Transcoding Audio EAC5.1 - FFMPEG very very slow!

[GiGo 103]

This is really doing my head in now. No matter what system I run the emby server on it will not transcode EAC5.1 audio to AAC at a decent speed I am getting 15-19FPS.

I can run it on a 3rd Gen i3 and I get the same results as running it on a 6th Gen i7!  FFMPEG appears to be using no more than 2% maximum of my CPU!

Is this an issue with FFMPEG or an issue with emby or an issue with my Roku's? I've gone into task manager and set FFMPEG to high priority and it still results on the very same slow transcoding of audio.

Could very much do with a hand telling me what is going on? Files will happily play locally on the server PC via VLC but on any Roku I seem to use it fails.... I even upgraded my Roku to a 4K Ultra as this is meant to have a EAC5.1 decoder, but it still fails.

 

embyserver.txt ffmpeg-remux-6f1b60cd-d2cc-4879-972e-ba9a7c29cbbd_1.txt hardware_detection-63835142140.txt

[speechles 1920]

It is the very high number of (25) subtitles contained inside the media. Emby isn't just transcoding the audio. Subtitles have to also be passed into the manifest in case you want to enable them. Emby is choosing (likely for sanity reasons) to only push 6 of these into the manifest. So it is transcoding the audio _AND_ converting those 6 subtitles into webvtt.

You can use MKVToolNix GUI to remove the subtitles you will never use. Or better yet, remove all the subtitles, then rip/download them as external SRT. That should make it easier to transcode

Edited November 9, 2023 by speechles

[GiGo 103]

1 minute ago, speechles said:

It is the very high number (25) of subtitles contained inside the media. Emby isn't just transcoding the audio. Subtitles have to also be passed into the manifest in case you want to enable them. Emby is choosing (likely for sanity reasons) to only push 6 of these into the manifest. So it is transcoding the audio _AND_ converting those 6 subtitles into webvtt.

You can use MKVToolNix GUI to remove the subtitles you will never use or remove all the subtitles if you never use them and download external SRT. That should make it easier to transcode

Right! Can I just disable the subtitles? 

[speechles 1920]

6 minutes ago, GiGo said:

Right! Can I just disable the subtitles? 

Because they are internal they will still be pushed into the manifest. Otherwise you could never enable them when transcoding since you can only use what is in the manifest when transcoding.

You can disable them in your user on the Emby dashboard settings. That might make a difference, but likely it will still happen because these are internal subrip. The Roku does not support internal subrip during transcoding and these must be converted into webvtt. This is what is causing the issue.

External SRT are easier (less CPU) for the Roku to consume when transcoding.

Edited November 9, 2023 by speechles

[GiGo 103]

1 minute ago, speechles said:

Because they are internal they will still be pushed into the manifest. Otherwise you could never enable them when transcoding since you can only use what is in the manifest when transcoding.

You can disable them in your user on the Emby dashboard settings. That might make a difference, but likely it will still happen because these are internal subrip. The Roku does not support subrip during transcoding and these must be converted into webvtt. This is what is causing the issue.

External SRT are easier (less CPU) for the Roku to consume when transcoding.

Thank you! This makes sense, what I don't understand is why ffmpeg doesn't seem to be working harder by using the more cpu power? 

[speechles 1920]

Some Roku models will convert E-AC3 into 2 channel AAC natively. If you have a Roku Ultra or Roku Premiere both of these have hardware to convert the audio on the device. Make sure both the "Preferred streaming format" and "Digital output format" of your Roku Audio settings are both set to Auto. This on-device converting can only be done with Auto set on both of those settings. After you change this reboot the Roku and see if it now Direct Plays without any conversion on your Roku. If it does you will have no issues since the Roku can stream the file directly. All subtitles are available with zero issues.

With the Roku my best advice is try to make it Direct Play. Add a second audio track of the converted E-AC3 into AAC ffmpeg has made. Use MKVToolNix GUI to add this second AAC audio track into the media. You will do yourself a huge favor and have both stereo and surround available for Direct Play. You can then keep all the subtitles internal. The idea is make the Roku do the work not your CPU.

Edited November 9, 2023 by speechles

[GiGo 103]

Thank you!