Reworked handling of MPEG audio frame & file info: * Fixed frame size calculation for layer 1 (all versions) and layer 2 (V2/V2.5). * Exact frame time (expressed as a fraction) for way more precise playtime calculation at 44100/22050/11025Hz sample frequency. * Exact playtime<->position conversion for CBR also used for resume position. * More compact code, long policy.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7505 a1c6a512-1295-4272-9138-f99709370657

5 files changed, 125 insertions, 146 deletions

diff --git a/firmware/export/id3.h b/firmware/export/id3.h
index 6c6507159a..47a084d67a 100644
--- a/firmware/export/id3.h
+++ b/firmware/export/id3.h
@@ -61,39 +61,37 @@ struct mp3entry {
     unsigned char genre;
     unsigned int codectype;
     unsigned int bitrate;
-    unsigned int frequency;
-    unsigned int id3v2len;
-    unsigned int id3v1len;
-    unsigned int first_frame_offset; /* Byte offset to first real MP3 frame.
-                                        Used for skipping leading garbage to
-                                        avoid gaps between tracks. */
-    unsigned int vbr_header_pos;
-    unsigned int filesize; /* in bytes */
-    unsigned int length;   /* song length */
-    unsigned int elapsed;  /* ms played */
-
-    int lead_trim;         /* Number of samples to skip at the beginning */
-    int tail_trim;         /* Number of samples to remove from the end */
+    unsigned long frequency;
+    unsigned long id3v2len;
+    unsigned long id3v1len;
+    unsigned long first_frame_offset; /* Byte offset to first real MP3 frame.
+                                         Used for skipping leading garbage to
+                                         avoid gaps between tracks. */
+    unsigned long vbr_header_pos;
+    unsigned long filesize; /* without headers; in bytes */
+    unsigned long length;   /* song length in ms */
+    unsigned long elapsed;  /* ms played */
+
+    int lead_trim;          /* Number of samples to skip at the beginning */
+    int tail_trim;          /* Number of samples to remove from the end */
 
     /* Added for Vorbis */
-    unsigned long samples; /* number of samples in track */
+    unsigned long samples;  /* number of samples in track */
 
     /* MP3 stream specific info */
-    long bpf;              /* bytes per frame */
-    long tpf;              /* time per frame */
-    long frame_count;      /* number of frames in the file (if VBR) */
+    unsigned long frame_count; /* number of frames in the file (if VBR) */
 
     /* Xing VBR fields */
     bool vbr;
-    bool has_toc;    /* True if there is a VBR header in the file */
-    unsigned char toc[100];/* table of contents */
+    bool has_toc;           /* True if there is a VBR header in the file */
+    unsigned char toc[100]; /* table of contents */
 
     /* these following two fields are used for local buffering */
     char id3v2buf[300];
     char id3v1buf[3][32];
 
     /* resume related */
-    int offset;            /* bytes played */
+    unsigned long offset;  /* bytes played */
     int index;             /* playlist index */
 
     /* FileEntry fields */
diff --git a/firmware/export/mp3data.h b/firmware/export/mp3data.h
index db1a93b8d6..3961664815 100644
--- a/firmware/export/mp3data.h
+++ b/firmware/export/mp3data.h
@@ -20,9 +20,9 @@
 #ifndef _MP3DATA_H_
 #define _MP3DATA_H_
 
-#define MPEG_VERSION2_5 0
-#define MPEG_VERSION1   1
-#define MPEG_VERSION2   2
+#define MPEG_VERSION1   0
+#define MPEG_VERSION2   1
+#define MPEG_VERSION2_5 2
 
 struct mp3info {
     /* Standard MP3 frame header fields */
@@ -30,23 +30,25 @@ struct mp3info {
     int layer;
     bool protection;
     int bitrate;
-    int frequency;
+    long frequency;
     int padding;
     int channel_mode;
     int mode_extension;
     int emphasis;
-    int frame_size; /* Frame size in bytes */
-    int frame_time; /* Frame duration in milliseconds */
+    int frame_size;   /* Frame size in bytes */
+    int frame_samples; /* Samples per frame */
+    int ft_num;       /* Numerator of frametime in milliseconds */
+    int ft_den;       /* Denominator of frametime in milliseconds */
 
