options: add option to prevent decoder audio downmixing

Also rename --a52drc to --ad-lavc-ac3drc, and add --ad-lavc-o.

DOCS/man/en/changes.rst

@@ -124,6 +124,7 @@ Command line switches
     -afm hwac3                          --ad=spdif:ac3,spdif:dts
     -x W, -y H                          --geometry=WxH + --no-keepaspect
     -xy W                               --autofit=W
+    -a52drc level                       --ad-lavc-ac3drc=level
     =================================== ===================================
 
 *NOTE*: ``-opt val`` becomes ``--opt=val``.

DOCS/man/en/options.rst

@@ -1,11 +1,3 @@
---a52drc=<level>
-    Select the Dynamic Range Compression level for AC-3 audio streams. <level>
-    is a float value ranging from 0 to 1, where 0 means no compression and 1
-    (which is the default) means full compression (make loud passages more
-    silent and vice versa). Values up to 2 are also accepted, but are purely
-    experimental. This option only shows an effect if the AC-3 stream contains
-    the required range compression information.
-
 --abs=<value>
     (``--ao=oss`` only) (OBSOLETE)
     Override audio driver/card buffer size detection.
@@ -37,6 +29,25 @@
     ``--ad=help``
         List all available decoders.
 
+--ad-lavc-ac3drc=<level>
+    Select the Dynamic Range Compression level for AC-3 audio streams. <level>
+    is a float value ranging from 0 to 1, where 0 means no compression and 1
+    (which is the default) means full compression (make loud passages more
+    silent and vice versa). Values up to 2 are also accepted, but are purely
+    experimental. This option only shows an effect if the AC-3 stream contains
+    the required range compression information.
+
+--ad-lavc-downmix=<yes|no>
+    Whether to request audio channel downmixing from the decoder (default: yes).
+    Some decoders, like AC-3, AAC and DTS, can remix audio on decoding. The
+    requested number of output channels is set with the ``--channels`` option.
+    Useful for playing surround audio on a stereo system.
+
+--ad-lavc-o=<key>=<value>[,<key>=<value>[,...]]
+    Pass AVOptions to libavcodec decoder. Note, a patch to make the o=
+    unneeded and pass all unknown options through the AVOption system is
+    welcome. A full list of AVOptions can be found in the FFmpeg manual.
+
 --af=<filter1[=parameter1:parameter2:...],filter2,...>
     Specify a list of audio filters to apply to the audio stream. See
     `audio_filters` for details and descriptions of the available filters.

audio/decode/ad_lavc.c

@@ -32,6 +32,7 @@
 #include "core/codecs.h"
 #include "core/mp_msg.h"
 #include "core/options.h"
+#include "core/av_opts.h"
 
 #include "ad_internal.h"
 #include "audio/reorder_ch.h"
@@ -52,6 +53,15 @@ struct priv {
     int previous_data_left;  // input demuxer packet data
 };
 
+#define OPT_BASE_STRUCT struct MPOpts
+
+const m_option_t ad_lavc_decode_opts_conf[] = {
+    OPT_FLOATRANGE("ac3drc", ad_lavc_param.ac3drc, 0, 0, 2),
+    OPT_FLAG("downmix", ad_lavc_param.downmix, 0),
+    OPT_STRING("o", ad_lavc_param.avopt, 0),
+    {0}
+};
+
 struct pcm_map
 {
     int tag;
@@ -190,7 +200,8 @@ static void set_from_wf(AVCodecContext *avctx, WAVEFORMATEX *wf)
 
 static int init(sh_audio_t *sh_audio, const char *decoder)
 {
-    struct MPOpts *opts = sh_audio->opts;
+    struct MPOpts *mpopts = sh_audio->opts;
+    struct ad_lavc_param *opts = &mpopts->ad_lavc_param;
     AVCodecContext *lavc_context;
     AVCodec *lavc_codec;
 
@@ -216,12 +227,22 @@ static int init(sh_audio_t *sh_audio, const char *decoder)
     lavc_context->codec_type = AVMEDIA_TYPE_AUDIO;
     lavc_context->codec_id = lavc_codec->id;
 
-    lavc_context->request_channels = opts->audio_output_channels;
+    if (opts->downmix)
+        lavc_context->request_channels = mpopts->audio_output_channels;
 
