[vdr] Re: Problems playing DVD

[Christoph Rieder <christoph.rieder@web.de>]

Sorry, if this gets a little bit OT...

Andreas Schultz wrote:

>> should not do any ac3 decoding, right?
> 
> 
> no, we always do the decoding, that is needed to get the analog audio 
> out working. You could remove the AC3 decoding from 
> cDVDplayBuffer::decode_packet().

You were right!!! It was the ac3decoding. After I commented out the 
decoding the video plays perfectly (but a little bit quiet...)

> 
>> And why do we have to decode AC3 into PCM? shouldn't DVD's contain PCM 
>> audio?
> 
> 
> almost all DVD's i have seen do not

Sorry, I've mixed up something:

Audio DVD's have to contain PCM but not video DVD's.
But http://www.mpeg.org/MPEG/DVD/Book_B/Audio.html says:

* Dolby AC-3 used mandatory for 525/60 (NTSC) players and MPEG-2 is 
mandatory for 625/50 (PAL) players, but optional on discs themselves.
* A 625/50 disc must contain either MPEG-2 audio or LPCM. Due to 
bandwidth efficiency, most titles will use the more compact Dolby AC-3 
or MPEG-2 audio.

If I understand correctly, a PAL disc contains either PCM (unlikely) or 
MPEG-2 audio. This means that there is no need to decode AC3 for Stereo 
sound.



Christoph