audio: add AVChannelLayout helpers to convert from/to mp_chmap

This is the new FFmpeg channel layout structure, which now
combines channel count and layout into a single location.

Only unspecified (channel count only) and native (channel layout
mask based) layouts are currently supported for the initial move
towards non-deprecated APIs.

audio/chmap_avchannel.c

@@ -0,0 +1,51 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv 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.
+ *
+ * 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libavutil/channel_layout.h>
+
+#include "chmap.h"
+#include "chmap_avchannel.h"
+
+bool mp_chmap_from_av_layout(struct mp_chmap *dst, const AVChannelLayout *src)
+{
+    *dst = (struct mp_chmap) {0};
+
+    switch (src->order) {
+    case AV_CHANNEL_ORDER_UNSPEC:
+        mp_chmap_from_channels(dst, src->nb_channels);
+        return dst->num == src->nb_channels;
+    case AV_CHANNEL_ORDER_NATIVE:
+        mp_chmap_from_lavc(dst, src->u.mask);
+        return dst->num == src->nb_channels;
+    default:
+        // TODO: handle custom layouts
+        return false;
+    }
+}
+
+void mp_chmap_to_av_layout(AVChannelLayout *dst, const struct mp_chmap *src)
+{
+    *dst = (AVChannelLayout){
+        .order = AV_CHANNEL_ORDER_UNSPEC,
+        .nb_channels = src->num,
+    };
+
+    // TODO: handle custom layouts
+    if (!mp_chmap_is_unknown(src)) {
+        av_channel_layout_from_mask(dst, mp_chmap_to_lavc(src));
+    }
+}

audio/chmap_avchannel.h

@@ -0,0 +1,32 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv 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.
+ *
+ * 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <libavutil/channel_layout.h>
+
+#include "config.h"
+
+#include "chmap.h"
+
+#if HAVE_AV_CHANNEL_LAYOUT
+
+bool mp_chmap_from_av_layout(struct mp_chmap *dst, const AVChannelLayout *src);
+
+void mp_chmap_to_av_layout(AVChannelLayout *dst, const struct mp_chmap *src);
+
+#endif

meson.build

@@ -15,9 +15,11 @@ build_root = meson.project_build_root()
 source_root = meson.project_source_root()
 python = find_program('python3')
 
+avutil = dependency('libavutil', version: '>= 56.12.100')
+
 ffmpeg = {
     'name': 'ffmpeg',
-    'deps': [dependency('libavutil', version: '>= 56.12.100'),
+    'deps': [avutil,
              dependency('libavcodec', version: '>= 58.12.100'),
              dependency('libavformat', version: '>= 58.9.100'),
              dependency('libswscale', version: '>= 5.0.101'),
@@ -595,6 +597,12 @@ endif
 
 
 # misc dependencies
+av_ch_layout_available = avutil.version().version_compare('>= 57.24.100')
+if av_ch_layout_available
+    features += 'av-channel-layout'
+    sources += files('audio/chmap_avchannel.c')
+endif
+
 cdda_opt = get_option('cdda').require(
     get_option('gpl'),
     error_message: 'the build is not GPL!',
@@ -1696,6 +1704,7 @@ conf_data.set_quoted('FULLCONFIG', feature_str)
 conf_data.set10('HAVE_ALSA', alsa.found())
 conf_data.set10('HAVE_ANDROID', android)
 conf_data.set10('HAVE_AUDIOUNIT', audiounit['use'])
+conf_data.set10('HAVE_AV_CHANNEL_LAYOUT', av_ch_layout_available)
 conf_data.set10('HAVE_BSD_FSTATFS', bsd_fstatfs)
 conf_data.set10('HAVE_BSD_THREAD_NAME', bsd_thread_name)
 conf_data.set10('HAVE_CACA', caca.found())

wscript

@@ -411,6 +411,10 @@ libav_dependencies = [
         'req': True,
         'fmsg': "Unable to find development files for some of the required \
 FFmpeg libraries. Git master is recommended."
+    }, {
+        'name': 'av-channel-layout',
+        'desc': 'FFmpeg AVChannelLayout API',
+        'func': check_pkg_config('libavutil', '>= 57.24.100'),
     }, {
         'name': '--libavdevice',
         'desc': 'libavdevice',

wscript_build.py

@@ -230,6 +230,7 @@ def build(ctx):
         ## Audio
         ( "audio/aframe.c" ),
         ( "audio/chmap.c" ),
+        ( "audio/chmap_avchannel.c", "av-channel-layout" ),
         ( "audio/chmap_sel.c" ),
         ( "audio/decode/ad_lavc.c" ),
         ( "audio/decode/ad_spdif.c" ),