Jump to content

Emby Server 4.0 on DS916+ Observations and questions


hgpuke

Recommended Posts

Yesterday I downloaded the new version of Emby Server to my Synology DS916+.

I had so much hopes for this new version, especially when it comes to transcoding performance.

Here are my observations after running a small test with different transcoding options.

 

Test movie: Jurassic World, BD-rip done by standard settings in DVDFab 11 resulting in a 1080p H264 MP4 container and Subtitles in VOBSUB format included in the MP4. 5Mb/s bitrate.

                    SRT subtitle added by Emby.

 

Server: Emby Server 4.0.0.2 running on Synology DS916+ using an Intel Pentium N3710 CPU with 4 cores and 8GB of RAM.

Client: Emby Web client running in Microsoft Edge browser.

 

Use case 1: No subtitles or SRT subtitle:

Results: No transcoding needed (hence Direct Play). Very little CPU used (below 5%) in the NAS.

 

Use case 2: 1080P original bitrate (no downsampling). VOBSUB subtitle. HW assisted decoding and encoding (VAAPI).

Results: 15-17 fps transcoding speed. Dropped frames. Stuttering playback. 23% CPU load on the NAS. Verdict: Not usable.

 

Use case 3: 1080P original bitrate (no downsampling). VOBSUB subtitle. SW decoding and encoding.

Results: 30+ fps transcoding speed. No dropped frames. Perfect playback. 95-99% CPU load on NAS. Verdict: Usable, but only for one stream and no other activity on the NAS.

 

Use case 4: 1080P original bitrate (no downsampling). VOBSUB subtitle. SW decoding, HW assisted encoding (VAAPI).

Results: 18 fps transcoding speed. Dropped frames. Stuttering playback. 32% CPU load on the NAS. Verdict: Not usable.

 

Use case 5: 1080P original bitrate (no downsampling). VOBSUB subtitle. HW assisted decoding (VAAPI), SW encoding.

Results: 27fps transcoding speed. Few dropped frames. Good playback. 70-80% CPU load on the NAS. Verdict: Usable but only for one stream. Other activity on the NAS is possible.

 

Use case 6: 1080P downscaling to 720P@2Mbps. No subtitle or SRT subtitle (does not matter). HW assisted decoding, SW encoding.

Results: 57fps transcoding speed. No dropped frames. Good playback. 40% CPU load on the NAS. Verdict: Usable

 

Use case 6: 1080P downscaling to 720P@4Mbps. No subtitle or SRT subtitle (does not matter). HW assisted decoding, SW encoding.

Results: 57fps transcoding speed. No dropped frames. Good playback. 60-70% CPU load on the NAS. Verdict: Usable

 

So on to my conclusions:

 

Using embedded "picture type" subtitles like VOBSUB makes the server transcode, leading to a high workload for the NAS. Always use SRT subtitles when possible.

If VOBSUB subtitles have to be used, using HW assisted decoding and SW encoding results in a usable solution for 1080P resolution films.

 

So on to my questions:

 

1. Are my results in line with your expectations?

2. Could a future version of the server either

    a) be made to transcode quicker, or

    B) dynamically switch between HW assisted and SW transcoding depending on what framerate it is able to acheive?

 

Thanks for a great product!

Link to comment
Share on other sites

solabc16

Hello @@hgpuke

 

Thanks for the detailed feedback, that's really useful and appreciated.

 

If you are able to run the Send Logs utility, I can analyse the data in more detail : https://github.com/MediaBrowser/Wiki/wiki/Synology-:-How-to-Send-us-Support-Logs

 

VOBSUB is a challenge and not specific to Emby Server, we have an active discussion going on around this - so for now, all I can say is stay tuned.

 

Best

- James

Link to comment
Share on other sites

Hi @@solabc16! Thanks for your answer,

I will try to send you the log file once I get back home today (I have no access to ssh from work due to security restrictions).

I suppose you have no use of the logs that I can get from inside the server control panel?

