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QTMRF 04 - QuickTime Sound (1-May-95)

Q I am developing code which allows users to mix an additional sound into the sound track of a QuickTime movie playing under Windows. Since this cannot be accomplished when the CD- ROM is mastered -- the placement of the sound effect must be controlled by the user -- I am extracting the sound samples from the QuickTime movie and blending them with a WAV file which contains the sound effect.

While testing this technique using one of the sample movies from the QuickTime for Windows beta CD- ROM, I discovered that the SoundDescription record returned by GetMediaSample contained the constant 'sowt' in the dataFormat field.

The only three formats documented in the QuickTime documentation are raw, MAC3, and MAC6. I need to know what the format of the 'sowt' samples is so I can mix them with the WAV samples.

A You're reading the byte backwards. 'sowt' is actually 'twos', which means that the values of the samples go from a minimum point to a maximum point, unlike the raw format, which has a binary offset from zero. In all other aspects, 'twos' and 'raw' samples are the same.

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