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Video Transcoding when only audio transcoding is needed - SRT subtitles related

kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

Hi everybody!

I just dicovered an issue with PMS and/or Plex for Androiv TV. I have PMS installed in my NVIDIA SHIELD but the same issue happens with my Synology as PMS so I think issue is related to the Plex Player for Android TV. The problem is that as we know, the NVIDIA SHIELD TV Plex player cannot decode AC3 or DTS like Kodi does. Because of this, PMS transcodes the Audio. The problem is that in my case the Video is also being transcoded for no reason. This does not happen for instance if I use the player on my old Samsung TV (2012 model). TV can decode AC3 using internal player so both video and audio are Direct Play (sigh, on a side note, and even if I understand the reasons, it is just plainly wrong I can direct play most of my videos in the Samsung Plex app and not in a Nvidia Shield.. this needs to be addressed...)

After some testing I think I know the reason, subtitles. If a subtitle is selected when the Audio needs to be transcoded, then the video is also transcoded. I guess subtitles are being burned in, but why? They are in SRT format, no image subtitles. Again, in my Samsung TV using the Plex Player 2.007 all works fine but then again, there it's not transcoding the audio. I have tried the Plex plugin for Kodi. It also Directs Play the audio and video so no problem here either.

I guess this is a bug with the internal player, tried to look for it but couldn't find anything (was also not completely sure which search terms to use). Does somebody know if this is a known bug and whether this is being looked at? I really didn't expect I would need to use alternatives to the official Plex Player in my new Shield like the Kodi plugin or my old TV :sweat: ... disappointed... :(

Sorry for the long post, thanks!

Comments

  • zpaolo11xzpaolo11x Posts: 1,208Members, Plex Pass Plex Pass
    edited October 12

    What format is the video? Something similar happens when the video format is suitable for direct play but not for direct streaming, because it's not supported by the streaming transport method used.

  • kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

    i have tried many different videos, all of them x264 mkv's. I don't think this is the issue because if I deactivate subtitles, the video uses direct stream as far as I understand (Video shows as Direct Play, Audio as Transcoding).

  • zpaolo11xzpaolo11x Posts: 1,208Members, Plex Pass Plex Pass

    @kikeminchas said:
    i have tried many different videos, all of them x264 mkv's. I don't think this is the issue because if I deactivate subtitles, the video uses direct stream as far as I understand (Video shows as Direct Play, Audio as Transcoding).

    It might be that the transport method doesn't support external SRT packaging

  • kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

    so any time audio needs transcoding video will have to be transcoded as well to burn in subtitles? Is this expected behavior because that will force me to basically abandon the Plex player :( ...

  • Jecht SinJecht Sin Posts: 88Members ✭✭

    I wrote a similar thread for the same problem. In my case the transcoding always happens with HEVC (x265) videos where the audio isn't supported. I have got x264 videos with unsupported audio (but no subtitles) that get only the audio transcoded.

    I've never got an answer from Plex. But from what I have read in a thread for the Apple TV 4K it may be a matter of wrong profiles in the Plex Server app. The xml files for samsung are indeed quite elaborated compared to many others. While Android.xml (if it is the right file) doesn't even include the mkv format (probably it uses some default settings).

    I tried modifying Android.xml a bit yesterday but nothing changed. So I really would like to know if that is the right profile.

  • zpaolo11xzpaolo11x Posts: 1,208Members, Plex Pass Plex Pass

    @Jecht Sin said:
    I wrote a similar thread for the same problem. In my case the transcoding always happens with HEVC (x265) videos where the audio isn't supported. I have got x264 videos with unsupported audio (but no subtitles) that get only the audio transcoded.

    I've never got an answer from Plex. But from what I have read in a thread for the Apple TV 4K it may be a matter of wrong profiles in the Plex Server app.

