Technical Q&A QA1418

Using ConvertMovieToFile or ConvertMovieToDataRef to convert movies without displaying the settings dialog

Q: I have a source movie in DV format and I need to convert it to a MPEG-4 file and set some of the attributes like compression quality, image size, frame rate, and so on. However, I'd like to do this programatically without displaying the settings dialog. Is this possible?

A: Yes. The recommended technique for performing a conversion without displaying the dialog involves a two-stage process in which you create a set of settings "presets" which are retrieved later to configure the exporter. Here's an overview:

Creating Settings Presets to Configure the Exporter

1) Create a Tool to Configure/Save Exporter Settings

First, create a simple tool (separate from your real application) to manufacture any number of exporter settings presets which can be retrieved later to configure the exporter. Here's how:

Write a simple application which brings up the exporter dialog. Now use the dialog to configure the desired settings for your file export and save these settings to a file so they can be easily retrieved later. You can create any number of different exporter settings presets in this manner to suit your particular needs.

Here's the detailed steps:

• Find and open the desired export component.

• Call MovieExportDoUserDialog to bring up the settings dialog.

• Adjust the export settings in the dialog as appropriate, and dismiss the dialog.

• Call MovieExportGetSettingsAsAtomContainer to retrieve and save the newly configured exporter settings.

• Close the exporter component.

This technique is demonstrated in Technical Q&A QTMTB62, 'Batch Exporting movie sound tracks with ConvertMovieToFile' and in the QTDataExchange and BackgroundExporter sample code projects.

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2) Configure the Exporter with your Saved Settings and Perform the Export

Finally, in your real application, retrieve the desired settings preset, configure the export component with these saved settings and perform the conversion with the fully configured export component.

Here's the detailed steps:

• Find and open the desired export component.

• Call MovieExportSetSettingsFromAtomContainer with the AtomContainer for the previously saved settings to configure the exporter

• Call ConvertMovieToFile or ConvertMovieToDataRef to perform the conversion, passing the fully configured export component as the last parameter to this function.

This technique is also demonstrated in Technical Q&A QTMTB62, 'Batch Exporting movie sound tracks with ConvertMovieToFile' and in the QTDataExchange and BackgroundExporter sample code projects.

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Alternate Approach

Alternately, you can manually configure the exporter using the various QTAtom routines.

To use this technique, first get the default settings from the exporter, use the functions which operate on QuickTime atoms to locate the atoms associated with the desired settings, then update the atoms for the new settings. Next, configure the exporter with the new settings. Finally, call ConvertMovieToFile or ConvertMovieToDataRef to perform the conversion, passing the fully configured export component as the last parameter to this function.

Here's the detailed steps:

• Find and open the desired export component.

• Call MovieExportGetSettingsAsAtomContainer to retrieve the default settings from the export component

• Use the QTAtom routines to locate the particular atoms

• Change the atom settings as desired

• Call MovieExportSetSettingsFromAtomContainer to set the exporter settings

• Call ConvertMovieToFile or ConvertMovieToDataRef to perform the conversion, passing the fully configured export component as the last parameter to this function.

This technique is demonstrated in Technical Q&A QA1147, 'Programmatic configuration of a Movie Export Component'.

As noted above, only part of the settings atoms used to configure the exporters are documented. Therefore, it may not be possible to fully configure the exporter using this technique.

However, the definitions for the settings atoms used with the Standard Image Compression Dialog component and functions such as SCSetInfo can be found in the QuickTimeComponents.h header file.

Atoms for the visual settings can be found in the kQTSettingsVideo ('vide') container atom. Atoms for the audio settings can be found in the kQTSettingsSound ('soun') container atom.

For example, the spatial compression parameters used with the Standard Image Compression Dialog component are stored in the 'vide' container atom in an atom with ID scSpatialSettingsType ('sptl') and data in an SCSpatialSettings structure:

struct SCSpatialSettings {
  CodecType           codecType;
  CodecComponent      codec;
  short               depth;
  CodecQ              spatialQuality;
};

Similarly, temporal compression parameters are stored in an atom with ID scTemporalSettingsType ('tprl') and data in an SCTemporalSettings structure:

struct SCTemporalSettings {
  CodecQ              temporalQuality;
  Fixed               frameRate;
  long                keyFrameRate;
};

Compression data rate settings are stored in an atom with ID scDataRateSettingsType ('drat') and data in an SCDataRateSettings structure:

struct SCDataRateSettings {
  long                dataRate;
  long                frameDuration;
  CodecQ              minSpatialQuality;
  CodecQ              minTemporalQuality;
};

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References

• Technical Q&A QTMTB62, 'Batch Exporting movie sound tracks with ConvertMovieToFile'

• Technical Q&A QA1147, 'Programmatic configuration of a Movie Export Component'

• QTDataExchange sample code

• BackgroundExporter sample code

• Finding Movie Export Components

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Document Revision History

Posted: 2005-03-22