如何使用h.264参考软件在Python中提取运动矢量

Question

I'm trying to decode an h.264 video so that I can access the motion vectors. I found the reference software:

http://iphome.hhi.de/suehring/tml/download/

but I'm having difficulty implementing this in python to parse out the relevant data that I want. What is a good way to approach this problem?

Answer 1

Parsing H.264 in Python can be done, but it's usually not the best tool for the job. If you really do want to use it you should start with the H.264 standard, not the reference software, although having both to hand is useful.

As I said Python isn't well suited to decoding video so there isn't much out there to help you. I have used it in the past to get or change the odd parameter and wrote a module ( bitstring ) to help. There is an example of parsing a H.264 structure in the documentation :

This example creates a class that parses a structure that is part of the H.264 video standard.

class seq_parameter_set_data(object):
    def __init__(self, s):
        """Interpret next bits in BitString s as an SPS."""
        # Read and interpret bits in a single expression:
        self.profile_idc = s.read('uint:8')
        # Multiple reads in one go returns a list:
        self.constraint_flags = s.readlist('4*uint:1')
        self.reserved_zero_4bits = s.read('bin:4')
        self.level_idc = s.read('uint:8')
        self.seq_parameter_set_id = s.read('ue')
        if self.profile_idc in [100, 110, 122, 244, 44, 83, 86]:
            self.chroma_format_idc = s.read('ue')
            if self.chroma_format_idc == 3:
                self.separate_colour_plane_flag = s.read('uint:1')
            self.bit_depth_luma_minus8 = s.read('ue')
            self.bit_depth_chroma_minus8 = s.read('ue')
            # etc.

>>> s = BitStream('0x6410281bc0')
>>> sps = seq_parameter_set_data(s)
>>> print(sps.profile_idc)
100
>>> print(sps.level_idc)
40
>>> print(sps.reserved_zero_4bits)
0b0000
>>> print(sps.constraint_flags)
[0, 0, 0, 1]