codal_port/modaudio: Always round up AudioFrame size to chunk size.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/modaudio.c

@@ -332,8 +332,6 @@ STATIC mp_obj_t microbit_audio_frame_new(const mp_obj_type_t *type_in, size_t n_
         mp_raise_ValueError(MP_ERROR_TEXT("size out of bounds"));
     } else {
         size = args[ARG_duration].u_int * rate / 1000;
-        // Round up the size to the nearest AUDIO_CHUNK_SIZE.
-        size = (size + AUDIO_CHUNK_SIZE - 1) & ~(AUDIO_CHUNK_SIZE - 1);
     }
 
     return microbit_audio_frame_make_new(size, rate);
@@ -522,6 +520,10 @@ MP_DEFINE_CONST_OBJ_TYPE(
     );
 
 microbit_audio_frame_obj_t *microbit_audio_frame_make_new(size_t size, uint32_t rate) {
+    // Round up the size to the nearest AUDIO_CHUNK_SIZE.
+    // This is needed to simplify the playback code, which works in chunks of size AUDIO_CHUNK_SIZE.
+    size = (size + AUDIO_CHUNK_SIZE - 1) & ~(AUDIO_CHUNK_SIZE - 1);
+
     microbit_audio_frame_obj_t *res = m_new_obj_var(microbit_audio_frame_obj_t, data, uint8_t, size);
     res->base.type = &microbit_audio_frame_type;
     res->alloc_size = size;