input: decoder: add cc.lock for sub-decoders

Sub-decoders are decoders whose state is defined by previous decoders.
Specifically in the current case, picture frames with specific SEI data
can convey subtitles as closed captions and report them from the decoder
implementation itself.

Since the core never locks the implementation, and the implementation
can be asynchronously reporting subtitles, a common lock need to be
setup so that the core can then check and use the sub-decoders being
created without racing against the upper decoder implementation.

Co-authored-by: François Cartegnie <fcvlcdev@free.fr>

src/input/decoder.c

@@ -169,6 +169,7 @@ struct vlc_input_decoder_t
 #define MAX_CC_DECODERS 64 /* The es_out only creates one type of es */
     struct
     {
+        vlc_mutex_t lock;
         bool b_supported;
         decoder_cc_desc_t desc;
         vlc_input_decoder_t *pp_decoder[MAX_CC_DECODERS];
@@ -996,6 +997,7 @@ static void DecoderPlayCc( vlc_input_decoder_t *p_owner, vlc_frame_t *p_cc,
 {
     vlc_mutex_lock( &p_owner->lock );
 
+    vlc_mutex_lock(&p_owner->cc.lock);
     p_owner->cc.desc = *p_desc;
 
     /* Fanout data to all decoders. We do not know if es_out
@@ -1019,6 +1021,7 @@ static void DecoderPlayCc( vlc_input_decoder_t *p_owner, vlc_frame_t *p_cc,
             p_cc = NULL; /* was last dec */
         }
     }
+    vlc_mutex_unlock(&p_owner->cc.lock);
 
     vlc_mutex_unlock( &p_owner->lock );
 
@@ -1509,6 +1512,7 @@ static void DecoderThread_Flush( vlc_input_decoder_t *p_owner )
         p_dec->pf_flush( p_dec );
 
     /* flush CC sub decoders */
+    vlc_mutex_lock(&p_owner->cc.lock);
     if( p_owner->cc.b_supported )
     {
         for( int i=0; i<MAX_CC_DECODERS; i++ )
@@ -1520,6 +1524,7 @@ static void DecoderThread_Flush( vlc_input_decoder_t *p_owner )
             vlc_input_decoder_Flush(p_ccowner);
         }
     }
+    vlc_mutex_unlock(&p_owner->cc.lock);
 
     vlc_mutex_lock( &p_owner->lock );
 #ifdef ENABLE_SOUT
@@ -1975,6 +1980,7 @@ CreateDecoder( vlc_object_t *p_parent, const struct vlc_input_decoder_cfg *cfg )
     }
 
     /* */
+    vlc_mutex_init(&p_owner->cc.lock);
     p_owner->cc.b_supported = ( cfg->sout == NULL );
 
     p_owner->cc.desc.i_608_channels = 0;
@@ -2448,8 +2454,12 @@ int vlc_input_decoder_SetCcState( vlc_input_decoder_t *p_owner, vlc_fourcc_t cod
     decoder_t *p_dec = &p_owner->dec;
     //msg_Warn( p_dec, "vlc_input_decoder_SetCcState: %d @%x", b_decode, i_channel );
 
+    vlc_mutex_lock(&p_owner->cc.lock);
     if( !vlc_input_decoder_HasCCChanFlag( p_owner, codec, i_channel ) )
+    {
+        vlc_mutex_unlock(&p_owner->cc.lock);
         return VLC_EGENERIC;
+    }
 
     if( b_decode )
     {
@@ -2477,32 +2487,31 @@ int vlc_input_decoder_SetCcState( vlc_input_decoder_t *p_owner, vlc_fourcc_t cod
             vlc_dialog_display_error( p_dec,
                 _("Streaming / Transcoding failed"), "%s",
                 _("VLC could not open the decoder module.") );
+            vlc_mutex_unlock(&p_owner->cc.lock);
             return VLC_EGENERIC;
         }
         else if( !p_ccowner->dec.p_module )
         {
             DecoderUnsupportedCodec( p_dec, &fmt, true );
             vlc_input_decoder_Delete(p_ccowner);
+            vlc_mutex_unlock(&p_owner->cc.lock);
             return VLC_EGENERIC;
         }
         p_ccowner->p_clock = p_owner->p_clock;
 
-        vlc_mutex_lock( &p_owner->lock );
         p_owner->cc.pp_decoder[i_channel] = p_ccowner;
-        vlc_mutex_unlock( &p_owner->lock );
     }
     else
     {
         vlc_input_decoder_t *p_cc;
 
-        vlc_mutex_lock( &p_owner->lock );
         p_cc = p_owner->cc.pp_decoder[i_channel];
         p_owner->cc.pp_decoder[i_channel] = NULL;
-        vlc_mutex_unlock( &p_owner->lock );
 
         if( p_cc )
             vlc_input_decoder_Delete(p_cc);
     }
+    vlc_mutex_unlock(&p_owner->cc.lock);
     return VLC_SUCCESS;
 }