I have a Synology DS918+ which has a Intel Celeron J3455
I am running PMS 1.9.7.4441
I have hardware transcoding enabled under server settings. I can transcode MPEG4 to H264 just fine. The problem comes when I try to stream OTA content via Plex Live TV (sourcing from HDHomeRun) doing MPEG2VIDEO to H264 (hw) transcoding. Consistently, once a minute the stream freezes for 5-10 seconds. If I let the stream buffer ahead, I will not experience stream freezes until I catch up to the buffer, then I continue to get a 5-10 freeze every minute.
The NAS can perform MPEG2VIDEO to H264 transcoding in software, but it uses 90% CPU from the 4-cores.
My question is, is the CPU/GPU not capable of performing hardware transcoding for MPEG2VIDEO to H264? Or is this a software issue?
MPEG2 is decoded in software , not hardware. Engineering hasn’t made MPEG2VIDEO hardwrae decoding available yet. As the result of that, if the CPU gets busy, it can and will drop frames. (what you see) because it’s running so close to the CPU limit at 90%
Thanks for the response. I hope mpeg2video hardware decoding moves up engineering’s priority list. It will make a world of difference to us hdhomerun users with Plex DVR
I found that enabling hardware decoding on my Synology Nas seemed to limit the ability to playback MPEG2 streams in the same way you describe, @scottz . It seems like with hardware transcoding enabled, Plex is only using one core of the processor, so one core is trying to decode (software) MPEG2, and encode H.264 (hardware). No way can only one core of a Synology keep up with software transcoding, so it buffers every few seconds. If you disable HW transcoding, and let Plex do both in software, then the system uses all cores, and while CPU usage is very high (like 90% on my DS916+), you can at least watch one stream of live TV. The down side of this is post-processing takes a long time also.
Until Plex gets this issue updated, I’ve still left my old Tablo DVR up, but once this gets sorted, I’m planning to switch to plex for all our DVR needs (I can’t wait!).
Hopefully Plex gets the MPEG2 HW transcoding done soon, since with DVR, it’s become nessecarry. I know @ChuckPA has been advocating this to the engineering team for us.
@silence21 I never thought of the hardware transcoding being single threaded, you are probably right there! If that is the case, we are probably dead in the water for transcoding MPEG2VIDEO in hardware on the J3455 unless they can multithread the task.
I have a DS418play and I tried live tv using plex competitor (the green logo). They fully support hardware transcoding on this model including mpeg2video hardware decoding. A live tv transcode session took around 30% of the CPU. So if Plex can activate mpeg2video hardware decoding, everything will be fine.
@scottz said: @silence21 I never thought of the hardware transcoding being single threaded, you are probably right there! If that is the case, we are probably dead in the water for transcoding MPEG2VIDEO in hardware on the J3455 unless they can multithread the task.
Nah, once they enable hardware transcoding, it should be able to transcode with a single thread.
