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How to calculate video dimensions using SPS, PPS information in H.264 stream

Tags:

video

h.264

I have corrupted video stream with this header/parameters in the beginning.

[sps]
00 00 00 01 
67 64 00 2A AD 84 01 0C 20 08 61 00 43 08 02 18 40 10 C2 00 84 2B 50 3C 01 13 F2 C2 00 00 03 00 02 00 00 03 00 79 08

[pps]
68 EE 3C B0

I’m trying to figure out the actual values, but i didn't.

Does anybody know what other bytes stand for?

I want to know how to calculate video dimensions (Width x Height).

like image 687
gerrardon Avatar asked Feb 13 '23 19:02

gerrardon


1 Answers

Here you go:

### Sequence Parameter Set

profile_idc 100 
constraint_set0_flag 0 
constraint_set1_flag 0 
constraint_set2_flag 0 
constraint_set3_flag 0 
level_idc 42 
seq_parameter_set_id 0 
chroma_format_idc 1 
// TODO: ... 
// TODO: ... 
num_ref_frames 1 
gaps_in_frame_num_value_allowed_flag 1 
pic_width_in_mbs_minus1 119 
pic_height_in_map_units_minus1 67 
frame_mbs_only_flag 1 
direct_8x8_inference_flag 1 
frame_cropping_flag 1 
frame_crop_left_offset 0 
frame_crop_right_offset 0 
frame_crop_top_offset 0 
frame_crop_bottom_offset 4 
vui_parameters_present_flag 1 
// TODO: ... 

### Picture Parameter Set

pic_parameter_set_id 0 
seq_parameter_set_id 0 
entropy_coding_mode_flag 1 
num_slice_groups_minus1 0 
// TODO: ... 

It's 1920x1080 video: you basically parse out the values per specification, and then you calculate the dimensions as described in this post: Fetching the dimensions of a H264Video stream

Specifically:

width = ((pic_width_in_mbs_minus1 + 1) * 16)
  - (frame_crop_left_offset + frame_crop_right_offset) * 2
height= (2 - frame_mbs_only_flag) * ((pic_height_in_map_units_minus1 + 1) * 16)
  - (frame_crop_top_offset + frame_crop_bottom_offset) * 2

gets you 120 * 16 by 68 * 16 - 8 (Assuming 4:2:0 Color Sampling).

2014-10-10 UPD: I am putting this up from edit/comment:

The conversion from field to frame (2 - frame_mbs_only_flag) is applied to the clipping region as well. The x2 for subWidthC and subHeightC is only for Color sampling 4:2:0. 4:4:4, 4:2:2, and Monochrome use x1 for one or both of the x2s.

like image 165
Roman R. Avatar answered May 06 '23 03:05

Roman R.