Add Scaletempo audio filter

Scaletempo maintains the audio pitch when playback rate != 1.0 (i.e.
no chipmunk effect).  This fixes the pitch scaling caused by using the
resampler to handle playback rate.

Ported from GStreamer.  Inspired by SoundTouch library by Olli Parviainen.
Signed-off-by: Rémi Denis-Courmont <rdenis@simphalempin.com>

configure.ac

@@ -1216,6 +1216,7 @@ if test "${SYS}" != "mingwce"; then
   VLC_ADD_PLUGIN([normvol])
   VLC_ADD_PLUGIN([equalizer])
   VLC_ADD_PLUGIN([param_eq])
+  VLC_ADD_PLUGIN([scaletempo])
   VLC_ADD_PLUGIN([converter_float])
   VLC_ADD_PLUGIN([a52tospdif])
   VLC_ADD_PLUGIN([dtstospdif])

modules/audio_filter/Modules.am

@@ -3,3 +3,4 @@ SOURCES_equalizer = equalizer.c equalizer_presets.h
 SOURCES_normvol = normvol.c
 SOURCES_audio_format = format.c
 SOURCES_param_eq = param_eq.c
+SOURCES_scaletempo = scaletempo.c

modules/audio_filter/scaletempo.c

+/*****************************************************************************
+ * scaletempo.c: Scale audio tempo while maintaining pitch
+ *****************************************************************************
+ * Copyright © 2008 the VideoLAN team
+ * $Id$
+ *
+ * Authors: Rov Juvano <rovjuvano@users.sourceforge.net>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+/*****************************************************************************
+ * Preamble
+ *****************************************************************************/
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <vlc_common.h>
+#include <vlc_plugin.h>
+#include <vlc_aout.h>
+
+#include <string.h> /* for memset */
+#include <limits.h> /* form INT_MIN */
+
+/*****************************************************************************
+ * Module descriptor
+ *****************************************************************************/
+static int  Open( vlc_object_t * );
+static void Close( vlc_object_t * );
+static void DoWork( aout_instance_t *, aout_filter_t *,
+                    aout_buffer_t *, aout_buffer_t * );
+
+vlc_module_begin();
+    set_description( N_("Scale audio tempo in sync with playback rate") );
+    set_shortname( N_("Scaletempo") );
+    set_capability( "audio filter", 0 );
+    set_category( CAT_AUDIO );
+    set_subcategory( SUBCAT_AUDIO_AFILTER );
+
+    add_integer_with_range( "scaletempo-stride", 30, 1, 2000, NULL,
+        N_("Stride Length"), N_("Length in milliseconds to output each stride"), true );
+    add_float_with_range( "scaletempo-overlap", .20, 0.0, 1.0, NULL,
+        N_("Overlap Length"), N_("Percentage of stride to overlap"), true );
+    add_integer_with_range( "scaletempo-search", 14, 0, 200, NULL,
+        N_("Search Length"), N_("Length in milliseconds to search for best overlap position"), true );
+
+    set_callbacks( Open, Close );
+vlc_module_end();
+
+/*
+ * Scaletempo works by producing audio in constant sized chunks (a "stride") but
+ * consuming chunks proportional to the playback rate.
+ *
+ * Scaletempo then smooths the output by blending the end of one stride with
+ * the next ("overlap").
+ *
+ * Scaletempo smooths the overlap further by searching within the input buffer
+ * for the best overlap position.  Scaletempo uses a statistical cross correlation
+ * (roughly a dot-product).  Scaletempo consumes most of its CPU cycles here.
