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Author Topic: Strange decoding of mpeg.ts 5.1 audio - center channel in both L, R and C  (Read 1915 times)

Mikkel

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Hello JRiver-team,

I am having a strange problem - and have had it for quite a while, I just never found the time to report it.

When I playback recorded tv-shows or movies (mpeg ts-format recorded from a DVB-C signal) that features 5.1 audio it seems like the center channel audio is sent to the left and right channels as well. E.g. if in Room Correction I set the Left or Right channel to play solo when people speak in the show, speach is quite audible in these channels.

It does not occur with DVDs or blurays, and I have tried disabling all sorts of DSPs to ensure I hadn't mistakenly caused the problem myself.

If I switch to the 2.0 stream of the same show, the upmixing works perfectly with perfect channel separation.

Any help is appreciated. Perhaps someone could test it on their own recorded tv-show.

Oh, btw, of course there is the possibility that it is the encoding from the broadcaster that is wrong but it happens irrespective of which broadcaster I use. But I'm open to the suggestion.


Best regards,
Mikkel
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Hendrik

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Its quite common that the content of the center channel is at least partially present in the left/right channels.
I don't think MC would be capable of doing something crazy here, especially if you output to 5.1 speakers as well and no mixing is required - unless you use a PEQ filter yourself that would cause it.

Considering it only happens on your TV content, and not from DVD/Blu-ray, which in technical terms are all really just the same (5.1 audio is 5.1 audio), I'm inclined to say its in the recording like this.

If you want to be sure, you could cut a small part of such a file and upload it somewhere, and I can tell you for sure whats going on.
MPEG-TS files can be split rather arbitrarily without worrying too much, as long as its at least big enough to contain a bit of content still.
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Mikkel

  • Galactic Citizen
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  • Posts: 321

Its quite common that the content of the center channel is at least partially present in the left/right channels.
I don't think MC would be capable of doing something crazy here, especially if you output to 5.1 speakers as well and no mixing is required - unless you use a PEQ filter yourself that would cause it.

Considering it only happens on your TV content, and not from DVD/Blu-ray, which in technical terms are all really just the same (5.1 audio is 5.1 audio), I'm inclined to say its in the recording like this.

If you want to be sure, you could cut a small part of such a file and upload it somewhere, and I can tell you for sure whats going on.
MPEG-TS files can be split rather arbitrarily without worrying too much, as long as its at least big enough to contain a bit of content still.

Hi Hendrik,

Thanks for your reply. If I upload a small bit of a file tonight when I get home from work, would you try and play it on your system and see whether it is the file that is the problem?


Best regards,
Mikkel
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Hendrik

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Sure, I can check it out.
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~ nevcairiel
~ Author of LAV Filters

Mikkel

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Sure, I can check it out.

Thank you very much. Here is the file: https://www.dropbox.com/s/8tryrfrkg0jd6fy/TEST.ts (extract from The Last Samurai).


Best regards,
Mikkel
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Hendrik

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It seems like Left/Right and Center contain very similar audio in this clip. If I play Center solo, you can hear pretty much everything fine, but equally so if you play Left or Right solo.
But it certainly is like this in the file itself.
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~ nevcairiel
~ Author of LAV Filters

Mikkel

  • Galactic Citizen
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It seems like Left/Right and Center contain very similar audio in this clip. If I play Center solo, you can hear pretty much everything fine, but equally so if you play Left or Right solo.
But it certainly is like this in the file itself.

Sorry about the center channel. My 3 year daughter had turned down the volume on the amplifier  ;D.
I'll call the cable tv distributor and hear what is wrong.


Best regards,
Mikkel
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Mikkel

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Btw Hendrik,

Is there any reason to suspect the TV-tuner for this? I'm just wondering if it could be caused by hardware, since it seems really odd the either the cable tv distributor or the broadcaster would stream 5.1-audio this way.


Best regards,
Mikkel
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Hendrik

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Usually with Digital TV, the tuner just records the audio/video as it comes from the station. But I'm not all that experienced with all weird tuners.
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Mikkel

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Turns out that shows that are not encoded in 5.1 audio still has a 5.1-stream but with discrete 2.0 inside a 5.1 container.

Stupid system but luckily nothing to do with JRiver or my hardware.
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