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foxbox/lib/rbcodec/codecs/libm4a/demux.c
Aidan MacDonald 4dd3c2b33e codecs: m4a: improve seek accuracy 
Seeking doesn't work well in M4A files with very few chunks due to
the seek method used (chunk based using the info in the 'stco' atom).
According to libm4a/demux.c the expected seek resolution using this
method is 1/4 to 1/2 seconds. However, ffmpeg generates files with a
1 megabyte chunk size, so the resolution is much worse than expected
on some files: around 30-40 seconds at 256kbps.

There was a bug with the seek position reported back to Rockbox: the
codec pretended it could seek exactly to the requested sample, but it
would only seek to the start of a chunk. This could leave the UI in a
confusing state because the real playback position was different from
what the elapsed time showed. Fix this by recalculating the reported
sample position using the chunk start.

To fix the low seek accuracy, use the table in the 'stsz' atom to skip
individual packets within a chunk. This is very accurate, but it takes
a lot of RAM to allocate the table. Currently the table is not allowed
to use more than half of the codec RAM, which should suffice for short
files on most targets. On files where the table is too large the codec
will fall back to the less accurate chunk-based seek method.

Change-Id: Ide38ea846c1cdd69691e9b1e1cd87eb0fa11cf78
2022-05-02 12:16:21 -04:00

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/*
* ALAC (Apple Lossless Audio Codec) decoder
* Copyright (c) 2005 David Hammerton
* All rights reserved.
*
* This is the quicktime container demuxer.
*
* http://crazney.net/programs/itunes/alac.html
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
*/
#include <string.h>
#include <inttypes.h>
#include <stdlib.h>
#include "codeclib.h"
#include "m4a.h"
#undef DEBUGF
#if defined(DEBUG)
#define DEBUGF qtmovie->stream->ci->debugf
#else
#define DEBUGF(...)
#endif
typedef struct
{
stream_t *stream;
demux_res_t *res;
} qtmovie_t;
/* chunk handlers */
static void read_chunk_ftyp(qtmovie_t *qtmovie, size_t chunk_len)
{
fourcc_t type;
size_t size_remaining = chunk_len - 8;
type = stream_read_uint32(qtmovie->stream);
size_remaining-=4;
if ((type != MAKEFOURCC('M','4','A',' ')) &&
(type != MAKEFOURCC('m','4','a',' ')) &&
(type != MAKEFOURCC('M','4','B',' ')) &&
(type != MAKEFOURCC('m','p','4','2')) &&
(type != MAKEFOURCC('3','g','p','6')) &&
(type != MAKEFOURCC('q','t',' ',' ')) &&
(type != MAKEFOURCC('i','s','o','m')))
{
DEBUGF("not M4A file\n");
return;
}
/* minor_ver = */ stream_read_uint32(qtmovie->stream);
size_remaining-=4;
/* compatible brands */
while (size_remaining)
{
/* unused */
/*fourcc_t cbrand =*/ stream_read_uint32(qtmovie->stream);
size_remaining-=4;
}
}
static uint32_t mp4ff_read_mp4_descr_length(stream_t* stream)
{
uint8_t b;
uint8_t numBytes = 0;
uint32_t length = 0;
do
{
b = stream_read_uint8(stream);
numBytes++;
length = (length << 7) | (b & 0x7F);
} while ((b & 0x80) && numBytes < 4);
return length;
}
/* The following function is based on mp4ff */
static bool read_chunk_esds(qtmovie_t *qtmovie, size_t chunk_len)
{
uint8_t tag;
uint32_t temp;
(void)chunk_len;
/* version and flags */
temp=stream_read_uint32(qtmovie->stream);
/* get and verify ES_DescrTag */
tag = stream_read_uint8(qtmovie->stream);
if (tag == 0x03)
{
/* read length */
if (mp4ff_read_mp4_descr_length(qtmovie->stream) < 5 + 15)
{
return false;
}
/* skip 3 bytes */
stream_skip(qtmovie->stream,3);
} else {
/* skip 2 bytes */
stream_skip(qtmovie->stream,2);
}
/* get and verify DecoderConfigDescrTab */
if (stream_read_uint8(qtmovie->stream) != 0x04)
{
return false;
}
/* read length */
temp = mp4ff_read_mp4_descr_length(qtmovie->stream);
if (temp < 13) return false;
/* audioType = */ stream_read_uint8(qtmovie->stream);