+ *
+ * NOTE:
+ * sample: a single audio sample for one channel
+ * frame: a single set of samples, one for each channel
+ * VLC uses these terms differently
+ */
+typedef struct aout_filter_sys_t
+{
+    /* Filter static config */
+    double    scale;
+    /* parameters */
+    uint      ms_stride;
+    double    percent_overlap;
+    uint      ms_search;
+    /* audio format */
+    uint      samples_per_frame;  /* AKA number of channels */
+    uint      bytes_per_sample;
+    uint      bytes_per_frame;
+    uint      sample_rate;
+    /* stride */
+    double    frames_stride_scaled;
+    double    frames_stride_error;
+    uint      bytes_stride;
+    double    bytes_stride_scaled;
+    uint      bytes_queue_max;
+    uint      bytes_queued;
+    uint      bytes_to_slide;
+    uint8_t  *buf_queue;
+    /* overlap */
+    uint      samples_overlap;
+    uint      samples_standing;
+    uint      bytes_overlap;
+    uint      bytes_standing;
+    void     *buf_overlap;
+    void     *table_blend;
+    void    (*output_overlap)( aout_filter_t *p_filter, void *p_out_buf, uint bytes_off );
+    /* best overlap */
+    uint      frames_search;
+    void     *buf_pre_corr;
+    void     *table_window;
+    uint    (*best_overlap_offset)( aout_filter_t *p_filter );
+    /* for "audio filter" only, manage own buffers */
+    int       i_buf;
+    uint8_t  *p_buffers[2];
+} aout_filter_sys_t;
+
+/*****************************************************************************
+ * best_overlap_offset: calculate best offset for overlap
+ *****************************************************************************/
+static uint best_overlap_offset_float( aout_filter_t *p_filter )
+{
+    aout_filter_sys_t *p = p_filter->p_sys;
+    float *pw, *po, *ppc, *search_start;
+    float best_corr = INT_MIN;
+    uint best_off = 0;
+    uint i, off;
+
+    pw  = p->table_window;
+    po  = p->buf_overlap;
+    po += p->samples_per_frame;
+    ppc = p->buf_pre_corr;
+    for( i = p->samples_per_frame; i < p->samples_overlap; i++ ) {
+      *ppc++ = *pw++ * *po++;
+    }
+
+    search_start = (float *)p->buf_queue + p->samples_per_frame;
+    for( off = 0; off < p->frames_search; off++ ) {
+      float corr = 0;
+      float *ps = search_start;
+      ppc = p->buf_pre_corr;
+      for( i = p->samples_per_frame; i < p->samples_overlap; i++ ) {
+        corr += *ppc++ * *ps++;
+      }
+      if( corr > best_corr ) {
+        best_corr = corr;
+        best_off  = off;
+      }
+      search_start += p->samples_per_frame;
+    }
+
+    return best_off * p->bytes_per_frame;
+}
+
+/*****************************************************************************
+ * output_overlap: blend end of previous stride with beginning of current stride
+ *****************************************************************************/
+static void output_overlap_float( aout_filter_t   *p_filter,
+                                  void            *buf_out,
+                                  uint             bytes_off )
+{
+    aout_filter_sys_t *p = p_filter->p_sys;
+    float *pout = buf_out;
+    float *pb   = p->table_blend;
+    float *po   = p->buf_overlap;
+    float *pin  = (float *)( p->buf_queue + bytes_off );
+    uint i;
+    for( i = 0; i < p->samples_overlap; i++ ) {
+        *pout++ = *po - *pb++ * ( *po - *pin++ ); po++;
+    }
+}
+
+/*****************************************************************************
+ * fill_queue: fill p_sys->buf_queue as much possible, skipping samples as needed
+ *****************************************************************************/
+static size_t fill_queue( aout_filter_t *p_filter,
+                          uint8_t       *p_buffer,
+                          size_t         i_buffer,
+                          size_t         offset )
+{
+    aout_filter_sys_t *p = p_filter->p_sys;
+    uint bytes_in = i_buffer - offset;
+    size_t offset_unchanged = offset;
+
+    if( p->bytes_to_slide > 0 ) {
+        if( p->bytes_to_slide < p->bytes_queued ) {
+            uint bytes_in_move = p->bytes_queued - p->bytes_to_slide;
+            memmove( p->buf_queue,
