Bitstream (re-encode) vs Bitstream (audiophile) with 5.1 receiver

[taylorw]

I have been using a Samsung bd-p1500 blu-ray player connected to a 5.1 Sony str-dh500 receiver via optical. The str-dh500 is an hdmi receiver but strangely enough does not support audio over hdmi. So I opted for optical as the receiver can decode DTS and DD 5.1 on its own.
So far I have been setting the bluray player to Bitsream (audiophile) and my receiver outputs either DTS or DD 5.1 depending on the source.
However, I cannot hear secondary audio (menu, PIP, Bonusview) unless I set the bluray player to Bitstream (re-encode) which automatically converts everything to DTS.
My question is whether it is better to leave the bluray output set to Bitstream (audiophile) and allow the receiver to decode on its own (even though its not 7.1 DTS-HD or True HD capable) or to set to re-encode which will convert everything to DTS on the fly?
Being that the receiver is not 7.1 capable in the first place, perhaps setting the bluray to re-encode would not degrade the quality much at all.
Or maybe the Audiophile setting is inappropriate in the first place for a 5.1 receiver. Does the Audiophile setting on the Samsung bluray player output 7.1 to the receiver causing loss of channels or does my receiver compensate and output all sound through 5.1?

[callas01]

typically, a blu-ray player will either decode the audio and send it over via LPCM(Linear Pulse Code Modulation; consider this like discrete multi-channel stereo) or Bitstream so that the receiver can decode the audio. Both are the same thing. Its just a matter of where the conversion happens. Most BDPs have to do the conversion internally to play the Secondary Audio and when set to bitstream(so the receiver does the decoding) it shuts off the Secondary Audio.

[BIslander]

When you play a lossless codecs for Bitstream Audiophile output over optical, the player will send the DTS core instead of dts-MA or an embedded DD 5.1 track instead of TrueHD. Those are the same legacy codecs available on DVDs, but they are encoded at higher bitrates. Secondary audio (menu effects and PIP commentaries) is not sent because it is not part of the movie soundtrack.

When set to Re-encode, the player will decode the track and run it through a mixer to fold in secondary audio. Then, it re-encodes the mix as DTS for bitstream output to the receiver.

The output is lossy either way and there really should be no difference in quality for the movie itself. 7.1 is not part of the equation here. The lossy output over optical is limited to 5.1 either way. Rear channels are downmixed into the surrounds so that you don't lose any of the audio. Plus, lossless audio is about resolution, not the number of channels.

Bottom line: if you use secondary audio often, then set the player to re-encode and leave it. If you rarely bother with secondary audio, then Audiophile is probably a better way to go. But, it's probably not going matter much either way.

[taylorw]

Thanks for the quick replies! I imagined it was playing the core 5.1 tracks... I rarely use the secondary audio so thus far I have left it on Bitstream (audiophile). I realize 5.1 is lossy but by re-encoding to DTS do I lose further quality?
For example, when I set to re-encode and a DD5.1 soundtrack is converted to DTS, am I experiencing worse quality than if I were to just pipe through the original DD5.1?
Also, if the soundtrack is already standard DTS will the player (set on re-encode) output the sound untouched or will it convert to PCM and back to DTS?

[BIslander]

Originally Posted by taylorw

Thanks for the quick replies! I imagined it was playing the core 5.1 tracks... I rarely use the secondary audio so thus far I have left it on Bitstream (audiophile). I realize 5.1 is lossy but by re-encoding to DTS do I lose further quality?

I don't think so.

For example, when I set to re-encode and a DD5.1 soundtrack is converted to DTS, am I experiencing worse quality than if I were to just pipe through the original DD5.1?

I don't think there's any decoding and re-encoding when the source material is only DD 5.1 or DTS. As far as I know, it only happens with lossless sources. But, that's easy enough to check. Set the player to re-encode, play a BD with a DD 5.1 track, and see whether is comes out as DTS with secondary audio mixed in. But, of course, there aren't many BDs with a DD 5.1 option - mostly off-brands and catalgue titles. Try The Dark Knight, which has both TrueHD and DD 5.1.

Also, I think Samsung players decode lossless tracks when mixing secondary audio. So, it's a high resolution source that's being encoded for lossy bitstream output.

Also, if the soundtrack is already standard DTS will the player (set on re-encode) output the sound untouched or will it convert to PCM and back to DTS?

The same thing goes there. There aren't many Blu-ray releases with DTS tracks. Nearly all of them have dts-MA tracks and a few have DTS-HD HRA.

[taylorw]

So then re-encoding a TrueHD signal to DTS is no worse than allowing the receiver to accept the TrueHD signal and output it as regular DD5.1?

I guess I figured that allowing the receiver to do all the work was the best way to get the purest signal... but basically since its a 5.1 receiver, setting the BD to re-encode makes little difference?

As for the Samsung BD-P1500, setting to re-encode converts everything to DTS, including standard DD 5.1.

I guess I will just leave the BluRay player set to Audiophile unless I plan on using secondary audio. That way, Dolby stays Dolby and no 'on the fly' encoding is necessary.

[BIslander]

Originally Posted by taylorw

So then re-encoding a TrueHD signal to DTS is no worse than allowing the receiver to accept the TrueHD signal and output it as regular DD5.1?

That's not how it works. Optical connections do not support lossless bitstreams. So, the player outputs the embedded DD 5.1 track instead of TrueHD and DTS instead of dts-MA. The receiver has nothing to do with it. The AVR simply decodes whatever gets sent by the player.

I guess I figured that allowing the receiver to do all the work was the best way to get the purest signal... but basically since its a 5.1 receiver, setting the BD to re-encode makes little difference?

The number of channels is not relevant. A non-HDMI 7.1 AVR has the exact same limitations. The player will still only output lossy DD 5.1 and DTS over an optical connection no matter what it attached at the other end.

As for the Samsung BD-P1500, setting to re-encode converts everything to DTS, including standard DD 5.1.

Thanks. That's good to know.

[taylorw]

Ok so then what re-encode (through optical) does is: take the core track and mix in the secondary audio and output to DTS?
Although optical only supports lossy output I still feel quality is lost further when re-encoding.

[BIslander]

Originally Posted by taylorw

Ok so then what re-encode (through optical) does is: take the core track and mix in the secondary audio and output to DTS?

I'm don't know whether it decodes the lossless track or a lossy version.

Although optical only supports lossy output I still feel quality is lost further when re-encoding.

OK. I'm not sure why that would be. But, you are certainly entitled to that opinion.

[taylorw]

Ok. Well thanks for all the info. Im pretty OCD with the audio setup I know... It would be interesting to know whether or not the re-encode mixes the lossless into lossy or just uses the core...
I know it seems like a pretty pointless thing to worry about to someone with a crispier setup but I appreciate you attempting to help!