[mythtv-users] Court rules commercial-skipping in recordings covered under Fair Use

[Richard Hulme]

On 25/07/13 04:51, Stephen Worthington wrote:
> On Wed, 24 Jul 2013 18:48:34 -0400, you wrote:
>
>> Tom Dexter wrote:
>>> DVDs??...that you MUST watch all copyrighted content only in it's
>>> entirety, in order?
>>
>> Don't they do this with DVDs now?  I played 'One' DVD on a player, many
>> years ago, and it refused to allow me to skip forward past the coming
>> attractions. To date, I haven't bought a DVD or BD player.  I rip 'em to
>> MythVideo instead and skip when I please.
>>
>> Doug
>
> You can do that to DVDs in various ways.  The first is PUOs =
> Prohibited User Operations, where the DVD is programmed not to allow
> the skip buttons or menu buttons to work.  That is easy to fix -
> either use a DVD player that ignores PUOs or rip the DVD and run a
> program such as PGCEdit on it to remove the PUOs and add navigation
> options.  That is easy as PGCEdit has a menu option to remove PUOs
> automatically.
>
> The worse way that turns up on some DVDs is to make the "first play"
> menu ie VIDEO_TS.VOB into a real bit of video, rather than a null file
> or just a few seconds of menu.   If you look at the contents of a DVD
> and VIDEO_TS.VOB is of any substantial size, then it probably has this
> problem.  MythTV and an awful lot of DVD players and player software
> do not do skipping inside a menu (as far as I can tell, the DVD
> standard does not allow it).  So the fix for that is to rip the DVD

It depends on how you define 'menu'.  Being in a certain domain or 
having buttons defined?

The upcoming 0.27 release has changed the definition to 'having buttons 
defined'.  This should make it easier to skip over the stuff at the 
beginning of a DVD (among other things).  Be aware though, that it's 
possible to define fully transparent buttons (i.e. invisible), which 
could have you scratching your head wondering why you can skip on that 
DVD but not on this one.

Also, you can usually jump directly to one of the menus without needing 
to skip through anything.

Having said that, a lot depends on the way the DVD has been authored. 
The entry points for 'title', 'root', 'chapter' menus etc. are really 
nothing more than markers.  There is no necessity to actually have a 
menu there.  It's feasible for the DVD author to put some code in there 
that checks whether a certain point has been passed on the DVD (e.g. all 
the trailers have been watched) and jump on to the real menu if so, or 
back to the beginning of the trailers if not.

Myth currently ignores the prohibited user operation flags, which allows 
the user a lot more freedom.  That *can* come at a price, though.  A DVD 
is effectively run in a small virtual machine, which executes code found 
on the DVD.  There are a number of variables available which can be used 
to store values.  Jumps can be performed conditionally (like the example 
I gave about trailers) based on the value stored in one of these 
variables.  By skipping parts that can't (according to the prohibited 
user operations) be skipped over, it's possible to miss some of these 
instructions that may be important later.  This could lead to odd 
playback behaviour.  A bit like arriving in the middle of a conversation 
and getting the wrong end of the stick because you missed the beginning.

Most of the time, this doesn't happen, but it is possible.

Richard.