Timestamp convertTimeToStreamPos(const Timestamp &where, int rate, bool isStereo) { Timestamp result(where.convertToFramerate(rate * (isStereo ? 2 : 1))); // When the Stream is a stereo stream, we have to assure // that the sample position is an even number. if (isStereo && (result.totalNumberOfFrames() & 1)) result = result.addFrames(-1); // We cut off one sample here. // Since Timestamp allows sub-frame-precision it might lead to odd behaviors // when we would just return result. // // An example is when converting the timestamp 500ms to a 11025 Hz based // stream. It would have an internal frame counter of 5512.5. Now when // doing calculations at frame precision, this might lead to unexpected // results: The frame difference between a timestamp 1000ms and the above // mentioned timestamp (both with 11025 as framerate) would be 5512, // instead of 5513, which is what a frame-precision based code would expect. // // By creating a new Timestamp with the given parameters, we create a // Timestamp with frame-precision, which just drops a sub-frame-precision // information (i.e. rounds down). return Timestamp(result.secs(), result.numberOfFrames(), result.framerate()); }