Quote:
Originally Posted by benwaggoner
Anyway, if you can upload a file that shows this behavior, I'll pass it on to the Xbox media guys.
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Okay, sorry for the delay. I've been busy with other things but I wanted to do more testing with this, and after testing it in widescreen mode I can see now that SAR flags are obeyed as long as they are on the list of approved numbers from the MP4 spec. It doesn't make any difference for a square display because the image is basically the size of the full screen to begin with, and in the case of an invalid SAR it just stretches to fill the whole screen anyway. That's why I couldn't tell that it was doing anything before, as I hadn't tested a widescreen image.
That still does not explain the needless resizing of the image that the XBox does for all videos that it plays, as well as still images. Only DVD playback is not affected. For all video files and still images, the image is reduced in width by 15 pixels, almost as if it is compensating for an assumption that the video content is 704 stretched to fit a 720 width image. If that were the case then reducing the width by 15 pixels would indeed provide the desired 4:3 result, but my content is from television, so the active image area is already limited to the middle 704 pixels. Further horizontal compression makes the image thinner than it should be.
There is also a problem with the vertical resolution, or some sort of problem with interlacing perhaps. There are ghost lines on the 360's MP4 playback, so it either is resizing vertically for no reason, or it isn't handling the interlacing properly.
My tests were done over an S-Video connection, so I do not know if this problem affects the HDMI output, and I am wondering if perhaps something was not tested properly on the analog output, so perhaps this problem slipped through the cracks that way.
Anyway, I have attached a zip file containing a text file with a basic explanation of the problem, and a PSD with my test results so that you can clearly see what I am talking about just by turning on the layers. There is also an MP4 file that demonstrates the problem very obviously, but it affects any video file that is played on the XBox.
Thanks for taking the time to read all this crap. Hopefully someone can figure something out.