shithub: mp3dec

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mp3dec_ex: better vbr tag detect

--- a/minimp3_ex.h

+++ b/minimp3_ex.h

@@ -129,7 +129,6 @@

 static int mp3dec_check_vbrtag(const uint8_t *frame, int frame_size, uint32_t *frames, int *delay, int *padding)

 {

-    int i;

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

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

 #define FRAMES_FLAG     1

@@ -136,36 +135,43 @@

 #define BYTES_FLAG      2

 #define TOC_FLAG        4

 #define VBR_SCALE_FLAG  8

-    /* TODO: skip side-info?

-    /  Side info offsets afrer header:

+    /* Side info offsets afrer header:

     /                Mono  Stereo

     /  MPEG1          17     32

     /  MPEG2 & 2.5     9     17*/

-    for (i = 5; i < frame_size - 36; i++)

-    {

-        const uint8_t *tag = frame + i;

-        if (memcmp(g_xing_tag, tag, 4) && memcmp(g_info_tag, tag, 4))

-            continue;

-        int flags = tag[7];

-        if (!((flags & FRAMES_FLAG)))

-            break;

-        tag += 8;

-        (*frames) = (uint32_t)(tag[0] << 24) | (tag[1] << 16) | (tag[2] << 8) | tag[3];

+    bs_t bs[1];

+    L3_gr_info_t gr_info[4];

+    bs_init(bs, frame + HDR_SIZE, frame_size - HDR_SIZE);

+    if (HDR_IS_CRC(frame))

+        get_bits(bs, 16);

+    if (L3_read_side_info(bs, gr_info, frame) < 0)

+        return 0; /* side info corrupted */

+

+    const uint8_t *tag = frame + HDR_SIZE + bs->pos/8;

+    if (memcmp(g_xing_tag, tag, 4) && memcmp(g_info_tag, tag, 4))

+        return 0;

+    int flags = tag[7];

+    if (!((flags & FRAMES_FLAG)))

+        return 0;

+    tag += 8;

+    *frames = (uint32_t)(tag[0] << 24) | (tag[1] << 16) | (tag[2] << 8) | tag[3];

+    tag += 4;

+    if (flags & BYTES_FLAG)

         tag += 4;

-        if (flags & BYTES_FLAG)

-            tag += 4;

-        if (flags & TOC_FLAG)

-            tag += 100;

-        if (flags & VBR_SCALE_FLAG)

-            tag += 4;

+    if (flags & TOC_FLAG)

+        tag += 100;

+    if (flags & VBR_SCALE_FLAG)

+        tag += 4;

+    *delay = *padding = 0;

+    if (*tag)

+    {   /* extension, LAME, Lavc, etc. Should be the same structure. */

         tag += 21;

-        if (tag - frame + 2 >= frame_size)

-            break;

+        if (tag - frame + 14 >= frame_size)

+            return 0;

         *delay   = ((tag[0] << 4) | (tag[1] >> 4)) + (528 + 1);

         *padding = (((tag[1] & 0xF) << 8) | tag[2]) - (528 + 1);

-        return 1;

     }

-    return 0;

+    return 1;

 }

 void mp3dec_load_buf(mp3dec_t *dec, const uint8_t *buf, size_t buf_size, mp3dec_file_info_t *info, MP3D_PROGRESS_CB progress_cb, void *user_data)