     // Always try to set - option only exists for AC3 at the moment
-    av_opt_set_double(lavc_context, "drc_scale", opts->drc_level,
+    av_opt_set_double(lavc_context, "drc_scale", opts->ac3drc,
                       AV_OPT_SEARCH_CHILDREN);
 
+    if (opts->avopt) {
+        if (parse_avopts(lavc_context, opts->avopt) < 0) {
+            mp_msg(MSGT_DECVIDEO, MSGL_ERR,
+                   "ad_lavc: setting AVOptions '%s' failed.\n", opts->avopt);
+            uninit(sh_audio);
+            return 0;
+        }
+    }
+
     lavc_context->codec_tag = sh_audio->format;
     lavc_context->sample_rate = sh_audio->samplerate;
     lavc_context->bit_rate = sh_audio->i_bps * 8;

core/cfg-mplayer.h

@@ -276,6 +276,7 @@ const m_option_t msgl_config[]={
 };
 
 extern const m_option_t lavc_decode_opts_conf[];
+extern const m_option_t ad_lavc_decode_opts_conf[];
 
 #define OPT_BASE_STRUCT struct MPOpts
 
@@ -424,8 +425,6 @@ const m_option_t common_opts[] = {
     // ignore header-specified delay (dwStart)
     OPT_FLAG("ignore-start", ignore_start, 0),
 
-    OPT_FLOATRANGE("a52drc", drc_level, 0, 0, 2),
-
 // ------------------------- codec/vfilter options --------------------
 
     // MP3-only: select stereo/left/right
@@ -466,6 +465,8 @@ const m_option_t common_opts[] = {
 
     {"lavdopts", (void *) lavc_decode_opts_conf, CONF_TYPE_SUBCONFIG, 0, 0, 0, NULL},
     {"lavfdopts", (void *) lavfdopts_conf, CONF_TYPE_SUBCONFIG, 0, 0, 0, NULL},
+
+    {"ad-lavc", (void *) ad_lavc_decode_opts_conf, CONF_TYPE_SUBCONFIG},
 // ------------------------- subtitles options --------------------
 
     OPT_STRINGLIST("sub", sub_name, 0),

core/defaultopts.c

@@ -74,7 +74,6 @@ void set_default_mplayer_options(struct MPOpts *opts)
         .audio_output_channels = 2,
         .audio_output_format = -1,  // AF_FORMAT_UNKNOWN
         .playback_speed = 1.,
-        .drc_level = 1.,
         .movie_aspect = -1.,
         .sub_auto = 1,
         .osd_bar_visible = 1,
@@ -90,6 +89,10 @@ void set_default_mplayer_options(struct MPOpts *opts)
             .workaround_bugs = 1, // autodetect
             .error_concealment = 3,
         },
+        .ad_lavc_param = {
+            .ac3drc = 1.,
+            .downmix = 1,
+        },
         .input = {
              .key_fifo_size = 7,
              .ar_delay = 100,

core/mplayer.c

@@ -1562,8 +1562,8 @@ void reinit_audio_chain(struct MPContext *mpctx)
         mpctx->ao = ao_create(opts, mpctx->input);
         mpctx->ao->samplerate = opts->force_srate;
         mpctx->ao->format = opts->audio_output_format;
-        if (mpctx->sh_audio->channels != opts->audio_output_channels &&
-            opts->audio_output_channels == 2)
+        // Automatic downmix
+        if (opts->audio_output_channels == 2 && mpctx->sh_audio->channels != 2)
             mpctx->ao->channels = 2;
     }
     ao = mpctx->ao;

core/options.h

@@ -155,7 +155,6 @@ typedef struct MPOpts {
     int force_srate;
     int dtshd;
     float playback_speed;
-    float drc_level;
     struct m_obj_settings *vf_settings;
     float movie_aspect;
     int flip;
@@ -204,6 +203,12 @@ typedef struct MPOpts {
         char *avopt;
     } lavc_param;
 
+    struct ad_lavc_param {
+        float ac3drc;
+        int downmix;
+        char *avopt;
+    } ad_lavc_param;
+
     struct lavfdopts {
         int probesize;
         int probescore;