+                     p->buf_queue + p->bytes_to_slide,
+                     bytes_in_move );
+            p->bytes_to_slide = 0;
+            p->bytes_queued   = bytes_in_move;
+        } else {
+            uint bytes_in_skip;
+            p->bytes_to_slide -= p->bytes_queued;
+            bytes_in_skip      = __MIN( p->bytes_to_slide, bytes_in );
+            p->bytes_queued    = 0;
+            p->bytes_to_slide -= bytes_in_skip;
+            offset            += bytes_in_skip;
+            bytes_in          -= bytes_in_skip;
+        }
+    }
+
+    if( bytes_in > 0 ) {
+        uint bytes_in_copy = __MIN( p->bytes_queue_max - p->bytes_queued, bytes_in );
+        memcpy( p->buf_queue + p->bytes_queued,
+                p_buffer + offset,
+                bytes_in_copy );
+        p->bytes_queued += bytes_in_copy;
+        offset          += bytes_in_copy;
+    }
+
+    return offset - offset_unchanged;
+}
+
+/*****************************************************************************
+ * transform_buffer: main filter loop
+ *****************************************************************************/
+static size_t transform_buffer( aout_filter_t   *p_filter,
+                                uint8_t         *p_buffer,
+                                size_t           i_buffer,
+                                uint8_t         *pout )
+{
+    aout_filter_sys_t *p = p_filter->p_sys;
+
+    size_t offset_in = fill_queue( p_filter, p_buffer, i_buffer, 0 );
+    uint bytes_out = 0;
+    while( p->bytes_queued >= p->bytes_queue_max ) {
+        uint bytes_off = 0;
+
+        // output stride
+        if( p->output_overlap ) {
+            if( p->best_overlap_offset ) {
+                bytes_off = p->best_overlap_offset( p_filter );
+            }
+            p->output_overlap( p_filter, pout, bytes_off );
+        }
+        memcpy( pout + p->bytes_overlap,
+                p->buf_queue + bytes_off + p->bytes_overlap,
+                p->bytes_standing );
+        pout += p->bytes_stride;
+        bytes_out += p->bytes_stride;
+
+        // input stride
+        memcpy( p->buf_overlap,
+                p->buf_queue + bytes_off + p->bytes_stride,
+                p->bytes_overlap );
+        double frames_to_slide = p->frames_stride_scaled + p->frames_stride_error;
+        uint   frames_to_stride_whole = (int)frames_to_slide;
+        p->bytes_to_slide       = frames_to_stride_whole * p->bytes_per_frame;
+        p->frames_stride_error  = frames_to_slide - frames_to_stride_whole;
+
+        offset_in += fill_queue( p_filter, p_buffer, i_buffer, offset_in );
+    }
+
+    return bytes_out;
+}
+
+/*****************************************************************************
+ * calculate_output_buffer_size
+ *****************************************************************************/
+static size_t calculate_output_buffer_size( aout_filter_t   *p_filter,
+                                            size_t           bytes_in )
+{
+    aout_filter_sys_t *p = p_filter->p_sys;
+    size_t bytes_out = 0;
+    int bytes_to_out = bytes_in + p->bytes_queued - p->bytes_to_slide;
+    if( bytes_to_out >= (int)p->bytes_queue_max ) {
+      /* while (total_buffered - stride_length * n >= queue_max) n++ */
+      bytes_out = p->bytes_stride * ( (uint)(
+          ( bytes_to_out - p->bytes_queue_max + /* rounding protection */ p->bytes_per_frame )
+          / p->bytes_stride_scaled ) + 1 );
+    }
+    return bytes_out;
+}
+
+/*****************************************************************************
+ * reinit_buffers: reinitializes buffers in p_filter->p_sys
+ *****************************************************************************/
+static int reinit_buffers( aout_filter_t *p_filter )
+{
+    aout_filter_sys_t *p = p_filter->p_sys;
+    uint i,j;
+
+    uint frames_stride = p->ms_stride * p->sample_rate / 1000.0;
+    p->bytes_stride = frames_stride * p->bytes_per_frame;
+
+    /* overlap */
+    uint frames_overlap = frames_stride * p->percent_overlap;
+    if( frames_overlap < 1 ) { /* if no overlap */
+        p->bytes_overlap    = 0;
+        p->bytes_standing   = p->bytes_stride;
