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AV1 Drawbacks

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Admin9705 edited this page Dec 11, 2024 · 5 revisions

Drawbacks of AV1 Encoding (For Plex)

While AV1 encoding offers significant efficiency and storage savings, it’s not a one-size-fits-all solution. Understanding the potential drawbacks is crucial, especially if your Plex users rely on devices or networks that don’t fully support AV1. These limitations often surface when Plex must transcode AV1 content to H.264 for older devices, potentially affecting performance, bandwidth, and overall user experience.

1. Compatibility Issues with Older Devices

Many legacy devices—including older smartphones, smart TVs, and media players—lack native AV1 decoding capability. If an end-user tries to watch an AV1-encoded stream on such a device, Plex must transcode it in real-time to a more widely supported format like H.264.

Why This Matters

Transcoding Complexity:

  • Plex dynamically adjusts the stream to ensure playback compatibility. For AV1 files, this might mean a significant increase in processing workload to transform AV1 into H.264 on-the-fly.

Increased GPU/CPU Load:

  • Real-time transcoding puts additional stress on your GPU or CPU, potentially leading to higher power consumption, elevated temperatures, and reduced headroom for other server tasks.

Example of Bandwidth Inflation

Hypothetical Scenario:

  • Original AV1 stream: ~2 Mbps
  • Transcoded H.264 stream: ~4-6 Mbps or more

When scaling this up:

  • 1 user might not notice, but 10 simultaneous users could mean a 20 Mbps AV1 load turning into a 40-60 Mbps H.264 load.
  • For a 4K AV1 stream at 15 Mbps, the H.264 transcode could jump to 30-45 Mbps per user. Ten such users mean 300-450 Mbps total—well beyond what many home internet connections can handle.

This bandwidth inflation can lead to buffering, quality drops, or service interruptions, especially if you’re hosting remote users and your upload speed is limited.

2. Higher CPU/GPU Utilization

AV1 encoding and decoding are more complex than older codecs like H.264. While AV1 saves storage space and improves compression efficiency, it demands more computational resources.

Impact on Your Server

  • Real-Time Transcoding Stress:
    When Plex transcodes AV1 content for an older device, your server’s CPU/GPU usage spikes. If you run multiple streams, this can degrade overall server performance or slow down other tasks, like downloads, backup operations, or additional transcoding jobs.

  • Longer Processing Times for Batch Encoding:
    Converting an entire media library to AV1 can be time-consuming. Expect longer encode times and higher energy consumption during these bulk operations, potentially reducing the time your server can spend on other tasks.

3. Limited Support for Hardware Acceleration

While newer hardware—such as Intel ARC GPUs or certain NVIDIA and AMD cards—supports AV1, older hardware might not. Without hardware acceleration, the CPU shoulders more of the transcoding load.

Consequences of No Hardware Acceleration

  • Increased CPU Load:
    Without GPU acceleration, AV1 transcoding can saturate CPU cores, leaving fewer resources for other server functions like running containers, VMs, or background tasks.

  • Performance Bottlenecks:
    On older systems, AV1 transcoding may be sluggish or infeasible, leading to poor user experiences. If your media server primarily serves older devices and runs on aging hardware, AV1 may not deliver the expected benefits.

4. Network Bandwidth and Storage Considerations

While AV1 excels at shrinking file sizes, its benefits can erode when real-time transcoding is required for playback on incompatible devices.

Key Trade-Offs

  • Increased Streaming Bandwidth Post-Transcode:
    The efficiency gains of AV1 vanish once you transcode to H.264. The final streamed video might be larger and consume more bandwidth, increasing the load on your network and potentially causing buffering.

  • Multi-Codec Storage Overheads:
    If you maintain multiple copies of the same content (e.g., one AV1 version for newer devices and an H.264 fallback for older ones), you erode the original AV1 storage savings. You may find yourself juggling multiple versions of the same file, increasing complexity and storage overhead.

Mitigation Strategies

While these drawbacks are real, you can take steps to minimize their impact:

  • Hardware Upgrades:
    Invest in newer GPUs or transcoding hardware that supports AV1, reducing CPU load and improving transcoding efficiency.

  • Selective AV1 Use:
    Only encode frequently accessed, modern files in AV1. Keep legacy formats intact for content frequently watched on older devices.

  • Bandwidth Management:
    Use Plex’s built-in bandwidth limits or advanced settings to control remote playback quality, ensuring users on slow connections receive appropriate transcoding bitrates.

  • Testing and Tuning:
    Experiment with different quality levels, presets, and device profiles to find a balance that works best for your unique environment.

Conclusion

AV1’s storage and efficiency benefits are compelling, but they come with potential trade-offs in terms of hardware compatibility, transcoding complexity, and network load. By understanding these drawbacks, you can make informed decisions about when and how to implement AV1 in your Plex setup. This foresight allows you to maintain a smooth viewing experience for all users, regardless of their device capabilities, while still reaping the long-term advantages of AV1 encoding.

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