audio: add --audio-spdif as new method for enabling passthrough

This provides a new method for enabling spdif passthrough. The old
method via --ad (--ad=spdif:ac3 etc.) is deprecated. The deprecated
method will probably stop working at some point.

This also supports PCM fallback. One caveat is that it will lose at
least 1 audio packet in doing so. (I don't care enough to prevent this.)

(This is named after the old S/PDIF connector, because it uses the same
underlying technology as far as the higher level protoco is concerned.
Also, the user should be renamed that passthrough is backwards.)

DOCS/interface-changes.rst

@@ -20,6 +20,8 @@ Interface changes
 ::
 
  --- mpv 0.10.0 will be released ---
+    - deprecate --ad-spdif-dtshd and enabling passthrough via --ad
+      add --audio-spdif as replacement
     - remove "get_property" command
     - remove --slave-broken
     - add vo opengl custom shader suboptions (source-shader, scale-shader,

DOCS/man/options.rst

@@ -855,6 +855,25 @@ Audio
     ``--af-clr`` exist to modify a previously specified list, but you
     should not need these for typical use.
 
+``--audio-spdif=<codecs>``
+    List of codecs for which compressed audio passthrough should be used. This
+    works for both classic S/PDIF and HDMI.
+
+    Possible codecs are ``ac3``, ``dts``, ``dts-hd``. Multiple codecs can be
+    specified by separating them with ``,``. ``dts`` refers to low bitrate DTS
+    core, while ``dts-hd`` refers to DTS MA (receiver and OS support varies).
+    You should only use either ``dts`` or ``dts-hd`` (if both are specified,
+    and ``dts`` comes first, only ``dts`` will be used).
+
+    In general, all codecs in the ``spdif`` family listed with ``--ad=help``
+    are supported in theory.
+
+    .. admonition:: Warning
+
+        There is not much reason to use this. HDMI supports uncompressed
+        multichannel PCM, and mpv supports lossless DTS-HD decoding via
+        FFmpeg's libdcadec wrapper.
+
 ``--ad=<[+|-]family1:(*|decoder1),[+|-]family2:(*|decoder2),...[-]>``
     Specify a priority list of audio decoders to be used, according to their
     family and decoder name. Entries like ``family:*`` prioritize all decoders
@@ -882,6 +901,11 @@ Audio
         ``--ad=help``
             List all available decoders.
 
+    .. admonition:: Warning
+
+        Enabling compressed audio passthrough (AC3 and DTS via SPDIF/HDMI) with
+        this option is deprecated. Use ``--audio-spdif`` instead.
+
 ``--volume=<value>``
     Set the startup volume. 0 means silence, 100 means no volume reduction or
     amplification. A value of -1 (the default) will not change the volume. See
@@ -953,17 +977,12 @@ Audio
     welcome. A full list of AVOptions can be found in the FFmpeg manual.
 
 ``--ad-spdif-dtshd=<yes|no>``, ``--dtshd``, ``--no-dtshd``
-    When using DTS pass-through, output any DTS-HD track as-is.
-    With ``ad-spdif-dtshd=no`` (the default), only the DTS Core parts will be
-    output.
+    If DTS is passed through, use DTS-HD.
 
-    DTS-HD tracks can be sent over HDMI but not over the original
-    coax/TOSLINK S/PDIF system.
+    .. admonition:: Warning
 
-    Some receivers don't accept DTS core-only when ``--ad-spdif-dtshd=yes`` is
-    used, even though they accept DTS-HD.
-
-    ``--dtshd`` and ``--no-dtshd`` are deprecated aliases.
+        This and enabling passthrough via ``--ad`` are deprecated in favor of
+        using ``--audio-spdif=dts-hd``.
 
