Build librbcodec with DSP and metadata.

All associated files are moved to /lib/rbcodec.

Change-Id: I572ddd2b8a996aae1e98c081d06b1ed356dce222

1 files changed, 842 insertions, 0 deletions

diff --git a/lib/rbcodec/metadata/mp4.c b/lib/rbcodec/metadata/mp4.c
new file mode 100644
index 0000000..df16443
--- /dev/null
+++ b/lib/rbcodec/metadata/mp4.c
@@ -0,0 +1,842 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2005 Magnus Holmgren
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <inttypes.h>
+
+#include "system.h"
+#include "errno.h"
+#include "metadata.h"
+#include "metadata_common.h"
+#include "metadata_parsers.h"
+#include "logf.h"
+#include "debug.h"
+#include "replaygain.h"
+
+#ifdef DEBUGF
+#undef DEBUGF
+#define DEBUGF(...)
+#endif
+
+#define MP4_3gp6 FOURCC('3', 'g', 'p', '6')
+#define MP4_aART FOURCC('a', 'A', 'R', 'T')
+#define MP4_alac FOURCC('a', 'l', 'a', 'c')
+#define MP4_calb FOURCC(0xa9, 'a', 'l', 'b')
+#define MP4_cART FOURCC(0xa9, 'A', 'R', 'T')
+#define MP4_cgrp FOURCC(0xa9, 'g', 'r', 'p')
+#define MP4_cgen FOURCC(0xa9, 'g', 'e', 'n')
+#define MP4_chpl FOURCC('c', 'h', 'p', 'l')
+#define MP4_cnam FOURCC(0xa9, 'n', 'a', 'm')
+#define MP4_cwrt FOURCC(0xa9, 'w', 'r', 't')
+#define MP4_ccmt FOURCC(0xa9, 'c', 'm', 't')
+#define MP4_cday FOURCC(0xa9, 'd', 'a', 'y')
+#define MP4_covr FOURCC('c', 'o', 'v', 'r')
+#define MP4_disk FOURCC('d', 'i', 's', 'k')
+#define MP4_esds FOURCC('e', 's', 'd', 's')
+#define MP4_ftyp FOURCC('f', 't', 'y', 'p')
+#define MP4_gnre FOURCC('g', 'n', 'r', 'e')
+#define MP4_hdlr FOURCC('h', 'd', 'l', 'r')
+#define MP4_ilst FOURCC('i', 'l', 's', 't')
+#define MP4_isom FOURCC('i', 's', 'o', 'm')
+#define MP4_M4A  FOURCC('M', '4', 'A', ' ')
+#define MP4_m4a  FOURCC('m', '4', 'a', ' ') /*technically its "M4A "*/
+#define MP4_M4B  FOURCC('M', '4', 'B', ' ') /*but files exist with lower case*/
+#define MP4_mdat FOURCC('m', 'd', 'a', 't')
+#define MP4_mdia FOURCC('m', 'd', 'i', 'a')
+#define MP4_mdir FOURCC('m', 'd', 'i', 'r')
+#define MP4_meta FOURCC('m', 'e', 't', 'a')
+#define MP4_minf FOURCC('m', 'i', 'n', 'f')
+#define MP4_moov FOURCC('m', 'o', 'o', 'v')
+#define MP4_mp4a FOURCC('m', 'p', '4', 'a')
+#define MP4_mp42 FOURCC('m', 'p', '4', '2')
+#define MP4_qt   FOURCC('q', 't', ' ', ' ')
+#define MP4_soun FOURCC('s', 'o', 'u', 'n')
+#define MP4_stbl FOURCC('s', 't', 'b', 'l')
+#define MP4_stsd FOURCC('s', 't', 's', 'd')
+#define MP4_stts FOURCC('s', 't', 't', 's')
+#define MP4_trak FOURCC('t', 'r', 'a', 'k')
+#define MP4_trkn FOURCC('t', 'r', 'k', 'n')
+#define MP4_udta FOURCC('u', 'd', 't', 'a')
+#define MP4_extra FOURCC('-', '-', '-', '-')
+
+/* Read the tag data from an MP4 file, storing up to buffer_size bytes in
+ * buffer.
