[FFmpeg-devel] [PATCH] avcodec/dcaenc: Use ffmpeg mdct instead of own implementation

James Almer jamrial at gmail.com
Sat Jan 13 01:37:09 EET 2018


On 1/12/2018 8:12 PM, Даниил Чередник wrote:
> Hysterically dcaenc uses own implementation of time->frequency
> transformation used by psychoacoustic. But actually function named fft in
> original dcaenc code is not fft. Power spectrum looks similar to mdct, and
> Alexander E. Patrakov told me it is MDCT. But for me it is still a bit
> strange, because of output size, and absent phase shift sensitivity. I was
> thinking about MCLT. But again, result of transformation original function
> was different. So I decided to use ffmpeg mdct transformation here.
> 
> 
> Results:
> 
> I could not hear the difference between original and modified version.
> 
> I got approximately 10% performance boost.


> From 39e7f15886f1c083f3a3d37d52778882c8949a93 Mon Sep 17 00:00:00 2001
> From: Daniil Cherednik <dan.cherednik at gmail.com>
> Date: Sun, 7 Jan 2018 22:39:22 +0000
> Subject: [PATCH] avcodec/dcaenc: Use ffmpeg mdct instead of own implementation
> 
> Signed-off-by: Daniil Cherednik <dan.cherednik at gmail.com>
> ---
>  libavcodec/dcaenc.c   | 107 ++++++++++++++------------------------------------
>  tests/fate/acodec.mak |   4 +-
>  2 files changed, 32 insertions(+), 79 deletions(-)
> 
> diff --git a/libavcodec/dcaenc.c b/libavcodec/dcaenc.c
> index dd601ffae0..b924c58185 100644
> --- a/libavcodec/dcaenc.c
> +++ b/libavcodec/dcaenc.c
> @@ -21,6 +21,9 @@
>   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>   */
>  
> +#define FFT_FLOAT 0
> +#define FFT_FIXED_32 1
> +
>  #include "libavutil/avassert.h"
>  #include "libavutil/channel_layout.h"
>  #include "libavutil/common.h"
> @@ -33,6 +36,7 @@
>  #include "dca_core.h"
>  #include "dcadata.h"
>  #include "dcaenc.h"
> +#include "fft.h"
>  #include "internal.h"
>  #include "mathops.h"
>  #include "put_bits.h"
> @@ -56,6 +60,7 @@ typedef struct DCAEncContext {
>      AVClass *class;
>      PutBitContext pb;
>      DCAADPCMEncContext adpcm_ctx;
> +    FFTContext mdct;
>      CompressionOptions options;
>      int frame_size;
>      int frame_bits;
> @@ -154,6 +159,7 @@ static int encode_init(AVCodecContext *avctx)
>      DCAEncContext *c = avctx->priv_data;
>      uint64_t layout = avctx->channel_layout;
>      int i, j, min_frame_bits;
> +    int rv;

We normally use ret for variables meant to hold a return value.

>  
>      if (subband_bufer_alloc(c))
>          return AVERROR(ENOMEM);
> @@ -231,6 +237,9 @@ static int encode_init(AVCodecContext *avctx)
>  
>      avctx->frame_size = 32 * SUBBAND_SAMPLES;
>  
> +    if ((rv = ff_mdct_init(&c->mdct, 9, 0, 1.0)) < 0)
> +        return rv;
> +
>      if (!cos_table[0]) {
>          int j, k;
>  
> @@ -297,6 +306,7 @@ static av_cold int encode_close(AVCodecContext *avctx)
>  {
>      if (avctx->priv_data) {
>          DCAEncContext *c = avctx->priv_data;
> +        ff_mdct_end(&c->mdct);
>          subband_bufer_free(c);
>          ff_dcaadpcm_free(&c->adpcm_ctx);
>      }
> @@ -398,78 +408,6 @@ static void lfe_downsample(DCAEncContext *c, const int32_t *input)
>      }
>  }
>  
> -typedef struct {
> -    int32_t re;
> -    int32_t im;
> -} cplx32;
> -
> -static void fft(const int32_t in[2 * 256], cplx32 out[256])
> -{
> -    cplx32 buf[256], rin[256], rout[256];
> -    int i, j, k, l;
> -
> -    /* do two transforms in parallel */
> -    for (i = 0; i < 256; i++) {
> -        /* Apply the Hann window */
> -        rin[i].re = mul32(in[2 * i], 0x3fffffff - (cos_t(8 * i + 2) >> 1));
> -        rin[i].im = mul32(in[2 * i + 1], 0x3fffffff - (cos_t(8 * i + 6) >> 1));
> -    }
> -    /* pre-rotation */
> -    for (i = 0; i < 256; i++) {
> -        buf[i].re = mul32(cos_t(4 * i + 2), rin[i].re)
> -                  - mul32(sin_t(4 * i + 2), rin[i].im);
> -        buf[i].im = mul32(cos_t(4 * i + 2), rin[i].im)
> -                  + mul32(sin_t(4 * i + 2), rin[i].re);
> -    }
> -
> -    for (j = 256, l = 1; j != 1; j >>= 1, l <<= 1) {
> -        for (k = 0; k < 256; k += j) {
> -            for (i = k; i < k + j / 2; i++) {
> -                cplx32 sum, diff;
> -                int t = 8 * l * i;
> -
> -                sum.re = buf[i].re + buf[i + j / 2].re;
> -                sum.im = buf[i].im + buf[i + j / 2].im;
> -
> -                diff.re = buf[i].re - buf[i + j / 2].re;
> -                diff.im = buf[i].im - buf[i + j / 2].im;
> -
> -                buf[i].re = half32(sum.re);
> -                buf[i].im = half32(sum.im);
> -
> -                buf[i + j / 2].re = mul32(diff.re, cos_t(t))
> -                                  - mul32(diff.im, sin_t(t));
> -                buf[i + j / 2].im = mul32(diff.im, cos_t(t))
> -                                  + mul32(diff.re, sin_t(t));
> -            }
> -        }
> -    }
> -    /* post-rotation */
> -    for (i = 0; i < 256; i++) {
> -        int b = ff_reverse[i];
> -        rout[i].re = mul32(buf[b].re, cos_t(4 * i))
> -                   - mul32(buf[b].im, sin_t(4 * i));
> -        rout[i].im = mul32(buf[b].im, cos_t(4 * i))
> -                   + mul32(buf[b].re, sin_t(4 * i));
> -    }
> -    for (i = 0; i < 256; i++) {
> -        /* separate the results of the two transforms */
> -        cplx32 o1, o2;
> -
> -        o1.re =  rout[i].re - rout[255 - i].re;
> -        o1.im =  rout[i].im + rout[255 - i].im;
> -
> -        o2.re =  rout[i].im - rout[255 - i].im;
> -        o2.im = -rout[i].re - rout[255 - i].re;
> -
> -        /* combine them into one long transform */
> -        out[i].re = mul32( o1.re + o2.re, cos_t(2 * i + 1))
> -                  + mul32( o1.im - o2.im, sin_t(2 * i + 1));
> -        out[i].im = mul32( o1.im + o2.im, cos_t(2 * i + 1))
> -                  + mul32(-o1.re + o2.re, sin_t(2 * i + 1));
> -    }
> -}
> -
>  static int32_t get_cb(int32_t in)
>  {
>      int i, res;
> @@ -494,21 +432,36 @@ static int32_t add_cb(int32_t a, int32_t b)
>      return a + cb_to_add[a - b];
>  }
>  
> -static void adjust_jnd(int samplerate_index,
> +static void calc_power(DCAEncContext *c,
> +                       const int32_t in[2 * 256], int32_t power[256])
> +{
> +    int i;
> +    DECLARE_ALIGNED(32, int32_t, data)[512];
> +    DECLARE_ALIGNED(32, int32_t, coeff)[256];

