h26x-extractor 0.10.0

Extract NAL units from H.264 bitstreams

h26x-extractor

Author: Werner Robitza, with contributions from @chemag, Paulo Sherring, Thomas Jammet.

Extracts NAL units from H.264 bitstreams and decodes their type and content, if supported.

⚠️ h26x-extractor is neither fast nor robust to bitstream errors. It's rather a playground for parsing bitstreams. Use with caution! This program is no longer maintained, PRs are welcome.

Contents:

• Installation
• Status
• Usage
• Programmatic usage (API)
• API
• Alternatives

Installation

Requirements: Python 3.9 or higher

Via pip:

pip3 install h26x_extractor

Status

Currently supported:

• Parsing of H.264 bitstreams
• Parsing of NALU
• Parsing of AUD
• Parsing of CodedSlice(s)
• Parsing of SPS
• Parsing of PPS
• Parsing of Prefix for Scalable Video Coding

Currently planned:

• Parsing of SEI
• Parsing of H.265 bitstreams

Usage

If you installed the program via pip, you can run it directly:

h26x-extractor [options] <input-file>...

Otherwise you can clone this repo and run it via:

python3 -m h26x_extractor [options] <input-file>...

You can pass the -v flag to enable verbose output, e.g. the following. You will get, for each NAL unit:

• The byte position range
• The offset from the start of the stream
• The overall length including start code
• The type (also translated in plaintext)
• Its content in raw bytes, encoded as hex
• Its RBSP content
• A table with its content decoded, if supported

Example:

NALU bytepos:   [0, 28]
NALU offset:    0 Bytes
NALU length:    29 Bytes (including start code)
NALU type:      7 (Sequence parameter set)
NALU bytes:     0x0000000167f4000d919b28283f6022000003000200000300641e28532c
NALU RBSP:      0xf4000d919b28283f602200000002000000641e28532c

SPS (payload size: 22.0 Bytes)
+--------------------------------------+---------+
| field                                | value   |
+======================================+=========+
| constraint_set0_flag                 | 0       |
+--------------------------------------+---------+
| constraint_set1_flag                 | 0       |
+--------------------------------------+---------+
....

Programmatic usage (API)

API

This program has a simple API that can be used to integrate it into other Python programs.

For more information see the API documentation.

Here is an example:

from h26x_extractor.h26x_parser import H26xParser

def do_something(nalu):
    pass
    # do something with the NALU instance

H26xParser.set_callback("nalu", do_something)
H26xParser.parse()

The callback is called for each type of info found. Valid callbacks are:

• sps
• pps
• slice
• aud
• nalu
• prefix

The callback returns an instance of the NALU type. You can access the s property to get the whole data including the RBSP. You can use the set_allcallbacks method to set callbacks for all types.

You can also call the nalutypes classes to decode the individual fields, e.g. nalutypes.SPS:

from h26x_extractor.nalutypes import SPS
from bitstring import BitStream

nal_payload = "0x0000000167f4000d919b28283f6022000003000200000300641e28532c"
sps = SPS(BitStream(nal_payload))
sps.print_verbose()

See the test/test.py file for more examples.

Alternatives

h264bitstream is a proper H.264 parser.

FFmpeg can also parse bitstream data:

ffmpeg -i video.h264 -c copy -bsf:v trace_headers -f null - 2> output.txt

License

The MIT License (MIT)

Copyright (c) 2017-2025 h26x-extractor contributors

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Changelog

v0.10.0 (2025-03-08)

• Bump version to 0.10.0.

• Update readme.

• Add temporal SVC parse, fix vui parse (#10)

  • [feat] add h264 temporal SVC parse

  • [fix] fix vui parse

• Fix PEP 625 naming.

• Link to API docs.

v0.9.0 (2025-02-05)

• Bump version to 0.9.0.

• Remove irrelevant comment.

• Update copyright, readme.

• Update tests.

• Drop python 3.8 support.

• Refactor and finish the parser implementation (#9)

  • feat: refactor and finish the parser implementation

  • Complete SPS, PPS implementation

  • Factorize and complete slice parsing in CodedSlice class

  • Move verbose support in the main process

  • add option --verbose-types to display only some NALU types

  • feat: add set_allcallbacks helper function

  • Add set_allcallbacks helper function to set all callbacks in one go

  • Change the order of callback arguments to have the nalu first

  • Fix a typo in h26x_parser.py

  • test: update test.py

  • docs(README): update README

• Update README.

