audio/filters: add af_force

Its main purpose is for testing in case channel layout stuff breaks, in
particular in connection with old audio filters.

DOCS/man/en/af.rst

@@ -210,6 +210,34 @@ channels=nch[:nr:from1:to1:from2:to2:from3:to3:...]
         Would change the number of channels to 6 and set up 4 routes that copy
         channel 0 to channels 0 to 3. Channel 4 and 5 will contain silence.
 
+force=in-format:in-srate:in-channels:out-format:out-srate:out-channels
+    Force a specific audio format/configuration without actually changing the
+    audio data. Keep in mind that the filter system might auto-insert actual
+    conversion filters before or after this filter if needed.
+
+    All parameters are optional. The ``in-`` variants restrict what the filter
+    accepts as input. The ``out-`` variants change the audio format, without
+    actually doing a conversion. The data will be 'reinterpreted' by the
+    filters or audio outputs following this filter.
+
+    <in-format>
+        Force conversion to this format. See ``format`` filter for valid audio
+        format values.
+
+    <in-srate>
+        Force conversion to a specific sample rate. The rate is an integer,
+        48000 for example.
+
+    <in-channels>
+        Force mixing to a specific channel layout. See ``--channels`` option
+        for possible values.
+
+    <out-format>
+
+    <out-srate>
+
+    <out-channels>
+
 format[=format]
     Convert between different sample formats. Automatically enabled when
     needed by the sound card or another filter. See also ``--format``.
@@ -293,6 +321,11 @@ pan=n[:L00:L01:L02:...L10:L11:L12:...Ln0:Ln1:Ln2:...]
         channels 0 and 1 into output channel 2 (which could be sent to a
         subwoofer for example).
 
+    *NOTE*: if you just want to force remixing to a certain output channel
+    layout, it's easier to use the ``force`` filter. For example,
+    ``mpv '--af=force=channels=5.1' '--channels=5.1'`` would always force
+    remixing audio to 5.1 and output it like this.
+
 sub[=fc:ch]
     Adds a subwoofer channel to the audio stream. The audio data used for
     creating the subwoofer channel is an average of the sound in channel 0 and

Makefile

@@ -139,6 +139,7 @@ SOURCES = talloc.c \
           audio/filter/af_dummy.c \
           audio/filter/af_equalizer.c \
           audio/filter/af_extrastereo.c \
+          audio/filter/af_force.c \
           audio/filter/af_format.c \
           audio/filter/af_hrtf.c \
           audio/filter/af_karaoke.c \

audio/audio.c

@@ -56,6 +56,12 @@ void mp_audio_copy_config(struct mp_audio *dst, const struct mp_audio *src)
     dst->rate = src->rate;
 }
 
+bool mp_audio_config_equals(const struct mp_audio *a, const struct mp_audio *b)
+{
+    return a->format == b->format && a->rate == b->rate &&
+           mp_chmap_equals(&a->channels, &b->channels);
+}
+
 char *mp_audio_fmt_to_str(int srate, const struct mp_chmap *chmap, int format)
 {
     char *chstr = mp_chmap_to_str(chmap);

audio/audio.h

@@ -38,6 +38,7 @@ void mp_audio_set_num_channels(struct mp_audio *mpa, int num_channels);
 void mp_audio_set_channels_old(struct mp_audio *mpa, int num_channels);
 void mp_audio_set_channels(struct mp_audio *mpa, const struct mp_chmap *chmap);
 void mp_audio_copy_config(struct mp_audio *dst, const struct mp_audio *src);
+bool mp_audio_config_equals(const struct mp_audio *a, const struct mp_audio *b);
 
 char *mp_audio_fmt_to_str(int srate, const struct mp_chmap *chmap, int format);
 char *mp_audio_config_to_str(struct mp_audio *mpa);

audio/filter/af.c

@@ -29,6 +29,7 @@ extern struct af_info af_info_dummy;
 extern struct af_info af_info_delay;
 extern struct af_info af_info_channels;
 extern struct af_info af_info_format;
+extern struct af_info af_info_force;
 extern struct af_info af_info_volume;
 extern struct af_info af_info_equalizer;
 extern struct af_info af_info_pan;
@@ -52,6 +53,7 @@ static struct af_info* filter_list[] = {
     &af_info_dummy,
     &af_info_delay,
     &af_info_channels,
+    &af_info_force,
     &af_info_volume,
     &af_info_equalizer,
     &af_info_pan,

