The Video tab in the Publishing Settings dialog is for Opus Video Creator publications only. This allows you to set video codec and size options for the published video file.
1. Select the required codec from the list of available codecs. This list is dependent on the codecs installed on the computer Opus is being run on. The codec used to encode a video is also required to play it back, so if you are planning on distributing the published video it is best to use a common codec; such as Cinepak or Indeo R3.2 If you are going to edit the video in a video editing package it is best to use a lossless codec (such as Huffyuv) or the None option to maintain image quality.
Note:
The video files produced by the "none" option are uncompressed and therefore tend to be extremely large files. A lossless codec will result in the same image quality but with much smaller files.
2. Use the Format panel to set the size and frame rate of the final video.
The Width and Height settings control the dimensions of the video. If the output format aspect ratio does not match that of the original Opus publication the pages will be scaled to fit and centred within the output video frame.
The Frame rate setting controls the number of frames that will be generated per second. A higher frame rate will produce a smoother video at the expense of file size and processor time required to play the video back.
Note:
Some codecs only support a number of fixed frame rates or a limited range of sizes. This is a codec specific issue.
3. Use the Advanced panel to fine-tune the settings for the selected codec.
All the elements of the Advanced panel are dependent on the selected codec and are only enabled if the codec uses those settings.
- The Key Frame option determines how often a key frame is inserted into the video. Using more frequent key frames can result in better image quality, at the expense of the output video file size. Key frames are also used when seeking within a video. A video can only start to play from a key frame, so if the gap between key frames is large it can be impossible to seek accurately.
The "ideal" key frame value is very codec specific and it is best to find the specifications for the codec being used and use the suggested values.
- The Settings… button is only enabled for those codecs that provide their own settings dialogs. These are specific to the codec and so cannot be described here.
- The Bit Rate option and the Quality slider are usually mutually exclusive (that is, if one is enabled the other will be disabled). They control the balance between image quality and file size.
Codecs can encode data at a constant bit rate (CBR) or variable bit rate (VBR). CBR codecs use a single fixed data rate throughout the video. VBR codecs attempt to vary the compression used over time to result in smaller files. If a scene has little motion the bit rate is reduced to save space, but during high motion scenes the bit rate is increased to preserve the image quality. VBR codecs tend to be slower to encode than CBR codecs and require more processor power to play them back.
If the codec uses a constant bit rate then the Bit Rate option is used to set that rate.
If the codec uses a variable bit rate the Quality slider is used to control the balance between the minimum and maximum rates used.
Lower bit rate or quality settings will tend to result in smaller files at the expense of image fidelity, while higher settings will result in larger files that preserve more information.
4. Make your changes to the other tabs in the Publish Settings dialog, then click the OK button to close the dialog and return to the third page of the Publish Wizard to start publishing.