How to Use transpose_vaapi in FFmpeg

This article provides a quick guide on how to use the transpose_vaapi filter in FFmpeg to perform hardware-accelerated video rotation and flipping. By leveraging Intel’s Video Acceleration API (VAAPI), you can rotate videos efficiently with minimal CPU usage using practical command-line examples.

Understanding transpose_vaapi Parameters

The transpose_vaapi filter requires the dir (direction) parameter to specify how the video should be rotated or flipped. The parameter accepts the following integer values:

• 0: Rotate 90 degrees counter-clockwise and flip vertically.
• 1: Rotate 90 degrees clockwise.
• 2: Rotate 90 degrees counter-clockwise.
• 3: Rotate 90 degrees clockwise and flip vertically.

FFmpeg Command Examples

To use VAAPI filters, you must initialize your hardware acceleration device (usually /dev/dri/renderD128 on Linux).

Example 1: Full Hardware Pipeline (Decode, Rotate, and Encode)

The most efficient way to use transpose_vaapi is to keep the entire pipeline inside the GPU. The following command decodes the input video using VAAPI, rotates it 90 degrees clockwise (dir=1), and encodes the output using the H.264 VAAPI encoder:

ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -hwaccel_output_format vaapi -i input.mp4 -vf "transpose_vaapi=dir=1" -c:v h264_vaapi output.mp4

Example 2: Rotating 180 Degrees

The transpose_vaapi filter does not have a single 180-degree rotation parameter. To rotate a video 180 degrees, you must chain two 90-degree rotation filters together in the filtergraph:

ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -hwaccel_output_format vaapi -i input.mp4 -vf "transpose_vaapi=dir=1,transpose_vaapi=dir=1" -c:v h264_vaapi output.mp4

Example 3: Software Input to VAAPI Rotate and Encode

If your source video cannot be decoded via hardware, you can decode it using the CPU, upload the frames to the GPU using hwupload, apply the rotation, and encode with VAAPI:

ffmpeg -init_hw_device vaapi=gpu:/dev/dri/renderD128 -filter_hw_device gpu -i input.mp4 -vf "format=nv12,hwupload,transpose_vaapi=dir=2" -c:v h264_vaapi output.mp4