avfilter/af_biquads: add different transform types

2 files changed, 287 insertions, 8 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 610cb09a8c..1aec9f15c7 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1573,6 +1573,14 @@ Enabling it will normalize magnitude response at DC to 0dB.
 
 @item order, o
 Set the filter order, can be 1 or 2. Default is 2.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Commands
@@ -2693,6 +2701,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Commands
@@ -2756,6 +2772,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Commands
@@ -2826,6 +2850,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Commands
@@ -2884,6 +2916,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @section bs2b
@@ -3607,6 +3647,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Examples
@@ -4084,6 +4132,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Commands
@@ -4410,6 +4466,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Examples
@@ -5530,6 +5594,14 @@ Specify which channels to filter, by default all available are filtered.
 @item normalize, n
 Normalize biquad coefficients, by default is disabled.
 Enabling it will normalize magnitude response at DC to 0dB.
+
+@item transform, a
+Set transform type of IIR filter.
+@table @option
+@item di
+@item dii
+@item tdii
+@end table
 @end table
 
 @subsection Commands
diff --git a/libavfilter/af_biquads.c b/libavfilter/af_biquads.c
index 81cdb0c10e..84f9c94bc3 100644
--- a/libavfilter/af_biquads.c
+++ b/libavfilter/af_biquads.c
@@ -93,6 +93,13 @@ enum WidthType {
     NB_WTYPE,
 };
 
+enum TransformType {
+    DI,
+    DII,
+    TDII,
+    NB_TTYPE,
+};
+
 typedef struct ChanCache {
     double i1, i2;
     double o1, o2;
@@ -106,6 +113,7 @@ typedef struct BiquadsContext {
     int width_type;
     int poles;
     int csg;
+    int transform_type;
 
     double gain;
     double frequency;
@@ -258,6 +266,101 @@ BIQUAD_FILTER(s32, int32_t, INT32_MIN, INT32_MAX, 1)
 BIQUAD_FILTER(flt, float,   -1., 1., 0)
 BIQUAD_FILTER(dbl, double,  -1., 1., 0)
 
+#define BIQUAD_DII_FILTER(name, type, min, max, need_clipping)                \
+static void biquad_dii_## name (BiquadsContext *s,                            \
+                            const void *input, void *output, int len,         \
+                            double *z1, double *z2,                           \
+                            double *unused1, double *unused2,                 \
+                            double b0, double b1, double b2,                  \
+                            double a1, double a2, int *clippings,             \
+                            int disabled)                                     \
+{                                                                             \
+    const type *ibuf = input;                                                 \
+    type *obuf = output;                                                      \
+    double w1 = *z1;                                                          \
+    double w2 = *z2;                                                          \
+    double wet = s->mix;                                                      \
+    double dry = 1. - wet;                                                    \
+    double in, out, w0;                                                       \
+                                                                              \
+    a1 = -a1;                                                                 \
+    a2 = -a2;                                                                 \
+                                                                              \
+    for (int i = 0; i < len; i++) {                                           \
+        in = ibuf[i];                                                         \
+        w0 = in + a1 * w1 + a2 * w2;                                          \
+        out = b0 * w0 + b1 * w1 + b2 * w2;                                    \
+        w2 = w1;                                                              \
+        w1 = w0;                                                              \
+        out = out * wet + in * dry;                                           \
+        if (disabled) {                                                       \
+            obuf[i] = in;                                                     \
+        } else if (need_clipping && out < min) {                              \
+            (*clippings)++;                                                   \
+            obuf[i] = min;                                                    \
+        } else if (need_clipping && out > max) {                              \
+            (*clippings)++;                                                   \
+            obuf[i] = max;                                                    \
+        } else {                                                              \
+            obuf[i] = out;                                                    \
+        }                                                                     \
+    }                                                                         \
+    *z1 = w1;                                                                 \
+    *z2 = w2;                                                                 \
+}
+
+BIQUAD_DII_FILTER(s16, int16_t, INT16_MIN, INT16_MAX, 1)
+BIQUAD_DII_FILTER(s32, int32_t, INT32_MIN, INT32_MAX, 1)
+BIQUAD_DII_FILTER(flt, float,   -1., 1., 0)
+BIQUAD_DII_FILTER(dbl, double,  -1., 1., 0)
+
+#define BIQUAD_TDII_FILTER(name, type, min, max, need_clipping)               \
+static void biquad_tdii_## name (BiquadsContext *s,                           \
+                            const void *input, void *output, int len,         \
+                            double *z1, double *z2,                           \
+                            double *unused1, double *unused2,                 \
+                            double b0, double b1, double b2,                  \
+                            double a1, double a2, int *clippings,             \
+                            int disabled)                                     \
+{                                                                             \
+    const type *ibuf = input;                                                 \
+    type *obuf = output;                                                      \
+    double w1 = *z1;                                                          \
+    double w2 = *z2;                                                          \
+    double wet = s->mix;                                                      \
+    double dry = 1. - wet;                                                    \
+    double in, out;                                                           \
+                                                                              \
+    a1 = -a1;                                                                 \
+    a2 = -a2;                                                                 \
+                                                                              \
+    for (int i = 0; i < len; i++) {                                           \
+        in = ibuf[i];                                                         \
+        out = b0 * in + w1;                                                   \
+        w1 = b1 * in + w2 + a1 * out;                                         \
+        w2 = b2 * in + a2 * out;                                              \
+        out = out * wet + in * dry;                                           \
+        if (disabled) {                                                       \
+            obuf[i] = in;                                                     \
+        } else if (need_clipping && out < min) {                              \
+            (*clippings)++;                                                   \
+            obuf[i] = min;                                                    \
+        } else if (need_clipping && out > max) {                              \
+            (*clippings)++;                                                   \
+            obuf[i] = max;                                                    \
+        } else {                                                              \
+            obuf[i] = out;                                                    \
+        }                                                                     \
+    }                                                                         \
+    *z1 = w1;                                                                 \
+    *z2 = w2;                                                                 \
+}
+
+BIQUAD_TDII_FILTER(s16, int16_t, INT16_MIN, INT16_MAX, 1)
+BIQUAD_TDII_FILTER(s32, int32_t, INT32_MIN, INT32_MAX, 1)
+BIQUAD_TDII_FILTER(flt, float,   -1., 1., 0)
+BIQUAD_TDII_FILTER(dbl, double,  -1., 1., 0)
+
 static int config_filter(AVFilterLink *outlink, int reset)
 {
     AVFilterContext *ctx    = outlink->src;
@@ -437,15 +540,64 @@ static int config_filter(AVFilterLink *outlink, int reset)
     if (reset)
         memset(s->cache, 0, sizeof(ChanCache) * inlink->channels);
 
