/**
* Standard complex to complex FFT with sample data type AVComplexFloat.
* Output is not 1/len normalized. Scaling currently unsupported.
+ * The stride parameter is ignored.
*/
AV_TX_FLOAT_FFT = 0,
+
/**
* Standard MDCT with sample data type of float and a scale type of
* float. Length is the frame size, not the window size (which is 2x frame)
+ * For forward transforms, the stride specifies the spacing between each
+ * sample in the output array in bytes. The input must be a flat array.
+ *
+ * For inverse transforms, the stride specifies the spacing between each
+ * sample in the input array in bytes. The output will be a flat array.
+ * Stride must be a non-zero multiple of sizeof(float).
+ *
+ * NOTE: the inverse transform is half-length, meaning the output will not
+ * contain redundant data. This is what most codecs work with.
*/
AV_TX_FLOAT_MDCT = 1,
+
/**
* Same as AV_TX_FLOAT_FFT with a data type of AVComplexDouble.
*/
AV_TX_DOUBLE_FFT = 2,
+
/**
* Same as AV_TX_FLOAT_MDCT with data and scale type of double.
+ * Stride must be a non-zero multiple of sizeof(double).
*/
AV_TX_DOUBLE_MDCT = 3,
+
/**
* Same as AV_TX_FLOAT_FFT with a data type of AVComplexInt32.
*/
AV_TX_INT32_FFT = 4,
+
/**
* Same as AV_TX_FLOAT_MDCT with data type of int32_t and scale type of float.
* Only scale values less than or equal to 1.0 are supported.
+ * Stride must be a non-zero multiple of sizeof(int32_t).
*/
AV_TX_INT32_MDCT = 5,
};
* @param s the transform context
* @param out the output array
* @param in the input array
- * @param stride the input or output stride (depending on transform direction)
- * in bytes, currently implemented for all MDCT transforms
+ * @param stride the input or output stride in bytes
+ *
+ * The out and in arrays must be aligned to the maximum required by the CPU
+ * architecture unless the AV_TX_UNALIGNED flag was set in av_tx_init().
+ * The stride must follow the constraints the transform type has specified.
*/
typedef void (*av_tx_fn)(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
+/**
+ * Flags for av_tx_init()
+ */
+enum AVTXFlags {
+ /**
+ * Performs an in-place transformation on the input. The output argument
+ * of av_tn_fn() MUST match the input. May be unsupported or slower for some
+ * transform types.
+ */
+ AV_TX_INPLACE = 1ULL << 0,
+
+ /**
+ * Relaxes alignment requirement for the in and out arrays of av_tx_fn().
+ * May be slower with certain transform types.
+ */
+ AV_TX_UNALIGNED = 1ULL << 1,
+};
+
/**
* Initialize a transform context with the given configuration
- * Currently power of two lengths from 4 to 131072 are supported, along with
- * any length decomposable to a power of two and either 3, 5 or 15.
+ * (i)MDCTs with an odd length are currently not supported.
*
* @param ctx the context to allocate, will be NULL on error
* @param tx pointer to the transform function pointer to set
* @param inv whether to do an inverse or a forward transform
* @param len the size of the transform in samples
* @param scale pointer to the value to scale the output if supported by type
- * @param flags currently unused
+ * @param flags a bitmask of AVTXFlags or 0
*
* @return 0 on success, negative error code on failure
*/