+ */
+static unsigned long read_mp4_tag(int fd, unsigned int size_left, char* buffer,
+                                  unsigned int buffer_left)
+{
+    unsigned int bytes_read = 0;
+    
+    if (buffer_left == 0)
+    {
+        lseek(fd, size_left, SEEK_CUR);     /* Skip everything */
+    } 
+    else 
+    {
+        /* Skip the data tag header - maybe we should parse it properly? */
+        lseek(fd, 16, SEEK_CUR); 
+        size_left -= 16;
+
+        if (size_left > buffer_left)
+        {
+            read(fd, buffer, buffer_left);
+            lseek(fd, size_left - buffer_left, SEEK_CUR);
+            bytes_read = buffer_left;
+        } 
+        else
+        {
+            read(fd, buffer, size_left);
+            bytes_read = size_left;
+        }
+    }
+    
+    return bytes_read;
+}
+
+/* Read a string tag from an MP4 file */
+static unsigned int read_mp4_tag_string(int fd, int size_left, char** buffer,
+                                        unsigned int* buffer_left, char** dest)
+{
+    unsigned int bytes_read = read_mp4_tag(fd, size_left, *buffer,
+        *buffer_left > 0 ? *buffer_left - 1 : 0);
+    unsigned int length = 0;
+
+    if (bytes_read)
+    {
+        /* Do not overwrite already available metadata. Especially when reading
+         * tags with e.g. multiple genres / artists. This way only the first 
+         * of multiple entries is used, all following are dropped. */
+        if (*dest == NULL)
+        {
+            (*buffer)[bytes_read] = 0; /* zero-terminate for correct strlen().*/
+            length = strlen(*buffer) + 1;
+            length = MIN(length, ID3V2_MAX_ITEM_SIZE); /* Limit item size. */
+
+            *dest = *buffer;
+            (*buffer)[length-1] = 0; /* zero-terminate buffer. */
+            *buffer_left -= length;
+            *buffer += length;
+        }
+    }
+    else
+    {
+        *dest = NULL;
+    }
+    
+    return length;
+}
+
+static unsigned int read_mp4_atom(int fd, uint32_t* size, 
+                                  uint32_t* type, uint32_t size_left)
+{
+    read_uint32be(fd, size);
+    read_uint32be(fd, type);
+
+    if (*size == 1)
+    {
+        /* FAT32 doesn't support files this big, so something seems to 
+         * be wrong. (64-bit sizes should only be used when required.)
+         */
+        errno = EFBIG;
+        *type = 0;
+        return 0;
+    }
+
+    if (*size > 0)
+    {
+        if (*size > size_left)
+        {
+            size_left = 0;
+        }
+        else
+        {
+            size_left -= *size;
+        }
+        
+        *size -= 8;
+    }
+    else
+    {
+        *size = size_left;
+        size_left = 0;
+    }
+    
+    return size_left;
+}
+
+static unsigned int read_mp4_length(int fd, uint32_t* size)
+{
+    unsigned int length = 0;
+    int bytes = 0;
+    unsigned char c;
+
+    do
+    {
+        read(fd, &c, 1);
+        bytes++;
+        (*size)--;
+        length = (length << 7) | (c & 0x7F);
+    }
+    while ((c & 0x80) && (bytes < 4) && (*size > 0));
+
+    return length;
+}
+
+static bool read_mp4_esds(int fd, struct mp3entry* id3, uint32_t* size)
+{
+    unsigned char buf[8];
+    bool sbr = false;
+
+    lseek(fd, 4, SEEK_CUR);     /* Version and flags. */
+    read(fd, buf, 1);           /* Verify ES_DescrTag. */
+    *size -= 5;
+
+    if (*buf == 3)
+    {
+        /* read length */
+        if (read_mp4_length(fd, size) < 20)
+        {
+            return sbr;
+        }
+
+        lseek(fd, 3, SEEK_CUR);
+        *size -= 3;
+    } 
+    else
+    {
+        lseek(fd, 2, SEEK_CUR);
+        *size -= 2;
+    }
+
+    read(fd, buf, 1);           /* Verify DecoderConfigDescrTab. */
+    *size -= 1;
+
+    if (*buf != 4)
+    {
+        return sbr;
+    }
+
+    if (read_mp4_length(fd, size) < 13)
+    {
+        return sbr;
+    }
+    
+    lseek(fd, 13, SEEK_CUR);    /* Skip audio type, bit rates, etc. */
+    read(fd, buf, 1);
+    *size -= 14;
+    
+    if (*buf != 5)              /* Verify DecSpecificInfoTag. */
+    {
+        return sbr;
+    }
+
+    {
+        static const int sample_rates[] =
+        {
+            96000, 88200, 64000, 48000, 44100, 32000,
+            24000, 22050, 16000, 12000, 11025, 8000
+        };
+        unsigned long bits;
+        unsigned int length;
+        unsigned int index;
+        unsigned int type;
+        
+        /* Read the (leading part of the) decoder config. */
+        length = read_mp4_length(fd, size);
+        length = MIN(length, *size);
+        length = MIN(length, sizeof(buf));
+        memset(buf, 0, sizeof(buf));
+        read(fd, buf, length);
+        *size -= length;
+        
+        /* Maybe time to write a simple read_bits function... */
+
+        /* Decoder config format:
+         * Object type           - 5 bits
+         * Frequency index       - 4 bits
+         * Channel configuration - 4 bits
+         */
+        bits = get_long_be(buf);
+        type = bits >> 27;              /* Object type - 5 bits */
+        index = (bits >> 23) & 0xf;     /* Frequency index - 4 bits */
+
+        if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
+        {
+            id3->frequency = sample_rates[index];
+        }
+    
+        if (type == 5)
+        {
+            unsigned int old_index = index;
+
+            sbr = true;
+            index = (bits >> 15) & 0xf; /* Frequency index - 4 bits */
+    
+            if (index == 15)
+            {
+                /* 17 bits read so far... */
+                bits = get_long_be(&buf[2]);
+                id3->frequency = (bits >> 7) & 0x00ffffff;
+            }
+            else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
+            {
+                id3->frequency = sample_rates[index];
+            }
+            
+            if (old_index == index)
+            {
+                /* Downsampled SBR */
+                id3->frequency *= 2;
+            }
+        }
+        /* Skip 13 bits from above, plus 3 bits, then read 11 bits */
+        else if ((length >= 4) && (((bits >> 5) & 0x7ff) == 0x2b7))
+        {
+            /* We found an extensionAudioObjectType */
+            type = bits & 0x1f;         /* Object type - 5 bits*/
+            bits = get_long_be(&buf[4]);
+            
+            if (type == 5)
+            {
+                sbr = bits >> 31;
+
+                if (sbr)
+                {
+                    unsigned int old_index = index;
+                    
+                    /* 1 bit read so far */
+                    index = (bits >> 27) & 0xf; /* Frequency index - 4 bits */
+
+                    if (index == 15)
+                    {
+                        /* 5 bits read so far */
+                        id3->frequency = (bits >> 3) & 0x00ffffff;
+                    }
+                    else if (index < (sizeof(sample_rates) / sizeof(*sample_rates)))
+                    {
+                        id3->frequency = sample_rates[index];
+                    }
+
+                    if (old_index == index)
+                    {
+                        /* Downsampled SBR */
+                        id3->frequency *= 2;
+                    }
+                }
+            }
+        }
+        
+        if (!sbr && (id3->frequency <= 24000) && (length <= 2))
+        {
+            /* Double the frequency for low-frequency files without a "long" 
+             * DecSpecificConfig header. The file may or may not contain SBR,
+             * but here we guess it does if the header is short. This can
+             * fail on some files, but it's the best we can do, short of 
+             * decoding (parts of) the file.
+             */
+            id3->frequency *= 2;
+            sbr = true;
+        }
+    }
+    
+    return sbr;
+}
+
+static bool read_mp4_tags(int fd, struct mp3entry* id3, 
+                          uint32_t size_left)
+{
+    uint32_t size;
+    uint32_t type;
+    unsigned int buffer_left = sizeof(id3->id3v2buf) + sizeof(id3->id3v1buf);
+    char* buffer = id3->id3v2buf;
+    bool cwrt = false;
+
+    do
+    {
+        size_left = read_mp4_atom(fd, &size, &type, size_left);
+
+        /* DEBUGF("Tag atom: '%c%c%c%c' (%d bytes left)\n", type >> 24 & 0xff, 
+            type >> 16 & 0xff, type >> 8 & 0xff, type & 0xff, size); */
+
+        switch (type)
+        {
+        case MP4_cnam:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left, 
+                &id3->title);
+            break;
+
+        case MP4_cART:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left, 
+                &id3->artist);
+            break;
+
+        case MP4_aART:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                &id3->albumartist);
+            break;
+
+        case MP4_cgrp:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                &id3->grouping);
+            break;
+        
+        case MP4_calb:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                &id3->album);
+            break;
+        
+        case MP4_cwrt:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                &id3->composer);
+            cwrt = false;
+            break;
+
+        case MP4_ccmt:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                &id3->comment);
+            break;
+
+        case MP4_cday:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                                &id3->year_string);
+ 
+            /* Try to parse it as a year, for the benefit of the database.
