diff --git a/apps/beep.c b/apps/beep.c
index 3b02e5d8a3..0152900bfc 100644
--- a/apps/beep.c
+++ b/apps/beep.c
@@ -54,7 +54,7 @@ beep_get_more(const void **start, size_t *size)
     {
         count = MIN(count, BEEP_BUF_COUNT);
         beep_count -= count;
-        *start = (unsigned char *)beep_buf;
+        *start = beep_buf;
         *size = count * 2 * sizeof (int16_t);
         beep_generate((void *)beep_buf, count, &beep_phase,
                       beep_step, beep_amplitude);
diff --git a/apps/misc.c b/apps/misc.c
index ca99a1d9ac..3cb314fc51 100644
--- a/apps/misc.c
+++ b/apps/misc.c
@@ -42,7 +42,6 @@
 #include "usb_screen.h"
 #include "talk.h"
 #include "audio.h"
-#include "mp3_playback.h"
 #include "settings.h"
 #include "storage.h"
 #include "ata_idle_notify.h"
@@ -88,6 +87,8 @@
 #include "playback.h"
 #if CONFIG_CODEC == SWCODEC
 #include "voice_thread.h"
+#else
+#include "mp3_playback.h"
 #endif
 
 #ifdef BOOTFILE
diff --git a/apps/mpeg.c b/apps/mpeg.c
index b3e79aadd9..0ecf68fc53 100644
--- a/apps/mpeg.c
+++ b/apps/mpeg.c
@@ -876,7 +876,7 @@ static void reset_mp3_buffer(void)
 }
 
  /* DMA transfer end interrupt callback */
-static void transfer_end(unsigned char** ppbuf, size_t* psize)
+static void transfer_end(const void** ppbuf, size_t* psize)
 {
     if(playing && !paused)
     {
diff --git a/apps/plugin.h b/apps/plugin.h
index cd2440abdc..8123414ff0 100644
--- a/apps/plugin.h
+++ b/apps/plugin.h
@@ -637,8 +637,8 @@ struct plugin_api {
                                          unsigned int band_setting);
 #endif /* AUDIOHW_HAVE_EQ */
 #if (CONFIG_PLATFORM & PLATFORM_NATIVE)
-    void (*mp3_play_data)(const unsigned char* start, int size,
-                          void (*get_more)(unsigned char** start, size_t* size));
+    void (*mp3_play_data)(const void* start, size_t size,
+                          mp3_play_callback_t get_more);
     void (*mp3_play_pause)(bool play);
     void (*mp3_play_stop)(void);
     bool (*mp3_is_playing)(void);
diff --git a/apps/plugins/chip8.c b/apps/plugins/chip8.c
index 0e1b9c5213..b2faed5d80 100644
--- a/apps/plugins/chip8.c
+++ b/apps/plugins/chip8.c
@@ -1268,7 +1268,7 @@ static unsigned char beep[]={255,
 111,181,184,144, 17,148, 21,101,166,227,100, 86, 85, 85, 85}; 
 
 /* callback to request more mp3 data */
-static void callback(unsigned char** start, size_t* size)
+static void callback(const void** start, size_t* size)
 {
     *start = beep; /* give it the same frame again */
     *size = sizeof(beep);
diff --git a/apps/plugins/metronome.c b/apps/plugins/metronome.c
index 297405571f..54af82fa76 100644
--- a/apps/plugins/metronome.c
+++ b/apps/plugins/metronome.c
@@ -683,7 +683,7 @@ int bpm_step_counter = 0;
 #define MET_IS_PLAYING rb->mp3_is_playing()
 #define MET_PLAY_STOP rb->mp3_play_stop()
 
-static void callback(unsigned char** start, size_t* size)
+static void callback(const void** start, size_t* size)
 {
     (void)start; /* unused parameter, avoid warning */
     *size = 0; /* end of data */
diff --git a/apps/plugins/video.c b/apps/plugins/video.c
index 9053ae7fb0..6a66324a79 100644
--- a/apps/plugins/video.c
+++ b/apps/plugins/video.c
@@ -448,7 +448,7 @@ static void timer4_isr(void)
 