 

- Hans-Göran

Link to comment
Share on other sites

Use case 2: 1080P original bitrate (no downsampling). VOBSUB subtitle. HW assisted decoding and encoding (VAAPI).

Results: 15-17 fps transcoding speed. Dropped frames. Stuttering playback. 23% CPU load on the NAS. Verdict: Not usable.

 

Use case 3: 1080P original bitrate (no downsampling). VOBSUB subtitle. SW decoding and encoding.

Results: 30+ fps transcoding speed. No dropped frames. Perfect playback. 95-99% CPU load on NAS. Verdict: Usable, but only for one stream and no other activity on the NAS.

 

Use case 4: 1080P original bitrate (no downsampling). VOBSUB subtitle. SW decoding, HW assisted encoding (VAAPI).

Results: 18 fps transcoding speed. Dropped frames. Stuttering playback. 32% CPU load on the NAS. Verdict: Not usable.

 

Use case 5: 1080P original bitrate (no downsampling). VOBSUB subtitle. HW assisted decoding (VAAPI), SW encoding.

Results: 27fps transcoding speed. Few dropped frames. Good playback. 70-80% CPU load on the NAS. Verdict: Usable but only for one stream. Other activity on the NAS is possible.

For these examples, burning in subtitles is a very costly process, so this isn't too much of a surprise.

Link to comment
Share on other sites

For these examples, burning in subtitles is a very costly process, so this isn't too much of a surprise.

 

Yes, I am aware that "burning" subtitles is a costly process.

I had high hopes that the use of hardware assisted encoding and decoding would make it more feasible, however.

In my case, it turns out that the CPU part of the Pentium N processor was more capable at doing this than the GPU part.

This came as a surprise to me, at least.

@@softworkz

 

Having said that, I am very delighted with the hardware acceleration of "normal" transcoding, i e downsampling either resolution and/or bitrate.

As an example, downsampling a movie using native 1080P resolution from 13 Mbps to 6 Mbps uses only 15% of the CPU at times when the transcoding buffer is filled, and almost nothing in between.

Edited by hgpuke
Link to comment
Share on other sites

Normally this would be a surprise indeed.

 

But there's a bit more to it: The comparison is not quite fair in many cases, because the software usually produces a video of much lower bitrate than actually requested, while most hardware encoders are closely matching those values.

 

You may check this on your system by comparing the file sizes of the transcoded segment files (*.ts) between hardware and software transcoding.

(please make sure that you don't resume but start playback from the beginning in both cases.)

Link to comment
Share on other sites

solabc16

Hello @@hgpuke

 

You need to take into consideration my update to your post on this thread as well : https://emby.media/community/index.php?/topic/67225-newbie-looking-for-advice-on-how-to-avoid-transcoding-with-subs/?p=680420

 

In scenario #2, it's not a coincidence that the CPU is pegged at ~25%.

 

This is a four core machine, and with respect to the above post, this is one thread on one core trying to process the VOBSUB subtitle.

 

The h/w assisted decoding and encoding (VAAPI) is indeed doing its thing and doing it well, hence the relatively low CPU utilisation. However, as the raw horsepower of the CPU isn't sufficient to handle the part that can only be performed in software, the overall suitability for the workload is negative.

 

Best

- James

Edited by solabc16
Link to comment
Share on other sites

Hello @@hgpuke

 

You need to take into consideration my update to your post on this thread as well : https://emby.media/community/index.php?/topic/67225-newbie-looking-for-advice-on-how-to-avoid-transcoding-with-subs/?p=680420

 

In scenario #2, it's not a coincidence that the CPU is pegged at ~25%.

 

This is a four core machine, and with respect to the above post, this is one thread on one core trying to process the VOBSUB subtitle.

 

The h/w assisted decoding and encoding (VAAPI) is indeed doing its thing and doing it well, hence the relatively low CPU utilisation. However, as the raw horsepower of the CPU isn't sufficient to handle the part that can only be performed in software, meaning the overall suitability for the workload is negative.

 

Best

- James

 

Thanks for the clarification! Now I think I understand this topic well! :)

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...