shithub: mp3dec

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support VBR tags

--- a/minimp3_ex.h

+++ b/minimp3_ex.h

@@ -51,7 +51,7 @@

 #ifndef MINIMP3_NO_STDIO

     int is_file;

 #endif

-    int seek_method;

+    int seek_method, vbr_tag_found;

     int buffer_samples, buffer_consumed, to_skip;

 } mp3dec_ex_t;

@@ -70,7 +70,7 @@

 int mp3dec_ex_open_buf(mp3dec_ex_t *dec, const uint8_t *buf, size_t buf_size, int seek_method);

 /*int mp3dec_ex_open_cb(mp3dec_ex_t *dec, MP3D_READ_CB cb, void *user_data, uint64_t file_size, int seek_method);*/

 void mp3dec_ex_close(mp3dec_ex_t *dec);

-void mp3dec_ex_seek(mp3dec_ex_t *dec, uint64_t position);

+int mp3dec_ex_seek(mp3dec_ex_t *dec, uint64_t position);

 size_t mp3dec_ex_read(mp3dec_ex_t *dec, int16_t *buf, size_t samples);

 #ifndef MINIMP3_NO_STDIO

 /* stdio versions with file pre-load */

@@ -237,6 +237,25 @@

     (void)frame_size;

     mp3dec_frame_t *idx_frame;

     mp3dec_ex_t *dec = (mp3dec_ex_t *)user_data;

+    if (!dec->index.frames && !dec->vbr_tag_found)

+    {   /* detect VBR tag and try to avoid full scan */

+        dec->info = *info;

+        static const char g_xing_tag[4] = { 'X', 'i', 'n', 'g' };

+        static const char g_info_tag[4] = { 'I', 'n', 'f', 'o' };

+        for (int i = 5; i < frame_size - 12; i++)

+        {

+            const uint8_t *tag = frame + i;

+            if (!memcmp(g_xing_tag, tag, 4) || !memcmp(g_info_tag, tag, 4))

+            {

+                if (!((tag[7] & 1))/* frames field present */)

+                    break;

+                uint64_t frames = (uint32_t)(tag[8] << 24) | (tag[9] << 16) | (tag[10] << 8) | tag[11];

+                dec->samples += hdr_frame_samples(frame)*info->channels*frames;

+                dec->vbr_tag_found = 1;

+                return 1;

+            }

+        }

+    }

     if (dec->index.num_frames + 1 > dec->index.capacity)

     {

         if (!dec->index.capacity)

@@ -245,10 +264,8 @@

             dec->index.capacity *= 2;

         dec->index.frames = (mp3dec_frame_t *)realloc((void*)dec->index.frames, sizeof(mp3dec_frame_t)*dec->index.capacity);

         if (!dec->index.frames)

-            return -1;

+            return MP3D_E_MEMORY;

     }

-    if (!dec->samples)

-        dec->info = *info;

     idx_frame = &dec->index.frames[dec->index.num_frames++];

     idx_frame->offset = offset;

     idx_frame->sample = dec->samples;

@@ -263,19 +280,33 @@

     dec->file.size   = buf_size;

     dec->seek_method = seek_method;

     mp3dec_init(&dec->mp3d);

-    if (mp3dec_iterate_buf(dec->file.buffer, dec->file.size, mp3dec_load_index, dec) > 0 && !dec->index.frames)

+    if (mp3dec_iterate_buf(dec->file.buffer, dec->file.size, mp3dec_load_index, dec) > 0 && !dec->index.frames && !dec->vbr_tag_found)

         return MP3D_E_MEMORY;

     return 0;

 }

-void mp3dec_ex_seek(mp3dec_ex_t *dec, uint64_t position)

+int mp3dec_ex_seek(mp3dec_ex_t *dec, uint64_t position)

 {

     size_t i;

     if (MP3D_SEEK_TO_BYTE == dec->seek_method)

     {

         dec->offset = position;

-        return;

+        return 0;

     }

+    if (0 == position)

+    {   /* optimize seek to zero, no index needed */

+seek_zero:

+        dec->offset  = 0;

+        dec->to_skip = 0;

+        goto do_exit;

+    }

+    if (!dec->index.frames && dec->vbr_tag_found)

+    {   /* no index created yet (vbr tag used to calculate track length) */

+        if (mp3dec_iterate_buf(dec->file.buffer, dec->file.size, mp3dec_load_index, dec) > 0 && !dec->index.frames)

+            return MP3D_E_MEMORY;

+    }

+    if (!dec->index.frames)

+        goto seek_zero; /* no frames in file - seek to zero */

     for (i = 0; i < dec->index.num_frames; i++)

     {

         if (dec->index.frames[i].sample > position)

@@ -285,9 +316,11 @@

         i--;

     dec->offset = dec->index.frames[i].offset;

     dec->to_skip = position - dec->index.frames[i].sample;

+do_exit:

     dec->buffer_samples  = 0;

     dec->buffer_consumed = 0;

     mp3dec_init(&dec->mp3d);

+    return 0;

 }

 size_t mp3dec_ex_read(mp3dec_ex_t *dec, int16_t *buf, size_t samples)