+        p->samples_standing = p->bytes_standing / p->bytes_per_sample;
+        p->output_overlap   = NULL;
+    } else {
+        uint prev_overlap   = p->bytes_overlap;
+        p->bytes_overlap    = frames_overlap * p->bytes_per_frame;
+        p->samples_overlap  = frames_overlap * p->samples_per_frame;
+        p->bytes_standing   = p->bytes_stride - p->bytes_overlap;
+        p->samples_standing = p->bytes_standing / p->bytes_per_sample;
+        p->buf_overlap      = malloc( p->bytes_overlap );
+        p->table_blend      = malloc( p->samples_overlap * 4 ); /* sizeof (int32|float) */
+        if( ! p->buf_overlap || ! p->table_blend ) {
+            return VLC_ENOMEM;
+        }
+        if( p->bytes_overlap > prev_overlap ) {
+            memset( (uint8_t *)p->buf_overlap + prev_overlap, 0, p->bytes_overlap - prev_overlap );
+        }
+        float *pb = p->table_blend;
+        float t = (float)frames_overlap;
+        for( i = 0; i<frames_overlap; i++ ) {
+            float v = i / t;
+            for( j = 0; j < p->samples_per_frame; j++ ) {
+                *pb++ = v;
+            }
+        }
+        p->output_overlap = output_overlap_float;
+    }
+
+    /* best overlap */
+    p->frames_search = ( frames_overlap <= 1 ) ? 0 : p->ms_search * p->sample_rate / 1000.0;
+    if( p->frames_search < 1 ) { /* if no search */
+        p->best_overlap_offset = NULL;
+    } else {
+        uint bytes_pre_corr = ( p->samples_overlap - p->samples_per_frame ) * 4; /* sizeof (int32|float) */
+        p->buf_pre_corr = malloc( bytes_pre_corr );
+        p->table_window = malloc( bytes_pre_corr );
+        if( ! p->buf_pre_corr || ! p->table_window ) {
+            return VLC_ENOMEM;
+        }
+        float *pw = p->table_window;
+        for( i = 1; i<frames_overlap; i++ ) {
+            float v = i * ( frames_overlap - i );
+            for( j = 0; j < p->samples_per_frame; j++ ) {
+                *pw++ = v;
+            }
+        }
+        p->best_overlap_offset = best_overlap_offset_float;
+    }
+
+    uint new_size = ( p->frames_search + frames_stride + frames_overlap ) * p->bytes_per_frame;
+    if( p->bytes_queued > new_size ) {
+        if( p->bytes_to_slide > p->bytes_queued ) {
+          p->bytes_to_slide -= p->bytes_queued;
+          p->bytes_queued    = 0;
+        } else {
+            uint new_queued = __MIN( p->bytes_queued - p->bytes_to_slide, new_size );
+            memmove( p->buf_queue,
+                     p->buf_queue + p->bytes_queued - new_queued,
+                     new_queued );
+            p->bytes_to_slide = 0;
+            p->bytes_queued   = new_queued;
+        }
+    }
+    p->bytes_queue_max = new_size;
+    p->buf_queue = malloc( p->bytes_queue_max );
+    if( ! p->buf_queue ) {
+        return VLC_ENOMEM;
+    }
+
+    p->bytes_stride_scaled  = p->bytes_stride * p->scale;
+    p->frames_stride_scaled = p->bytes_stride_scaled / p->bytes_per_frame;
+
+    msg_Dbg( VLC_OBJECT(p_filter),
+             "%.3f scale, %.3f stride_in, %i stride_out, %i standing, %i overlap, %i search, %i queue, %s mode",
+             p->scale,
+             p->frames_stride_scaled,
+             (int)( p->bytes_stride / p->bytes_per_frame ),
+             (int)( p->bytes_standing / p->bytes_per_frame ),
+             (int)( p->bytes_overlap / p->bytes_per_frame ),
+             p->frames_search,
+             (int)( p->bytes_queue_max / p->bytes_per_frame ),
+             "fl32");
+
+    return VLC_SUCCESS;
+}
+
+/*****************************************************************************
+ * Open: initialize as "audio filter"
+ *****************************************************************************/
+static int Open( vlc_object_t *p_this )
+{
+    aout_filter_t     *p_filter = (aout_filter_t *)p_this;
+    aout_filter_sys_t *p_sys;
+    bool b_fit = true;
+
+    if( p_filter->input.i_format != VLC_FOURCC('f','l','3','2' ) ||
+        p_filter->output.i_format != VLC_FOURCC('f','l','3','2') )
+    {
+        b_fit = false;
+        p_filter->input.i_format = p_filter->output.i_format = VLC_FOURCC('f','l','3','2');
+        msg_Warn( p_filter, "bad input or output format" );
+    }
