[Samsung Galaxy Nexus] CouttsPhotog:
I was tinkering with media_profiles.xml yesterday and it appears that modifying the bitrate settings in here affects the camera. The stock bitrate min/max values are:

min: 64000

max: 12000000

Videos shot with these settings are usually 6-10mbps bitrate. I have changed these values to:

min: 35000000

max: 60000000

And my videos are now between 20mbps and 50mbps (huge leap!). The file sizes are bigger but I'm assuming this has to mean the videos will be somewhat better quality (my guess is mostly in low light when the ISO is cranked higher). I don't understand very well how these values are all used in here, but adjusting the bitrate ones does make a difference. Although framerate for 1080p says 30 here, they always come off camera at 24fps so I'm not sure if framerate (or any other changes) will work here.

Any value higher than 60000000 for the max will cause the camera app to crash, so I think this is a good max for now. This mod has been done on countless other devices, so I'm in no way discovering anything new, I just decided to poke around and see what changes work :)

Here's some more details for what to modify (to apply this mod to 720p and 1080p):

Starting at line 127:

<EncoderProfile quality="720p" fileFormat="mp4" duration="30">
<Video codec="h264"
[COLOR="Red"][b]bitRate="60000000"[/b][/COLOR]
width="1280"
height="720"
frameRate="30" />
<Audio codec="aac"
bitRate="96000"
sampleRate="48000"
channels="1" />
</EncoderProfile>

<EncoderProfile quality="1080p" fileFormat="mp4" duration="30">
<Video codec="h264"
[COLOR="red"][b]bitRate="60000000"[/b][/COLOR]
width="1920"
height="1080"
frameRate="30" />
<Audio codec="aac"
bitRate="96000"
sampleRate="48000"
channels="1" />
</EncoderProfile>

And one other spot, line 340:

<VideoEncoderCap name="h264" enabled="true"
minBitRate="[COLOR="red"][b]35000000[/b][/COLOR]" maxBitRate="[COLOR="red"][b]60000000[/b][/COLOR]"
minFrameWidth="176" maxFrameWidth="1920"
minFrameHeight="144" maxFrameHeight="1080"
minFrameRate="15" maxFrameRate="30" />

Additional mod:

People have claimed on other devices changing this setting produces higher quality images from the camera, starting at line 216:

<ImageEncoding quality="[COLOR="red"][b]100[/b][/COLOR]" />
<ImageEncoding quality="80" />
<ImageEncoding quality="70" />
<ImageDecoding memCap="20000000" />

Steps to apply the mod:

1) have ADB setup and working (not explaining that here, plenty of other threads for this)

2) cd to some directory to work in (I just use the desktop), ensure ADB is in your path (google that part)

3)

adb pull /etc/media_profiles.xml .

to pull the media_profiles.xml file to whatever folder you're in with the terminal.

4) Make your modifications, save the file (maybe keep a backup of the original file if you want).

--- workaround because adb remount doesn't work] ---

5)

adb push media_profiles.xml /sdcard/download

6) Use root explorer to move the media_profiles.xml file from your downloads folder to the /etc folder (make sure to mount /etc as R/W before you try to move).

7) Reboot phone, all set!

EDIT

- or just use Root Explorer (available in the market) to do the changes, reboot the phone and you're done!

edit

Demo video shot at 45mbps:

http://www.youtube.com/watch?v=J2r6zPYlRD0

http://www.youtube.com/watch?v=XCbNs1hEEjU

Hope somebody else finds this as useful as me!