Arduino support: reduce stack required

Author: pschatzmann

README.md

@@ -1,9 +1,9 @@
 # arduino-minimp3
 
-Minimalistic, single-header library for decoding MP3. minimp3 is designed to be
-small, fast (with SSE and NEON support), and accurate (ISO conformant). Further information can be found in the [oringal readme](README.original).
+Minimalistic, single-header library for decoding MP3. minimp3 is designed to be small, fast (with SSE and NEON support), and accurate (ISO conformant). Further information can be found in the [oringal readme](README.original).
+
+I have extended the project, so that it can be used as Arduino library. The result however is not very convincing: The decoder is too slow (e.g. on an ESP32) to decode any audio with a rate >= 32000 samples per second and the audio quality is quite poor. 
 
-I have extended the project so that it can be used as Arduino library.
 
 ### Installation in Arduino
 

minimp3.h

@@ -9,6 +9,49 @@
 #include <stdint.h>
 
 #define MINIMP3_MAX_SAMPLES_PER_FRAME (1152*2)
+#define MAX_BITRESERVOIR_BYTES      511
+#define MAX_FREE_FORMAT_FRAME_SIZE  2304    /* more than ISO spec's */
+#define MAX_L3_FRAME_PAYLOAD_BYTES  MAX_FREE_FORMAT_FRAME_SIZE /* MUST be >= 320000/8/32000*1152 = 1440 */
+
+#ifndef MINIMP3_STACK_OPT
+#define MINIMP3_STACK_OPT 1
+#endif
+
+typedef struct
+{
+    const uint8_t *buf;
+    int pos, limit;
+} bs_t;
+
+typedef struct
+{
+    float scf[3*64];
+    uint8_t total_bands, stereo_bands, bitalloc[64], scfcod[64];
+} L12_scale_info;
+
+typedef struct
+{
+    uint8_t tab_offset, code_tab_width, band_count;
+} L12_subband_alloc_t;
+
+typedef struct
+{
+    const uint8_t *sfbtab;
+    uint16_t part_23_length, big_values, scalefac_compress;
+    uint8_t global_gain, block_type, mixed_block_flag, n_long_sfb, n_short_sfb;
+    uint8_t table_select[3], region_count[3], subblock_gain[3];
+    uint8_t preflag, scalefac_scale, count1_table, scfsi;
+} L3_gr_info_t;
+
+
+typedef struct
+{
+    bs_t bs;
+    uint8_t maindata[MAX_BITRESERVOIR_BYTES + MAX_L3_FRAME_PAYLOAD_BYTES];
+    L3_gr_info_t gr_info[4];
+    float grbuf[2][576], scf[40], syn[18 + 15][2*32];
+    uint8_t ist_pos[2][39];
+} mp3dec_scratch_t;
 
 typedef struct
 {
@@ -20,6 +63,12 @@ typedef struct
     float mdct_overlap[2][9*32], qmf_state[15*2*32];
     int reserv, free_format_bytes;
     unsigned char header[4], reserv_buf[511];
+#if MINIMP3_STACK_OPT
+    mp3dec_scratch_t scratch;
+#  ifndef MINIMP3_ONLY_MP3
+    L12_scale_info sci;
+#  endif
+#endif
 } mp3dec_t;
 
 #ifdef __cplusplus
@@ -46,14 +95,11 @@ int mp3dec_decode_frame(mp3dec_t *dec, const uint8_t *mp3, int mp3_bytes, mp3d_s
 #include <stdlib.h>
 #include <string.h>
 
-#define MAX_FREE_FORMAT_FRAME_SIZE  2304    /* more than ISO spec's */
 #ifndef MAX_FRAME_SYNC_MATCHES
 #define MAX_FRAME_SYNC_MATCHES      10
 #endif /* MAX_FRAME_SYNC_MATCHES */
 
-#define MAX_L3_FRAME_PAYLOAD_BYTES  MAX_FREE_FORMAT_FRAME_SIZE /* MUST be >= 320000/8/32000*1152 = 1440 */
 
-#define MAX_BITRESERVOIR_BYTES      511
 #define SHORT_BLOCK_TYPE            2
 #define STOP_BLOCK_TYPE             3
 #define MODE_MONO                   3
@@ -203,40 +249,6 @@ static __inline__ __attribute__((always_inline)) int32_t minimp3_clip_int16_arm(
 #define HAVE_ARMV6 0
 #endif
 
