Preamble
The GP-Tune OFX Plugin has been developed to provide an accurate correction of GoPro footage. The Plugin works across numerous NLE and VFX applications that support the OFX plugin standard. The GP-Tune Plugin includes Natural, Protune Flat, GP-Log and GoPro Labs LogB custom curve transforms. For reference, the characteristic curves for GP-Log and Protune Flat have been plotted in the graph below. Middle-Gray for Protune Flat is 68% IRE whilst Middle-Gray for GP-Log at 0EV is 76% IRE (HERO12 Firmware 1.20 onwards) or -2 EV Exposure at 49% IRE (HERO12 firmware prior to 1.20).
Prerequisites
The GP-Tune Plugin has been developed using the OpenFX 1.4 standard.
It includes GPU acceleration using OpenCL 1.2, CUDA 10.2 and Metal 2.0 as well as CPU Multi-threading support.
The Plugin is supported on 64-bit instances of Linux, Windows and MacOS.
MacOS support is built from OSX 10.13 onwards, though the plugin may also work on older OSX releases.
Installation
The installer files must be extracted from the zip file. The respective installer will manage installation to the required locations.
The GPTune.ofx.bundle package MUST be installed to the designated OFX Plugin folder for the relevant operating system.
Windows
The Windows Installer will place the OFX Plugin to the following folder:
C:\Program Files\Common Files\OFX\Plugins\
MacOS
The MacOS Package Installer will place the OFX Plugin to the following folder:
/Library/OFX/Plugins/
Note that some Mac Users may experience issues with Gatekeeper Security. A security prompt may appear and prevent the plugin from being installed or used. In this scenario, the OFX Plugin will need to be allowed through the Mac Security settings under System Preferences > Security & Privacy > General.
Linux
The OFX Installer will need to be executed through a command terminal. The run command may look like:
./GPTune_OFX_v1.0_Linux.run
The OFX Plugin will be copied to the following folder:
/usr/OFX/Plugins/
Uninstall
The Plugin can be uninstalled on Windows systems via the “Add or remove programs” feature.
For the MacOS and Linux operating systems, simply delete the GPTune.ofx.bundle package from the designated folder of your Operating System.
For MacOS, this package is located under:
/Library/OFX/Plugins/
For Linux, this package is located under:
/usr/OFX/Plugins/
Usage
The GP-Tune Plugin has been developed to work across numerous workflows, including ACES. The plugin has been developed with some internal smarts, allowing default parameters to be altered based on the host application. The sections below will outline the parameters available and sample workflows.
Usage Parameters
The sections below will outline the parameters available and sample workflows for the GP-Tune Plugin.
Exposure Correction
The Exposure Correction Parameter allows for exposure adjustment in Exposure Values (EV) from -6 to +6. The values can be manipulated using the slider or by inputting the EV directly in the designated field. Source footage that is either over-exposed or under-exposed can be corrected this way.
Curve Preset
Select the desired Curve Preset based on the source footage:
- Natural
- Protune Flat
- GP-Log
- Custom Log
Only the Custom Log option will apply customized Log Base and Offset parameter values.
Log Base
The Log Base is a customizable parameter that is only available when the Curve Preset is set to Custom Log. This parameter can be adjusted based on the settings applied on cameras with the GoPro Labs firmware. The default value is 113 for standard Protune. Only HERO11 and above cameras support this parameter.
Offset
The Offset is a customizable parameter that is only available when the Curve Preset is set to Custom Log. This parameter can be adjusted based on the settings applied on cameras with the GoPro Labs firmware. The default value is 0 for standard Protune. Only HERO11 and above cameras support this parameter.
Camera Model
Select the respective GoPro camera model. This setting will determine the appropriate channel gain to apply when using the NATIVE color space.
Models with specific color data include:
- HERO13 Black
- HERO12 Black
- HERO11 Black
- HERO10 Black
- HERO9 Black
- HERO8 Black
- HERO7 Black
- HERO6 Black
- HERO5 Black
Camera Color
Select the respective Color Space based on source input:
- NATIVE
- WIDE
- Rec.709
- Rec.2020
- Custom WRGB
Custom Red, Green and Blue WRGB Gains
Set custom White Balance gains. Ideal for WRGB values obtained from gpmf stream in each video. Example extract from gmpf-parser shows respective Red, Green and Blue WRGB parameters:
> gpmf-parser GX010024.MP4 -fWRGB
VIDEO FRAMERATE:
25.000 with 105 frames
PAYLOAD TIME:
0.000 to 1.040 seconds
SCALED DATA:
WRGB 2.234, 1.000, 1.840,
WRGB 2.234, 1.000, 1.840,
WRGB 2.238, 1.000, 1.840,
WRGB 2.238, 1.000, 1.840,
WRGB 2.234, 1.000, 1.840,
WRGB 2.238, 1.000, 1.840,
WRGB 2.238, 1.000, 1.840,
WRGB 2.238, 1.000, 1.840,
WRGB 2.238, 1.000, 1.840,
...Highlight Rolloff
Tone mapping adjustment. Set to zero for no tone mapping or set to highest level for significant tone mapping. Set between 0.25 and 0.5 for smooth roll-off.
