@@ -12,6 +12,7 @@ version next:

 - XML output in ffprobe

 - asplit audio filter

 - tinterlace video filter

+- astreamsync audio filter

 version 0.9:

@@ -237,6 +237,35 @@ For example:

 will create two separate outputs from the same input, one cropped and

 one padded.

+@section astreamsync

+

+Forward two audio streams and control the order the buffers are forwarded.

+

+The argument to the filter is an expression deciding which stream should be

+forwarded next: if the result is negative, the first stream is forwarded; if

+the result is positive or zero, the second stream is forwarded. It can use

+the following variables:

+

+@table @var

+@item b1 b2

+number of buffers forwarded so far on each stream

+@item s1 s2

+number of samples forwarded so far on each stream

+@item t1 t2

+current timestamp of each stream

+@end table

+

+The default value is @code{t1-t2}, which means to always forward the stream

+that has a smaller timestamp.

+

+Example: stress-test @code{amerge} by randomly sending buffers on the wrong

+input, while avoiding too much of a desynchronization:

+@example

+amovie=file.ogg [a] ; amovie=file.mp3 [b] ;

+[a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;

+[a2] [b2] amerge

+@end example

+

 @section earwax

 Make audio easier to listen to on headphones.

@@ -30,6 +30,7 @@ OBJS-$(CONFIG_ANULL_FILTER)                  += af_anull.o

 OBJS-$(CONFIG_ARESAMPLE_FILTER)              += af_aresample.o

 OBJS-$(CONFIG_ASHOWINFO_FILTER)              += af_ashowinfo.o

 OBJS-$(CONFIG_ASPLIT_FILTER)                 += af_asplit.o

+OBJS-$(CONFIG_ASTREAMSYNC_FILTER)            += af_astreamsync.o

 OBJS-$(CONFIG_EARWAX_FILTER)                 += af_earwax.o

 OBJS-$(CONFIG_PAN_FILTER)                    += af_pan.o

 OBJS-$(CONFIG_VOLUME_FILTER)                 += af_volume.o

new file mode 100644

@@ -0,0 +1,209 @@

+/*

+ * Copyright (c) 2011 Nicolas George <nicolas.george@normalesup.org>

+ *

+ * This file is part of FFmpeg.

+ *

+ * FFmpeg is free software; you can redistribute it and/or

+ * modify it under the terms of the GNU Lesser General Public

+ * License as published by the Free Software Foundation; either

+ * version 2.1 of the License, or (at your option) any later version.

+ *

+ * FFmpeg 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 Lesser General Public

+ * License along with FFmpeg; if not, write to the Free Software

+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

+ */

+

+/**

+ * @file

+ * Stream (de)synchronization filter

+ */

+

+#include "libavutil/eval.h"

+#include "avfilter.h"

+#include "internal.h"

+

+#define QUEUE_SIZE 16

+

+static const char * const var_names[] = {

+    "b1", "b2",

+    "s1", "s2",

+    "t1", "t2",

+    NULL

+};

+

+enum var_name {

+    VAR_B1, VAR_B2,

+    VAR_S1, VAR_S2,

+    VAR_T1, VAR_T2,

+    VAR_NB

+};

+

+typedef struct {

+    AVExpr *expr;

+    double var_values[VAR_NB];

+    struct buf_queue {

+        AVFilterBufferRef *buf[QUEUE_SIZE];

+        unsigned tail, nb;

+        /* buf[tail] is the oldest,

+           buf[(tail + nb) % QUEUE_SIZE] is where the next is added */

+    } queue[2];

+    int req[2];

+    int next_out;

+    int eof; /* bitmask, one bit for each stream */

+} AStreamSyncContext;

+

+static const char *default_expr = "t1-t2";

+

+static av_cold int init(AVFilterContext *ctx, const char *args0, void *opaque)

+{

+    AStreamSyncContext *as = ctx->priv;

+    const char *expr = args0 ? args0 : default_expr;

+    int r, i;

+

+    r = av_expr_parse(&as->expr, expr, var_names,

+                      NULL, NULL, NULL, NULL, 0, ctx);

+    if (r < 0) {

+        av_log(ctx, AV_LOG_ERROR, "Error in expression \"%s\"\n", expr);

+        return r;

+    }

+    for (i = 0; i < 42; i++)

+        av_expr_eval(as->expr, as->var_values, NULL); /* exercize prng */

+    return 0;

+}

+

+static int query_formats(AVFilterContext *ctx)

+{

+    int i;

+    AVFilterFormats *formats;

+

+    for (i = 0; i < 2; i++) {

+        formats = ctx->inputs[i]->in_formats;

+        avfilter_formats_ref(formats, &ctx->inputs[i]->out_formats);

+        avfilter_formats_ref(formats, &ctx->outputs[i]->in_formats);

+        formats = ctx->inputs[i]->in_packing;

+        avfilter_formats_ref(formats, &ctx->inputs[i]->out_packing);

+        avfilter_formats_ref(formats, &ctx->outputs[i]->in_packing);

+        formats = ctx->inputs[i]->in_chlayouts;

