Compare encoding methods (A/B Compare)
A/B Compare mode helps you achieve the desired balance between file size and perceived video (and audio) quality. By using this feature, you can simultaneously compare the visual results of different profile settings applied to your videos and compare the final estimated file sizes of your videos, depending on the profile settings that you apply. By providing quick test renders of your media, A/B Compare encourages experimentation and helps you quickly decide on the ideal encoding method.
A/B Compare divides your video into two separate streams. Microsoft Expression Encoder displays the streams in one of four different modes: split screen, bands, side by side, or difference, with each segment or side representing a separate stream. You can choose and then use an encoding profile to match one of the streams. When you complete the encoding, you use the dual screen mode to visually compare one version of the stream with another.
A/B Compare mode is not available in a Live Broadcasting Project.
In split-screen mode, you can split the video either horizontally or vertically. The viewer pane displays the split video with a yellow line bisecting the frame. You can drag this yellow line to compare different-sized regions, or to directly compare the effect of two encoding methods on one subject in the image.
Bands mode is similar to split-screen mode, but has more than one divider. By placing the pointer over the divider and dragging the divider to the left or right, you can increase or decrease the number of divisions displayed in the video. You can also display the divisions either horizontally or vertically.
In side-by-side mode, the viewer displays full-screen images of your two streams.
Difference mode is similar to side-by-side mode, but shows the difference in grayscale. You can invert the color of the difference area by double-clicking the area. Difference mode displays the difference in quality as a contrast between black and white. For example, if you have two streams of the same quality, the difference will appear as black. If you have one stream that is the original, and another stream that is a much lower quality, the difference between the two encodings will appear as white on a black background.
When you play back your video, the viewer simultaneously plays back both streams of video, in sync, to allow for the most precise comparison. The video loops during playback. If there is any audio in your file, Expression Encoder plays back the encoded version.
To choose the video to compare, and to choose the comparison mode, you use a combination of three menus, all located under the transport controls.
To compare different encoding methods, you perform the test encodings, and then choose the versions to compare from the first two lists. For example, if you set the lists as they are in the preceding figure, on the left side of the compare viewer, you will see the original, unencoded video, and, on the right side, you will see the encoded version which uses the first encoding profile that you chose. You see these two streams in split-screen mode, as designated in the Compare Mode list. You can perform multiple successive test encodings, and then subsequently compare any of the previous encodings with each other.
If your mouse has a mouse wheel, you can also use the mouse to zoom in toward and out from the video. Click anywhere in the video and rotate the mouse wheel to zoom in and out. The position of the mouse determines the center of the zoom.
For longer videos, a scroll bar appears at the bottom of the video. You can use the mouse to scroll forward and back through the video by dragging the scroll box in the scroll bar.
To use A/B Compare to visually compare encoding methods
In the Media Content panel (Transcoding Project or the Sources panel (Silverlight Project), select the video that you want to use as a source.
In the area next to the transport controls, click Enter A/B Compare, or, on the View menu, click A/B Compare.
The comparison view uses split-screen mode, with a vertical split. Double-click the yellow line to toggle it from vertical to horizontal. To view your video by using another mode, select the mode from the Compare Mode list.
Add a preset or specify an encoding option for your video.
In the Preview panel, click the section that reads "Click here to build preview," or, in the area above the Compare viewer, click the Build Preview button. By default, Expression Encoder encodes only a 6-second segment of your video. To encode a longer duration, or a different segment, drag the white bars in the Timeline .
To compare more encoding methods, repeat steps 4 and 5. Select previously encoded images from the A and B menus above the Compare viewer to compare all the versions of your video.
To clear the version list, in either the A menu or the B menu, click Clear Versions.
To exit A/B Compare mode, click Exit A/B compare.