[vdr] Re: Playing DVD ?

["Tilo Renkl" <tilo@diredare.de>]

As I many many times wrote here and on every board:

Why don't we use Xine for DVD-Playback ? The only thing to do is
to integrate the dvb API for output (DXR3 works already).

Pros:
- very good DVD-Playback
- very good at A/V-Sync
- lirc-support
- already supports realtime mpeg encoding for output (DXR3)
...

Cons:
- only DVB-Input for now, no output :-((

Tilo


> [...]
>
> > A other thing: often i hear "the Error is the DVD because
> itīs structure is
> > not DVD Conform" - i canīt understand this because most of
> other Player
> > (also Software-Player for WIN) play this DVDīs correct and
> iīm sure they
> > will not ask a VDR user to produce a "konform" DVD  :-)
>
> There is a fundamental difference between all those
> software/hardware players
> and VDR: VDR uses a DVB card. People tend to forget that the
> av711x and the
> firmware where not designed for DVD but for DVB streams.
> There are things on
> commercial DVD's that are not DVD standard konform but are
> still resonably
> within the limits of the MPEG specification that a normal
> MPEG decoder can
> deal with them. The DVB card on the other hand is not so forgiving.
>
> Some real-life examples:
>
> 1. audio/video latency
>
> MPEG specification allows up to one second of audio/video
> latency. The DVB
> card, due to the limited buffer memory will produce
> significant distortions
> if the latency exceeds something around 300-400 ms or about
> 200kbyte worth of
> data (this is just a guess based on prior observation).
>
> 2. screwed audio/video PTS
>
> Getting video and audio in sync is not easy. Early version of
> the dvd stuff
> had serious problems with that. The solution is to let the
> DVB card do the
> syncing. The syncing done by the card is based mostly on the
> PTS (presentaion
> time stamp). I have seen DVD's where the progress in  the PTS
> did not match
> the amount of data present. Basicly the PTS was increased at
> only half the
> speed of the audio stream. This will obviously screw
> audio/video sync big
> time.
>
> 3. PTS jumps
>
> PTS might be reset (restarted) across chapter boundaries.
> They are guaranteed
> to jump during menu transitions. The DVB cards firmware
> handles those jumps
> very badly, resulting in short stutter when a chapter
> transition happens.
>
>
> Some of the above problems can (and should) be worked around.
> Others require
> an amount of mpeg stream preprocessing that only an mpeg
> expert will be able
> to implement. Until you find such an expert or become one,
> you will have to
> accept those limitations.
>
> Have fun
>
> Andreas
>
>
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