 ``--audio-channels=<number|layout>``
     Request a channel layout for audio output (default: auto). This  will ask

audio/decode/dec_audio.c

@@ -52,6 +52,7 @@ static const struct ad_functions * const ad_drivers[] = {
 
 static void uninit_decoder(struct dec_audio *d_audio)
 {
+    audio_reset_decoding(d_audio);
     if (d_audio->ad_driver) {
         MP_VERBOSE(d_audio, "Uninit audio decoder.\n");
         d_audio->ad_driver->uninit(d_audio);
@@ -59,6 +60,8 @@ static void uninit_decoder(struct dec_audio *d_audio)
     d_audio->ad_driver = NULL;
     talloc_free(d_audio->priv);
     d_audio->priv = NULL;
+    d_audio->afilter->initialized = -1;
+    d_audio->decode_format = (struct mp_audio){0};
 }
 
 static int init_audio_codec(struct dec_audio *d_audio, const char *decoder)
@@ -81,11 +84,21 @@ struct mp_decoder_list *audio_decoder_list(void)
     return list;
 }
 
-static struct mp_decoder_list *audio_select_decoders(const char *codec,
-                                                     char *selection)
+static struct mp_decoder_list *audio_select_decoders(struct dec_audio *d_audio)
 {
+    struct MPOpts *opts = d_audio->opts;
+    const char *codec = d_audio->header->codec;
+
     struct mp_decoder_list *list = audio_decoder_list();
-    struct mp_decoder_list *new = mp_select_decoders(list, codec, selection);
+    struct mp_decoder_list *new =
+        mp_select_decoders(list, codec, opts->audio_decoders);
+    if (d_audio->spdif_passthrough) {
+        struct mp_decoder_list *spdif =
+            mp_select_decoder_list(list, codec, "spdif", opts->audio_spdif);
+        mp_append_decoders(spdif, new);
+        talloc_free(new);
+        new = spdif;
+    }
     talloc_free(list);
     return new;
 }
@@ -99,14 +112,13 @@ static const struct ad_functions *find_driver(const char *name)
     return NULL;
 }
 
-int audio_init_best_codec(struct dec_audio *d_audio, char *audio_decoders)
+int audio_init_best_codec(struct dec_audio *d_audio)
 {
+    uninit_decoder(d_audio);
     assert(!d_audio->ad_driver);
-    audio_reset_decoding(d_audio);
 
     struct mp_decoder_entry *decoder = NULL;
-    struct mp_decoder_list *list =
-        audio_select_decoders(d_audio->header->codec, audio_decoders);
+    struct mp_decoder_list *list = audio_select_decoders(d_audio);
 
     mp_print_decoders(d_audio->log, MSGL_V, "Codec list:", list);
 

audio/decode/dec_audio.h

@@ -30,6 +30,7 @@ struct dec_audio {
     struct mp_log *log;
     struct MPOpts *opts;
     struct mpv_global *global;
+    bool spdif_passthrough;
     const struct ad_functions *ad_driver;
     struct sh_stream *header;
     struct af_stream *afilter;
@@ -57,7 +58,7 @@ enum {
 };
 
 struct mp_decoder_list *audio_decoder_list(void);
-int audio_init_best_codec(struct dec_audio *d_audio, char *audio_decoders);
+int audio_init_best_codec(struct dec_audio *d_audio);
 int audio_decode(struct dec_audio *d_audio, struct mp_audio_buffer *outbuf,
                  int minsamples);
 int initial_audio_decode(struct dec_audio *d_audio);

common/codecs.c

@@ -130,6 +130,28 @@ struct mp_decoder_list *mp_select_decoders(struct mp_decoder_list *all,
     return list;
 }
 