-    bool is_vbr;     /* True if the file is VBR */
-    bool has_toc;    /* True if there is a VBR header in the file */
+    bool is_vbr;      /* True if the file is VBR */
+    bool has_toc;     /* True if there is a VBR header in the file */
     bool is_xing_vbr; /* True if the VBR header is of Xing type */
     bool is_vbri_vbr; /* True if the VBR header is of VBRI type */
     unsigned char toc[100];
-    long frame_count; /* Number of frames in the file (if VBR) */
-    long byte_count;  /* File size in bytes */
-    long file_time;   /* Length of the whole file in milliseconds */
-    int vbr_header_pos;
+    unsigned long frame_count; /* Number of frames in the file (if VBR) */
+    unsigned long byte_count;  /* File size in bytes */
+    unsigned long file_time;   /* Length of the whole file in milliseconds */
+    unsigned long vbr_header_pos;
     int enc_delay;    /* Encoder delay, fetched from LAME header */
     int enc_padding;  /* Padded samples added to last frame. LAME header */
 };
diff --git a/firmware/id3.c b/firmware/id3.c
index f1aa821fba..dfbcb9699d 100644
--- a/firmware/id3.c
+++ b/firmware/id3.c
@@ -863,10 +863,10 @@ static int getid3v2len(int fd)
  */
 static int getsonglength(int fd, struct mp3entry *entry)
 {
-    unsigned int filetime = 0;
+    unsigned long filetime = 0;
     struct mp3info info;
-    int bytecount;
-    
+    long bytecount;
+
     /* Start searching after ID3v2 header */ 
     if(-1 == lseek(fd, entry->id3v2len, SEEK_SET))
         return 0;
@@ -912,8 +912,6 @@ static int getsonglength(int fd, struct mp3entry *entry)
          * always multiples of 8, and it avoids overflows. */
     }
 
-    entry->tpf = info.frame_time;
-    entry->bpf = info.frame_size;
     entry->frame_count = info.frame_count;
 
     entry->vbr = info.is_vbr;
diff --git a/firmware/mp3data.c b/firmware/mp3data.c
index 6f4c560578..c2d4cd2c37 100644
--- a/firmware/mp3data.c
+++ b/firmware/mp3data.c
@@ -31,6 +31,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdbool.h>
+#include <limits.h>
 #include "debug.h"
 #include "logf.h"
 #include "mp3data.h"
@@ -39,7 +40,7 @@
 
 #define DEBUG_VERBOSE
 
-#define BYTES2INT(b1,b2,b3,b4) (((long)(b1 & 0xFF) << (3*8)) |      \
+#define BYTES2INT(b1,b2,b3,b4) (((long)(b1 & 0xFF) << (3*8)) | \
                                 ((long)(b2 & 0xFF) << (2*8)) | \
                                 ((long)(b3 & 0xFF) << (1*8)) | \
                                 ((long)(b4 & 0xFF) << (0*8)))
@@ -58,37 +59,34 @@
 #define ORIGINAL_MASK (1L << 2)
 #define EMPHASIS_MASK 3L
 
-/* Table of bitrates for MP3 files, all values in kilo.
- * Indexed by version, layer and value of bit 15-12 in header.
- */
-const int bitrate_table[2][3][16] =
-{
-    {
-        {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,0},
-        {0,32,48,56, 64,80, 96, 112,128,160,192,224,256,320,384,0},
-        {0,32,40,48, 56,64, 80, 96, 112,128,160,192,224,256,320,0}
-    },
-    {
-        {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,0},
-        {0, 8,16,24,32,40,48, 56, 64, 80, 96,112,128,144,160,0},
-        {0, 8,16,24,32,40,48, 56, 64, 80, 96,112,128,144,160,0}
-    }
+/* MPEG Version table, sorted by version index */
+static const signed char version_table[4] = {
+    MPEG_VERSION2_5, -1, MPEG_VERSION2, MPEG_VERSION1
 };
 
-/* Table of samples per frame for MP3 files.
- * Indexed by layer. Multiplied with 1000.
- */
-const long bs[3] = {384000, 1152000, 1152000};
+/* Bitrate table for mpeg audio, indexed by row index and birate index */
+static const short bitrates[5][16] = {
+    {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,0}, /* V1 L1 */
+    {0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,0}, /* V1 L2 */
+    {0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,0}, /* V1 L3 */
+    {0,32,48,56, 64, 80, 96,112,128,144,160,176,192,224,256,0}, /* V2 L1 */
+    {0, 8,16,24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160,0}  /* V2 L2+L3 */
+};
 
-/* Table of sample frequency for MP3 files.
- * Indexed by version and layer.
- */
+/* Bitrate pointer table, indexed by version and layer */
+static const short *bitrate_table[3][3] =
+{
+    {bitrates[0], bitrates[1], bitrates[2]},
+    {bitrates[3], bitrates[4], bitrates[4]},
+    {bitrates[3], bitrates[4], bitrates[4]}
+};
 
-const int freqtab[][4] =
+/* Sampling frequency table, indexed by version and frequency index */
+static const long freq_table[3][3] =
 {
-    {11025, 12000, 8000, 0},  /* MPEG version 2.5 */
-    {44100, 48000, 32000, 0}, /* MPEG Version 1 */
-    {22050, 24000, 16000, 0}, /* MPEG version 2 */
+    {44100, 48000, 32000}, /* MPEG Version 1 */
+    {22050, 24000, 16000}, /* MPEG version 2 */
+    {11025, 12000,  8000}, /* MPEG version 2.5 */
 };
 
