---
title: "HEVC Batch Re-Encode for Plex Using VAAPI (AMD GPU)"
domain: streaming
category: plex
tags: [plex, ffmpeg, hevc, vaapi, amd, gpu, encode, storage, rx480]
status: published
created: 2026-05-15
updated: 2026-05-15
---
# HEVC Batch Re-Encode for Plex Using VAAPI (AMD GPU)

## Problem

Plex NVMe storage is filling up from a large library of H.264-encoded video files (YouTube downloads, stream archives, etc.). Re-encoding to HEVC (H.265) reclaims 30–50% of disk space. The catch: Plex tracks each file's "date added" in a SQLite database, and that order matters for playback queues. Naive re-encode-and-replace approaches can corrupt or reset that metadata.

## Solution

Use `ffmpeg` with `hevc_vaapi` (AMD GPU hardware encoder) to batch re-encode files in-place using an atomic rename swap that preserves the Plex database record — including `added_at` — without any Plex downtime or database editing.

---

## How Plex Stores "Date Added"

Plex does **not** use file modification time (`mtime`) for "date added." It stores a Unix timestamp in its SQLite database:

```sql
-- Plex DB location (override via systemd unit may differ — check):
-- /var/lib/plexmediaserver/Library/Application Support/Plex Media Server/
--   Plug-in Support/Databases/com.plexapp.plugins.library.db
-- (or wherever PLEX_MEDIA_SERVER_APPLICATION_SUPPORT_DIR points)

SELECT mi.added_at, datetime(mi.added_at, 'unixepoch'), mp.file
FROM metadata_items mi
JOIN media_items me ON me.metadata_item_id = mi.id
JOIN media_parts mp ON mp.media_item_id = me.id
WHERE mp.file LIKE '%your-file%';
```

> **Note:** If the default path returns 0 rows, check your actual data directory:
> ```bash
> systemctl cat plexmediaserver | grep APPLICATION_SUPPORT
> ```

The `added_at` field is keyed to the **file path** in `media_parts`. As long as the file path doesn't change, the database record — including `added_at` — is untouched even after the file's content is replaced.

---

## Why VAAPI Instead of libx265

On a host with an AMD RX 480/580 (or similar Polaris GPU), hardware HEVC encoding via VAAPI is roughly **9× faster** than software libx265 at comparable quality:

| Encoder | Speed (1080p) | Notes |
|---|---|---|
| libx265 -preset medium | ~21 fps / 0.35× | Best quality/size ratio |
| hevc_vaapi QP 28 | ~186 fps / 3.1× | Sufficient for streaming content |

For 1080p streaming content (game streams, podcasts, YouTube archival), the quality difference is imperceptible. libx265 is preferable only for archival encodes where absolute quality matters.

### Verify VAAPI is working

```bash
vainfo 2>&1 | grep -E "vaapi|HEVC|hevc|Driver"
ls /dev/dri/renderD128
```

You need `VAProfileHEVCMain : VAEntrypointEncSlice` in the output. If missing, install `mesa-va-drivers-freeworld` (RPM Fusion) for AMD hardware.

---

## The Atomic Swap Strategy

The key insight: `mv file.tmp file` on the **same filesystem** is an atomic inode rename at the kernel level. Plex sees the same path still present — it never fires a "file removed" event, so the `metadata_items` record (including `added_at`) is preserved.

**Safe sequence:**
1. Encode source → `.hevc.tmp.mp4` alongside the original
2. Verify the output with `ffprobe`
3. `touch -r original.mp4 temp.mp4` — copy mtime (cosmetic, not required)
4. `mv temp.mp4 original.mp4` — atomic replace

**The one pitfall:** if the original file is deleted *before* the `mv`, Plex orphans the DB record (removes `metadata_items` entry on next scan) and re-indexes the new file with a fresh `added_at`. The original must still exist at swap time.

---

## The Batch Script

Script lives at `~/hevc_batch.sh` on majorhome.

```bash
# Dry run — scan and report what would be encoded, no changes
bash ~/hevc_batch.sh --dry-run

# Full run (default: files >1GB, QP 28)
tmux new-session -d -s hevc_batch 'bash ~/hevc_batch.sh'

# Custom options
bash ~/hevc_batch.sh --min-size-gb 2 --qp 26
```

### Queue and resume

The script writes a queue file at `~/hevc_queue.txt` on first run (scanning all files with ffprobe — takes ~10 min for a large library). On subsequent runs it resumes from where it left off. Completed files are logged to `~/hevc_done.txt`. Failed files go to `~/hevc_failed.txt`.

To restart from scratch: `rm ~/hevc_queue.txt ~/hevc_done.txt`

### Log output

```bash
# Structured log lines only (skip ffmpeg progress noise)
grep '^\[20' ~/hevc_batch.log

# Watch live progress
tail -f ~/hevc_batch.log | grep '^\[20'
```

Each file logs:
- Source size and codec
- `Plex added_at before: <unix timestamp>`
- ffmpeg exit code and elapsed time
- Output size and savings
- `DB check: added_at PRESERVED ✓` (or WARN if changed)

### Space guard

The script aborts if free space on the Plex volume drops below 20GB (`MIN_FREE_GB`). Worst-case headroom needed is `source_size + tmp_size` simultaneously — on a 4GB source file that's ~8GB peak.

---

## ffmpeg Command

```bash
ffmpeg \
  -vaapi_device /dev/dri/renderD128 \
  -i "input.mp4" \
  -vf 'format=nv12,hwupload' \
  -c:v hevc_vaapi -rc_mode CQP -qp 28 \
  -c:a copy \
  -movflags +faststart \
  -y "output.tmp.mp4"
```

- `-rc_mode CQP -qp 28` — constant quantizer; higher value = smaller file / lower quality. QP 24 is high quality, QP 28 is good for streaming content.
- `-vf 'format=nv12,hwupload'` — required to move frames to GPU memory for VAAPI encoding.
- `-c:a copy` — passes audio through untouched.
- `hevc_vaapi` does not support 10-bit output on Polaris (RX 480/580). For 10-bit HDR sources, fall back to `libx265` with color signaling flags.

---

## Plex Data Directory Override

On majorhome, the Plex data directory is overridden in the systemd unit — the default path `/var/lib/plexmediaserver/` is empty:

```bash
systemctl cat plexmediaserver | grep APPLICATION_SUPPORT
# Environment=PLEX_MEDIA_SERVER_APPLICATION_SUPPORT_DIR=/plex/plexdata/Library/Application Support
```

The actual DB path is therefore:
```
/plex/plexdata/Library/Application Support/Plex Media Server/Plug-in Support/Databases/com.plexapp.plugins.library.db
```

---

## Related

- [[plex-4k-codec-compatibility]] — Apple TV Direct Play compatibility, HEVC HDR notes
- [[snapraid-mergerfs-setup]] — MajorRAID storage pool setup
- [[SnapRAID-Majorhome]] — majorhome SnapRAID project