[MPlayer-dev-eng] [PATCH] Remove leading/trailing margin for VCD

[Zuxy Meng]

Hi,

2007/3/13, Nico Sabbi <nsabbi at email.it>:
> Zuxy Meng wrote:
>
> > Hi,
> >
> > Playing around with VCD, I found that the MPEG packs don't start
> > precisely at the beginning of a track, and don't end precisely at the
> > end of a track either: they are wrapped by all zero sectors. I don't
> > have a copy of the White Book so I can't tell if it's mandated by the
> > standard or just an implementation issue.
>
> the sources of vcdimager may help

Can vcdimager produce a VCD image from a bunch of mpeg files?

> > I guess the rationale behind
> > these margins is that old VCD players have problems in accurate
> > seeking. Nevertheless, the leading margin makes lavf demuxer reject it
> > as a legitimate MPEG PS stream.
> >
> > Two notes about the patch:
> > 1. Experience shows that reading sector by sector in the backward
> > direction is extremely slow so I commented such code out. As a result
> > trailing margin isn't stripped and fortunately it doesn't cause much
> > trouble in demuxing too.
> > 2. Each MPEG pack (as well as a non-null VCD sector) begins with
> > 0x000001ba and I picked the last byte (0xba) as the probe.
>
>
> I'd like to know what's the content that you want to skip before
> removing it.
> I'll help you to search in vcdimager

Thanks! Margin consists purely of all-zero sectors (all the 2324-byte
user data in a CDXA sector are zero) in my experiment.
-- 
Zuxy
Beauty is truth,
While truth is beauty.
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