• [feat] add parse VUI in SPS for h264 (#8)

v0.8.1 (2023-01-08)

• Bump version to 0.8.1.

• Organize imports.

• Update module structure, readme.

v0.8.0 (2021-11-12)

• Bump version to 0.8.0.

• Remove unneeded imports.

• Rename test dir.

• Apply formatting with black.

• Parse as bytearray instead of BitStream.

• Update copyright year.

• Add requirements.txt.

• Update badge link.

• Update README.

v0.7.0 (2021-03-10)

• Bump version to 0.7.0.

• Add python_requires to setup.py.

• Remove release script.

v0.6 (2021-03-06)

• Bump version to 0.6.

• Switch version to string.

• Format setup.py and switch to markdown.

• Update badge URL.

v0.5 (2020-12-30)

• Bump version to 0.5.

• Apply formatting.

• Rm python 2.x support, README fixes.

• Fix frame_crop_left_offset typo (#5)

• Formatting.

• Import local package for tests.

• Add pypi badge.

• Add missing gitchangelog template.

v0.4 (2020-04-12)

• Bump version to 0.4.

• Update release script.

• Update readme.

• H26x_extractor: add deeper slice_header parsing (#4)

  Includes:

  • passing the SPS and PPS NALUs to CodedSliceIDR and CodedSliceNonIDR (which need them to go further)
  • adding an optional concept of order in the verbose printing, so that NALU parameters are printed in the order they are parsed
  • implementing ordering in SPS, PPS, and CodedSliceIDR NALUs
  • fix on the SPS parser based on profile_idc values, per 2016-02 standard (Section 7.3.2.1.1, page 44). Note in particular that the if loop does not include value 144
  • fix minor type (s/slice_gropu_change_rate_minus1/slice_group_change_rate_minus1/)

  Tested:

  $ h26x-extractor -v file.264
  ...
  SPS (payload size: 21.0 Bytes)
  +--------------------------------------+---------+
  | field                                | value   |
  +======================================+=========+
  | profile_idc                          | 66      |
  +--------------------------------------+---------+
  | constraint_set0_flag                 | 1       |
  +--------------------------------------+---------+
  | constraint_set1_flag                 | 1       |
  +--------------------------------------+---------+
  | constraint_set2_flag                 | 0       |
  +--------------------------------------+---------+
  | constraint_set3_flag                 | 0       |
  +--------------------------------------+---------+
  ...
  NALU type:  5 (Coded slice of an IDR picture)
  NALU bytes: 0x000000016588841afffffc2f14000416fd78e06380de6a1306bb224a722233e54ffa7cb9526c188ed1189699e7c6fd1a2307f757de5c3fca2f3d22b7fc667ccb6ff6b6a8dabb515b59fe53f8a7d83a8beb6ff17988adbfde818bdf2dafc5e7a2b5fde4a0bca4156137f8ceadff19bd5bfe233e152fbefbefbe2fab6dfe...
  NALU RBSP:  0x88841afffffc2f14000416fd78e06380de6a1306bb224a722233e54ffa7cb9526c188ed1189699e7c6fd1a2307f757de5c3fca2f3d22b7fc667ccb6ff6b6a8dabb515b59fe53f8a7d83a8beb6ff17988adbfde818bdf2dafc5e7a2b5fde4a0bca4156137f8ceadff19bd5bfe233e152fbefbefbe2fab6dfed6d62d6ad7...
  
  CodedSliceIDR (payload size: 4538.0 Bytes)
  +----------------------+---------+
  | field                | value   |
  +======================+=========+
  | first_mb_in_slice    | 0       |
  +----------------------+---------+
  | slice_type           | 7       |
  +----------------------+---------+
  | slice_type_clear     | I       |
  +----------------------+---------+
  | pic_parameter_set_id | 0       |
  +----------------------+---------+
  | frame_num            | 0       |
  +----------------------+---------+
  | idr_pic_id           | 0       |
  ...
  

• Fix offset-by-one (#3)

  • h26x-extractor: add a simple parsing test

  Needed to refactor the parser constructor in order to allow testing binary blobs.

