8 replies to this topic

[anudanan]

I´ve an older AVR which is not able to decode AC3+ but only AC3

 

normally many channels use AC3 and I like to decode AC3 with my AVR and not with the sat box to Multi PCM. The reason is inside the AC3 audio tracks there are some meta informations which the AC3 decoder of the AVR can use. But if the sat box decodes it to multi PCM than these informations are not inside the PCM streams to the AVR.

 

For users which have an older AVR without the AC3+ feature it is usefull to have different multi PCM enable settings. AC3+ multi PCM enable/disable and AC3 multi PCM enable/disable

 

Is there a way to implement this in openpli?

[littlesat]

Until now the conversion is only to stereo... no ac3+ to ac3 without +.. until now this cannot be done by hardware/drivers... I fully agree for older surround sets or TVs this might be an improvement.
To do this in software might have lisence issues (Dolby, or DTS) especially as you also need to encode here.

Edited by littlesat, 17 March 2019 - 15:16.

[twol]

It depends on what the sat receiver supports - if it supports AC3+ and has the options like downmix (which some boxes support) then its possible to check the procs and pick up the available options and implement accordingly without having to have special receiver specific code - except of course Vu+ who do their own thing as usual
... of course it also depends on OpenPli having the time to implement.

[anudanan]

I´v tested my uno4kse with openpli 7.0

 

AC3 Downmix off, multi PCM off

- AC3 audiostream goes transparent to the AVR and the AVR sees AC3 and decode it and sound works

- AC3+ audiostream goes transparent to the AVR and only AVR with AC3+ support can decode it. Older AVR can´t do it and no sound is there

 

AC3 Downmix on, multi PCM off

- the box converts AC3 to stereo and the AVR sees two PCM streams for left and right. Sound works.

- the box converts AC3+  to stereo and the AVR sees two PCM streams for left and right. Sound works.

 

AC3 Downmox off. multi PCM on

- the box converts AC3 to a 6 channel PCM stream (5.1) and the AVR sees 6 PCM channels. Sound works.

- the box converts AC3+ to a 6 channel PCM stream (5.1) and the AVR sees 6 PCM channels. Sound works.

 

 

So the HW can decode AC3+ to PCM (not to AC3) but today it is a global switch für AC3 and AC3+ and not a different switches for AC3 and on other for AC3+ 

[anudanan]

Are there any plans to implement the above feature into the audio setuo menu like?

 

AC3 downmix on/off

AC3+ downmix on/off (new)

AC3 to PCM on/off

AC3+ to PCM on/off (new)

[WanWizard]

No.

[Erik Slagter]

Do I understand correctly that the TS requests for a real-time transcoding of AC3+ (EAC3) to AC3? Most STB's CPUs will be powerful enough to do it, but it's not simple.

 

The conversion ("downmix") from AC3(+) is done opaquely by the drivers, probably with aid of some specialised piece of hardware.

 

It looks like AC3+ was solely developed to pester owners of older media amplifiers, because it doesn't really offer much advantages.

[Trial]

Hi,

not completely Erik. The TS wants AC3+ -> multichannel PCM and AC3 as bitstream as separate options.

 

Ralf

[Erik Slagter]

The first is already possible afaik, so leaves the second as discussed.