af: add metadata field to af_stream and af_instance

This allows to propagate metadata information to audio filters.

Closes #632

audio/decode/dec_audio.c

@@ -213,6 +213,8 @@ int audio_init_filters(struct dec_audio *d_audio, int in_samplerate,
     mp_audio_set_channels(&afs->output, out_channels);
     mp_audio_set_format(&afs->output, *out_format);
 
+    afs->metadata = d_audio->metadata;
+
     char *s_from = mp_audio_config_to_str(&afs->input);
     char *s_to = mp_audio_config_to_str(&afs->output);
     MP_VERBOSE(d_audio, "Building audio filter chain for %s -> %s...\n", s_from, s_to);

audio/decode/dec_audio.h

@@ -21,6 +21,7 @@
 
 #include "audio/chmap.h"
 #include "audio/audio.h"
+#include "demux/demux.h"
 #include "demux/stheader.h"
 
 struct mp_audio_buffer;
@@ -35,6 +36,7 @@ struct dec_audio {
     struct mp_audio_buffer *decode_buffer;
     struct af_stream *afilter;
     char *decoder_desc;
+    struct mp_tags *metadata;
     // set by decoder
     struct mp_audio decoded;    // format of decoded audio (no data, temporarily
                                 // different from decode_buffer during format

audio/filter/af.c

@@ -204,6 +204,7 @@ static struct af_instance *af_create(struct af_stream *s, char *name,
         .mul = 1,
         .data = talloc_zero(af, struct mp_audio),
         .log = mp_log_new(af, s->log, name),
+        .metadata = s->metadata,
     };
     struct m_config *config = m_config_from_obj_desc(af, s->log, &desc);
     if (m_config_apply_defaults(config, name, s->opts->af_defs) < 0)

audio/filter/af.h

@@ -59,6 +59,7 @@ struct af_info {
 struct af_instance {
     const struct af_info *info;
     struct mp_log *log;
+    struct mp_tags *metadata;
     int (*control)(struct af_instance *af, int cmd, void *arg);
     void (*uninit)(struct af_instance *af);
     /* flags is a bit mask of AF_FILTER_FLAG_* values
@@ -90,6 +91,7 @@ struct af_stream {
 
     struct mp_log *log;
     struct MPOpts *opts;
+    struct mp_tags *metadata;
 };
 
 // Return values

player/audio.c

@@ -125,6 +125,7 @@ void reinit_audio_chain(struct MPContext *mpctx)
         mpctx->d_audio->global = mpctx->global;
         mpctx->d_audio->opts = opts;
         mpctx->d_audio->header = sh;
+        mpctx->d_audio->metadata = mpctx->demuxer->metadata;
         if (!audio_init_best_codec(mpctx->d_audio, opts->audio_decoders))
             goto init_error;
     }