Add audio overlays
Using Microsoft Expression Encoder, you can insert an audio overlay for your video in both a Transcoding Project and a Silverlight Project. An audio overlay is an audio file that is played at the same time as the video file that you have encoded. You can adjust the volume for the original video file, for the audio for the visual overlay if it also has an audio track, and for the audio overlay, thereby combining as many as three audio streams in the output file. Expression Encoder supports the following audio file types: .aiff, .m4A, .m4B, .bwf, .mp3, .wav, and .wma. You must have Apple QuickTime installed in order to use .aiff, .m4A, and .m4B.
You can also add visual overlays. For more information, see Add visual overlays.
Timeline (blue) with audio overlay
To add an audio overlay
In the Media Content panel, select the video to which you want to add the overlay. You can add an overlay to only one video at a time.
If you want to add an audio overlay to a video file that does not already contain audio, you must first click the Encode tab and select Audio. For more information on setting audio options, see Set Output formats.
If you can't see the Enhance panel, on the Window menu, click Enhance to select it. If the panel is selected, but you still can't see it, on the right side of the application, click the Enhance tab.
Expand the Audio Overlay category.
In the Audio Overlay settings category, select Add Audio Overlay.
Browse to a compatible audio file, and then click Open. The path of the audio overlay appears in the File box, and the audio clip appears as a green track in the Timeline under your media track, indicating that there is an audio overlay applied.
Drag the Volume value to the right to increase the volume, or drag it to the left to decrease the volume.
This volume value applies to the audio overlay file. To adjust the volume of the audio track in the visual overlay, return to the Visual Overlay category and adjust the volume there. To adjust the original audio file for the video, see Set Pre-Processing options.
If necessary, click Show/Hide properties to access the remaining options.
Set the Duration options according to the following instructions:
On the Apply to menu, click Whole Sequence to apply the overlay to all of the video, including leaders and trailers. Click Custom to set a specific duration for the overlay.
If you chose to specify a custom duration, in the Start and End boxes, enter the respective times (relative to the duration of the video) at which you want the overlay to play. Alternatively, in the viewing area, you can drag the playhead to a location on the Timeline and then, in the Duration section, click either Set the audio overlay start time to current playhead position or Set the audio overlay end time to current playhead position to set the time to the playhead location.
Select Loop Overlay if you want the overlay to play back from the beginning once it reaches the end of its duration. The overlay will continue to loop for the length of the video. To specify a time between each loop of the overlay, enter a length in the Overlay Looping Gap box.
If you want the overlay to fade in and out, enter the appropriate duration in the Fade Duration section. Alternatively, in the viewing area, you can drag the playhead to a location on the Timeline and then, in the Fade Duration section, click either Set the fade in duration using playhead position or Set the fade out duration using playhead position to set the time to the playhead location. The application calculates the fade relative to the start and end times of the overlay.
In the Audio overlay options menu , click Reset to return to the settings that appeared on import of the audio overlay.
To replace an audio overlay
In the Media Content panel, select the media file that includes the overlay that you want to replace.
If you can't see the Enhance panel, on the Window menu, click Enhance to select it. If the panel is selected on the menu, but you still can't see it in the interface, on the right side of the application, click the Enhance tab.
In the Audio Overlay category, in the File box, type the path of the overlay graphic, or click Browse to browse to the file.
When you locate the file, click Open to replace the existing file. Expression Encoder retains the settings that you chose for the previous overlay.
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