[M4IF Technotes] B-frames in Simple? Which Levels?

[Ben Waggoner]

Rob,
    Yeah, I didn't mean to sound overly pessimistic.  Most of what I'm
testing is unreleased tools, obviously, so there is still time to get the
issues ironed out.  Overall, the problems seem to be in the players more
than the encoded content.  For stuff that should work, the problems tend the
be the video not playing in the right part of the window, oddly enough, like
the entire frame being shifted up 32 pixels up and to the left.
    It does work seamlessly in many cases, too.  It was pretty magical to
see a bitstream from one unreleased tool work in an unreleased player from
another vendor.
    I think an important step for players will be to do some kind of
validation on the source to make sure they can play it, and give some kind
of warning if it is out of profile for them.  A lot of stuff is going to get
assigned to the .mp4 extension, with different requirements.
    Anything happening with including a profile descriptor in a MIME type so
that web-based content could be more accurately steered to an appropriate
player?
Ben Waggoner
Interframe Media <http://www.interframemedia.com>
Digital Video Compression Consulting, Training, and Encoding
on 1/23/02 3:51 PM, Rob Koenen at rkoenen   intertrust.com wrote:
> There was some chaos but it is rapdily decreasing.
> Over 20 companies have done (and are doing) interop testing
> in M4IF, and we are doing these by the Profile, concentrating on
> Simple and Advanced Simple.
> 
> I cannot comment on individual companies (I will gladly leave that
> to their representatives) but I do know that the behavior you
> have observed is disappearing. I thought this was also the case
> for the exampe that you mention.
> 
> Profiles and Levels define decoder requirements - the lower bounds,
> that is. Implicitly, they also define upper bounds onwhat the
> encoder can spit out.
> 
> We are migrating from a situation in which people just stated "I am
> doing MPEG-4" (and they didn't have a clue about Profiles and Levels)
> to one in which people say "I am doing MPEG-4 X profile at Y Level."
> (and sometimes they add "oh, by the way, my encoder doesn't do tool Z
> yet, but it will be done next month").
> 
> ISMA helps, having picked concrete Advanced Simple Profile from the
> MPEG-4 spec for its own 1.0 spec.
> 
> M4IF will help further by designing a process of (self) certification.
> The MPEG-4 syntax contains info on Profiles and Levels, but I am not
> aware of any tools, except for the Video analysis tools of Interra,
> http://www.interra.tv/products/Mpeg4_analysis.htm