+// selection is a ","-separated list of decoders, all in the given family.
+struct mp_decoder_list *mp_select_decoder_list(struct mp_decoder_list *all,
+                                               const char *codec,
+                                               const char *family,
+                                               const char *selection)
+{
+    struct mp_decoder_list *list = talloc_zero(NULL, struct mp_decoder_list);
+    bstr sel = bstr0(selection);
+    while (sel.len) {
+        bstr decoder;
+        bstr_split_tok(sel, ",", &decoder, &sel);
+        add_new(list, find_decoder(all, bstr0(family), decoder), codec);
+    }
+    return list;
+}
+
+void mp_append_decoders(struct mp_decoder_list *list, struct mp_decoder_list *a)
+{
+    for (int n = 0; n < a->num_entries; n++)
+        add_new(list, &a->entries[n], NULL);
+}
+
 void mp_print_decoders(struct mp_log *log, int msgl, const char *header,
                        struct mp_decoder_list *list)
 {

common/codecs.h

@@ -37,6 +37,13 @@ struct mp_decoder_list *mp_select_decoders(struct mp_decoder_list *all,
                                            const char *codec,
                                            const char *selection);
 
+struct mp_decoder_list *mp_select_decoder_list(struct mp_decoder_list *all,
+                                               const char *codec,
+                                               const char *family,
+                                               const char *selection);
+
+void mp_append_decoders(struct mp_decoder_list *list, struct mp_decoder_list *a);
+
 struct mp_log;
 void mp_print_decoders(struct mp_log *log, int msgl, const char *header,
                        struct mp_decoder_list *list);

options/options.c

@@ -279,6 +279,8 @@ const m_option_t mp_opts[] = {
     OPT_STRING("ad", audio_decoders, 0),
     OPT_STRING("vd", video_decoders, 0),
 
+    OPT_STRING("audio-spdif", audio_spdif, 0),
+
     OPT_FLAG("ad-spdif-dtshd", dtshd, 0),
 
     OPT_CHOICE("hwdec", hwdec_api, 0,

options/options.h

@@ -109,6 +109,7 @@ typedef struct MPOpts {
 
     char *audio_decoders;
     char *video_decoders;
+    char *audio_spdif;
 
     int osd_level;
     int osd_duration;

player/audio.c

@@ -190,8 +190,9 @@ void reinit_audio_chain(struct MPContext *mpctx)
         mpctx->d_audio->pool = mp_audio_pool_create(mpctx->d_audio);
         mpctx->d_audio->afilter = af_new(mpctx->global);
         mpctx->d_audio->afilter->replaygain_data = sh->audio->replaygain_data;
+        mpctx->d_audio->spdif_passthrough = true;
         mpctx->ao_buffer = mp_audio_buffer_create(NULL);
-        if (!audio_init_best_codec(mpctx->d_audio, opts->audio_decoders))
+        if (!audio_init_best_codec(mpctx->d_audio))
             goto init_error;
         reset_audio_state(mpctx);
 
@@ -264,6 +265,18 @@ void reinit_audio_chain(struct MPContext *mpctx)
         }
 
         if (!mpctx->ao) {
+            // If spdif was used, try to fallback to PCM.
+            if (AF_FORMAT_IS_SPECIAL(afs->output.format) &&
+                mpctx->d_audio->spdif_passthrough)
+            {
+                mpctx->d_audio->spdif_passthrough = false;
+                if (!audio_init_best_codec(mpctx->d_audio))
+                    goto init_error;
+                reset_audio_state(mpctx);
+                reinit_audio_chain(mpctx);
+                return;
+            }
+
             MP_ERR(mpctx, "Could not open/initialize audio device -> no sound.\n");
             mpctx->error_playing = MPV_ERROR_AO_INIT_FAILED;
             goto init_error;

player/main.c

@@ -278,6 +278,10 @@ static bool handle_help_options(struct MPContext *mpctx)
         talloc_free(list);
         opt_exit = 1;
     }
+    if (opts->audio_spdif && strcmp(opts->audio_spdif, "help") == 0) {
+        MP_INFO(mpctx, "Choices: ac3,dts-hd,dts (and possibly more)\n");
+        opt_exit = 1;
+    }
     if (opts->video_decoders && strcmp(opts->video_decoders, "help") == 0) {
         struct mp_decoder_list *list = video_decoder_list();
         mp_print_decoders(log, MSGL_INFO, "Video decoders:", list);