 /* check if 'head' is a valid mp3 frame header */
@@ -117,97 +115,77 @@ static bool is_mp3frameheader(unsigned long head)
 
 static bool mp3headerinfo(struct mp3info *info, unsigned long header)
 {
-    int bittable = 0;
-    int bitindex;
-    int freqindex;
-    
+    int bitindex, freqindex;
+
     /* MPEG Audio Version */
-    switch((header & VERSION_MASK) >> 19) {
-    case 0:
-        /* MPEG version 2.5 is not an official standard */
-        info->version = MPEG_VERSION2_5;
-        bittable = MPEG_VERSION2 - 1; /* use the V2 bit rate table */
-        break;
-
-    case 1:
+    info->version = version_table[(header & VERSION_MASK) >> 19];
+    if (info->version < 0)
         return false;
 
-    case 2:
-        /* MPEG version 2 (ISO/IEC 13818-3) */
-        info->version = MPEG_VERSION2;
-        bittable = MPEG_VERSION2 - 1;
-        break;
-        
-    case 3:
-        /* MPEG version 1 (ISO/IEC 11172-3) */
-        info->version = MPEG_VERSION1;
-        bittable = MPEG_VERSION1 - 1;
-        break;
-    }
-
-    switch((header & LAYER_MASK) >> 17) {
-    case 0:
+    /* Layer */
+    info->layer = 3 - ((header & LAYER_MASK) >> 17);
+    if (info->layer == 3)
         return false;
-    case 1:
-        info->layer = 2;
-        break;
-    case 2:
-        info->layer = 1;
-        break;
-    case 3:
-        info->layer = 0;
-        break;
-    }
 
-    info->protection = (header & PROTECTION_MASK)?true:false;
+    info->protection = (header & PROTECTION_MASK) ? true : false;
     
     /* Bitrate */
-    bitindex = (header & 0xf000) >> 12;
-    info->bitrate = bitrate_table[bittable][info->layer][bitindex];
+    bitindex = (header & BITRATE_MASK) >> 12;
+    info->bitrate = bitrate_table[info->version][info->layer][bitindex];
     if(info->bitrate == 0)
         return false;
-    
+
     /* Sampling frequency */
-    freqindex = (header & 0x0C00) >> 10;
-    info->frequency = freqtab[info->version][freqindex];
-    if(info->frequency == 0)
+    freqindex = (header & SAMPLERATE_MASK) >> 10;
+    if (freqindex == 3)
         return false;
+    info->frequency = freq_table[info->version][freqindex];
 
-    info->padding = (header & 0x0200)?1:0;
+    info->padding = (header & PADDING_MASK) ? 1 : 0;
 
     /* Calculate number of bytes, calculation depends on layer */
-    switch(info->layer) {
-    case 0:
-        info->frame_size = info->bitrate * 48000;
-        info->frame_size /=
-            freqtab[info->version][freqindex] << bittable;
-        break;
-    case 1:
-    case 2:
-        info->frame_size = info->bitrate * 144000;
-        info->frame_size /=
-            freqtab[info->version][freqindex] << bittable;
-        break;
-    default:
-        info->frame_size = 1;
+    if (info->layer == 0) {
+        info->frame_samples = 384;
+        info->frame_size = (12000 * info->bitrate / info->frequency 
+                            + info->padding) * 4;
+    }
+    else {
+        if ((info->version > MPEG_VERSION1) && (info->layer == 2))
+            info->frame_samples = 576;
+        else
+            info->frame_samples = 1152;
+        info->frame_size = (1000/8) * info->frame_samples * info->bitrate
+                           / info->frequency + info->padding;
     }
     
-    info->frame_size += info->padding;
-
-    /* Calculate time per frame */
-    info->frame_time = bs[info->layer] /
-        (freqtab[info->version][freqindex] << bittable);
+    /* Frametime fraction calculation.
+       This fraction is reduced as far as possible. */
+    if (freqindex != 0) { /* 48/32/24/16/12/8 kHz */
+        /* integer number of milliseconds, denominator == 1 */
+        info->ft_num = 1000 * info->frame_samples / info->frequency;
+        info->ft_den = 1;
+    }
+    else {                /* 44.1/22.05/11.025 kHz */
+        if (info->layer == 0) {
+            info->ft_num = 147000 * 384 / info->frequency;
+            info->ft_den = 147;
+        }
+        else {
+            info->ft_num = 49000 * info->frame_samples / info->frequency;
+            info->ft_den = 49;
+        }
+    }
 