Gamut Mapping
Gamut compression mapping to map Sensor native gamut to smaller color space.
Desaturate
Toggle desaturation of colors. If enabled, saturation is reduced by 25%.
Clamp Negatives
The signal is clamped between zero and the highest value by default.
NATIVE will use the camera’s raw sensor data with a gain applied based on the specific camera model.
WIDE will use the camera’s raw sensor data with Auto white balancing. This is the WIDE=1 parameter in GoPro Labs firmware.
The Rec.709 option is when Auto or other specific White Balance parameters are used as the camera will limit to a Rec.709/sRGB color gamut.
Rec.2020 is only for GoPro Labs firmware where Rec.2020 color values are defined using the 2020=1 parameter.
Custom WRGB allows for the use of custom White Balance gains.
Lighting Preset
The colorimetry has been calculated based on a Daylight and Tungsten preset. Tungsten may be preferred for yellow ambient lighting scenarios such as older street lights. Daylight is the default option.
Timeline Color Space
This setting will convert the source to the desired color space, normally aligning with the Timeline Color Space in Resolve.
The Color Space Options are:
- ACES AP0
- ACES AP1
- P3 (D65)
- Rec. 709 / sRGB
- Rec. 2020
- DaVinci Wide Gamut
ACES AP1 is the color space associated with ACEScc, ACEScct and ACEScg. ACES AP0 consists of the ACES 2065-1 color primaries. The default color space is set to Rec.709
Timeline Gamma
This setting will convert the source to the desired Gamma, normally aligning with the Timeline Gamma settings in Resolve.
The Gamma Options are:
- Linear
- ACEScc
- ACEScct
- ITU-R BT.709 (Scene)
- Gamma 2.2
- Gamma 2.4
- Gamma 2.6
- DaVinci Intermediate
- sRGB
The default Gamma is set to ITU-R BT.709 (Scene) for standard SDR workflows.
Example Workflows
DaVinci Resolve
ACEScc or ACEScct
Using the GP-Tune plugin inside an ACES workflow is fairly straightforward. Any source media must firstly be set to have No Input Transform. The plugin can then be added into the Node structure of the designated clip. The To Gamma must be set to the required ACEScc(t) parameter as per the project settings. The To Color Space will automatically change to ACES AP0 as a result.
DaVinci YRGB & YRGB Color Managed
When editing in DaVinci YRGB Color Managed workflows, the source media’s Input Color Space must be set to Bypass or Same as Timeline depending on the version of Resolve. The To Color Space and To Gamma must also match the settings of the project appropriately. In a Color Managed workflow, these parameters will be dependent on the project Timeline color settings. In a Non-Color Managed workflow, these will be dependent on the Output color settings.
In Resolve 16 and below, the default timeline option is normally Rec.709 for Color Space and Gamma 2.4 for Gamma. In Resolve 17 and above, the default gamma option will vary between Gamma 2.4 and Scene, depending on whether the installation is completely new or updated from earlier versions.
There are additional caveats to be aware of when using Resolve 17 and above. In Color Managed workflows, Resolve will now set Tone and Gamut mapping on input and output settings by default – these are referred to as Input DRT and Output DRT. Enabling DRT may have adverse impacts to the scene before it is normalized. To avoid issues with tone and gamut mapping when using SDR presets, it is recommended to select the Custom preset and to disable the Input DRT by selecting None. One may also choose to select the the DaVinci Wide Gamut preset first before changing to Custom and output to an SDR format such as Rec.709. This preset will expand the project to a wider Color Gamut and Dynamic Range, similar to an ACES workflow. Regardless, it is recommended that Input DRT be explicitly disabled across all projects.
Vegas Pro
The default output in Vegas Pro is set to Rec.709 Color Space and Scene (ITU-R BT.709) Gamma. This is to cater for the most common 8-bit project settings. When switching to 32-bit floating point, consider changing Timeline Color Space and Timeline Gamma to align with the project settings.
VFX Applications
When using the plugin inside VFX applications such as Fusion Studio, Nuke and Natron, the To Color Space option automatically defaults to ACES AP1 (also referred to as ACEScg). The To Gamma setting also defaults to Linear in order to cater for the required Visual Effects workflows.