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HW-ACCEL

## Hardware Acceleration

OpenShot now has experimental support for hardware acceleration, which uses 1 (or more) graphics cards to offload some of the work for both decoding and encoding. This is very new and experimental (as of May 2019), but we look forward to "accelerating" our support for this in the future!

The following table summarizes our current level of support:

| Linux Decode | Linux Encode | Mac Decode | Mac Encode | Windows Decode | Windows Encode | Notes
--- | --- | --- | --- | --- | --- | --- | ---
VA-API | ✔️ | ✔️ | - | - | - | - | Linux Only
VDPAU | ✔️ 1 | ✅ 2 | - | - | - | - | Linux Only
CUDA (NVDEC/NVENC) | ❌ 3 | ✔️ | - | - | - | ✔️ | Cross Platform
VideoToolBox | - | - | ✔️ | ❌ 4 | - | - | Mac Only
DXVA2 | - | - | - | - | ❌ 3 | - | Windows Only
D3D11VA | - | - | - | - | ❌ 3 | - | Windows Only
QSV | ❌ 3 | ❌ | ❌ | ❌ | ❌ | ❌ | Cross Platform

#### Notes

1. VDPAU for some reason needs a card number one higher than it really is
2. VDPAU is a decoder only
3. Green frames (pixel data not correctly tranferred back to system memory)
4. Crashes and burns

## Supported FFmpeg Versions

- HW accel is supported from FFmpeg version 3.4
- HW accel was removed for nVidia drivers in Ubuntu for FFmpeg 4+

Notice: The FFmpeg versions of Ubuntu and PPAs for Ubuntu show the same behaviour. FFmpeg 3 has working nVidia hardware acceleration while FFmpeg 4+ has no support for nVidia hardware acceleration included.

## OpenShot Settings

The following settings are use by libopenshot to enable, disable, and control the various hardware acceleration features.

int HARDWARE_DECODER = 0;
/* 0 - No acceleration
1 - Linux VA-API
2 - nVidia NVDEC
3 - Windows D3D9
4 - Windows D3D11
5 - MacOS / VideoToolBox
6 - Linux VDPAU
7 - Intel QSV */
int OMP_THREADS = 12;
int FF_THREADS = 8;
int DE_LIMIT_HEIGHT_MAX = 1100;
int DE_LIMIT_WIDTH_MAX = 1950;
int HW_DE_DEVICE_SET = 0;
int HW_EN_DEVICE_SET = 0;

## Libva / VA-API (Video Acceleration API)

The correct version of libva is needed (libva in Ubuntu 16.04 or libva2 in Ubuntu 18.04) for the AppImage to work with hardware acceleration. An AppImage that works on both systems (supporting libva and libva2), might be possible when no libva is included in the AppImage.

- vaapi is working for intel and AMD
- vaapi is working for decode only for nouveau
- nVidia driver is working for export only

## AMD Graphics Cards (RadeonOpenCompute/ROCm)

Decoding and encoding on the (AMD) GPU is possible with the default drivers. On systems where ROCm is installed and run a future use for GPU acceleration of effects could be implemented (contributions welcome).

## Multiple Graphics Cards

If the computer has multiple graphics cards installed, you can choose which should be used by libopenshot. Also, you can optionally use one card for decoding and the other for encoding (if both cards support acceleration). This is currently only supported on Linux, due to the device name FFmpeg expects (i.e. **/dev/dri/render128**). Contributions welcome if anyone can determine what string format to pass for Windows and Mac.

## Help Us Improve Hardware Support

This information might be wrong, and we would love to continue improving our support for hardware acceleration in OpenShot. Please help us update this document if you find an error or discover new and/or useful information.

FFmpeg 4 + nVidia The manual at: https://www.tal.org/tutorials/ffmpeg_nvidia_encode works pretty well. We could compile and install a version of FFmpeg 4.1.3 on Mint 19.1 that supports the GPU on nVidia cards. A version of openshot with hardware support using these libraries could use the nVidia GPU.

BUG: Hardware supported decoding still has some bugs (as you can see from the chart above). Also, the speed gains with decoding are not as great as with encoding. Currently, if hardware decoding fails, there is no fallback (you either get green frames or an "invalid file" error in OpenShot). This needs to be improved to successfully fall-back to software decoding.

Needed:

- A way to get options and limits of the GPU, such as supported dimensions (width and height).
- A way to list the actual Graphic Cards available to FFmpeg (for the user to choose which card for decoding and encoding, as opposed to "Graphics Card X")

Further improvement: Right now the frame can be decoded on the GPU, but the frame is then copied to CPU memory for modifications. It is then copied back to GPU memory for encoding. Using the GPU for both decoding and modifications will make it possible to do away with these two copies. A possible solution would be to use Vulkan compute which would be available on Linux and Windows natively and on MacOS via MoltenVK.

## Credit

A big thanks to Peter M (https://github.com/eisneinechse) for all his work on integrating hardware acceleration into libopenshot! The community thanks you for this major contribution!