By default, YouTube will show you the Normal version. If you encode your videos using the specs below, YouTube will give you the "watch in HD" option at the bottom-right of the video display.
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Adobe Premiere Pro CS3 Export Settings
(Use (Adobe Media Encoder" not "Export Movie")
Format: QuickTime
Range: ~
Preset: YouTube HD (this is the name of MY preset
Summary: 1280x720, 29.97 [fps], Progressive, 24-bit - Color
Apple Lossless, 32 kHz, Stereo
Alternates: 0
Video Codec: H.264
Quality: 100
Frame Width [pixels]: 1,280
Frame Height [pixes]: 720
Frame Rate [fps]: 29.97
Field Order: Non (Progressive)
Pixel Aspect Ratio: Square Pixels (1.0)
Set Bitrate [kbps]: 5,000 kbps
Uncheck everything else in Filters, Alternates, and Others
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Here's the MediaInfo:
Format : MPEG-4
Format profile : QuickTime
Codec ID : qt
File size : 25.4 MiB
Duration : 43s 777ms
Overall bit rate : 4 858 Kbps
Encoded date : UTC 2008-12-03 05:09:23
Tagged date : UTC 2008-12-03 05:13:09
Video
Format : AVC
Format/Info : Advanced Video Codec
Format profile : Main@L3.1
Format settings, CABAC : No
Format settings, ReFrames : 2 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 43s 777ms
Bit rate mode : Variable
Bit rate : 4 236 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16/9
Frame rate mode : Constant
Frame rate : 29.970 fps
Resolution : 24 bits
Colorimetry : 4:2:0
Scan type : Progressive
Bits/(Pixel*Frame) : 0.153
Stream size : 22.1 MiB (87%)
Encoded date : UTC 2008-12-03 05:09:23
Tagged date : UTC 2008-12-03 05:13:08
Audio
Format : ALAC
Codec ID : alac
Codec ID/Info : Apple Lossless Format
Duration : 43s 777ms
Bit rate mode : Variable
Bit rate : 616 Kbps
Channel(s) : 2 channels
Sampling rate : 32.0 KHz
Resolution : 16 bits
Stream size : 3.22 MiB (13%)
Encoded date : UTC 2008-12-03 05:09:23
Tagged date : UTC 2008-12-03 05:13:08