-    switch (inlink->format) {
-    case AV_SAMPLE_FMT_S16P: s->filter = biquad_s16; break;
-    case AV_SAMPLE_FMT_S32P: s->filter = biquad_s32; break;
-    case AV_SAMPLE_FMT_FLTP: s->filter = biquad_flt; break;
-    case AV_SAMPLE_FMT_DBLP: s->filter = biquad_dbl; break;
-    default: av_assert0(0);
-    }
 
-    s->block_align = av_get_bytes_per_sample(inlink->format);
+    switch (s->transform_type) {
+    case DI:
+        switch (inlink->format) {
+        case AV_SAMPLE_FMT_S16P:
+            s->filter = biquad_s16;
+            break;
+        case AV_SAMPLE_FMT_S32P:
+            s->filter = biquad_s32;
+            break;
+        case AV_SAMPLE_FMT_FLTP:
+            s->filter = biquad_flt;
+            break;
+        case AV_SAMPLE_FMT_DBLP:
+            s->filter = biquad_dbl;
+            break;
+        default: av_assert0(0);
+        }
+        break;
+    case DII:
+        switch (inlink->format) {
+        case AV_SAMPLE_FMT_S16P:
+            s->filter = biquad_dii_s16;
+            break;
+        case AV_SAMPLE_FMT_S32P:
+            s->filter = biquad_dii_s32;
+            break;
+        case AV_SAMPLE_FMT_FLTP:
+            s->filter = biquad_dii_flt;
+            break;
+        case AV_SAMPLE_FMT_DBLP:
+            s->filter = biquad_dii_dbl;
+            break;
+        default: av_assert0(0);
+        }
+        break;
+    case TDII:
+        switch (inlink->format) {
+        case AV_SAMPLE_FMT_S16P:
+            s->filter = biquad_tdii_s16;
+            break;
+        case AV_SAMPLE_FMT_S32P:
+            s->filter = biquad_tdii_s32;
+            break;
+        case AV_SAMPLE_FMT_FLTP:
+            s->filter = biquad_tdii_flt;
+            break;
+        case AV_SAMPLE_FMT_DBLP:
+            s->filter = biquad_tdii_dbl;
+            break;
+        default: av_assert0(0);
+        }
+        break;
+    default:
+        av_assert0(0);
+     }
+
+     s->block_align = av_get_bytes_per_sample(inlink->format);
 
     return 0;
 }
@@ -610,6 +762,11 @@ static const AVOption equalizer_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -636,6 +793,11 @@ static const AVOption bass_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -662,6 +824,11 @@ static const AVOption treble_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -687,6 +854,11 @@ static const AVOption bandpass_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -711,6 +883,11 @@ static const AVOption bandreject_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -737,6 +914,11 @@ static const AVOption lowpass_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -763,6 +945,11 @@ static const AVOption highpass_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -789,6 +976,11 @@ static const AVOption allpass_options[] = {
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"order", "set filter order", OFFSET(order), AV_OPT_TYPE_INT, {.i64=2}, 1, 2, FLAGS},
     {"o",     "set filter order", OFFSET(order), AV_OPT_TYPE_INT, {.i64=2}, 1, 2, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -815,6 +1007,11 @@ static const AVOption lowshelf_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -841,6 +1038,11 @@ static const AVOption highshelf_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };
 
@@ -860,6 +1062,11 @@ static const AVOption biquad_options[] = {
     {"c",        "set channels to filter", OFFSET(channels), AV_OPT_TYPE_CHANNEL_LAYOUT, {.i64=-1}, INT64_MIN, INT64_MAX, FLAGS},
     {"normalize", "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
     {"n",         "normalize coefficients", OFFSET(normalize), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, FLAGS},
+    {"transform", "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"a",         "set transform type", OFFSET(transform_type), AV_OPT_TYPE_INT, {.i64=0}, 0, NB_TTYPE-1, AF, "transform_type"},
+    {"di",   "direct form I",  0, AV_OPT_TYPE_CONST, {.i64=DI}, 0, 0, AF, "transform_type"},
+    {"dii",  "direct form II", 0, AV_OPT_TYPE_CONST, {.i64=DII}, 0, 0, AF, "transform_type"},
+    {"tdii", "transposed direct form II", 0, AV_OPT_TYPE_CONST, {.i64=TDII}, 0, 0, AF, "transform_type"},
     {NULL}
 };