#### Source code

#### Revision control

#### Copy as Markdown

#### Other Tools

```
/*
```

```
* This file is part of FFmpeg.
```

```
*
```

```
* FFmpeg is free software; you can redistribute it and/or
```

```
* modify it under the terms of the GNU Lesser General Public
```

```
* License as published by the Free Software Foundation; either
```

```
* version 2.1 of the License, or (at your option) any later version.
```

```
*
```

```
* FFmpeg is distributed in the hope that it will be useful,
```

```
* but WITHOUT ANY WARRANTY; without even the implied warranty of
```

```
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
```

```
* Lesser General Public License for more details.
```

```
*
```

```
* You should have received a copy of the GNU Lesser General Public
```

```
* License along with FFmpeg; if not, write to the Free Software
```

```
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
```

```
*/
```

```
```

```
#ifndef AVUTIL_TX_H
```

```
#define AVUTIL_TX_H
```

```
```

```
#include <stdint.h>
```

```
#include <stddef.h>
```

```
```

```
typedef struct AVTXContext AVTXContext;
```

```
```

```
typedef struct AVComplexFloat {
```

```
float re, im;
```

```
} AVComplexFloat;
```

```
```

```
typedef struct AVComplexDouble {
```

```
double re, im;
```

```
} AVComplexDouble;
```

```
```

```
typedef struct AVComplexInt32 {
```

```
int32_t re, im;
```

```
} AVComplexInt32;
```

```
```

```
enum AVTXType {
```

```
/**
```

```
* Standard complex to complex FFT with sample data type of AVComplexFloat,
```

```
* AVComplexDouble or AVComplexInt32, for each respective variant.
```

```
*
```

```
* Output is not 1/len normalized. Scaling currently unsupported.
```

```
* The stride parameter must be set to the size of a single sample in bytes.
```

```
*/
```

```
AV_TX_FLOAT_FFT = 0,
```

```
AV_TX_DOUBLE_FFT = 2,
```

```
AV_TX_INT32_FFT = 4,
```

```
```

```
/**
```

```
* Standard MDCT with a sample data type of float, double or int32_t,
```

```
* respecively. For the float and int32 variants, the scale type is
```

```
* 'float', while for the double variant, it's 'double'.
```

```
* If scale is NULL, 1.0 will be used as a default.
```

```
*
```

```
* 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 must be a flat array.
```

```
*
```

```
* NOTE: the inverse transform is half-length, meaning the output will not
```

```
* contain redundant data. This is what most codecs work with. To do a full
```

```
* inverse transform, set the AV_TX_FULL_IMDCT flag on init.
```

```
*/
```

```
AV_TX_FLOAT_MDCT = 1,
```

```
AV_TX_DOUBLE_MDCT = 3,
```

```
AV_TX_INT32_MDCT = 5,
```

```
```

```
/**
```

```
* Real to complex and complex to real DFTs.
```

```
* For the float and int32 variants, the scale type is 'float', while for
```

```
* the double variant, it's a 'double'. If scale is NULL, 1.0 will be used
```

```
* as a default.
```

```
*
```

```
* For forward transforms (R2C), stride must be the spacing between two
```

```
* samples in bytes. For inverse transforms, the stride must be set
```

```
* to the spacing between two complex values in bytes.
```

```
*
```

```
* The forward transform performs a real-to-complex DFT of N samples to
```

```
* N/2+1 complex values.
```

```
*
```

```
* The inverse transform performs a complex-to-real DFT of N/2+1 complex
```

```
* values to N real samples. The output is not normalized, but can be
```

```
* made so by setting the scale value to 1.0/len.
```

```
* NOTE: the inverse transform always overwrites the input.
```

```
*/
```

```
AV_TX_FLOAT_RDFT = 6,
```

```
AV_TX_DOUBLE_RDFT = 7,
```

```
AV_TX_INT32_RDFT = 8,
```

```
```

```
/**
```

```
* Real to real (DCT) transforms.
```

```
*
```

```
* The forward transform is a DCT-II.
```

```
* The inverse transform is a DCT-III.
```

```
*
```

```
* The input array is always overwritten. DCT-III requires that the
```

```
* input be padded with 2 extra samples. Stride must be set to the
```

```
* spacing between two samples in bytes.
```

```
*/
```

```
AV_TX_FLOAT_DCT = 9,
```

```
AV_TX_DOUBLE_DCT = 10,
```

```
AV_TX_INT32_DCT = 11,
```

```
```

```
/**
```

```
* Discrete Cosine Transform I
```

```
*
```

```
* The forward transform is a DCT-I.
```

```
* The inverse transform is a DCT-I multiplied by 2/(N + 1).
```

```
*
```

```
* The input array is always overwritten.
```

```
*/
```

```
AV_TX_FLOAT_DCT_I = 12,
```

```
AV_TX_DOUBLE_DCT_I = 13,
```

```
AV_TX_INT32_DCT_I = 14,
```

```
```

```
/**
```

```
* Discrete Sine Transform I
```

```
*
```

```
* The forward transform is a DST-I.
```

```
* The inverse transform is a DST-I multiplied by 2/(N + 1).
```

```
*
```

```
* The input array is always overwritten.
```

```
*/
```

```
AV_TX_FLOAT_DST_I = 15,
```

```
AV_TX_DOUBLE_DST_I = 16,
```

```
AV_TX_INT32_DST_I = 17,
```

```
```

```
/* Not part of the API, do not use */
```

```
AV_TX_NB,
```

```
};
```

```
```

```
/**
```

```
* Function pointer to a function to perform the transform.
```

```
*
```

```
* @note Using a different context than the one allocated during av_tx_init()
```

```
* is not allowed.
```

```
*
```

```
* @param s the transform context
```

```
* @param out the output array
```

```
* @param in the input array
```

```
* @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 {
```

```
/**
```

```
* Allows for in-place transformations, where input == output.
```

```
* 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,
```

```
```

```
/**
```

```
* Performs a full inverse MDCT rather than leaving out samples that can be
```

```
* derived through symmetry. Requires an output array of 'len' floats,
```

```
* rather than the usual 'len/2' floats.
```

```
* Ignored for all transforms but inverse MDCTs.
```

```
*/
```

```
AV_TX_FULL_IMDCT = 1ULL << 2,
```

```
```

```
/**
```

```
* Perform a real to half-complex RDFT.
```

```
* Only the real, or imaginary coefficients will
```

```
* be output, depending on the flag used. Only available for forward RDFTs.
```

```
* Output array must have enough space to hold N complex values
```

```
* (regular size for a real to complex transform).
```

```
*/
```

```
AV_TX_REAL_TO_REAL = 1ULL << 3,
```

```
AV_TX_REAL_TO_IMAGINARY = 1ULL << 4,
```

```
};
```

```
```

```
/**
```

```
* Initialize a transform context with the given configuration
```

```
* (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 type type the type of transform
```

```
* @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 a bitmask of AVTXFlags or 0
```

```
*
```

```
* @return 0 on success, negative error code on failure
```

```
*/
```

```
int av_tx_init(AVTXContext **ctx, av_tx_fn *tx, enum AVTXType type,
```

```
int inv, int len, const void *scale, uint64_t flags);
```

```
```

```
/**
```

```
* Frees a context and sets *ctx to NULL, does nothing when *ctx == NULL.
```

```
*/
```

```
void av_tx_uninit(AVTXContext **ctx);
```

```
```

```
#endif /* AVUTIL_TX_H */
```