Technical Q&A QA1062

Limiting the component list in SCRequestImageSettings

Q: How can I display a limited set of components in the SCRequestImageSettings dialog? I've been able to select a component and make it the default, but I cannot remove the other components from the list. I tried using scListEveryCodec but that didn't seem to help.

A: Although documented in the 'Sound Dialog Selectors' section of the QuickTime API reference, the selector you're looking for is scCompressionListType.

Use this selector with SCSetInfo. Pass in a pointer to a handle which contains an array of values of type OSType indicating the codecs you want presented to the user. Passing in NULL will reset the list. See Listing 1.

Listing 1: Limiting the codec list.

const UInt8 kNumberOfTypes = 4;

Handle    theTypesList = NULL;
OSTypePtr pTypesList = NULL;
SCSpatialSettings theDefaultChoice = { kSorenson3CodecType,
                                       (CodecComponent)kSorenson3CodecType,
                                       32,
                                       codecNormalQuality };

...

// limit the list to four - or however many you want
theTypesList = NewHandle(sizeof(OSType) * kNumberOfTypes);
if (theTypesList) {
   HLock(theTypesList);
   *pTypesList = (OSTypePtr)*theTypesList;

   pTypesList[0] = kH261CodecType;
   pTypesList[1] = kH263CodecType;
   pTypesList[2] = kSorensonCodecType;
   pTypesList[3] = kSorenson3CodecType;

   SCSetInfo(ci, scCompressionListType, &theTypesList);
   DisposeHandle(theTypesList);
}

// set up the default choice
SCSetInfo(ci, scSpatialSettingsType, &theDefaultChoice);

...

SCRequestImageSettings(ci);

You shouldn't need to use scListEveryCodec, it will show multiple variants for a given codec. For example, if you have your own JPEG codec it will show yours as well as the one built into QuickTime.

Document Revision History

Posted: 2006-01-12