+             */
+            if(id3->year_string)
+            {
+                id3->year = atoi(id3->year_string);
+                if (id3->year < 1900)
+                {
+                    id3->year = 0;
+                }
+            }
+            else
+                id3->year = 0;
+
+            break;
+
+        case MP4_gnre:
+            {
+                unsigned short genre;
+                
+                read_mp4_tag(fd, size, (char*) &genre, sizeof(genre));
+                id3->genre_string = id3_get_num_genre(betoh16(genre) - 1);
+            }
+            break;
+        
+        case MP4_cgen:
+            read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                &id3->genre_string);
+            break;
+
+        case MP4_disk:
+            {
+                unsigned short n[2];
+                
+                read_mp4_tag(fd, size, (char*) &n, sizeof(n));
+                id3->discnum = betoh16(n[1]);
+            }
+            break;
+
+        case MP4_trkn:
+            {
+                unsigned short n[2];
+                
+                read_mp4_tag(fd, size, (char*) &n, sizeof(n));
+                id3->tracknum = betoh16(n[1]);
+            }
+            break;
+
+#ifdef HAVE_ALBUMART
+        case MP4_covr:
+            {
+                int pos = lseek(fd, 0, SEEK_CUR) + 16;
+                
+                read_mp4_tag(fd, size, buffer, 8);
+                id3->albumart.type = AA_TYPE_UNKNOWN;
+                if (memcmp(buffer, "\xff\xd8\xff\xe0", 4) == 0)
+                {
+                    id3->albumart.type = AA_TYPE_JPG;
+                }
+                else if (memcmp(buffer, "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a", 8) == 0)
+                {
+                    id3->albumart.type = AA_TYPE_PNG;
+                }
+                
+                if (id3->albumart.type != AA_TYPE_UNKNOWN)
+                {
+                    id3->albumart.pos  = pos;
+                    id3->albumart.size = size - 16;
+                    id3->has_embedded_albumart = true;
+                }
+            }
+            break;
+#endif
+
+        case MP4_extra:
+            {
+                char tag_name[TAG_NAME_LENGTH];
+                uint32_t sub_size;
+                
+                /* "mean" atom */
+                read_uint32be(fd, &sub_size);
+                size -= sub_size;
+                lseek(fd, sub_size - 4, SEEK_CUR);
+                /* "name" atom */
+                read_uint32be(fd, &sub_size);
+                size -= sub_size;
+                lseek(fd, 8, SEEK_CUR);
+                sub_size -= 12;
+                
+                if (sub_size > sizeof(tag_name) - 1)
+                {
+                    read(fd, tag_name, sizeof(tag_name) - 1);
+                    lseek(fd, sub_size - (sizeof(tag_name) - 1), SEEK_CUR);
+                    tag_name[sizeof(tag_name) - 1] = 0;
+                }
+                else
+                {
+                    read(fd, tag_name, sub_size);
+                    tag_name[sub_size] = 0;
+                }
+                
+                if ((strcasecmp(tag_name, "composer") == 0) && !cwrt)
+                {
+                    read_mp4_tag_string(fd, size, &buffer, &buffer_left, 
+                        &id3->composer);
+                }   
+                else if (strcasecmp(tag_name, "iTunSMPB") == 0)
+                {
+                    char value[TAG_VALUE_LENGTH];
+                    char* value_p = value;
+                    char* any;
+                    unsigned int length = sizeof(value);
+
+                    read_mp4_tag_string(fd, size, &value_p, &length, &any);
+                    id3->lead_trim = get_itunes_int32(value, 1);
+                    id3->tail_trim = get_itunes_int32(value, 2);
+                    DEBUGF("AAC: lead_trim %d, tail_trim %d\n", 
+                        id3->lead_trim, id3->tail_trim);
+                }
+                else if (strcasecmp(tag_name, "musicbrainz track id") == 0)
+                {
+                    read_mp4_tag_string(fd, size, &buffer, &buffer_left,
+                        &id3->mb_track_id);
+                }
+                else if ((strcasecmp(tag_name, "album artist") == 0))
+                {
+                    read_mp4_tag_string(fd, size, &buffer, &buffer_left, 
+                        &id3->albumartist);
+                }   
+                else
+                {
+                    char* any = NULL;
