Snowball: Video Output Resolution limitation

Description:
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I found the default video resolution is 720p (1280x720, 16:9) on TV via HDMI, and 1024x768 (4:3) on LCD Monitor via HDMI/DVI. Though the display device could support higher resolution (e.g. 1080p), I can't change resolution and system also can't auto detect and change it. I think the max resolution should be supported.

I tested linaro 12.03.1 ubuntu emmc image and linaro 12.05 ubuntu sdcard image. The results are same.

I listed the display device details:
1. LCD, Dell E2011H, DVI works on 1027x768 (1600x900 max)
2. TV, Sony KLV-42EX410, HDMI works on 720p (1080p max)

Hardware:
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snowball V10

Software:
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Image URL : http://releases.linaro.org/12.03.1/ubuntu/leb-snowball/snowball_emmc-ubuntu-2012.03.1.img.gz
Used riff tool to flash emmc image on snowball hardware.

Image URL : http://releases.linaro.org/12.05/ubuntu/leb-snowball/
Used dd tool to flash sd image to sdcard and insert it in snowball.