GB-PVR and Australian HDTV...Is it possible?

[bjanssen]

Hi,

I am playing around trying to get GB-PVR (using BDA drivers for DVB-T) up and running as I have found Media Portal to be too unstable.

I have hit a snag with GB-PVR in that I can't seem to get it decoding AC3 (which is what Australian HD channels transmit their sound as). All I get is near silence with occasional loud popping and cracking noises.

The Audio decoder properties let me choose a decoder, and I can configure that decoder (in the external decoders settings) to do pass through via SPDIF, but to no avail? It's like GB-PVR is somehow bypassing my decoder settings?

Anyone out there able to get it working? If so, what decoder did you use and were you able to send the AC3 signal out via SPDIF or did you have to downconvert it? I don't want to downconvert as Dolby Digital sounds fantastic

Thanks.

BJ.

PS: HD picture works fine

[sub]

To be honest, I have no idea. Its not been tested against this sort of transmissions.

I would hope that with the appropriate filters installed on you machine, it should be able to play AC3 sound.

[daza67]

There seem to be a few issues preventing this one is a demuxer config problem as the ms demuxer defaults to mpeg audio pids even when ac3 is present.

The tuning function does not seem to pick up the ac3 pids when tuning for channels for example nine mpeg audio channel gets reports a tuning request of :
T:C8,191500,0,0,7~P:1025~V:513~A:660~N:>Nine Digital

Changing the tuning request to accomodate the AC3 pid ie:
T:C8,191500,0,0,7~P:1025~V:513~A:661~N:>Nine Digital

This results in no sound and mpeg audio reported by the audio decoder. It appears the Audio pin needs remapping in the demuxer from 0x294 (660) to 0x295 (661).

Even if this is fixed there also appear to be some issues with the Cyberlink muxer being unable to handle ac3 audio, see discussion at forums.dvbowners.com. Apparently the SSmuxer can handle ac3 audio but I have been unable to verify this.

[sub]

I dont know about Oz specifically, but the few places I've personally tried which have alternative ac3 PID, you'd typcially get the following listed during a scan:

T:C8,191500,0,0,7~P:1025~V:513~A:660~N:>Nine Digital
T:C8,191500,0,0,7~P:1025~V:513~A:661~N:>Nine Digital (AC3) (2)

I take you're not getting this for some reason?

[daza67]

Only the mpeg audio pids are getting picked up in the channel scan, see the example extract below. When ac3 audio is only present the audio pid appears set to 0.

T:C05,177500,0,0,7~P:1344~V:1025~A:1026~N:>7 Digital #mpeg only
T:C05,177500,0,0,7~P:1348~V:1089~A:1090~N:>7 HD Digital #ac3 is 1091
T:C05,177500,0,0,7~P:1350~V:1121~A:1122~N:>7 Guide #mpeg only
T:C07,191500,0,0,7~P:1025~V:513~A:660~N:>Nine Digital #ac3 is 661
T:C07,191500,0,0,7~P:1152~V:512~A:0~N:>Nine High Definition #ac3 is 651
T:C11,219500,0,0,7~P:1608~V:514~A:0~N:>TEN HD #ac3 is 672
T:C12,226500,0,0,7~P:576~V:2314~A:0~N:>ABC HDTV #ac3 is 2309
T:C12,226500,0,0,7~P:578~V:2309~A:2310~N:>ABC2 #mpeg only
T:C12,226500,0,0,7~P:577~V:512~A:650~N:>ABC TV Brisbane #ac3 is 651

In graphedit AC3 audio needs a different media type pin defined in the demuxer to the mpeg audio.

The showshifter muxer appears capable of writing a mpeg2 file with ac3 audio in graphedit. I could not get the intervideo or cyberlink muxers to do this. Although the intervideo muxer showed more promise.

Sub, let me know if you would like to take another look in my htpc again or some graphs.

This is getting very close to working.

[sub]

In graphedit AC3 audio needs a different media type pin defined in the demuxer to the mpeg audio

Yes, I'm already aware of that.

You problem seems to be more of a scanning issue. For some reason its not correctly identifying the AC3 channels.

Is <BDAScanType> set to '1' or '2' in you config.xml?

[daza67]

Currently set for 2, if it's set to 1 no channels at all are found at all. On both a twinhan and a dvico cards.

I've tried manually adding the ac3 pids to the SCAN-2.cache file. This results in the popping/crackling noise described.

The nvidia audio decoder properties while this is running report mpeg audio hence my suggestion at it being a media type pid mapping problem.

[sub]

Ah, I see. It'll definitely only find AC3 channels when you do a type '1' scan.

I've tried manually adding the ac3 pids to the SCAN-2.cache file. This results in the popping/crackling noise described.

Unfortunately thats not enough. It actually needs a couple of other things embedded in the tuning request string to tell it it's an AC3 audio channel. I've made a few AC3 related changes in the next release (due in a few days), and you're probably better off trying it then (especially since the old tuning request AC3 details, and AC3 filter requirement are a little hazy in my mind).

You're still likely to have the scanning difficulties in the next release though, since I dont think anything has been changed in this area of the application.

[daza67]

What is the syntax of the tuning request, can you give me an example of the other bits that may be missing ?

Would this work ?
T:C8,191500,0,0,7~P:1025~V:513~A:661~N:>Nine Digital (AC3) (2)

[daza67]

Sub,

FYI, it seems the failure of the bda tuning type 1 scan were due to xp MCE 2005. Type 2 scans work fine with both Twinhan and DVICO cards under xp pro.

Cheers
Darren