# AV1 vs. HEVC: Efficiently Archiving Ghibli Classics

I recently set out to optimize my Studio Ghibli collection by re-encoding Blu-ray discs into the **AV1** format. My goal was to significantly reduce file sizes without compromising visual quality. AV1 was the ideal candidate due to its high compression efficiency, royalty-free licensing, and growing hardware support.

For this experiment, I chose the 1991 film *"Only Yesterday"*. It is notoriously difficult to transcode due to persistent picture jitter and film grain (noise). Using **FFmpeg 6.0**, I compared HEVC and AV1, finding that a **10-bit** depth and **Constant Rate Factor (CRF)** yielded the best results for both.

### The Results

The AV1 encode was remarkably **four times smaller** (645 MB) than the HEVC version (2563 MB), despite maintaining nearly identical quality metrics. However, the trade-off was encoding time: using `libaom`, it took approximately **three days** to process the two-hour movie.

### Encoding Parameters

HEVC (x265):

\-c:v libx265 -preset slow -tune animation -profile:v main10 -pix\_fmt yuv420p10le -crf 22 -x265-params crf=22:no-sao=1:no-fast-intra=1

AV1 (libaom):

\-c:v libaom-av1 -pix\_fmt yuv420p10le -b:v 0 -crf 30 -threads 8 -cpu-used 4 -aq-mode 1 -tune ssim -lag-in-frames 35 -arnr-max-frames 15 -arnr-strength 4 -aom-params tune=ssim:cq-level=30:cpu-used=4:noise-sensitivity=2:tune-content=default:arnr-strength=4:arnr-maxframes=15:enable-qm=1:enable-chroma-deltaq=1:quant-b-adapt=1

### Quality Metrics Comparison

| **Metric** | **HEVC (2.5 GB)** | **AV1 (0.6 GB)** |
| --- | --- | --- |
| **PSNR (Average)** | 42.35 dB | 42.10 dB |
| **SSIM (All)** | 0.9634 | 0.9635 |

The metrics confirm that AV1 achieved the same visual fidelity as HEVC while using only **25% of the disk space**. For archival purposes where storage is at a premium and encoding time is not a concern, AV1 is the clear winner.