Tutorial: High-Touch Encoding With Microsoft Expression Encoder 2
—Keyframe Interval: 15 seconds—The longest gap between markers in the source is a hair less than 15 seconds, so this will prevent keyframe popping between cards, since our marker-based keyframes will "reset" the keyframe interval each time they are inserted.
—Profile: VC-1 Advanced Profile—VC-1 supports Simple, Main, and Advanced profiles. While Main is more compatible with older versions of Windows Media Player and generally provides equivalent quality, this is a Silverlight-only project, and we want to use Advanced so we can use Dquant, as discussed later.
—Mode: VBR Peak Constrained—This is a progressive download project, so VBR Peak Constrained is the optimal encoding mode. It’ll reduce bitrate on the easy parts of the video and then spend those bits on the hard parts.
—Bitrate (average): 488Kbps—This matches the original FLV’s actual bitrate.
—Peak bitrate: 895Kbps—Combined video plus audio (we’ll use 96Kbps later) plus overhead (9Kbps in this case) max bitrate is a consumer-broadband-friendly 1,000Kbps (1Mbps) total.
—Peak Buffer Size: 15 seconds—This way the buffer duration can contain an entire GOP (a keyframe and frames that reference it). Having the GOP length and the buffer size match helps make sure the keyframes can pull bits from the full range of surrounding frames.
—Width and Height: 640x480—This is the same as the source. The original project had both 320x240 and 640x480 encodes, but they used the same data rate, so I’m doing just the 640x480. The Silverlight embed can be set to the desired size to give the same end result.
Audio
—Codec: WMA—We’re targeting Silverlight 1.0 compatibility, so we need to use the legacy WMA codec. It’s still better bit-for-bit than the original clip’s MP3. We could use WMA Pro if we were targeting Silverlight 2.0.
—Mode: VBR—One nice thing about the WMA family of codecs is that they support the full range of rate-control modes of the Windows Media video codecs. Using VBR audio raises the bitrate on the hard parts and lowers it on the easier parts, making for more consistent quality and avoiding those times where the audio sounds great except for cymbals or some other percussion.
—Bitrate: 48Kbps—This matches the data rate of the FLV source. Also, this is the minimum bitrate for WMA VBR. I always try to use at least 48Kbps for WMA progressive for that reason; it’s a massive quality jump from 32Kbps CBR for typical content.