On Mon, 29 Feb 2016 03:33:45 +0100,
han.lu@xxxxxxxxx wrote:
>
> From: "Lu, Han" <han.lu@xxxxxxxxx>
>
> Truncate the sample frames to powers of 2, since the FFTW algorithm
> runs especially fast in this case, and other sizes may be computed
> by means of a slow, general-purpose algorithm.
> In my test environment applying the patch, a sound clip of 33072
> frames is cut off to 32768 frames before analysis, and the time
> cost is reduced from 6.128s to 0.224s.
>
> Signed-off-by: Lu, Han <han.lu@xxxxxxxxx>
Applied, thanks.
Takashi
>
> diff --git a/bat/analyze.c b/bat/analyze.c
> index 60e2d1c..5cfdac3 100644
> --- a/bat/analyze.c
> +++ b/bat/analyze.c
> @@ -256,6 +256,20 @@ static int reorder_data(struct bat *bat)
> return 0;
> }
>
> +/* truncate sample frames for faster FFT analysis process */
> +static int truncate_frames(struct bat *bat)
> +{
> + int shift = SHIFT_MAX;
> +
> + for (; shift > SHIFT_MIN; shift--)
> + if (bat->frames & (1 << shift)) {
> + bat->frames = 1 << shift;
> + return 0;
> + }
> +
> + return -EINVAL;
> +}
> +
> int analyze_capture(struct bat *bat)
> {
> int err = 0;
> @@ -263,6 +277,13 @@ int analyze_capture(struct bat *bat)
> int c;
> struct analyze a;
>
> + err = truncate_frames(bat);
> + if (err < 0) {
> + fprintf(bat->err, _("Invalid frame number for analysis: %d\n"),
> + bat->frames);
> + return err;
> + }
> +
> fprintf(bat->log, _("\nBAT analysis: signal has %d frames at %d Hz,"),
> bat->frames, bat->rate);
> fprintf(bat->log, _(" %d channels, %d bytes per sample.\n"),
> diff --git a/bat/common.h b/bat/common.h
> index b8f6670..ff03fc1 100644
> --- a/bat/common.h
> +++ b/bat/common.h
> @@ -68,6 +68,12 @@
> #define FOUND_DC (1<<1)
> #define FOUND_WRONG_PEAK (1<<0)
>
> +/* Truncate sample frames to (1 << N), for faster FFT analysis process. The
> + * valid range of N is (SHIFT_MIN, SHIFT_MAX). When N increases, the analysis
> + * will be more time-consuming, and the result will be more accurate. */
> +#define SHIFT_MAX (sizeof(int) * 8 - 2)
> +#define SHIFT_MIN 8
> +
> struct wav_header {
> unsigned int magic; /* 'RIFF' */
> unsigned int length; /* file len */
> --
> 2.5.0
>
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