VC1 video buffers with hardware transcoding on DS718+

Plex Media Server NAS & Devices
1

Hi, I’m having issues watching 1080p BluRay rips that are in VC1 format if hardware transcoding is on.
Video plays for a couple of seconds, then buffers, then plays some more etc. CPU usage is about 25%
If hardware decoding is off, it plays fine, CPU usage is about 75%
No problems with BluRay rips in other codecs - same 25% usage with hardware decoding on and no buffering issues.

Synology DS718+ / PMS 1.11.0.4666 64bit

2

I recommend backing down from the beta (1.11.0) version to the public (1.10.1) version.

There have been reports of issues with 1.11.0

3

Thanks for the tip - I didn’t realise 1.11 was a beta release.
After downgrading a situation I described has somewhat improved.
On a beta I couldn’t get a smooth playback with any quality settings with hardware transcode enabled. And now with 1.10 I can lower it down to a little disappointing 3Mbps 720p to get buffering free playback.
Still this looks strange to me that my NAS that is capable of smooth software encoding with 75% CPU load might be struggling with hardware enabled task while being used only in the range of 25-30%…

4

VC-1 has not enabled for hardware transcoding by engineering yet. The change you’re seeing with HW is only on the encoding (output) side.

5

VC-1 has not enabled for hardware transcoding by engineering yet.
That’s good to know, but still what I can’t understand is this:
Hardware transcoding off: VC-1 video is being played back smoothly, without buffering, CPU at 75% load
Hardware transcoding on: VC-1 video is interrupted with buffering, CPU at 25-30% load
It looks like a bug to me, I can’t find any logical explanation to this…

6

If you’d care to gather all the info I’d need to submit this, I’ll be happy to verify your results and write it up.

I will need:

  1. A sample of the file https://support.plex.tv/articles/201035968-generating-sample-files-from-media/
  2. The logs (Debug level only) from you trying to play the item in both modes. (Play just long enough to replicate the failure and same time stamp)
  3. If you can upload both sets of logs and provide a link to the sample, I will download and replicate.

If I cannot replicate, we’ll find out why.
If I can, I’ll write it up and submit it.

7

ChuckPA, I hope I’ve prepared the requested info correctly:
Here’s a link to a sample (1m 40s, appr. 300Mb): dropbox.com/s/vh5q9pmz3l7dtig/plex_issue_demo_file.mkv?dl=0
Two sets of logs are attached to this message (both demonstrating playback of the same 1m 40s)

8

THank you… Reviewing now.

9

Thank you for them but no playback activty shows. If you look, there is only a few Kilobytes in each. There should be 200-300 KB in each.

Can you recreate it again?

Also, between those times you purge the logs, Please remember to perform a proper PMS shutdown. It will give me the full picture by flushing all the buffers to disk

10

ChuckPA, I would like to help here but you’d have to be more specific about the steps I need to take.

What I did was this:

  1. Stopped the PMS and cleaned Logs folder contents
  2. Started the PMS, reproduced the issue, went to the PMS Settings and pressed ‘download logs’ button
  3. I repeated steps 1 and 2 for the scenario where there’s no issue

If you need me to gather logs differently, specify exact steps I need to follow, please

11
  1. Settings - Server - General
  2. Check the box: Enable Plex Media Server debug logging
  3. Save changes
  4. Rerun the test sequence.

Debug level logging shows me what is happening.

12

I have a similar issue when converting from MPEG2 (software) to H264 (HW). I’m convinced that when Plex has HW transcoding enabled, it is only using a single core for both tasks. Until they work this out, I’ve just disabled HW transcoding.

13

I can confirm the same issue on a Synology 918+ running 1.11.0.4666.

VC-1 Video, Dolby 5.1 PCM audio. With hardware transcode on, video studders to the point of being unplayable. With transcode off, video transcodes/plays fine.

Video behavior is the same regardless of wether the audio is being transcoded. I also tried on a VC-1/DTS-MA HD.

Player is on a Sony Android TV.

14

Problem also persists in 1.11.1.4760

15

VC-1 hardware transcode is not yet supported. The pre-release of libva contains it. We don’t have it yet.

16

I have a DS418Play, which I believe suffers from the same thing. (VC-1 HW transcode not supported) I’ve Optimized all my VC1 MKVs to h.264 versions in the interim. Any news on when this will be resolved? (DS418 play has the Apollo Lake CPU (Intel Celeron J3355))

Version 1.11.3.4803
DSM 6.1.5-15254

17

Plex doesn’t give roadmaps or schedules. (just how they do things).

I can tell you I see all the chatter about VC-1. I don’t have any hard details.

Re the DS418play, make certain you do bump up the memory. That seems to be important for those doing HEVC. I suspect VC-1 will have a similar relationship

1 Like
18

Thanks. Already bumped to 6GB RAM, which is the maximum supported. (according to Synology at least)

Would be interesting to see if it could take 16 GB- even though it wouldn’t be officially supported.

19

Those processors J3355 and J3455 max out at 8GB. (Per ark.intel.com)

Get a ‘matched set’ (aka 8 GB kit )

(Syno says 6 is max supported because they don’t sell 4GB sticks. I thought the same thing too about my DS1815+ - Atom C2538)

20

Just wanted to circle back with @ChuckPa to see if any progress had been made towards HW support for VC-1. Anything you can share would be greatly appreciated!