 
 /* ISR function to get more mp3 data */
-static void GetMoreMp3(unsigned char** start, size_t* size)
+static void GetMoreMp3(const void** start, size_t* size)
 {
     int available;
     int advance;
diff --git a/apps/talk.c b/apps/talk.c
index ba2050a9ca..4b0975083d 100644
--- a/apps/talk.c
+++ b/apps/talk.c
@@ -401,8 +401,8 @@ load_err:
 }
 
 
-/* called in ISR context if mp3 data got consumed */
-static void mp3_callback(unsigned char** start, size_t* size)
+/* called in ISR context (on HWCODEC) if mp3 data got consumed */
+static void mp3_callback(const void** start, size_t* size)
 {
     queue[queue_read].len -= sent; /* we completed this */
     queue[queue_read].buf += sent;
diff --git a/apps/voice_thread.c b/apps/voice_thread.c
index 5d23a74cbc..56d67a2284 100644
--- a/apps/voice_thread.c
+++ b/apps/voice_thread.c
@@ -117,9 +117,9 @@ enum voice_thread_messages
 struct voice_info
 {
     /* Callback to get more clips */
-    void (*get_more)(unsigned char** start, size_t* size);
+    mp3_play_callback_t get_more;
     /* Start of clip */
-    unsigned char *start;
+    const void *start;
     /* Size of clip */
     size_t size;
 };
@@ -200,15 +200,15 @@ static void voice_buf_commit(size_t size)
 }
 
 /* Stop any current clip and start playing a new one */
-void mp3_play_data(const unsigned char* start, int size,
-                   void (*get_more)(unsigned char** start, size_t* size))
+void mp3_play_data(const void *start, size_t size,
+                   mp3_play_callback_t get_more)
 {
-    if (get_more != NULL && start != NULL && (ssize_t)size > 0)
+    if (get_more != NULL && start != NULL && size > 0)
     {
         struct voice_info voice_clip =
         {
             .get_more = get_more,
-            .start    = (unsigned char *)start,
+            .start    = start,
             .size     = size,
         };
 
@@ -312,7 +312,8 @@ static enum voice_state voice_message(struct voice_thread_data *td)
         td->st = speex_decoder_init(&speex_wb_mode);
 
         /* Make bit buffer use our own buffer */
-        speex_bits_set_bit_buffer(&td->bits, td->vi.start, td->vi.size);
+        speex_bits_set_bit_buffer(&td->bits, (void *)td->vi.start,
+                                  td->vi.size);
         speex_decoder_ctl(td->st, SPEEX_GET_LOOKAHEAD, &td->lookahead);
 
         return VOICE_STATE_DECODE;
@@ -361,10 +362,11 @@ static enum voice_state voice_decode(struct voice_thread_data *td)
         if (td->vi.get_more != NULL)
             td->vi.get_more(&td->vi.start, &td->vi.size);
 
-        if (td->vi.start != NULL && (ssize_t)td->vi.size > 0)
+        if (td->vi.start != NULL && td->vi.size > 0)
         {
             /* Make bit buffer use our own buffer */
-            speex_bits_set_bit_buffer(&td->bits, td->vi.start, td->vi.size);
+            speex_bits_set_bit_buffer(&td->bits, (void *)td->vi.start,
+                                      td->vi.size);
             /* Don't skip any samples when we're stringing clips together */
             td->lookahead = 0;
         }
diff --git a/apps/voice_thread.h b/apps/voice_thread.h
index 49b2f3f930..4e4af1fc5c 100644
--- a/apps/voice_thread.h
+++ b/apps/voice_thread.h
@@ -23,8 +23,10 @@
 
 #include "config.h"
 