  Tested:

  Before the AUD fix patch:

  $ ./tests/simple_parsing.py
  
  ========================================================================================================
  
  NALU bytepos: [0, 5]
  NALU offset:  0 Bytes
  NALU length:  6 Bytes (including start code)
  NALU type:  9 (Access unit delimiter)
  NALU bytes: 0x000000010910
  NALU RBSP:
  
  E
  ======================================================================
  ERROR: testAUDParser (__main__.ParsingTest)
  Simple AUD parsing.
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "./tests/simple_parsing.py", line 17, in testAUDParser
      ex.parse()
    File "/usr/local/lib/python3.7/site-packages/h26x_extractor-0.3-py3.7.egg/h26x_extractor/h26x_parser.py", line 209, in parse
      aud = nalutypes.AUD(rbsp_payload, self.verbose)
    File "/usr/local/lib/python3.7/site-packages/h26x_extractor-0.3-py3.7.egg/h26x_extractor/nalutypes.py", line 120, in __init__
      self.primary_pic_type = self.s.read('uint:3')
    File "/usr/lib/python3.7/site-packages/bitstring.py", line 3902, in read
      value, self._pos = self._readtoken(name, self._pos, length)
    File "/usr/lib/python3.7/site-packages/bitstring.py", line 2016, in _readtoken
      "Tried to read {0} bits when only {1} available.".format(int(length), self.length - pos))
  bitstring.ReadError: Reading off the end of the data. Tried to read 3 bits when only 0 available.
  
  ----------------------------------------------------------------------
  Ran 1 test in 0.003s
  
  FAILED (errors=1)
  

  After the AUD fix patch:

  $ ./tests/simple_parsing.py
  
  ========================================================================================================
  
  NALU bytepos: [0, 5]
  NALU offset:  0 Bytes
  NALU length:  6 Bytes (including start code)
  NALU type:  9 (Access unit delimiter)
  NALU bytes: 0x000000010910
  NALU RBSP:  0x10
  
  AUD (payload size: 1.0 Bytes)
  +------------------+---------+
  | field            |   value |
  +==================+=========+
  | primary_pic_type |       0 |
  +------------------+---------+
  .
  ----------------------------------------------------------------------
  Ran 1 test in 0.001s
  
  OK
  

  • h26x_extractor: fix offset-by-1 in NALU parser

  Tested:

  Before the AUD fix patch:

  $ ./tests/simple_parsing.py
  
  ========================================================================================================
  
  NALU bytepos: [0, 5]
  NALU offset:  0 Bytes
  NALU length:  6 Bytes (including start code)
  NALU type:  9 (Access unit delimiter)
  NALU bytes: 0x000000010910
  NALU RBSP:
  
  E
  ======================================================================
  ERROR: testAUDParser (__main__.ParsingTest)
  Simple AUD parsing.
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "./tests/simple_parsing.py", line 17, in testAUDParser
      ex.parse()
    File "/usr/local/lib/python3.7/site-packages/h26x_extractor-0.3-py3.7.egg/h26x_extractor/h26x_parser.py", line 209, in parse
      aud = nalutypes.AUD(rbsp_payload, self.verbose)
    File "/usr/local/lib/python3.7/site-packages/h26x_extractor-0.3-py3.7.egg/h26x_extractor/nalutypes.py", line 120, in __init__
      self.primary_pic_type = self.s.read('uint:3')
    File "/usr/lib/python3.7/site-packages/bitstring.py", line 3902, in read
      value, self._pos = self._readtoken(name, self._pos, length)
    File "/usr/lib/python3.7/site-packages/bitstring.py", line 2016, in _readtoken
      "Tried to read {0} bits when only {1} available.".format(int(length), self.length - pos))
  bitstring.ReadError: Reading off the end of the data. Tried to read 3 bits when only 0 available.
  
  ----------------------------------------------------------------------
  Ran 1 test in 0.003s
  
  FAILED (errors=1)
  

  After the AUD fix patch:

  $ ./tests/simple_parsing.py
  
  ========================================================================================================
  
  NALU bytepos: [0, 5]
  NALU offset:  0 Bytes
  NALU length:  6 Bytes (including start code)
  NALU type:  9 (Access unit delimiter)
  NALU bytes: 0x000000010910
  NALU RBSP:  0x10
  
  AUD (payload size: 1.0 Bytes)
  +------------------+---------+
  | field            |   value |
  +==================+=========+
  | primary_pic_type |       0 |
  +------------------+---------+
  .
  ----------------------------------------------------------------------
  Ran 1 test in 0.001s
  
  OK
  

v0.3 (2020-03-15)

• Bump version to 0.3.

• Add release script.

• Python 3.7 and 3.8.

• Rename changelog.

v0.2 (2017-08-02)

• Many updates.

v0.1 (2017-07-17)

• Initial commit.