    I don't think the issue is in the PMS profiles: this is a well known "issue" related to the streaming container used with direct streaming. If you can send h265 video with supported audio your player will happily (direct)play it, but if Plex has to transcode the audio, and the streaming container doesn't support h265 video (like HLS), it can't re-package the original h265 video with that "new" audio, therefore even video needs to be transcoded.

  • kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

    I have to say again that for me, this only happens when I activate subtitles. All my movies are h264. Without subtitles, PMS transcodes audio, direct play video and direct streams the whole thing without issues. Subtitles are for sure the issue here. Once I got this clear I actually found several posts about the issue:

    http://forums.plex.tv/discussion/242369/bug-subtitle-requires-to-be-burned-in-for-what-seems-no-reason#latest
    http://forums.plex.tv/discussion/226208/bug-sony-android-tv-transcoding-subtitles-forcing-video-transcode/p2
    https://forums.plex.tv/discussion/226009/possible-bug-direct-play-activated-subtitles-nvidia-shield-client-linux-plex-server/p1

    It's a specific issue with the Android TV player. There are reports of this problem since more than a year ago. Not sure if an update to Exoplayer would fix it. There is no official answer from nobody at Plex. I guess I will have to keep on using Kodi at home with the Plex for Kodi plugin. In any case, this is extremely disappointing. Plex as player it's really subpar, if using Exoplayer is the reason behind this then a least we should have the option to switch players...

  • Dion250Dion250 Posts: 148Members, Plex Pass Plex Pass

    The bug was fixed in the Exoplayer for text subtitles going out of sync in HLS back in Dec of 2016. Plex has not undone there fix ( burn them ) since it was fixed.. So 10 months? Sounds about right for Plex development.

    Expect this to never be fixed kikeminchas. :(

  • kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

    Ok, so basically, Exoplayer is fixed but Plex just needs to basically acknowledge this and stop burning the subtitles? :s I am going to be more optimistic here and hope that they are still planning to fix this...

  • Jecht SinJecht Sin Posts: 88Members ✭✭
    edited October 15

    @zpaolo11x said:
    I don't think the issue is in the PMS profiles: this is a well known "issue" related to the streaming container used with direct streaming. If you can send h265 video with supported audio your player will happily (direct)play it, but if Plex has to transcode the audio, and the streaming container doesn't support h265 video (like HLS), it can't re-package the original h265 video with that "new" audio, therefore even video needs to be transcoded.

    But so, pardon my ignorance, the Plex server isn't using ffmpeg? ffmpeg can well copy the supported streams, converting only what's needed to be converted. At least I am talking about mkv containers (which is usually what I have) and that's what I have done manually for a couple of videos. I thought the same was the case for subtitles.

    As I don't understand indeed why it needs to convert anything when using muxed ASS subs.I even get a message like "transcoding because the ASS format isn't supported by the mkv container" or something similar. ASS is defined for mkv in the Android.xml profile (which I can confirm is the right one for Android TV, now) and even the stock Sony's Video app can play those files via DLNA. Unless it is the Plex server doing a different conversion (with no video conversion involved) when sending via DLNA, sure (does it?).

    PS: With AC3/EAC3 (DD) 5.1 and SRT subs everything plays fine. So I am not sure either why I get a different behaviour from @kikeminchas

  • _Francesco__Francesco_ Posts: 244Members, Plex Pass Plex Pass

    With my Sony bravia the situation is:
    Ac3 and srt subs: direct play
    Dts with no subs: only audio transcode ( it’s shouldn’t but that is a different problem i guess)
    Dts with srt subs: full transcode

  • kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

    @Jecht Sin said:

    @zpaolo11x said:
    I don't think the issue is in the PMS profiles: this is a well known "issue" related to the streaming container used with direct streaming. If you can send h265 video with supported audio your player will happily (direct)play it, but if Plex has to transcode the audio, and the streaming container doesn't support h265 video (like HLS), it can't re-package the original h265 video with that "new" audio, therefore even video needs to be transcoded.