+    if( ! AOUT_FMTS_SIMILAR( &p_filter->input, &p_filter->output ) )
+    {
+        b_fit = false;
+        memcpy( &p_filter->output, &p_filter->input, sizeof(audio_sample_format_t) );
+        msg_Warn( p_filter, "input and output formats are not similar" );
+    }
+
+    if( ! b_fit )
+    {
+        return VLC_EGENERIC;
+    }
+
+    p_filter->pf_do_work = DoWork;
+    p_filter->b_in_place = false;
+
+    /* Allocate structure */
+    p_sys = p_filter->p_sys = malloc( sizeof(aout_filter_sys_t) );
+    if( ! p_sys )
+    {
+        return VLC_ENOMEM;
+    }
+
+    p_sys->scale             = 1.0;
+    p_sys->sample_rate       = p_filter->input.i_rate;
+    p_sys->samples_per_frame = aout_FormatNbChannels( &p_filter->input );
+    p_sys->bytes_per_sample  = 4;
+    p_sys->bytes_per_frame   = p_sys->samples_per_frame * p_sys->bytes_per_sample;
+
+    msg_Dbg( p_this, "format: %5i rate, %i nch, %i bps, %s",
+             p_sys->sample_rate,
+             p_sys->samples_per_frame,
+             p_sys->bytes_per_sample,
+             "fl32" );
+
+    p_sys->ms_stride       = config_GetInt(   p_this, "scaletempo-stride" );
+    p_sys->percent_overlap = config_GetFloat( p_this, "scaletempo-overlap" );
+    p_sys->ms_search       = config_GetInt(   p_this, "scaletempo-search" );
+
+    msg_Dbg( p_this, "params: %i stride, %.3f overlap, %i search",
+             p_sys->ms_stride, p_sys->percent_overlap, p_sys->ms_search );
+
+    p_sys->i_buf = 0;
+    p_sys->p_buffers[0] = NULL;
+    p_sys->p_buffers[1] = NULL;
+
+    p_sys->buf_queue      = NULL;
+    p_sys->buf_overlap    = NULL;
+    p_sys->table_blend    = NULL;
+    p_sys->buf_pre_corr   = NULL;
+    p_sys->table_window   = NULL;
+    p_sys->bytes_overlap  = 0;
+    p_sys->bytes_queued   = 0;
+    p_sys->bytes_to_slide = 0;
+    p_sys->frames_stride_error = 0;
+    return reinit_buffers( p_filter );
+}
+
+static void Close( vlc_object_t *p_this )
+{
+    aout_filter_t *p_filter = (aout_filter_t *)p_this;
+    aout_filter_sys_t *p_sys = p_filter->p_sys;
+    free( p_sys->buf_queue );
+    free( p_sys->buf_overlap );
+    free( p_sys->table_blend );
+    free( p_sys->buf_pre_corr );
+    free( p_sys->table_window );
+    free( p_sys->p_buffers[0] );
+    free( p_sys->p_buffers[1] );
+    free( p_filter->p_sys );
+}
+
+/*****************************************************************************
+ * DoWork: aout_filter wrapper for transform_buffer
+ *****************************************************************************/
+static void DoWork( aout_instance_t * p_aout, aout_filter_t * p_filter,
+                    aout_buffer_t * p_in_buf, aout_buffer_t * p_out_buf )
+{
+    VLC_UNUSED(p_aout);
+    aout_filter_sys_t *p = p_filter->p_sys;
+
+    if( p_filter->input.i_rate == p->sample_rate ) {
+      memcpy( p_out_buf->p_buffer, p_in_buf->p_buffer, p_in_buf->i_nb_bytes );
+      p_out_buf->i_nb_bytes   = p_in_buf->i_nb_bytes;
+      p_out_buf->i_nb_samples = p_in_buf->i_nb_samples;
+      return;
+    }
+
+    double scale = p_filter->input.i_rate / (double)p->sample_rate;
+    if( scale != p->scale ) {
+      p->scale = scale;
+      p->bytes_stride_scaled  = p->bytes_stride * p->scale;
+      p->frames_stride_scaled = p->bytes_stride_scaled / p->bytes_per_frame;
+      p->bytes_to_slide = 0;
+      msg_Dbg( p_filter, "%.3f scale, %.3f stride_in, %i stride_out",
+               p->scale,
+               p->frames_stride_scaled,
+               (int)( p->bytes_stride / p->bytes_per_frame ) );
+    }
+
+    size_t i_outsize = calculate_output_buffer_size ( p_filter, p_in_buf->i_nb_bytes );
+    if( i_outsize > p_out_buf->i_size ) {
+        void *temp = realloc( p->p_buffers[ p->i_buf ], i_outsize );
+        if( temp == NULL )
+        {
+            return;
+        }
+        p->p_buffers[ p->i_buf ] = temp;
+        p_out_buf->p_buffer = p->p_buffers[ p->i_buf ];
+        p->i_buf = ! p->i_buf;
+    }
+
+    size_t bytes_out = transform_buffer( p_filter,
+        p_in_buf->p_buffer, p_in_buf->i_nb_bytes,
+        p_out_buf->p_buffer );
+
+    p_out_buf->i_nb_bytes   = bytes_out;
+    p_out_buf->i_nb_samples = bytes_out / p->bytes_per_frame;
+}