Transcode Video with FFmpeg hevc_amf Encoder

This article provides a straightforward guide on how to transcode video files using the AMD Advanced Media Framework (AMF) HEVC encoder (hevc_amf) in FFmpeg. You will learn the basic command syntax, hardware requirements, and key configuration parameters to leverage your AMD graphics card for high-speed hardware-accelerated video encoding.

Prerequisites

To use AMD’s hardware encoder in FFmpeg, you need: * An AMD Radeon graphics card that supports HEVC (H.265) hardware encoding. * Up-to-date AMD graphics drivers installed on your system. * A version of FFmpeg compiled with AMF support (enabled by default in most modern official builds for Windows and Linux).

To verify if your FFmpeg installation supports the encoder, run the following command in your terminal:

ffmpeg -encoders | findstr amf

(On Linux/macOS, replace findstr with grep). You should see hevc_amf listed in the output.

Basic Transcoding Command

The simplest way to transcode a video using the AMD HEVC hardware encoder is to specify hevc_amf as the video codec.

ffmpeg -i input.mp4 -c:v hevc_amf -c:a copy output.mp4

In this command: * -i input.mp4 specifies the source video file. * -c:v hevc_amf tells FFmpeg to encode the video stream using AMD’s HEVC encoder. * -c:a copy copies the audio stream directly from the source without re-encoding it, saving CPU power and time.

Advanced Configuration and Quality Tuning

To get the best balance between file size and video quality, you can customize the encoding parameters.

Controlling Bitrate and Rate Control Mode

AMF supports several rate control modes via the -rc flag. The most common modes are Constant QP (cqp), Constant Bitrate (cbr), and Variable Bitrate (vbr_latency or vbr_peak).

Constant Quality (CQP) Mode: CQP is recommended for archival purposes where quality is the priority. Lower values produce higher quality and larger files.

ffmpeg -i input.mp4 -c:v hevc_amf -rc cqp -qp_i 22 -qp_p 22 output.mp4

• -qp_i sets the QP value for I-frames.
• -qp_p sets the QP value for P-frames. A value between 18 and 28 is generally optimal.

Variable Bitrate (VBR) Mode: VBR is ideal for streaming or target file sizes.

ffmpeg -i input.mp4 -c:v hevc_amf -rc vbr_latency -b:v 5M -maxrate 8M output.mp4

• -b:v 5M sets the target average video bitrate to 5 Mbps.
• -maxrate 8M caps the maximum bitrate spike at 8 Mbps.

Adjusting the Quality Preset

You can instruct the encoder to prioritize either encoding speed or visual quality using the -quality parameter. * speed: Maximizes transcoding speed (ideal for live streaming). * balanced: The default setting balancing speed and quality. * quality: Prioritizes visual fidelity at the cost of processing speed.

ffmpeg -i input.mp4 -c:v hevc_amf -quality quality output.mp4

By combining these parameters, you can efficiently offload the heavy lifting of video transcoding to your AMD GPU, achieving rapid render times with minimal CPU usage.