+                    unsigned int length = read_mp4_tag_string(fd, size,
+                        &buffer, &buffer_left, &any);
+
+                    if (length > 0)
+                    {
+                        /* Re-use the read buffer as the dest buffer... */
+                        buffer -= length;
+                        buffer_left += length;
+                        
+                        parse_replaygain(tag_name, buffer, id3);
+                    }
+                }
+            }
+            break;
+        
+        default:
+            lseek(fd, size, SEEK_CUR);
+            break;
+        }
+    }
+    while ((size_left > 0) && (errno == 0));
+
+    return true;
+}
+
+static bool read_mp4_container(int fd, struct mp3entry* id3, 
+                               uint32_t size_left)
+{
+    uint32_t size    = 0;
+    uint32_t type    = 0;
+    uint32_t handler = 0;
+    bool rc = true;
+    bool done = false;
+    
+    do
+    {
+        size_left = read_mp4_atom(fd, &size, &type, size_left);
+        
+        /* DEBUGF("Atom: '%c%c%c%c' (0x%08lx, %lu bytes left)\n", 
+            (int) ((type >> 24) & 0xff), (int) ((type >> 16) & 0xff),
+            (int) ((type >> 8) & 0xff), (int) (type & 0xff),
+            type, size); */
+        
+        switch (type)
+        {
+        case MP4_ftyp:
+            {
+                uint32_t id;
+                
+                read_uint32be(fd, &id);
+                size -= 4;
+                
+                if ((id != MP4_M4A) && (id != MP4_M4B) && (id != MP4_mp42) 
+                    && (id != MP4_qt) && (id != MP4_3gp6) && (id != MP4_m4a)
+                    && (id != MP4_isom))
+                {
+                    DEBUGF("Unknown MP4 file type: '%c%c%c%c'\n", 
+                        (int)(id >> 24 & 0xff), (int)(id >> 16 & 0xff),
+                        (int)(id >> 8 & 0xff), (int)(id & 0xff));
+                    return false;
+                }
+            }
+            break;
+
+        case MP4_meta:
+            lseek(fd, 4, SEEK_CUR);  /* Skip version */
+            size -= 4;
+            /* Fall through */
+
+        case MP4_moov:
+        case MP4_udta:
+        case MP4_mdia:
+        case MP4_stbl:
+        case MP4_trak:
+            rc = read_mp4_container(fd, id3, size);
+            size = 0;
+            break;
+        
+        case MP4_ilst:
+            /* We need at least a size of 8 to read the next atom. */
+            if (handler == MP4_mdir && size>8)
+            {
+                rc = read_mp4_tags(fd, id3, size);
+                size = 0;
+            }
+            break;
+        
+        case MP4_minf:
+            if (handler == MP4_soun)
+            {
+                rc = read_mp4_container(fd, id3, size);
+                size = 0;
+            }
+            break;
+        
+        case MP4_stsd:
+            lseek(fd, 8, SEEK_CUR);
+            size -= 8;
+            rc = read_mp4_container(fd, id3, size);
+            size = 0;
+            break;
+        
+        case MP4_hdlr:
+            lseek(fd, 8, SEEK_CUR);
+            read_uint32be(fd, &handler);
+            size -= 12;
+            /* DEBUGF("    Handler '%c%c%c%c'\n", handler >> 24 & 0xff, 
+                handler >> 16 & 0xff, handler >> 8 & 0xff,handler & 0xff); */
+            break;
+        
+        case MP4_stts:
+            {
+                uint32_t entries;
+                unsigned int i;
+
+                /* Reset to false. */
+                id3->needs_upsampling_correction = false;
+
+                lseek(fd, 4, SEEK_CUR);
+                read_uint32be(fd, &entries);
+                id3->samples = 0;
+
+                for (i = 0; i < entries; i++)
+                {
+                    uint32_t n;
+                    uint32_t l;
+
+                    read_uint32be(fd, &n);
+                    read_uint32be(fd, &l);
+
+                    /* Some AAC file use HE profile. In this case the number
+                     * of output samples is doubled to a maximum of 2048 
+                     * samples per frame. This means that files which already 
+                     * report a frame size of 2048 in their header will not 
+                     * need any further special handling. */
+                    if (id3->codectype==AFMT_MP4_AAC_HE && l<=1024)
+                    {
+                        id3->samples += n * l * 2;
+                        id3->needs_upsampling_correction = true;
+                    }
+                    else
