FFmpeg HEVC NVENC: How to Transcode Videos

This article provides a straightforward guide on how to transcode videos using the hardware-accelerated HEVC encoder (hevc_nvenc) in FFmpeg. You will learn the system requirements, the basic command structure, and key configuration options for controlling quality, speed, and bitrate using NVIDIA graphics cards.

Prerequisites

To use NVIDIA’s hardware-accelerated HEVC encoder, you need: 1. An NVIDIA graphics card that supports NVENC HEVC encoding (Kepler generation or newer; GTX 960/980 Ti and newer for HEVC). 2. The latest NVIDIA graphics drivers installed. 3. A build of FFmpeg compiled with NVENC support. You can verify this by running the following command in your terminal:

ffmpeg -encoders | grep nvenc

If hevc_nvenc appears in the output list, your FFmpeg installation is ready.

Basic Transcoding Command

The simplest command to transcode an input video to HEVC (H.265) using your GPU is:

ffmpeg -i input.mp4 -c:v hevc_nvenc output.mp4

• -i input.mp4: Specifies the input file.
• -c:v hevc_nvenc: Selects the NVIDIA hardware-accelerated HEVC encoder.
• output.mp4: The resulting output file.

Controlling Quality and Bitrate

To optimize the output file size and visual quality, you should customize the bitrate or rate control mode.

Constant Quality (CQP)

Constant QP (CQP) is the recommended mode for one-pass file-based transcoding where file size is not a strict constraint. Lower values result in higher quality and larger file sizes. A range of 20 to 25 is ideal for most content.

ffmpeg -i input.mp4 -c:v hevc_nvenc -rc constqp -qp 23 output.mp4

Constant Bitrate (CBR) and Variable Bitrate (VBR)

If you need to target a specific file size or bandwidth limit, use the target bitrate option (-b:v).

To set a target bitrate with a maximum peak limit (VBR):

ffmpeg -i input.mp4 -c:v hevc_nvenc -b:v 5M -maxrate:v 8M -bufsize:v 16M output.mp4

Adjusting Speed and Quality Presets

NVIDIA’s NVENC hardware offers presets ranging from p1 (fastest performance, lowest quality) to p7 (slowest performance, highest quality). The default preset is p4.

To transcode with high quality:

ffmpeg -i input.mp4 -c:v hevc_nvenc -preset p6 -qp 23 output.mp4

Complete Practical Example

This command copies the original audio track without re-encoding to save time and preserve audio quality, while transcoding the video to HEVC using high-quality settings:

ffmpeg -i input.mp4 -c:v hevc_nvenc -preset p5 -rc constqp -qp 22 -c:a copy output.mp4