Transcode DTS/AC3 and lossless to LPCM?

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chris88
Posts: 2
Joined: Fri Jan 07, 2022 5:40 pm

Transcode DTS/AC3 and lossless to LPCM?

Post by chris88 »

Hello ladies and gentleman,
i am new here but an old user of UMS.
I would like to have your support about how to play my .m2ts and .mkv remuxes with lpcm 5.1 when i choose to. The issue is that UMS doesn't transcode audio to LPCM 5.1 even if i disable "Keep ac3".
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Nadahar
Posts: 1990
Joined: Tue Jun 09, 2015 5:57 pm

Re: Transcode DTS/AC3 and lossless to LPCM?

Post by Nadahar »

I'm not sure it's possible to transcode to LPCM 5.1 (or LPCM audio at all) in UMS. The main problem is that FFmpeg doesn't properly mux LPCM into MPEG-TS - so other solutions must be used like tsMuxeR. tsMuxeR can't transcode though, only mux, which means that to actually transcode to LPCM 5.1 one would have to transcode to WAVE 5.1 (or similar, maybe W64) in FFmeg and then mux it in tsMuxeR. I'm sure it could be done, but it would be complicated.

If your files already are LPCM 5.1 and you just want them to be streamed as-is, it should be no problem. You just need to specify that your renderer supports it in the renderer configuraton, but that requires that there's no other aspect of the media file that requires transcoding (like video codec, subtitles etc).
chris88
Posts: 2
Joined: Fri Jan 07, 2022 5:40 pm

Re: Transcode DTS/AC3 and lossless to LPCM?

Post by chris88 »

Nadahar wrote: Sat Jan 08, 2022 5:54 am I'm not sure it's possible to transcode to LPCM 5.1 (or LPCM audio at all) in UMS. The main problem is that FFmpeg doesn't properly mux LPCM into MPEG-TS - so other solutions must be used like tsMuxeR. tsMuxeR can't transcode though, only mux, which means that to actually transcode to LPCM 5.1 one would have to transcode to WAVE 5.1 (or similar, maybe W64) in FFmeg and then mux it in tsMuxeR. I'm sure it could be done, but it would be complicated.

If your files already are LPCM 5.1 and you just want them to be streamed as-is, it should be no problem. You just need to specify that your renderer supports it in the renderer configuraton, but that requires that there's no other aspect of the media file that requires transcoding (like video codec, subtitles etc).
Thank you!
Actually i need also the subtitle to be transcoded.
Ok then is there any other solution to keep the lossless audio when UMS trancode the movie with subtitles? Another issue i have, It seems that whatever i try even DTS audio gets trancoded to ac3. The "keep dts" is checked in the settings and the renderer support DTS.
Nadahar
Posts: 1990
Joined: Tue Jun 09, 2015 5:57 pm

Re: Transcode DTS/AC3 and lossless to LPCM?

Post by Nadahar »

I think the "keep DTS" setting has been broken for a very long time, but I won't swear on anything, since I haven't used UMS in some years now.

The decision UMS makes is whether to transcode or not. Many different things can cause transcoding, like subtitles. If it is decided that it must be transcoded, the output format is one of the pre-defined choices, none of which have lossless audio. It could be done differently, because FFmpeg can mux DTS (but not encode it) AFAICR, but it would require a more "advanced" logic than is currently there. I don't think that, even when "keep DTS" worked, that you would be able to keep the DTS track while transcoding the video.

So, in short, I'm not sure what you're asking can be done with UMS at this time.
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