[Matroska-devel] Re: Diferent frame sizes

Paul Bryson paul at comnetsystems.com
Wed Feb 22 14:35:30 CET 2006

Matroska can and does contain video streams of different resolution.  The
container itself, nor any of the muxing tools should ever have a problem
with this.  Programs used for playback may be another story.

"Austin Coté Williams" <sporks5000 at gmail.com> wrote in message
news:<658f9a740601191125vc00e9a3r823d57e891ab6881 at mail.gmail.com>...
Dear Developers of Matroska,

I noticed that Matroska doesn't seem to be able to contain two video
segments with different frame sizes. I can understand that - no other
container format (that I know of) offers such a feature - but it seems
that since one of the main points of Matroska is it's ability to do
anything, I thought that I'd recommend it, and see what people had to

I have no practical experience with programming, so this might be a
round-about way of accomplishing this, but it seems like it would be
possible to have the software that's compiling the video file,
MKVtoolnix, for example, set the frame size for the final video file
as the largest width from the video segments being merged by the
largest height from the video segments being merged.

In the properties for each segment, you'd be able to set where within
the frame that video segment would play (centered, top left, etc., or
you could specify the exact location of the upper right pixel of the
file using X and Y coordinates). A global tag would have to be
included to indicate what color any portion of the frame that isn't
being taken up by a video segment would be, (black would be default)
as well as whether the portions of the last frame of the last video
segment which aren't being overlapped by the following video segment
should remain on screen, or immediately be replaced by the background
color once their duration is up.

While it would be easy enough to re-size or add black (or the color of
your choice) pixels to the top, bottom, left, or right of each segment
until they're all the same size, this alternative would save time and
space because the black space wouldn't have to be encoded into the
video data but instead could easily be indicated only once in RRBBGG
format (or something similar).

Also, the ability to keep the last frame of a video segment on the
screen would allow space to be saved in instances where a portion of
the frame doesn't change for some duration of time, but the rest of
the frame does. The portion that doesn't change would be cropped out,
reducing the file size of the segment, and therefore the size of the
entire file.

Is it possible? Is it worth doing? Does anyone have any thoughts on this?

-Austin Williams
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