-typedef struct
-{
-    const uint8_t *buf;
-    int pos, limit;
-} bs_t;
-
-typedef struct
-{
-    float scf[3*64];
-    uint8_t total_bands, stereo_bands, bitalloc[64], scfcod[64];
-} L12_scale_info;
-
-typedef struct
-{
-    uint8_t tab_offset, code_tab_width, band_count;
-} L12_subband_alloc_t;
-
-typedef struct
-{
-    const uint8_t *sfbtab;
-    uint16_t part_23_length, big_values, scalefac_compress;
-    uint8_t global_gain, block_type, mixed_block_flag, n_long_sfb, n_short_sfb;
-    uint8_t table_select[3], region_count[3], subblock_gain[3];
-    uint8_t preflag, scalefac_scale, count1_table, scfsi;
-} L3_gr_info_t;
-
-typedef struct
-{
-    bs_t bs;
-    uint8_t maindata[MAX_BITRESERVOIR_BYTES + MAX_L3_FRAME_PAYLOAD_BYTES];
-    L3_gr_info_t gr_info[4];
-    float grbuf[2][576], scf[40], syn[18 + 15][2*32];
-    uint8_t ist_pos[2][39];
-} mp3dec_scratch_t;
 
 static void bs_init(bs_t *bs, const uint8_t *data, int bytes)
 {
@@ -1715,7 +1727,13 @@ int mp3dec_decode_frame(mp3dec_t *dec, const uint8_t *mp3, int mp3_bytes, mp3d_s
     int i = 0, igr, frame_size = 0, success = 1;
     const uint8_t *hdr;
     bs_t bs_frame[1];
+#if MINIMP3_STACK_OPT
+    mp3dec_scratch_t *p_scratch = &(dec->scratch);
+    memset(p_scratch,0,sizeof(mp3dec_scratch_t));
+#else 
     mp3dec_scratch_t scratch;
+    mp3dec_scratch_t *p_scratch = &scratch;
+#endif
 
     if (mp3_bytes > 4 && dec->header[0] == 0xff && hdr_compare(dec->header, mp3))
     {
@@ -1758,40 +1776,45 @@ int mp3dec_decode_frame(mp3dec_t *dec, const uint8_t *mp3, int mp3_bytes, mp3d_s
 
     if (info->layer == 3)
     {
-        int main_data_begin = L3_read_side_info(bs_frame, scratch.gr_info, hdr);
+        int main_data_begin = L3_read_side_info(bs_frame, p_scratch->gr_info, hdr);
         if (main_data_begin < 0 || bs_frame->pos > bs_frame->limit)
         {
             mp3dec_init(dec);
             return 0;
         }
-        success = L3_restore_reservoir(dec, bs_frame, &scratch, main_data_begin);
+        success = L3_restore_reservoir(dec, bs_frame, p_scratch, main_data_begin);
         if (success)
         {
             for (igr = 0; igr < (HDR_TEST_MPEG1(hdr) ? 2 : 1); igr++, pcm += 576*info->channels)
             {
-                memset(scratch.grbuf[0], 0, 576*2*sizeof(float));
-                L3_decode(dec, &scratch, scratch.gr_info + igr*info->channels, info->channels);
-                mp3d_synth_granule(dec->qmf_state, scratch.grbuf[0], 18, info->channels, pcm, scratch.syn[0]);
+                memset(p_scratch->grbuf[0], 0, 576*2*sizeof(float));
+                L3_decode(dec, p_scratch, p_scratch->gr_info + igr*info->channels, info->channels);
+                mp3d_synth_granule(dec->qmf_state, p_scratch->grbuf[0], 18, info->channels, pcm, p_scratch->syn[0]);
             }
         }
-        L3_save_reservoir(dec, &scratch);
+        L3_save_reservoir(dec, p_scratch);
     } else
     {
 #ifdef MINIMP3_ONLY_MP3
         return 0;
 #else /* MINIMP3_ONLY_MP3 */
+
+#if MINIMP3_STACK_OPT
+        L12_scale_info *sci=&(dec->sci);;
+        memset(sci,0,sizeof(L12_scale_info));
+#else
         L12_scale_info sci[1];
+#endif
         L12_read_scale_info(hdr, bs_frame, sci);
-
-        memset(scratch.grbuf[0], 0, 576*2*sizeof(float));
+        memset(p_scratch->grbuf[0], 0, 576*2*sizeof(float));
         for (i = 0, igr = 0; igr < 3; igr++)
         {
-            if (12 == (i += L12_dequantize_granule(scratch.grbuf[0] + i, bs_frame, sci, info->layer | 1)))
+            if (12 == (i += L12_dequantize_granule(p_scratch->grbuf[0] + i, bs_frame, sci, info->layer | 1)))
             {
                 i = 0;
-                L12_apply_scf_384(sci, sci->scf + igr, scratch.grbuf[0]);
-                mp3d_synth_granule(dec->qmf_state, scratch.grbuf[0], 12, info->channels, pcm, scratch.syn[0]);
-                memset(scratch.grbuf[0], 0, 576*2*sizeof(float));
+                L12_apply_scf_384(sci, sci->scf + igr, p_scratch->grbuf[0]);
+                mp3d_synth_granule(dec->qmf_state, p_scratch->grbuf[0], 12, info->channels, pcm, p_scratch->syn[0]);
+                memset(p_scratch->grbuf[0], 0, 576*2*sizeof(float));
                 pcm += 384*info->channels;
             }
             if (bs_frame->pos > bs_frame->limit)