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Chapter 3 - Image Compression Manager / Image Compression Manager Reference

Image Compression Manager Functions / Changing Sequence-Compression Parameters

SetCSequenceQuality

The SetCSequenceQuality function allows you to adjust the spatial or temporal quality for the current sequence.

pascal OSErr SetCSequenceQuality (ImageSequence seqID, 
                                    CodecQ spatialQuality,
                                    CodecQ temporalQuality);

seqID

Contains the unique sequence identifier that was returned by the CompressSequenceBegin function.

spatialQuality

Specifies the desired compressed image quality. See"Compression Quality Constants" on page 3-57 for available values.

temporalQuality

Specifies the desired sequence temporal quality. This parameter governs the level of compression you desire with respect to information between successive frames in the sequence. Set this parameter to 0 to prevent the compressor from applying temporal compression to the sequence.
See "Compression Quality Constants" beginning on page 3-57 for other available values.

DESCRIPTION

The spatial quality parameter indicates the image quality you desire for each frame in the sequence, which governs the level of spatial compression that the compressor may apply to each frame. The temporal quality parameter indicates the sequence quality you desire, which in turn governs the amount of temporal compression that the compressor may apply to the sequence. The new quality parameters take effect with the next frame in the sequence.

You set the default spatial and temporal quality values for a sequence with the spatialQuality and temporalQuality parameters to the CompressSequenceBegin function. For details on CompressSequenceBegin,
see page 3-100.

If you change the quality settings while processing an image sequence, you affect the maximum image size that you may receive during sequence compression. Consequently, you should call the GetMaxCompressionSize function (described on page 3-68)
after you change the quality settings. If the maximum size has increased, you should reallocate your image buffers to accommodate the larger image size.

RESULT CODES

noErr	0	No error
paramErr	-50	Invalid parameter specified