LOCAL_ALIGNED_32(int32_t, data,  [512]);
LOCAL_ALIGNED_32(int32_t, coeff, [256]);

> +    for (i = 0; i < 512; i++) {
> +        data[i] = norm__(mul32(in[i], 0x3fffffff - (cos_t(4 * i + 2) >> 1)), 4);
> +    }
> +    c->mdct.mdct_calc(&c->mdct, coeff, data);
> +    for (i = 0; i < 256; i++) {
> +        const int32_t cb = get_cb(coeff[i]);
> +        power[i] = add_cb(cb, cb);
> +    }
> +}
> +
> +static void adjust_jnd(DCAEncContext *c,
>                         const int32_t in[512], int32_t out_cb[256])
>  {
>      int32_t power[256];
> -    cplx32 out[256];
>      int32_t out_cb_unnorm[256];
>      int32_t denom;
>      const int32_t ca_cb = -1114;
>      const int32_t cs_cb = 928;
> +    const int samplerate_index = c->samplerate_index;
>      int i, j;
>  
> -    fft(in, out);
> +    calc_power(c, in, power);
>  
>      for (j = 0; j < 256; j++) {
> -        power[j] = add_cb(get_cb(out[j].re), get_cb(out[j].im));
>          out_cb_unnorm[j] = -2047; /* and can only grow */
>      }
>  
> @@ -586,7 +539,7 @@ static void calc_masking(DCAEncContext *c, const int32_t *input)
>                  data[i] = c->history[ch][k];
>              for (k -= 512; i < 512; i++, k++)
>                  data[i] = input[k * c->channels + chi];
> -            adjust_jnd(c->samplerate_index, data, c->masking_curve_cb[ssf]);
> +            adjust_jnd(c, data, c->masking_curve_cb[ssf]);
>          }
>      for (i = 0; i < 256; i++) {
>          int32_t m = 2048;
> diff --git a/tests/fate/acodec.mak b/tests/fate/acodec.mak
> index 5c3fea90c5..80d26de0f9 100644
> --- a/tests/fate/acodec.mak
> +++ b/tests/fate/acodec.mak
> @@ -104,14 +104,14 @@ fate-acodec-dca: tests/data/asynth-44100-2.wav
>  fate-acodec-dca: SRC = tests/data/asynth-44100-2.wav
>  fate-acodec-dca: CMD = md5 -i $(TARGET_PATH)/$(SRC) -c:a dca -strict -2 -f dts -flags +bitexact
>  fate-acodec-dca: CMP = oneline
> -fate-acodec-dca: REF = 7cd79a3717943a06b217f1130223a86f
> +fate-acodec-dca: REF = 2aa580ac67820fce4f581b96ebb34acc
>  
>  FATE_ACODEC-$(call ENCDEC, DCA, WAV) += fate-acodec-dca2
>  fate-acodec-dca2: CMD = enc_dec_pcm dts wav s16le $(SRC) -c:a dca -strict -2 -flags +bitexact
>  fate-acodec-dca2: REF = $(SRC)
>  fate-acodec-dca2: CMP = stddev
>  fate-acodec-dca2: CMP_SHIFT = -2048
> -fate-acodec-dca2: CMP_TARGET = 527
> +fate-acodec-dca2: CMP_TARGET = 535
>  fate-acodec-dca2: SIZE_TOLERANCE = 1632
>  
>  FATE_ACODEC-$(call ENCDEC, FLAC, FLAC) += fate-acodec-flac fate-acodec-flac-exact-rice
> -- 
> 2.13.5
> 


More information about the ffmpeg-devel mailing list