The Temporal Settings Request Type

Use the temporal settings request to retrieve or modify the current temporal compression parameters. These parameters govern sequence-compression operations.

You supply a pointer to a temporal settings structure. If you are retrieving these settings, the standard dialog component places the current settings into the specified structure; if you are changing the settings, place the new values into the structure--the component uses those values to update its settings.

The SCTemporalSettings data type defines the format and content of the temporal settings structure:



 
typedef struct {

    CodecQ      temporalQuality;                    /* desired quality */

    Fixed       frameRate;                          /* frame rate */

    long        keyFrameRate;                       /* key frame rate */

} SCTemporalSettings;

temporalQuality: Specifies the default setting of the motion quality slider in the dialog box. This slider controls the temporal quality of the compressed image, which influences the amount of temporal compression that can be achieved (note that Apple's component uses the same slider for both spatial and temporal quality). Temporal compression eliminates redundant information between frames in an image sequence. See the chapter "Image Compression Manager" in Inside Macintosh: QuickTime for valid compression quality values.; When the user clicks OK, the standard image-compression dialog component sets this field to the temporal quality value selected by the user. Note that the standard image-compression dialog component may adjust the quality value so that it corresponds to a value that is supported by the compressor that has been selected by the user.
frameRate: Specifies the default value of the text-edit box that controls the number of frames per second in the image sequence to be compressed. This dialog item allows the user to select the frame rate to be used when compressing the image sequence. Note that this field is stored as a fixed-point number, allowing the user to specify fractional frame rates.; When the user clicks OK, the standard image-compression dialog component sets this field to the frame rate value specified by the user. If you have set the scAllowZeroFrameRate flag to 1 in the scPreferenceFlagsType request, and the user specifies nothing or 0, the component sets this field to 0.; This dialog item can be useful in cases where your application cannot determine the frame rate of the source movie. For example, movies stored in PICT files do not include frame rate information. Therefore, the user must specify a frame rate for you. Alternatively, some users may want to create movies with different frame rates. This item allows the user to specify a rate for the compressed sequence.
keyFrameRate: Specifies the default value of the text-edit box that controls the frequency with which key frames are inserted into the compressed image sequence. Key frames provide points from which a temporally compressed sequence may be decompressed. For a more complete discussion of key frames, see the chapter "Image Compression Manager" in Inside Macintosh: QuickTime .; When the user clicks OK, the standard image-compression dialog component sets this field to the key frame rate value specified by the user. If you have set the scAllowZeroKeyFrameRate flag to 1 in the scPreferenceFlagsType request, and the user specifies nothing or 0, the component sets this field to 0.

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