My DS920+ used to peg all four cores to 100 percent the moment my sister streamed a 4K movie to her ancient iPad. The video stuttered, the fan spun up like a hairdryer, and I assumed the little Celeron just was not up to the job.
It was. I had simply never turned on the one feature that makes these boxes shine for Plex.
Intel Quick Sync is a dedicated chunk of silicon baked into most Synology CPUs that handles video encoding without touching the general-purpose cores. Flip it on correctly and a single stream that used to hammer your processor drops to almost nothing. Here is exactly how to get there, plus how to prove it actually worked.
Check that your Synology can even do this
Not every Synology has the right chip. You need an Intel CPU with Quick Sync Video, which rules out the ARM-based J-series and some value models.
Boxes like the DS920+, DS220+, DS224+, DS423+, DS720+, and the DS1520+ all use Intel Celeron chips with Quick Sync and work beautifully. The older DS918+ and DS218+ do too. If your model number ends in "play" or uses an AMD Ryzen or a Realtek ARM chip, hardware transcoding through Quick Sync is off the table.
To confirm your exact chip, open the Synology product page for your model and look under the hardware specs for the CPU name, then search that name to verify Quick Sync support.
You genuinely need Plex Pass
This is the part that trips up most people, so let me be blunt about it.
Hardware transcoding is a paid feature. Without an active Plex Pass, the option in your Plex settings is greyed out and there is no workaround that is worth your time. A lifetime Plex Pass runs around 120 US dollars, or you can pay roughly 5 dollars a month to test the waters.
The Plex Pass has to be tied to the same account that owns the Plex Media Server running on your Synology. I once spent twenty minutes confused because I bought the pass on my phone account, then signed the server in under my old email. Same person, two accounts, and the feature stayed locked.
Update Plex Media Server first
Synology ships Plex through its Package Center, but that version often lags weeks behind the official release. Hardware transcoding fixes land in the newer builds, so start fresh.
- Download the latest Synology package straight from the Plex downloads page, choosing your CPU architecture (most modern Intel Synology units are x86_64).
- In DSM, open Package Center, click Manual Install, and point it at the .spk file you just downloaded.
- Let it install over the top of your existing version. Your libraries and watch history stay intact.
- Reopen the Plex web app and confirm the server version under Settings matches what you downloaded.
Running a current build matters more than people think. An outdated server sometimes shows the transcode toggle but silently falls back to software anyway.
Turn on the transcoding toggle
Now for the actual switch. Open the Plex web app, click the wrench icon to reach Settings, and pick your server from the list on the left.
Scroll down to Transcoder. You may need to click "Show Advanced" in the top right to reveal every option.
Find the checkbox labelled Use hardware acceleration when available and tick it. While you are here, tick Use hardware-accelerated video encoding too, which handles the output side. Save your changes at the bottom of the page.
Prove it is actually working
Ticking a box is not proof. The only way to know Quick Sync fired is to watch the dashboard during a real transcode.
Play a video and deliberately force a lower quality from the player, say 720p 2Mbps, so the server has no choice but to transcode. Then open Settings and click Dashboard under Status.
Look at the active stream. If you see (hw) next to "Transcode," you are done. That two-letter tag is the whole payoff.
| Dashboard label | What it means |
|---|---|
| Transcode (hw) | Quick Sync is doing the work, CPU stays low |
| Transcode (hw) (hw) | Both decode and encode are hardware accelerated, ideal |
| Transcode | Software only, hardware never engaged |
| Direct Play | No transcoding at all, nothing to test here |
If it just says "Transcode" with no tag, jump to the next section.
When (hw) refuses to show up
The most common culprit is HDR content. Tone-mapping 4K HDR down to SDR is heavy, and on a modest Celeron it can still hammer the CPU even with Quick Sync helping the decode step.
Another frequent miss: the Plex package on Synology needs access to the Intel GPU device. On a handful of DSM versions the render device permissions get reset after a major update, which quietly disables acceleration. Reinstalling the latest package as described above usually restores it.
Check these in order if you are stuck:
- Confirm the stream is genuinely transcoding, not Direct Playing. A green "Direct Play" line means nothing is being converted.
- Verify your Plex Pass is active under your account, not expired.
- Reboot the NAS once after enabling the setting. I have seen the toggle need a full restart to take effect.
- Test with a plain h.264 1080p file first, since that is the friendliest format for Quick Sync and rules out HDR complications.
For a deeper reference on how the acceleration pipeline works, Intel's own Quick Sync Video overview explains which codecs each CPU generation supports, which helps if you have very new HEVC files.
What you should actually expect
On my DS920+, a single 1080p transcode went from roughly 80 percent total CPU load down to about 15 percent once (hw) kicked in. The fan went quiet, and I could run three simultaneous streams without the box breaking a sweat.
Do not expect miracles from 4K HDR though. Those files may still lag on entry-level hardware, and honestly the better fix there is to keep an SDR copy or nudge that one relative toward a client that can Direct Play.
Get the (hw) tag showing on a normal 1080p stream, and you have solved the problem that sends most people down this road. The quiet fan is your receipt.
A quick word on RAM and simultaneous streams
Quick Sync handles the video math, but each transcode still needs a little memory and disk space for its temporary buffers. On a 4GB DS920+ I comfortably ran three 1080p streams at once, and the box only started struggling around the fifth or sixth.
If you host for a large family, bumping the RAM to 8GB or more buys you real headroom. It will not make Quick Sync faster, but it stops DSM from swapping to disk when several people hit play at dinner time.
One setting worth double checking
After a big DSM upgrade, revisit the Transcoder page and confirm both hardware boxes are still ticked. I have watched a major system update quietly clear those settings, and the first sign was a hot, loud NAS and a confused family text thread on a Sunday night.
Thirty seconds of checking after every update saves you that whole detour.
Frequently asked questions
Does Plex hardware transcoding work without Plex Pass on Synology?
No. Hardware acceleration is a paid feature gated behind Plex Pass, and the checkbox in Transcoder settings stays greyed out without one. A lifetime pass is around 120 US dollars or roughly 5 dollars monthly. The pass must be on the same account that owns the server.
How do I know if my Synology has Intel Quick Sync?
Look up your exact CPU on the Synology product page under hardware specs. Intel Celeron chips in models like the DS920+, DS224+, and DS423+ have Quick Sync. AMD Ryzen boxes such as the DS1621+ and any ARM or Realtek model do not.
Why does my Plex dashboard show 'Transcode' but not '(hw)'?
The most common causes are HDR content that still loads the CPU, an expired Plex Pass, or GPU device permissions reset by a DSM update. Reboot the NAS once after enabling the setting and test with a plain 1080p h.264 file to isolate the issue.
Will hardware transcoding fix stuttering 4K HDR playback?
Not always. Tone-mapping 4K HDR down to SDR is heavy and can still tax an entry-level Celeron even with Quick Sync assisting. Keeping an SDR copy or steering that client toward Direct Play is usually a better fix than relying on transcoding alone.
Should I install Plex from Synology Package Center or plex.tv?
Download the latest package from plex.tv and install it manually through Package Center's Manual Install option. The version bundled in Package Center often lags weeks behind, and older builds sometimes fail to engage hardware acceleration even when the toggle appears enabled.
