[M4IF Technotes] Downloadable standard MPEG test sequences

[Ben Waggoner]

on 7/11/02 11:31 AM, Kris Huber at khuber   sorenson.com wrote:
> We have "ifdefs" in the code that dump and read these formats for internal
> conformance testing of our MPEG-4 products and to create/use m4if interop
> raw bitstreams as needed and to test using the MPEG4 conformance bitstreams
> as part of self-certification.  I suppose if conformance testing were being
> done by an external organization we could make this capability available in
> a more user-friendly way.  Apparently that capability is quite important to
> you?

    It'd be very useful, but I'm a somewhat atypical customer.  Still, if
you already have the code working, it might make sense to enable .yuv as a
source type in Squeeze.
> As for conversion out of raw .yuv, I know the .avi and .mov are quite
> flexible formats.  Although I'm less familiar with them than I should be, my
> guess is that it's possible to convert from raw .yuv to either one without
> doing a redundant color conversion.  I think it would depend on if anyone
> has registered a format for "raw YUV" for .mov and .avi.  The problem with
> that is that not all YUV's are equal, some having come from RGB through
> somewhat different processes.  In a raw YUV format you are on your own to
> know the color space and image resolution via external means.  There are no
> headers.  Some formats have one or more color spaces associated with them,
> although in actual usage the data in those formats are not always indicated
> or obeyed strictly.  In the MPEG-4 visual object (VO) header the color space
> information can be encoded.  Currently that information includes 6 choices
> of color primaries systems, 8 choices of opto-electronic transfer
> characteristic and 5 choices of colorspace conversion matrix (the one used
> to go from RGB to YCbCr), but there is ample reserved space to add more
> choices in the future as a need arises.  You can find more on the specific
> choices that are currently available near the end of subclause 6.3.2 of the
> video spec (ISO/IEC 14496-2:2001).

    Indeed, it is a pretty trivial feature conceptually.  It's just no one
has actually built the tool yet.  I believe QuickTime supports at lot of the
same color space information.
    I think the "right" solution would be for Apple or someone else to write
a QuickTime import component for .yuv, and make it part of the component
download program.
Ben Waggoner <http://www.benwaggoner.com>
Compressed Video Consulting, Training, and Encoding
Cleaner Tutorial:   http://www.saferseas.com/navseries/adclean.html
My Book:            http://www.benwaggoner.com/books.htm
Compression Books:  http://www.benwaggoner.com/bookshelf.htm
Compression classes at Stanford, July 15-19 and August 12-16:
http://www.digitalmediaacademy.org/courses/videocompress.html