    But so, pardon my ignorance, the Plex server isn't using ffmpeg? ffmpeg can well copy the supported streams, converting only what's needed to be converted. At least I am talking about mkv containers (which is usually what I have) and that's what I have done manually for a couple of videos. I thought the same was the case for subtitles.

    As I don't understand indeed why it needs to convert anything when using muxed ASS subs.I even get a message like "transcoding because the ASS format isn't supported by the mkv container" or something similar. ASS is defined for mkv in the Android.xml profile (which I can confirm is the right one for Android TV, now) and even the stock Sony's Video app can play those files via DLNA. Unless it is the Plex server doing a different conversion (with no video conversion involved) when sending via DLNA, sure (does it?).

    PS: With AC3/EAC3 (DD) 5.1 and SRT subs everything plays fine. So I am not sure either why I get a different behaviour from @kikeminchas

    You probably get a different result because your player can Direct Play AC3. Mine (Nvidia Shield) cannot so it needs to transcode audio. When this happens in combination with SRT subtitles (haven't tried ASS) video also transcodes for some reason.

  • emreunalemreunal Posts: 70Members, Plex Pass Plex Pass

    Francesco said:
    With my Sony bravia the situation is:
    Ac3 and srt subs: direct play
    Dts with no subs: only audio transcode ( it’s shouldn’t but that is a different problem i guess)
    Dts with srt subs: full transcode

    same problem. before the last update for smart tvs, it was:

    Ac3 and srt subs: direct play
    Dts with no subs: direct play
    Dts with srt subs: direct play

  • MovieFan.PlexMovieFan.Plex Posts: 15,895Members, Plex Pass, Plex Ninja Plex Employee

    Hi guys. I know I've answered this several times before. There is a current limitation in the media player that Plex uses(Exoplayer) that when either audio or video is not direct played, then subtitles cannot be direct played. Technically it can, but there is a timing issue that will show up where the subtitles and the voices get out of sync. Due to this problem, the Plex app will not direct play subtitles in this case.

  • Dion250Dion250 Posts: 148Members, Plex Pass Plex Pass

    Was fixed in Dec 2016. I already sent you the link to that fix in another thread too.

  • MovieFan.PlexMovieFan.Plex Posts: 15,895Members, Plex Pass, Plex Ninja Plex Employee

    As I mentioned in that thread, the fix was for Exoplayer v2. The Plex app currently only uses v1. Additionally, I spoke with a dev about that and apparently the fix only applies to WebVTT subtitles embedded in an MKV file. It does not help with embedded or external srt subtitles.

  • kikeminchaskikeminchas Posts: 8Members, Plex Pass Plex Pass

    Thanks for confirming this @MovieFan.Plex, not the answer I would like to hear but at least we know where we stand... Are there any deadlines or milestones to start using Exoplayer v2 or is this dependant on NVIDIA?

    I guess I will keep on using the Plex for Kodi plugin for the moment...

  • Markus & EddaMarkus & Edda Posts: 222Members, Plex Pass Plex Pass

    I‘m using the Plex for Kodi Plugin, too.
    In my case the official Plex on AFTV2 is just totally useless. The transcoding with enabled srt subs is one thing... that is even surpassed with missing ac3 passthrough...

    So its just a useless Plex client..

  • _Francesco__Francesco_ Posts: 244Members, Plex Pass Plex Pass

    well you guys are lucky, on my sony android tv if I enable passthrough on kodi I get no audio at all :(

  • MovieFan.PlexMovieFan.Plex Posts: 15,895Members, Plex Pass, Plex Ninja Plex Employee

    @kikeminchas said:
    Thanks for confirming this @MovieFan.Plex, not the answer I would like to hear but at least we know where we stand... Are there any deadlines or milestones to start using Exoplayer v2 or is this dependant on NVIDIA?

    We are working on it, but there are a lot of customization that needs to be done. It's not as easy as cut and paste over the current player.

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