-    info->channel_mode = (header & 0xc0) >> 6;
-    info->mode_extension = (header & 0x30) >> 4;
-    info->emphasis = header & 3;
+    info->channel_mode = (header & CHANNELMODE_MASK) >> 6;
+    info->mode_extension = (header & MODE_EXT_MASK) >> 4;
+    info->emphasis = header & EMPHASIS_MASK;
 
 #ifdef DEBUG_VERBOSE
-    DEBUGF( "Header: %08x, Ver %d, lay %d, bitr %d, freq %d, "
-            "chmode %d, mode_ext %d, emph %d, bytes: %d time: %d\n",
+    DEBUGF( "Header: %08x, Ver %d, lay %d, bitr %d, freq %ld, "
+            "chmode %d, mode_ext %d, emph %d, bytes: %d time: %d/%d\n",
             header, info->version, info->layer+1, info->bitrate,
             info->frequency, info->channel_mode, info->mode_extension,
-            info->emphasis, info->frame_size, info->frame_time);
+            info->emphasis, info->frame_size, info->ft_num, info->ft_den);
 #endif
     return true;
 }
@@ -252,7 +230,7 @@ static unsigned long __find_next_frame(int fd, long *offset, long max_offset,
     if(*offset)
         DEBUGF("Warning: skipping %d bytes of garbage\n", *offset);
 #endif
-    
+
     return header;
 }
 
@@ -380,9 +358,6 @@ int get_mp3file_info(int fd, struct mp3info *info)
 
     memset(info, 0, sizeof(struct mp3info));
     /* These two are needed for proper LAME gapless MP3 playback */
-    /* TODO: These can be found in a LAME Info header as well, but currently
-       they are only looked for in a Xing header. Xing and Info headers have
-       the exact same format, but Info headers are used for CBR files. */
     info->enc_delay = -1;
     info->enc_padding = -1;
     if(!mp3headerinfo(info, header))
@@ -435,7 +410,10 @@ int get_mp3file_info(int fd, struct mp3info *info)
         {
             info->frame_count = BYTES2INT(vbrheader[i], vbrheader[i+1],
                                           vbrheader[i+2], vbrheader[i+3]);
-            info->file_time = info->frame_count * info->frame_time;
+            if (info->frame_count <= ULONG_MAX / info->ft_num)
+                info->file_time = info->frame_count * info->ft_num / info->ft_den;
+            else
+                info->file_time = info->frame_count / info->ft_den * info->ft_num;
             i += 4;
         }
 
@@ -510,7 +488,10 @@ int get_mp3file_info(int fd, struct mp3info *info)
                                      vbrheader[12], vbrheader[13]);
         info->frame_count = BYTES2INT(vbrheader[14], vbrheader[15],
                                       vbrheader[16], vbrheader[17]);
-        info->file_time = info->frame_count * info->frame_time;
+        if (info->frame_count <= ULONG_MAX / info->ft_num)
+            info->file_time = info->frame_count * info->ft_num / info->ft_den;
+        else
+            info->file_time = info->frame_count / info->ft_den * info->ft_num;
         info->bitrate = info->byte_count * 8 / info->file_time;
 
         /* We don't parse the TOC, since we don't yet know how to (FIXME) */
diff --git a/firmware/mpeg.c b/firmware/mpeg.c
index ff74cf96a8..8d2d13b6ee 100644
--- a/firmware/mpeg.c
+++ b/firmware/mpeg.c
@@ -348,7 +348,7 @@ static void set_elapsed(struct mp3entry* id3)
             /* find wich percent we're at */
             for (i=0; i<100; i++ )
             {
-                if ( id3->offset < (int)(id3->toc[i] * (id3->filesize / 256)) )
+                if ( id3->offset < id3->toc[i] * (id3->filesize / 256) )
                 {
                     break;
                 }
@@ -388,8 +388,8 @@ static void set_elapsed(struct mp3entry* id3)
         }
     }
     else
-        /* constant bitrate == simple frame calculation */
-        id3->elapsed = id3->offset / id3->bpf * id3->tpf;
+        /* constant bitrate, use exact calculation */
+        id3->elapsed = id3->offset / (id3->bitrate / 8);
 }
 
 int audio_get_file_pos(void)
@@ -405,7 +405,7 @@ int audio_get_file_pos(void)
             unsigned int percent, remainder;
             int curtoc, nexttoc, plen;
                         
-            percent = (id3->elapsed*100)/id3->length; 
+            percent = (id3->elapsed*100)/id3->length;
             if (percent > 99)
                 percent = 99;
                         
@@ -431,8 +431,8 @@ int audio_get_file_pos(void)
                 (id3->elapsed / 1000);
         }
     }
-    else if (id3->bpf && id3->tpf)
-        pos = (id3->elapsed/id3->tpf)*id3->bpf;
+    else if (id3->bitrate)
+        pos = id3->elapsed * (id3->bitrate / 8);
     else
     {
         return -1;