-void mp3_play_data(const unsigned char* start, int size,
-                   void (*get_more)(unsigned char** start, size_t* size));
+typedef void (*mp3_play_callback_t)(const void **start, size_t *size);
+
+void mp3_play_data(const void *start, size_t size,
+                   mp3_play_callback_t get_more);
 void mp3_play_stop(void);
 void mp3_play_pause(bool play);
 bool mp3_is_playing(void);
diff --git a/firmware/export/mp3_playback.h b/firmware/export/mp3_playback.h
index 6fdaa31cac..de27a2a46d 100644
--- a/firmware/export/mp3_playback.h
+++ b/firmware/export/mp3_playback.h
@@ -26,6 +26,9 @@
 
 #include <stdbool.h>
 
+/* callback fn */
+typedef void (*mp3_play_callback_t)(const void **start, size_t* size);
+
 /* functions formerly in mpeg.c */
 void mp3_init(int volume, int bass, int treble, int balance, int loudness,
               int avc, int channel_config, int stereo_width,
@@ -42,9 +45,8 @@ void demand_irq_enable(bool on);
 #if CONFIG_CODEC == MAS3587F
 void mp3_play_init(void);
 #endif
-void mp3_play_data(const unsigned char* start, int size,
-    void (*get_more)(unsigned char** start, size_t* size) /* callback fn */
-);
+void mp3_play_data(const void* start, size_t size,
+                   mp3_play_callback_t get_more);
 void mp3_play_pause(bool play);
 bool mp3_pause_done(void);
 void mp3_play_stop(void);
diff --git a/firmware/target/sh/archos/audio-archos.c b/firmware/target/sh/archos/audio-archos.c
index 9dfcb9cb97..2c2579bec5 100644
--- a/firmware/target/sh/archos/audio-archos.c
+++ b/firmware/target/sh/archos/audio-archos.c
@@ -53,7 +53,7 @@ static bool paused; /* playback is paused */
 static bool playing; /* We are playing an MP3 stream */
 
 /* the registered callback function to ask for more mp3 data */
-static void (*callback_for_more)(unsigned char**, size_t*);
+static mp3_play_callback_t callback_for_more;
 
 /* list of tracks in memory */
 #define MAX_ID3_TAGS (1<<4) /* Must be power of 2 */
@@ -156,7 +156,7 @@ static void play_tick(void)
 void DEI3(void) __attribute__((interrupt_handler));
 void DEI3(void)
 {
-    unsigned char* start;
+    const void* start;
     size_t size = 0;
 
     if (callback_for_more != NULL)
@@ -469,9 +469,8 @@ void mp3_play_init(void)
 }
 #endif
 
-void mp3_play_data(const unsigned char* start, int size,
-    void (*get_more)(unsigned char** start, size_t* size) /* callback fn */
-)
+void mp3_play_data(const void* start, size_t size,
+                   mp3_play_callback_t get_more)
 {
     /* init DMA */
     DAR3 = 0x5FFFEC3;
diff --git a/uisimulator/common/stubs.c b/uisimulator/common/stubs.c
index 2a81587d83..1404c1e21b 100644
--- a/uisimulator/common/stubs.c
+++ b/uisimulator/common/stubs.c
@@ -36,6 +36,8 @@
 static bool storage_spinning = false;
 
 #if CONFIG_CODEC != SWCODEC
+#include "mp3_playback.h"
+
 void audio_set_buffer_margin(int seconds)
 {
      (void)seconds;
@@ -92,9 +94,8 @@ unsigned char* mp3_get_pos(void)
     return NULL;
 }
 
-void mp3_play_data(const unsigned char* start, int size,
-    void (*get_more)(unsigned char** start, size_t* size) /* callback fn */
-)
+void mp3_play_data(const void* start, size_t size,
+                   mp3_play_callback_t get_more)
 {
     (void)start; (void)size; (void)get_more;
 }