2 files changed, 31 insertions, 1 deletions

diff --git a/firmware/export/pcm_mixer.h b/firmware/export/pcm_mixer.h
index 69d2b894df..d424083002 100644
--- a/firmware/export/pcm_mixer.h
+++ b/firmware/export/pcm_mixer.h
@@ -106,7 +106,8 @@ enum channel_status mixer_channel_status(enum pcm_mixer_channel channel);
 size_t mixer_channel_get_bytes_waiting(enum pcm_mixer_channel channel);
 
 /* Return pointer to channel's playing audio data and the size remaining */
-const void * mixer_channel_get_buffer(enum pcm_mixer_channel channel, int *count);
+const void * mixer_channel_get_buffer(enum pcm_mixer_channel channel,
+                                      int *count);
 
 /* Calculate peak values for channel */
 void mixer_channel_calculate_peaks(enum pcm_mixer_channel channel,
@@ -116,6 +117,13 @@ void mixer_channel_calculate_peaks(enum pcm_mixer_channel channel,
 void mixer_adjust_channel_address(enum pcm_mixer_channel channel,
                                   off_t offset);
 
+/* Set a hook that is called upon getting a new source buffer for a channel
+   NOTE: Called for each buffer, not each mixer chunk */
+typedef void (*chan_buffer_hook_fn_type)(const void *start, size_t size);
+
+void mixer_channel_set_buffer_hook(enum pcm_mixer_channel channel,
+                                   chan_buffer_hook_fn_type fn);
+
 /* Stop ALL channels and PCM and reset state */
 void mixer_reset(void);
 
diff --git a/firmware/pcm_mixer.c b/firmware/pcm_mixer.c
index cddff431ec..34852e97e9 100644
--- a/firmware/pcm_mixer.c
+++ b/firmware/pcm_mixer.c
@@ -45,6 +45,7 @@ struct mixer_channel
     pcm_play_callback_type get_more; /* Registered callback */
     enum channel_status status;      /* Playback status */
     uint32_t amplitude;              /* Amp. factor: 0x0000 = mute, 0x10000 = unity */
+    chan_buffer_hook_fn_type buffer_hook; /* Callback for new buffer */
 };
 
 /* Forget about boost here for the moment */
@@ -106,6 +107,12 @@ static void mixer_pcm_callback(const void **addr, size_t *size)
     *size = next_size;
 }
 
+static inline void chan_call_buffer_hook(struct mixer_channel *chan)
+{
+    if (UNLIKELY(chan->buffer_hook))
+        chan->buffer_hook(chan->start, chan->size);
+}
+
 /* Buffering callback - calls sub-callbacks and mixes the data for next
    buffer to be sent from mixer_pcm_callback() */
 static enum pcm_dma_status MIXER_CALLBACK_ICODE
@@ -149,6 +156,8 @@ fill_frame:
                 channel_stopped(chan);
                 continue;
             }
+
+            chan_call_buffer_hook(chan);
         }
 
         /* Channel will play for at least part of this frame */
@@ -298,6 +307,7 @@ void mixer_channel_play_data(enum pcm_mixer_channel channel,
         chan->get_more = get_more;
 
         mixer_activate_channel(chan);
+        chan_call_buffer_hook(chan);
         mixer_start_pcm();
     }
     else
@@ -406,6 +416,18 @@ void mixer_adjust_channel_address(enum pcm_mixer_channel channel,
     pcm_play_unlock();
 }
 
+/* Set a hook that is called upon getting a new source buffer for a channel
+   NOTE: Called for each buffer, not each mixer chunk */
+void mixer_channel_set_buffer_hook(enum pcm_mixer_channel channel,
+                                   chan_buffer_hook_fn_type fn)
+{
+    struct mixer_channel *chan = &channels[channel];
+
+    pcm_play_lock();
+    chan->buffer_hook = fn;
+    pcm_play_unlock();
+}
+
 /* Stop ALL channels and PCM and reset state */
 void mixer_reset(void)
 {