On Mon, 21 Mar 2005, Matti Haveri wrote:
> Things were clear for a few days but now I'm confused again ;)
Yes, I think you managed to confuse yourself again :-)
> But I then noticed that QuickTime Player couldn't show the image of
> the VOB file or of the MPEG converted from it via MPEG Streamclip (a
That is true - the QT player doesn't completely understand the VOB
structure (maybe QT Player thinks that's the DVD Player's job only ;))
> Please correct if necessary:
Ok :)
> I then learned that the terms "MPEG-1" and "MPEG-2" not only
> designate two different VIDEO formats, but also two different
True enough - they are different video types (but a compliant MPEG-2
decoder is required to decode MPEG-1 streams)
> CONTAINERS for these video formats. One could call the MPEG-1
> container "MPEG system stream" and the MPEG-2 container "MPEG program stream".
Nope. Looking thru the reference books I see "program stream" and
"transport stream" (the latter is MPEG-2 only it appears) but not
"system stream".
One reference mentions:
"MPEG-2 systems define two bit stream constructs. The "program stream"
(PS) is modeled on MPEG-1, and complian PS decoders will decode MPEG-1
bit streams... The alternative is the MPEG-2 "transport stream"
(TS)..."
> The MPEG-1 container is expected to hold MPEG-1 video, and the MPEG-2
> container is expected to hold MPEG-2 video. But I can put MPEG-1
The output of an encoder (such as mpeg2enc) is an "elementary stream".
That's true for both MPEG-1 and MPEG-2.
> video in MPEG-2 containers and still be ISO compliant. I *can*, but
> obviously I can't expect it to work in all applications.
There's no difference in containers until you get to "VOB".
It's entirely possible (and I am beginning to think QT Player is
proof by existence) that a MPEG player might not fully understand
the VOB file type.
> This is where the problem with the QuickTime Player came from: the
> VOB file is ALWAYS an MPEG-2 container. But there is a number of DVD
It's quite possible that the Quicktime Player doesn't understand
MPEG-1 in a VOB container. That's another bug in the QT player.
> recorders that put MPEG-1 video in VOB files anyway. Also many DVD
> authoring apps will accept and put MPEG-1 into the VOB (MPEG-2)
> container. (I heard that DVD Studio Pro rejects any MPEG-1 file, though).
There was a problem for a while using (long) MPEG-1 streams in
DVDSP - it was a bug that was fixed in one of the updates (3.0.1 I
believe, but might have been 3.0.2). I've put MPEG-1 on a DVD and it
works fine - but I use MPlayer or DVD Player rather than QT Player
to do the playing.
> Apple's QuickTime Player (and the related MPEG-2 Playback Component)
> can't handle MPEG-1 inside a VOB but Apple's DVD Player can because
> they use different engines for playback.
Yep - that's what I thought was the case earlier: QT Player has a
shortcoming/bug.
I think QT Player and DVD Player share the MPEG-2 decoder though because
neither QT player or DVD player decode streams using DPME (Dual Prime
Motion Estimation) properly and stutter badly. That doesn't mean
there are different container formats for MPEG-1 and MPEG-2.
> I could fix the MPEG container issue by demultiplexing the file and
> then remultiplexing it with MPEG Streamclip. THEN the QuickTime
> Player showed the video part in it.
Right - you've turned a "VOB container" into a "program
stream" container which QT Player understands. 'mplex' could
also have done the multiplexing.
> I also learned that reporting whether a file is MPEG-1 or MPEG-2 is
> also difficult: what should an application say if the CONTAINER is
It's also not usually necessary since an MPEG-2 decoder can decode
MPEG-1 ;)
> ...So it seems that it is better to use 352x288 MPEG-2 video although
> some sources say that only MPEG-1 is valid for a DVD at this resolution??
Not really. I think the moral of the story is to not use QT Player
to play VOBs <grin>. Use something like MPlayer OR use the DVD Player
app to play the VIDEO_TS directory which contains the .ifo and .vob
files.
> <http://www.dvddemystified.com/dvdfaq.html#3.4>
> BTW, the page above says that MPEG-1 video rate is limited to 1.856 Mbps
> (just as Steven recalled).
Ah, good - nice to know my memory (and Apple's documentation) was
correct about that.
> Or can VOB used as a valid container for MPEG-1, too??
Of course. DVDs can contain MPEG-1 video. DVDs use VOB files. Thus
VOB files (can) contain MPEG-1. Q.E.D.?
All in all I think the only problem you ran into is that QT Player's
handling of VOB files isn't quite 100% complete.
It's safe to put the "VCD" size MPEG-1 on a DVD since DVD players
(such as the Pioneer 444 and the DVD-Player app) will handle it. Just
don't play the VOB files with QT Player :)
Cheers,
Steven Schultz
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