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e8f054b095
Required minimal changes to the code so made sense to implement. FFT and MDCT tested, the output of both was properly rounded. Fun fact: the non-power-of-two fixed-point FFT and MDCT are the fastest ever non-power-of-two fixed-point FFT and MDCT written. This can replace the power of two integer MDCTs in aac and ac3 if the MIPS optimizations are ported across. Unfortunately the ac3 encoder uses a 16-bit fixed point forward transform, unlike the encoder which uses a 32bit inverse transform, so some modifications might be required there. The 3-point FFT is somewhat less accurate than it otherwise could be, having minor rounding errors with bigger transforms. However, this could be improved later, and the way its currently written is the way one would write assembly for it. Similar rounding errors can also be found throughout the power of two FFTs as well, though those are more difficult to correct. Despite this, the integer transforms are more than accurate enough.
107 lines
3.4 KiB
C
107 lines
3.4 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVUTIL_TX_H
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#define AVUTIL_TX_H
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#include <stdint.h>
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#include <stddef.h>
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typedef struct AVTXContext AVTXContext;
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typedef struct AVComplexFloat {
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float re, im;
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} AVComplexFloat;
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typedef struct AVComplexDouble {
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double re, im;
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} AVComplexDouble;
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typedef struct AVComplexInt32 {
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int32_t re, im;
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} AVComplexInt32;
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enum AVTXType {
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/**
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* Standard complex to complex FFT with sample data type AVComplexFloat.
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* Output is not 1/len normalized. Scaling currently unsupported.
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*/
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AV_TX_FLOAT_FFT = 0,
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/**
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* Standard MDCT with sample data type of float and a scale type of
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* float. Length is the frame size, not the window size (which is 2x frame)
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*/
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AV_TX_FLOAT_MDCT = 1,
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/**
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* Same as AV_TX_FLOAT_FFT with a data type of AVComplexDouble.
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*/
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AV_TX_DOUBLE_FFT = 2,
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/**
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* Same as AV_TX_FLOAT_MDCT with data and scale type of double.
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*/
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AV_TX_DOUBLE_MDCT = 3,
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/**
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* Same as AV_TX_FLOAT_FFT with a data type of AVComplexInt32.
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*/
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AV_TX_INT32_FFT = 4,
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/**
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* Same as AV_TX_FLOAT_MDCT with data type of int32_t and scale type of float.
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* Only scale values less than or equal to 1.0 are supported.
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*/
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AV_TX_INT32_MDCT = 5,
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};
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/**
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* Function pointer to a function to perform the transform.
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*
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* @note Using a different context than the one allocated during av_tx_init()
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* is not allowed.
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*
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* @param s the transform context
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* @param out the output array
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* @param in the input array
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* @param stride the input or output stride (depending on transform direction)
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* in bytes, currently implemented for all MDCT transforms
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*/
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typedef void (*av_tx_fn)(AVTXContext *s, void *out, void *in, ptrdiff_t stride);
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/**
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* Initialize a transform context with the given configuration
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* Currently power of two lengths from 4 to 131072 are supported, along with
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* any length decomposable to a power of two and either 3, 5 or 15.
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*
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* @param ctx the context to allocate, will be NULL on error
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* @param tx pointer to the transform function pointer to set
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* @param type type the type of transform
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* @param inv whether to do an inverse or a forward transform
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* @param len the size of the transform in samples
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* @param scale pointer to the value to scale the output if supported by type
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* @param flags currently unused
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*
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* @return 0 on success, negative error code on failure
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*/
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int av_tx_init(AVTXContext **ctx, av_tx_fn *tx, enum AVTXType type,
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int inv, int len, const void *scale, uint64_t flags);
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/**
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* Frees a context and sets ctx to NULL, does nothing when ctx == NULL
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*/
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void av_tx_uninit(AVTXContext **ctx);
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#endif /* AVUTIL_TX_H */
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