PDA

View Full Version : Converting multichannel AC3 and DTS



daren
09-20-2007, 03:21 AM
Hi,

I need to convert some .ac3 and .dts surround sound audio files to other formats (WAV/RF64 and WMA), while retaining all audio channels (5.1 in my case).

I've found a directshow filter which does this (AC3Filter), but the dBpoweramp directshow codec only seems to work for two channels (i.e. I give it a surround file to decode, but the resulting WAV is stereo).

Has anyone else come across this? ..is it a problem in the dBpoweramp directshow codec, or something to do with the 3rd party AC3Filter package?

Best regards,
Daren.

Spoon
09-20-2007, 04:03 AM
There is a configuration program for ac3filter where you can allow 6 channel output.

daren
09-20-2007, 08:31 AM
Thanks. I've given it a go, but I'm getting messages like:

Error converting to Wave, 'D:\temp\Surround sound tests\Title1 - Chapter 02.dts' to 'D:\temp\Surround sound tests\Title1 - Chapter 02.wav'
Wave Encoder: Error Converting from 'Format Tag: 65534 Channels: 6 Bits per Sample: 16 Samples Per Second: 48000 Bytes Per Second: 576000 Block Align: 12 CB Size: 22 Extensible Sub-Format: 65534' to 'Format Tag: 65534 Channels: 6 Bits per Sample: 16 Samples Per Second: 48000 Bytes Per Second: 576000 Block Align: 12 CB Size: 22 Extensible Sub-Format: 1'

I get this with virtually anything apart from the setting "2/0 stereo".

When I use the "As is" setting, I get half speed audio....

Any ideas?
Daren

Spoon
09-20-2007, 08:42 AM
>Extensible Sub-Format: 65534

That does not look right, my routine will fall through as extensible for the subformat if it cannot recognize it, so it is not PCM, float, must still be DTS.

daren
09-25-2007, 09:24 AM
The strange thing is that if you run the AC3Filter in GraphEdit, it has no problem decoding/playing all 6 channels.

I've had a look at the AC3Filter source code and I think I can see why the Extensible Sub-Format = 65534. This will happen when the filter is acting in SPDIF pass-through mode. I tried to compile the project to take a closer look, but didn't get far (wouldn't compile, too many dependancies). So, I tried switching off everything to do with SPDIF in the config tool, but to no avail.

Is it possible that the DirectShow codec is negotiating and settling for the SPDIF stream instead of a linear stream for multichannel audio?

All the best,
Daren.

Spoon
09-27-2007, 03:59 AM
Not sure.