+        avfilter_formats_ref(formats, &ctx->inputs[i]->out_chlayouts);

+        avfilter_formats_ref(formats, &ctx->outputs[i]->in_chlayouts);

+    }

+    return 0;

+}

+

+static int config_output(AVFilterLink *outlink)

+{

+    AVFilterContext *ctx = outlink->src;

+    int id = outlink == ctx->outputs[1];

+    int i;

+

+    outlink->sample_rate = ctx->inputs[id]->sample_rate;

+    outlink->time_base   = ctx->inputs[id]->time_base;

+    return 0;

+}

+

+static void send_out(AVFilterContext *ctx, int out_id)

+{

+    AStreamSyncContext *as = ctx->priv;

+    struct buf_queue *queue = &as->queue[out_id];

+    AVFilterBufferRef *buf = queue->buf[queue->tail];

+

+    queue->buf[queue->tail] = NULL;

+    as->var_values[VAR_B1 + out_id]++;

+    as->var_values[VAR_S1 + out_id] += buf->audio->nb_samples;

+    if (buf->pts != AV_NOPTS_VALUE)

+        as->var_values[VAR_T1 + out_id] =

+            av_q2d(ctx->outputs[out_id]->time_base) * buf->pts;

+    as->var_values[VAR_T1 + out_id] += buf->audio->nb_samples /

+                                   (double)ctx->inputs[out_id]->sample_rate;

+    avfilter_filter_samples(ctx->outputs[out_id], buf);

+    queue->nb--;

+    queue->tail = (queue->tail + 1) % QUEUE_SIZE;

+    if (as->req[out_id])

+        as->req[out_id]--;

+}

+

+static void send_next(AVFilterContext *ctx)

+{

+    AStreamSyncContext *as = ctx->priv;

+    int i;

+

+    while (1) {

+        if (!as->queue[as->next_out].nb)

+            break;

+        send_out(ctx, as->next_out);

+        if (!as->eof)

+            as->next_out = av_expr_eval(as->expr, as->var_values, NULL) >= 0;

+    }

+    for (i = 0; i < 2; i++)

+        if (as->queue[i].nb == QUEUE_SIZE)

+            send_out(ctx, i);

+}

+

+static int request_frame(AVFilterLink *outlink)

+{

+    AVFilterContext *ctx = outlink->src;

+    AStreamSyncContext *as = ctx->priv;

+    int id = outlink == ctx->outputs[1];

+

+    as->req[id]++;

+    while (as->req[id] && !(as->eof & (1 << id))) {

+        if (as->queue[as->next_out].nb) {

+            send_next(ctx);

+        } else {

+            as->eof |= 1 << as->next_out;

+            avfilter_request_frame(ctx->inputs[as->next_out]);

+            if (as->eof & (1 << as->next_out))

+                as->next_out = !as->next_out;

+        }

+    }

+    return 0;

+}

+

+static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)

+{

+    AVFilterContext *ctx = inlink->dst;

+    AStreamSyncContext *as = ctx->priv;

+    int id = inlink == ctx->inputs[1];

+

+    as->queue[id].buf[(as->queue[id].tail + as->queue[id].nb++) % QUEUE_SIZE] =

+        insamples;

+    as->eof &= ~(1 << id);

+    send_next(ctx);

+}

+

+AVFilter avfilter_af_astreamsync = {

+    .name          = "astreamsync",

+    .description   = NULL_IF_CONFIG_SMALL("Copy two streams of audio data "

+                                          "in a configurable order."),

+    .priv_size     = sizeof(AStreamSyncContext),

+    .init          = init,

+    .query_formats = query_formats,

+

+    .inputs    = (const AVFilterPad[]) {

+        { .name             = "in1",

+          .type             = AVMEDIA_TYPE_AUDIO,

+          .filter_samples   = filter_samples,

+          .min_perms        = AV_PERM_READ, },

+        { .name             = "in2",

+          .type             = AVMEDIA_TYPE_AUDIO,

+          .filter_samples   = filter_samples,

+          .min_perms        = AV_PERM_READ, },

+        { .name = NULL }

+    },

+    .outputs   = (const AVFilterPad[]) {

+        { .name             = "out1",

+          .type             = AVMEDIA_TYPE_AUDIO,

+          .config_props     = config_output,

+          .request_frame    = request_frame, },

+        { .name             = "out2",

+          .type             = AVMEDIA_TYPE_AUDIO,

+          .config_props     = config_output,

+          .request_frame    = request_frame, },

+        { .name = NULL }

+    },

+};

@@ -40,6 +40,7 @@ void avfilter_register_all(void)

     REGISTER_FILTER (ARESAMPLE,   aresample,   af);

     REGISTER_FILTER (ASHOWINFO,   ashowinfo,   af);

     REGISTER_FILTER (ASPLIT,      asplit,      af);

+    REGISTER_FILTER (ASTREAMSYNC, astreamsync, af);

     REGISTER_FILTER (EARWAX,      earwax,      af);

     REGISTER_FILTER (PAN,         pan,         af);

     REGISTER_FILTER (VOLUME,      volume,      af);