Luma sample position indications: Luma sample top field Luma sample bottom field Chroma sample position indications, where grey fill indicates a bottom field sample type and no fill indicates a top field sample type: Chroma sample type 2 Chroma sample type 3 Chroma sample type 0 Chroma sample type 1 Chroma sample type 4 Chroma sample type 5 Figure E-1 - Location of chroma samples for top and bottom fields for chroma_format_idc equal to 1 (4:2:0 chroma format) as a function of chroma_sample_loc_type_top_field and chroma_sample_loc_type_bottom_field timing_info_present_flag equal to 1 specifies that num_units_in_tick, time scale and fixed_frame_rate_flag are present in the bitstream. timing_info_present_flag equal to 0 specifies that num_units_in_tick, time_scale and fixed_frame_rate_flag are not present in the bitstream. num_units_in_tick is the number of time units of a clock operating at the frequency time_scale Hz that corresponds to one increment (c