DTS over SP/DIF

[Bully9]

I've been playing movies over using VLC from my PC to my TV for years, using sp/dif for the audio to my 5.1 amp. Suddenly on one film there is no DTS audio over SP/DIF. All other movies play fine and i can find no substantive difference in the audio specs using mediainfo.

I did reencode to 5.1 ac3 in audacity (custom mix enabled) and the audio does now output to my amp, but for some reason the blue light indicating 5.1 still doesn't come on. (I double checked and mediainfo indicates 6 channels).

Any thoughts/possible explanations for either?

Thanks.

[El Heggunte]

I've been playing movies over using VLC from my PC to my TV for years, using sp/dif for the audio to my 5.1 amp. Suddenly on one film there is no DTS audio over SP/DIF.

All other movies play fine and i can find no substantive difference in the audio specs using mediainfo.

Well, that's not relevant. Just as an example, the DTS track may be 'little-endian', and your TV's firmware was designed to deal only with 'big-endian' DTS...

I did reencode to 5.1 ac3 in audacity (custom mix enabled) and the audio does now output to my amp, but for some reason the blue light indicating 5.1 still doesn't come on. (I double checked and mediainfo indicates 6 channels).

I don't use Audacity, so I don't know what "custom mix enabled" means. To the best of my knowledge, converting multichannel audio from one format to another format doesn't require any "custom mixes" or downmixes.

[pandy]

but for some reason the blue light indicating 5.1 still doesn't come on.

Blue light indicator is not standardized way of indication anything (perhaps except government agencies but usually it is in combination with red light) - provide more details...

[Bully9]

Thanks for the replies.

El Heggunte - many a time mediainfo has highlighted the reason for audio playback problems. The fact that it isn't now is the problem. But i'll check into "endian" because it's a new one on me. Any other examples? Custom mix is necessary in audacity to reencode 5.1 DTS to 5.1 ac3, otherwise it will downmix to stereo - i merely wanted to indicate that i had not made that mistake.
Pandy - i know it's not a standard. But on my sony amp it comes on when it recognises 5.1 and it's not doing so in this instance. So although mediainfo tells me it's 5.1, my amp is telling me that it isn't.

[stonesfan129]

How come you're using Audacity to convert DTS to AC3 and not ffmpeg? All you should have to do is run the command line pipes and remux them back into an .mkv container with MKVToolNix GUI.

Place it in C: drive. Go to command prompt and enter:

cd C:\ffmpeg.exe -i <location of source file> -vcodec copy -acodec ac3 -ab 640k -ar 48000 -ac 6 <output location>.ac3

This will produce an AC3 5.1 640kbps audio file. Then just remux it back in to the original. You can also change "640k" to 448k or 384k if you don't need the full 640 rate.

[Bully9]

Thanks stonesfan. The reason i use Audacity is that it works fine and i prefer a GUI. Producing the 5.1 ac3 is not the problem alas.

[pandy]

Hope you configured your player to output RAW AC3 over S/PDIF - normally software trying to produce PCM (to apply additional processing) - player must be capable to output AC3 stream directly to S/PDIF (and whole system with drivers capable to do so as well).

You can try to record some test DVD to verify this (or hook audio card S/PDIF input capable to create some S/PDIF analyzer - perhaps your amplifier is able to display what is at the input - if PCM then definitely there is issue).

[Bully9]

Hope you configured your player to output RAW AC3 over S/PDIF

I haven't configured the audio in VLC. I right-click on the screen audio>audio device>SPDIF interface. And the sound comes out of my 5.1 speakers. MusT have done this 100s of times over the years. Just this one film won't work with DTS at all or without recognising 5.1 with ac3.