AFGS1

Implementation of the standalone Alliance for Open Media Film Grain Synthesis (AFGS1) specification. This repository includes a library for creating AFGS1 bit-streams as well as two example applications. A first application demonstrates how to read "filmgrn1" parameter files and generate an AFGS1 payload. A second application demonstrates how to read "filmgrn1" parameter files, generate an AFGS1 payload, and insert the payload into an HEVC bit-stream as an SEI message using Recommendation ITU-T T.35 based signaling.

Building

Prerequisites

1. CMake version 3.16 or higher.
2. Git.

Get the code

The software can be downloaded with or without support for building the HEVC bit-stream example application. Depending on the desired behavior, please do one of the following:

Build library and example applications without HEVC support

    $ git clone git@github.com:asegallamz/libafgs1.git
    # By default, the above command stores the source in the libafgs1 directory:
    $ cd libafgs1

Build library and example applications with HEVC support

    $ git clone --recurse-submodule git@github.com:asegallamz/libafgs1.git
    # By default, the above command stores the source in the libafgs1 directory:
    $ cd libafgs1

Basic build

The build procedure uses CMake and supports a number of options. It is recommended to use the following process:

    $ mkdir build
    $ cd build
    $ cmake --DCMAKE_BUILD_TYPE=debug ..
    $ make

The above will generate a makefile and build the AFGS1 library and the first example application. Alternatively, the HEVC bit-stream insertion functionality can be enabled by using the following process:

    $ mkdir build
    $ cd build
    $ cmake --DCMAKE_BUILD_TYPE=debug -DBUILD_SEI_APP=ON ..
    $ make

Code Overview

The software is organized into three main components. An introduction is provided below.

libAFGS1

Support for the AFGS1 standard is provided in the libAFGS1 library that is contained in the Common directory. This is generally organized as follows:

• afgs1_params.* provides support to store the AFGS1 film grain parameters and read these parameters from a "filmgrn1" paramter file. These "filmgrn1" parameter files can be generated using the noise_model utility provided in libaom.
• afgs1_bitstream.* provides support for writing the AFGS1 syntax using the film grain parameters.
• afgs1_database.* is a helper class that can manage multiple film grain parameters. This allows for the selection of film grain parameters for a specific frame from the timeline of parameters provided in the "filmgrn1" file.
• afgs1_buffer.* is a helper class to emulate the buffering of AFGs1 parameters at a decoder.

T35Afgs1App

The T35Afgs1App is an example application for writing the AFGS1 syntax. It is located in the Apps/T35Afgs1App directory. The example is meant to be simple, and information on how to run the program is provided in the comments at the top of T35Afgs1App.cpp.

Note: The application should/will be renamed going forward, as it no longer encapsulates the AFGS1 syntax in a T.35 message. Instead, the application generates the AFGS1 payload (corresponding to the av1_film_grain_param_sets() function) that could be carried in any transport mechanism - as defined in the AFGS1 specification. An example of the ITU-T T.35 encapsulation is now included in the SEIAfgs1App (see below).

SEIAfgs1App

The SEIAfgs1App is an application capable of inserting AFGS1 messages into an HEVC bit-stream. The AFGS1 syntax is encapsulated in an SEI message using the Recommendation ITU-T T.35 message syntax. The application is located in the Apps/SEIAfgs1App directory. Information on how to run the program is provided in the comments at the top of SEIAfgsMain.cpp.