QuickTime 4 Reference

Providing Progress Information

If the ImageSubCodecDecompressRecord structure does not specify a progress function, your image decompressor component can implement codecProgressOpen and codecProgressClose functions to provide progress information. If the ImageSubCodecDecompressRecord structure does specify a progress function, your image decompressor component can implement the codecProgressUpdatePercent function to provide progress information during lengthy decompression operations. Implementing this function is optional.