Set thread count for FFmpeg decode (halves GPU memory during hw-trscd)

[Sungray 6]

GPU memory usage for a single high quality file is more than 1.2Gb. The same file for Plex "costs" only around 600Mb.

That means, with a GPU with 2Gb of memory, I can have 3 transcoding streams at the same time on Plex, and only one on Emby. The second stream will start with CPU transcoding.

The cause is that Emby does not set any FFmpeg decoding thread count (=auto). After setting the thread count to 1 using Diagnostics/Replace...

... the memory usage is now totally normal and on par with Plex, without any noticeable performance loss.

 

This seems like a very easy fix to be done, it would very much improve the hardware transcoding feature, and comes at no performance cost or any downside whatsoever that I can see.

Please consider fixing this soon.

Also, please note all these tests are done using the same source file.

This is a summary of the issue I opened here.

Thanks

Edited June 21, 2022 by Sungray

[Happy2Play 8281]

What is your Transcoding "Transcoding thread count:" set to?  Settings-Transcoding

Transcoding thread count:

Select the maximum number of threads to use when transcoding. Reducing the thread count will lower cpu usage but may not convert fast enough for a smooth playback experience. Not all encoders and decoders support multi-threading, so this may have an effect in some cases but not others.

 

[Sungray 6]

49 minutes ago, Happy2Play said:

What is your Transcoding "Transcoding thread count:" set to?  Settings-Transcoding

Transcoding thread count:

Select the maximum number of threads to use when transcoding. Reducing the thread count will lower cpu usage but may not convert fast enough for a smooth playback experience. Not all encoders and decoders support multi-threading, so this may have an effect in some cases but not others.

 

Auto. Reducing it doesn't help.

 

With transcoding thread count set to 1 :

First bump was when I still had the -copyts -threads:v:0 1 diagnostic/replace. Second is when I removed it.

I think this setting only impacts the encoding thread count. The decoding thread count is never set in the Emby ffmpeg cmd, and it should be set to 1.

Edited June 21, 2022 by Sungray

[Sungray 6]

On 22/06/2022 at 00:19, Happy2Play said:

What is your Transcoding "Transcoding thread count:" set to?  Settings-Transcoding

Transcoding thread count:

Select the maximum number of threads to use when transcoding. Reducing the thread count will lower cpu usage but may not convert fast enough for a smooth playback experience. Not all encoders and decoders support multi-threading, so this may have an effect in some cases but not others.

 

Hello, did you get the chance to look into this?

[Sungray 6]

Hello there!

@Happy2Play did you get a chance to look into this? Maybe confirm the problem, perhaps address it?

Again, I believe this is a big issue with an easy fix.

[Luke 37063]

@softworkz will be looking into this. Thanks.

[softworkz 3335]

It is fixed already.

@Luke just needs to merge my changes.

[Sungray 6]

7 hours ago, softworkz said:

It is fixed already.

@Luke just needs to merge my changes.

Thanks @softworkz.

[Sungray 6]

In which version will this fix become available? Any chance it gets pushed to be released in a stable version soon?

[softworkz 3335]

In the latest betas, the transcoding thread count doesn't have an effect anymore.

It will be removed from the settings UI in a future update.

For hw decoders, the thread count is set to 1, for sw decoders it remains to be unset (= auto: use maximum reasonable amount).

Starting with  4.8.0.9, there is a new thread count parameter for the H264 and HEVC software encoders (in the codec parameters dialog).

[Luke 37063]

@Sungray are you still having an issue with this?

[Sungray 6]

10 minutes ago, Luke said:

@Sungray are you still having an issue with this?

Fixed on 4.8.0.9 beta.