[Feature Request] Add hardware acceleration (QSV/VAAPI) support for preview generation

[Powerbock]

Feature Description

It would be great if XBVR could use hardware acceleration (Intel QSV, VAAPI, or NVENC) for preview/thumbnail generation instead of software encoding.

Current Behavior

Currently, pkg/tasks/preview.go uses software encoding:

cmd := buildCmd(GetBinPath("ffmpeg"), args...)

This is CPU-intensive, especially when generating previews for large libraries.

Proposed Solution

Add an environment variable like XBVR_HWACCEL to enable hardware acceleration:

XBVR_HWACCEL=qsv    # Intel Quick Sync
XBVR_HWACCEL=vaapi  # VAAPI (Linux)
XBVR_HWACCEL=nvenc  # NVIDIA

FFmpeg call would change to:

ffmpeg -hwaccel qsv -hwaccel_output_format qsv -i input.mp4 -c:v h264_qsv ...

Benefits

• Significantly faster preview generation
• Lower CPU usage
• Better utilization of available hardware

Environment

• XBVR running in Docker
• Intel CPU with QSV support (tested with HD 630 / Kaby Lake)
• Custom FFmpeg build with QSV enabled

Thank you for considering this feature!