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[vdr] Re: Problems playing DVD
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
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