Secondary soundtrack

[LeHobbit]

Could you explain me how the secondary soundtrack is mixed with a primary soundtrack in the player. I have heard that they are both decoded to PCM and mix together. If I understand it well, the PCM stream is then sent to the receiver. Is that right ? Is the PCM stream encoded or transcoded before being sent to the receiver ?
Thanks

[Kilian]

A Profile 1.1 or 2.0 player can send the mix as PCM, and optionally may also transcode and bitstream or convert the PCM mix to analogue, depending on the hardware capabilities, codec and user options (fig. 5 of the Dolby whitepaper).

The Panasonic BD30 can send PCM if you select PCM output, but 7.1 is reduced to 5.1 only via HDMI and 2.0 via S/PDIF. It can also bitstream DD 5.1 (via HDMI and S/PDIF) if you select "bitstream" option and decode to analogue 5.1. Since it cannot internally decode the lossless codecs, it will only decode the companion DD or core DTS in the primary track.

Bear in mind the secondary audio stream on BD-ROM is limited to 256 kbps, 48kHz and 5.1-channels.

[LeHobbit]

Originally Posted by Kilian

A Profile 1.1 or 2.0 player can send the mix as PCM, and optionally may also transcode and bitstream or convert the PCM mix to analogue, depending on the hardware capabilities, codec and user options (fig. 5 of the Dolby whitepaper).

For example, if the primary soundtrack is in Dolby TrueHD 7.1, is there any loss of data when mixing with the secondary sountrack ? That is to say, when the both soundtrack are mixed, is the PCM stream also in 7.1 ? I think it is, but I am not sure.

Originally Posted by Kilian

Bear in mind the secondary audio stream on BD-ROM is limited to 256 kbps, 48kHz and 5.1-channels.

Is it the same limit for DTS and Dolby ?

[Kilian]

Q.1. Currently as far as I know there aren't any BDs with PiP with Dolby TrueHD 7.1 primary audio so it remains to be seen how it works.

Q.2. Yes.
Edit: As secondary track, it is actually technically called DD+ and DTS-HD LBR, rather than just DD and DTS respectively.

[LeHobbit]

In fact th only thing I want to know is whether or not the PCM stream would be also in 7.1 when mixed with the secondary soundtrack.

[Kilian]

Currently there are only two BDs that I know of with profile 1.1 PiP of some kind that also have 7.1 primary audio. Neither are the straight forward PiP stuff - Rambo (DTS-HD MA 7.1) has a seamless branching PiP and War (LPCM 7.1) only has a short FX PiP featurette. So we don't know for sure if a player playing a BD with PiP that is running simultaneously with the main feature will output 7.1 audio. As I said above, the Panny BD30 manual says it will downmix 7.1 PCM to 5.1.

I can only count 10 profile 1.1 BDs (excluding the second encodes and branching types) out of the 658 BDs as listed on blu-raystats and that is a lowly 1.5% of the total. It just put things into perspective.