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Old 12-08-2018, 06:02 AM   #1
qrange
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ffmpeg, bluray audio tracks


I'm trying to convert bluray video to hevc+mkv.
The video has several audio tracks, among them these two:

- DTS-HD Stereo
- DTS-HD Surround 5.1

Is there a point in keeping both of them?
Can a Stereo track be later re-coded from 5.1 so that is the same quality as bluray stereo?
Can a mpv player 'transcode' 5.1 on-the-fly to stereo with same quality as original stereo track?

Thanks.
 
Old 12-08-2018, 06:57 AM   #2
business_kid
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I'm no fan of surround sound on PCs, personally. I'd rather up the sampling rate than bother with that. Have you 4 separate channels of audio out? If you put yourself in the middle of an orchestra pit, you might notice that the drums came from behind right, the strings from front right, the brass from rear left, with woodwind from front left; but I for one don't think that improves the overall sound. You'd also have all off-mic smells & noises, (the guy who ate garlic, shoe scrapes, burps, leguminous farts, etc.)

I'd junk the surround sound, but don't claim to be an audio buff.
 
Old 12-08-2018, 01:07 PM   #3
teckk
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Quote:
I'm trying to convert bluray video to hevc+mkv.
Look at x265 --help and ffmpeg...-c:v x265
Quote:
Is there a point in keeping both of them?
Up to you. If you keep both streams the output file will be larger.
Quote:
Can a Stereo track be later re-coded from 5.1 so that is the same quality as bluray stereo
Matter of opinion, and your ears. I don't see anything wrong with stereo. If you want it unchanged then use -c:a copy
Quote:
Can a mpv player 'transcode' 5.1
mpv is a media player. Maybe you meant something else.

You can use the -map switch of ffmpeg to get the streams that you want. You can map one audio stream to output. You can map both streams to output. You can leave it like it is and put it into a mp4 or mkv container. You can reencode the video to x264 video and aac audio. Or you can make a huge .iso out of the disk and play that.

https://wiki.gentoo.org/wiki/FFmpeg_..._Blu-Ray_Audio
https://stackoverflow.com/questions/...samsung-bluray
https://superuser.com/questions/7920...-and-subtitles
https://www.makemkv.com/
https://www.dvd-guides.com/guides/bl...sing-handbrake
 
Old 12-08-2018, 01:34 PM   #4
qrange
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the Stereo track seems redundant to me, if (and only if) the 5.1 can be perfectly converted to stereo.

various players, like potplayer (for eg.) have had an option to convert 5.1 to stereo 'on-the-fly', while playing the video.
I assumed mpv has such option too (no, I didn't mean something else.)

similarly, there is no need to deinterlace nowadays while encoding, as hardware is fast enough to do it while playing.

Last edited by qrange; 12-08-2018 at 01:35 PM.
 
Old 12-09-2018, 07:53 AM   #5
ondoho
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Quote:
Originally Posted by qrange View Post
Can a mpv player 'transcode' 5.1 on-the-fly to stereo with same quality as original stereo track?
my system does this.
i'm not sure if mpv is responsible for this, or ALSA itself, or maybe even the soundcard driver/firmware.

about the quality, i cannot say.

but on-the-fly conversion might produce varied/undesired results.
when you yourself include a mixdown stereo track, you have full control.
the increase in size should be negligable if you use a good compressed audio codec (AAC maybe).

there might be a performance hit when compared to no conversion, but for any system that is able to decode HEVC that shouldn't be an issue.
 
  


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