[vdr] Re: [Mplayer-dvb] DTS Sound

[Wolfgang Fiesel <fie@iis.fhg.de>]

Uwe Weissbach wrote:

> Wolfgang Fiesel wrote:
>
> > In IEC958 format each audio sample is embedded in a 32 bit frame granularity. It
> > looks like the following bit structure:
> > Sync Preamle : 0-3
> > Auxillary Audio Data : 4-7
> > Audio sample word : 8-27
> > (V)alidity bit: 28
> > (U)ser data: 29
> > (C)hannel status: 30
> > (P)arity bit: 31
> > ...
> > Ok, in case of raw PCM transmission it has to be zero to signalise the D/A converter
> > true audio data. In case of error's like changing of sampling rate the V-Flag is "1"
> > for some frame to force muting the D/A converter.
> > In our situation (IEC61937) it is recommend to set the validity bit to logical "1"
> > because we deliver not really more raw PCM data!!!
> > Unfortunatly as Uwe find out this bit is always "0". I can imagine that some
>
> Hi Wolfgang,
>
> No - misunderstanding! I did'nt found the validity bit (28) is wrong
> but the bit 1 (second) in the channel status word, witch is
> build from all the bits No. 30 is not set correct
>

What a pitty, sorry for my misunderstanding.
After reading your description more carefully I recognize the problem of the channel
status.
The IEC 61937 paper says:
"IEC 60958 channel status bit 1"
The purpose of channel status bit 1 is to indicate if IEC 60958 is used to convey linear
PCM, or to indicate that the interface is used for their purpose.
This bit shall set to "1" when IEC 60958 is used to convey non-linear PCM encoded audio
bitstreams(like AC-3, DTS,...).

Oh yeah, this is a big topic.

The problem is that the channel status information is composed of a loop sequence of 192
single channel status bits (C).
The meaning of these bits are:
bit 0: "0" = consumer use of channel status block
bit1: "0" = audio / "1" = digital data
bit2-192: definitions of copy mode, sampling rate, ....

Our topic is the bit 1.
On Standard SPDIF transmitter chips (Crystal,...) the definition of channel status can
mostly set by internal control registers or external pins. In case of our TI MPEG-Decoder
I see no change to modify these status bits on the first view because the TI chip is a
very complex chip and it seems that the developer have to limited all control features to
a practical subset.
I try to get a more detailed information on these TI Decoder but I fear we are at the end
of our way.
Perhaps the soundcard solution is the only accurate solution (damned) because programmable
SPDIF transmitter(Crystal) are used there.

Wolfi