audio/filter/af_force.c

@@ -0,0 +1,146 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv 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.
+ *
+ * mpv 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 mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+
+#include <libavutil/common.h>
+
+#include "core/m_config.h"
+#include "core/m_option.h"
+
+#include "audio/format.h"
+#include "af.h"
+
+struct priv {
+    struct m_config *config;
+
+    int in_format;
+    int in_srate;
+    struct mp_chmap in_channels;
+    int out_format;
+    int out_srate;
+    struct mp_chmap out_channels;
+
+    struct mp_audio data;
+    struct mp_audio temp;
+};
+
+static const struct priv defaults = {
+    .in_format = AF_FORMAT_UNKNOWN,
+    .out_format = AF_FORMAT_UNKNOWN,
+};
+
+#define OPT_BASE_STRUCT struct priv
+
+static const struct m_option options[] = {
+    OPT_AUDIOFORMAT("format", in_format, 0),
+    OPT_INTRANGE("srate", in_srate, 0, 1000, 8*48000),
+    OPT_CHMAP("channels", in_channels, CONF_MIN, .min = 0),
+    OPT_AUDIOFORMAT("out-format", out_format, 0),
+    OPT_INTRANGE("out-srate", out_srate, 0, 1000, 8*48000),
+    OPT_CHMAP("out-channels", out_channels, CONF_MIN, .min = 0),
+    {0}
+};
+
+static int control(struct af_instance *af, int cmd, void *arg)
+{
+    struct priv *priv = af->setup;
+
+    switch (cmd) {
+    case AF_CONTROL_REINIT: {
+        struct mp_audio *in = arg;
+        struct mp_audio orig_in = *in;
+        struct mp_audio *out = af->data;
+
+        if (priv->in_format != AF_FORMAT_UNKNOWN)
+            mp_audio_set_format(in, priv->in_format);
+
+        if (priv->in_channels.num)
+            mp_audio_set_channels(in, &priv->in_channels);
+
+        if (priv->in_srate)
+            in->rate = priv->in_srate;
+
+        mp_audio_copy_config(out, in);
+
+        if (priv->out_format != AF_FORMAT_UNKNOWN)
+            mp_audio_set_format(out, priv->out_format);
+
+        if (priv->out_channels.num)
+            mp_audio_set_channels(out, &priv->out_channels);
+
+        if (priv->out_srate)
+            out->rate = priv->out_srate;
+
+        if (in->nch != out->nch || in->bps != out->bps) {
+            mp_msg(MSGT_AFILTER, MSGL_ERR,
+                   "[af_force] Forced input/output format are incompatible.\n");
+            return AF_ERROR;
+        }
+
+        return mp_audio_config_equals(in, &orig_in) ? AF_OK : AF_FALSE;
+    }
+    case AF_CONTROL_COMMAND_LINE: {
+        if (m_config_parse_suboptions(priv->config, "af_force", (char *)arg) < 0)
+            return AF_ERROR;
+        return AF_OK;
+    }
+    }
+    return AF_UNKNOWN;
+}
+
+static struct mp_audio *play(struct af_instance *af, struct mp_audio *data)
+{
+    struct priv *priv = af->setup;
+    struct mp_audio *r = &priv->temp;
+
+    *r = *af->data;
+    r->audio = data->audio;
+    r->len = data->len;
+
+    return r;
+}
+
+static void uninit(struct af_instance *af)
+{
+    talloc_free(af->setup);
+}
+
+static int af_open(struct af_instance *af)
+{
+    af->control = control;
+    af->uninit = uninit;
+    af->play = play;
+    af->mul = 1;
+    struct priv *priv = talloc(NULL, struct priv);
+    af->setup = priv;
+    *priv = defaults;
+    priv->config = m_config_simple(priv);
+    talloc_steal(priv, priv->config);
+    m_config_register_options(priv->config, options);
+    af->data = &priv->data;
+    return AF_OK;
+}
+
+struct af_info af_info_force = {
+    "Force audio format",
+    "force",
+    "",
+    "",
+    0,
+    af_open
+};