+                    {
+                        id3->samples += n * l;
+                    }
+                }
+                
+                size = 0;
+            }
+            break;
+
+        case MP4_mp4a:
+            {
+                uint32_t subsize;
+                uint32_t subtype;
+
+                /* Move to the next expected mp4 atom. */
+                lseek(fd, 28, SEEK_CUR);
+                read_mp4_atom(fd, &subsize, &subtype, size);
+                size -= 36;
+
+                if (subtype == MP4_esds)
+                {
+                    /* Read esds metadata and return if AAC-HE/SBR is used. */
+                    if (read_mp4_esds(fd, id3, &size))
+                        id3->codectype = AFMT_MP4_AAC_HE;
+                    else
+                        id3->codectype = AFMT_MP4_AAC;
+                }
+            }
+            break;
+
+        case MP4_alac:
+            {
+                uint32_t frequency;
+                uint32_t subsize;
+                uint32_t subtype;
+
+                /* Move to the next expected mp4 atom. */
+                lseek(fd, 28, SEEK_CUR);
+                read_mp4_atom(fd, &subsize, &subtype, size);
+                size -= 36;
+#if 0
+                /* We might need to parse for the alac metadata atom. */
+                while (!((subsize==28) && (subtype==MP4_alac)) && (size>0))
+                {
+                    lseek(fd, -7, SEEK_CUR);
+                    read_mp4_atom(fd, &subsize, &subtype, size);
+                    size -= 1;
+                    errno = 0; /* will most likely be set while parsing */
+                }
+#endif
+                if (subtype == MP4_alac)
+                {
+                    lseek(fd, 24, SEEK_CUR);
+                    read_uint32be(fd, &frequency);
+                    size -= 28;
+                    id3->frequency = frequency;
+                    id3->codectype = AFMT_MP4_ALAC;
+                }
+            }
+            break;
+
+        case MP4_mdat:
+            /* Some AAC files appear to contain additional empty mdat chunks.
+               Ignore them. */
+            if(size == 0)
+                break;
+            id3->filesize = size;
+            if(id3->samples > 0) {
+                /* We've already seen the moov chunk. */
+                done = true;
+            }
+            break;
+
+        case MP4_chpl:
+            {
+                /* ADDME: add support for real chapters. Right now it's only
+                 * used for Nero's gapless hack */
+                uint8_t chapters;
+                uint64_t timestamp;
+
+                lseek(fd, 8, SEEK_CUR);
+                read_uint8(fd, &chapters);
+                size -= 9;
+
+                /* the first chapter will be used as the lead_trim */
+                if (chapters > 0) {
+                    read_uint64be(fd, &timestamp);
+                    id3->lead_trim = (timestamp * id3->frequency) / 10000000;
+                    size -= 8;
+                }
+            }
+            break;
+
+        default:
+            break;
+        }
+        
+        /* Skip final seek. */
+        if (!done)
+        {
+            lseek(fd, size, SEEK_CUR);
+        }
+    } while (rc && (size_left > 0) && (errno == 0) && !done);
+    
+    return rc;
+}
+
+bool get_mp4_metadata(int fd, struct mp3entry* id3)
+{
+    id3->codectype = AFMT_UNKNOWN;
+    id3->filesize = 0;
+    errno = 0;
+
+    if (read_mp4_container(fd, id3, filesize(fd)) && (errno == 0) 
+        && (id3->samples > 0) && (id3->frequency > 0) 
+        && (id3->filesize > 0))
+    {
+        if (id3->codectype == AFMT_UNKNOWN)
+        {
+            logf("Not an ALAC or AAC file");
+            return false;
+        }
+
+        id3->length = ((int64_t) id3->samples * 1000) / id3->frequency;
+
+        id3->vbr = true; /* ALAC is native VBR, AAC very unlikely is CBR. */
+
+        if (id3->length <= 0)
+        {
+            logf("mp4 length invalid!");
+            return false;
+        }
+
+        id3->bitrate = ((int64_t) id3->filesize * 8) / id3->length;
+        DEBUGF("MP4 bitrate %d, frequency %ld Hz, length %ld ms\n",
+            id3->bitrate, id3->frequency, id3->length);
+    }
+    else
+    {
+        logf("MP4 metadata error");
+        DEBUGF("MP4 metadata error. errno %d, samples %ld, frequency %ld, "
+            "filesize %ld\n", errno, id3->samples, id3->frequency,
+            id3->filesize);
+        return false;
+    }
+
+    return true;
+}