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lavu: support arbitrary-point FFTs and all even (i)MDCT transforms
This patch adds support for arbitrary-point FFTs and all even MDCT transforms. Odd MDCTs are not supported yet as they're based on the DCT-II and DCT-III and they're very niche. With this we can now write tests.
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Lynne
parent
ca21cb1e36
commit
06a8596825
@ -51,6 +51,8 @@ enum AVTXType {
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* For inverse transforms, the stride specifies the spacing between each
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* sample in the input array in bytes. The output will be a flat array.
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* Stride must be a non-zero multiple of sizeof(float).
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* NOTE: the inverse transform is half-length, meaning the output will not
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* contain redundant data. This is what most codecs work with.
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*/
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AV_TX_FLOAT_MDCT = 1,
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/**
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@ -93,8 +95,7 @@ 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 2 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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* (i)MDCTs with an odd length are currently not supported.
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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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@ -58,6 +58,7 @@ typedef void FFTComplex;
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(dim) = (are) * (bim) - (aim) * (bre); \
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} while (0)
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#define UNSCALE(x) (x)
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#define RESCALE(x) (x)
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#define FOLD(a, b) ((a) + (b))
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@ -85,6 +86,7 @@ typedef void FFTComplex;
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(dim) = (int)(((accu) + 0x40000000) >> 31); \
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} while (0)
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#define UNSCALE(x) ((double)x/2147483648.0)
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#define RESCALE(x) (av_clip64(lrintf((x) * 2147483648.0), INT32_MIN, INT32_MAX))
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#define FOLD(x, y) ((int)((x) + (unsigned)(y) + 32) >> 6)
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@ -108,6 +110,7 @@ struct AVTXContext {
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int m; /* Ptwo part */
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int inv; /* Is inverted */
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int type; /* Type */
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double scale; /* Scale */
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FFTComplex *exptab; /* MDCT exptab */
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FFTComplex *tmp; /* Temporary buffer needed for all compound transforms */
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@ -397,6 +397,31 @@ static void monolithic_fft(AVTXContext *s, void *_out, void *_in,
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fft_dispatch[mb](out);
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}
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static void naive_fft(AVTXContext *s, void *_out, void *_in,
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ptrdiff_t stride)
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{
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FFTComplex *in = _in;
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FFTComplex *out = _out;
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const int n = s->n;
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double phase = s->inv ? 2.0*M_PI/n : -2.0*M_PI/n;
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for(int i = 0; i < n; i++) {
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FFTComplex tmp = { 0 };
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for(int j = 0; j < n; j++) {
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const double factor = phase*i*j;
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const FFTComplex mult = {
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RESCALE(cos(factor)),
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RESCALE(sin(factor)),
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};
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FFTComplex res;
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CMUL3(res, in[j], mult);
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tmp.re += res.re;
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tmp.im += res.im;
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}
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out[i] = tmp;
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}
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}
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#define DECL_COMP_IMDCT(N) \
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static void compound_imdct_##N##xM(AVTXContext *s, void *_dst, void *_src, \
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ptrdiff_t stride) \
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@ -553,6 +578,57 @@ static void monolithic_mdct(AVTXContext *s, void *_dst, void *_src,
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}
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}
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static void naive_imdct(AVTXContext *s, void *_dst, void *_src,
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ptrdiff_t stride)
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{
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int len = s->n;
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int len2 = len*2;
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FFTSample *src = _src;
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FFTSample *dst = _dst;
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double scale = s->scale;
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const double phase = M_PI/(4.0*len2);
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stride /= sizeof(*src);
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for (int i = 0; i < len; i++) {
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double sum_d = 0.0;
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double sum_u = 0.0;
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double i_d = phase * (4*len - 2*i - 1);
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double i_u = phase * (3*len2 + 2*i + 1);
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for (int j = 0; j < len2; j++) {
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double a = (2 * j + 1);
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double a_d = cos(a * i_d);
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double a_u = cos(a * i_u);
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double val = UNSCALE(src[j*stride]);
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sum_d += a_d * val;
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sum_u += a_u * val;
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}
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dst[i + 0] = RESCALE( sum_d*scale);
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dst[i + len] = RESCALE(-sum_u*scale);
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}
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}
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static void naive_mdct(AVTXContext *s, void *_dst, void *_src,
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ptrdiff_t stride)
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{
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int len = s->n*2;
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FFTSample *src = _src;
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FFTSample *dst = _dst;
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double scale = s->scale;
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const double phase = M_PI/(4.0*len);
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stride /= sizeof(*dst);
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for (int i = 0; i < len; i++) {
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double sum = 0.0;
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for (int j = 0; j < len*2; j++) {
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int a = (2*j + 1 + len) * (2*i + 1);
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sum += UNSCALE(src[j]) * cos(a * phase);
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}
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dst[i*stride] = RESCALE(sum*scale);
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}
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}
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static int gen_mdct_exptab(AVTXContext *s, int len4, double scale)
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{
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const double theta = (scale < 0 ? len4 : 0) + 1.0/8.0;
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@ -575,11 +651,13 @@ int TX_NAME(ff_tx_init_mdct_fft)(AVTXContext *s, av_tx_fn *tx,
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const void *scale, uint64_t flags)
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{
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const int is_mdct = ff_tx_type_is_mdct(type);
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int err, n = 1, m = 1, max_ptwo = 1 << (FF_ARRAY_ELEMS(fft_dispatch) - 1);
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int err, l, n = 1, m = 1, max_ptwo = 1 << (FF_ARRAY_ELEMS(fft_dispatch) - 1);
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if (is_mdct)
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len >>= 1;
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l = len;
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#define CHECK_FACTOR(DST, FACTOR, SRC) \
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if (DST == 1 && !(SRC % FACTOR)) { \
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DST = FACTOR; \
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@ -601,12 +679,23 @@ int TX_NAME(ff_tx_init_mdct_fft)(AVTXContext *s, av_tx_fn *tx,
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s->inv = inv;
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s->type = type;
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/* Filter out direct 3, 5 and 15 transforms, too niche */
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/* If we weren't able to split the length into factors we can handle,
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* resort to using the naive and slow FT. This also filters out
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* direct 3, 5 and 15 transforms as they're too niche. */
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if (len > 1 || m == 1) {
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av_log(NULL, AV_LOG_ERROR, "Unsupported transform size: n = %i, "
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"m = %i, residual = %i!\n", n, m, len);
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return AVERROR(EINVAL);
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} else if (n > 1 && m > 1) { /* 2D transform case */
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if (is_mdct && (l & 1)) /* Odd (i)MDCTs are not supported yet */
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return AVERROR(ENOTSUP);
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s->n = l;
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s->m = 1;
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*tx = naive_fft;
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if (is_mdct) {
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s->scale = *((SCALE_TYPE *)scale);
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*tx = inv ? naive_imdct : naive_mdct;
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}
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return 0;
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}
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if (n > 1 && m > 1) { /* 2D transform case */
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if ((err = ff_tx_gen_compound_mapping(s)))
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return err;
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if (!(s->tmp = av_malloc(n*m*sizeof(*s->tmp))))
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@ -80,7 +80,7 @@
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#define LIBAVUTIL_VERSION_MAJOR 56
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#define LIBAVUTIL_VERSION_MINOR 63
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#define LIBAVUTIL_VERSION_MICRO 100
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#define LIBAVUTIL_VERSION_MICRO 101
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#define LIBAVUTIL_VERSION_INT AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
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LIBAVUTIL_VERSION_MINOR, \
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