/* temp = */ stream_read_int32(qtmovie->stream);//0x15000414 ????
/* maxBitrate = */ stream_read_int32(qtmovie->stream);
/* avgBitrate = */ stream_read_int32(qtmovie->stream);
/* get and verify DecSpecificInfoTag */
if (stream_read_uint8(qtmovie->stream) != 0x05)
{
return false;
}
/* read length */
qtmovie->res->codecdata_len = mp4ff_read_mp4_descr_length(qtmovie->stream);
if (qtmovie->res->codecdata_len > MAX_CODECDATA_SIZE)
{
DEBUGF("codecdata too large (%d) in esds\n",
(int)qtmovie->res->codecdata_len);
return false;
}
stream_read(qtmovie->stream, qtmovie->res->codecdata_len, qtmovie->res->codecdata);
/* will skip the remainder of the atom */
return true;
}
static bool read_chunk_stsd(qtmovie_t *qtmovie, size_t chunk_len)
{
unsigned int i;
int j;
uint32_t numentries;
size_t size_remaining = chunk_len - 8;
bool got_codec_data = false;
/* version */
stream_read_uint8(qtmovie->stream);
size_remaining -= 1;
/* flags */
stream_read_uint8(qtmovie->stream);
stream_read_uint8(qtmovie->stream);
stream_read_uint8(qtmovie->stream);
size_remaining -= 3;
numentries = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
/* if (numentries != 1)
{
DEBUGF("only expecting one entry in sample description atom!\n");
return false;
} */
for (i = 0; i < numentries; i++)
{
uint32_t entry_size;
uint32_t entry_remaining;
entry_size = stream_read_uint32(qtmovie->stream);
qtmovie->res->format = stream_read_uint32(qtmovie->stream);
DEBUGF("format: %c%c%c%c\n",SPLITFOURCC(qtmovie->res->format));
entry_remaining = entry_size;
entry_remaining -= 8;
/* sound info: */
/* reserved + data reference index + sound version + reserved */
stream_skip(qtmovie->stream, 6 + 2 + 2 + 6);
entry_remaining -= 6 + 2 + 2 + 6;
qtmovie->res->num_channels = stream_read_uint16(qtmovie->stream);
qtmovie->res->sound_sample_size = stream_read_uint16(qtmovie->stream);
entry_remaining -= 4;
/* packet size */
stream_skip(qtmovie->stream, 2);
qtmovie->res->sound_sample_rate = stream_read_uint32(qtmovie->stream);
/* reserved size */
stream_skip(qtmovie->stream, 2);
entry_remaining -= 8;
/* remaining is codec data */
if (qtmovie->res->format==MAKEFOURCC('a','l','a','c')) {
if (qtmovie->stream->ci->id3->codectype!=AFMT_MP4_ALAC) {
return false;
}
/* 12 = audio format atom, 8 = padding */
qtmovie->res->codecdata_len = entry_remaining + 12 + 8;
if (qtmovie->res->codecdata_len > MAX_CODECDATA_SIZE)
{
DEBUGF("codecdata too large (%d) in stsd\n",
(int)qtmovie->res->codecdata_len);
return false;
}
memset(qtmovie->res->codecdata, 0, qtmovie->res->codecdata_len);
/* audio format atom */
#if 0
/* The ALAC decoder skips these bytes, so there is no need to store them,
and this code isn't endian/alignment safe */
((unsigned int*)qtmovie->res->codecdata)[0] = 0x0c000000;
((unsigned int*)qtmovie->res->codecdata)[1] = MAKEFOURCC('a','m','r','f');
((unsigned int*)qtmovie->res->codecdata)[2] = MAKEFOURCC('c','a','l','a');
#endif
stream_read(qtmovie->stream,
entry_remaining,
((char*)qtmovie->res->codecdata) + 12);
entry_remaining -= entry_remaining;
got_codec_data = true;
if (entry_remaining)
stream_skip(qtmovie->stream, entry_remaining);
} else if (qtmovie->res->format==MAKEFOURCC('m','p','4','a')) {
if (qtmovie->stream->ci->id3->codectype!=AFMT_MP4_AAC &&
qtmovie->stream->ci->id3->codectype!=AFMT_MP4_AAC_HE) {
return false;
}
size_t sub_chunk_len;
fourcc_t sub_chunk_id;
sub_chunk_len = stream_read_uint32(qtmovie->stream);
if (sub_chunk_len <= 1 || sub_chunk_len > entry_remaining)
{
DEBUGF("strange size (%lu) for chunk inside mp4a\n",
(unsigned long)sub_chunk_len);
return false;
}
sub_chunk_id = stream_read_uint32(qtmovie->stream);
if (sub_chunk_id != MAKEFOURCC('e','s','d','s'))
{
DEBUGF("Expected esds chunk inside mp4a, found %c%c%c%c\n",SPLITFOURCC(sub_chunk_id));
return false;
}
j=qtmovie->stream->ci->curpos+sub_chunk_len-8;
if (read_chunk_esds(qtmovie,sub_chunk_len)) {
if (j!=qtmovie->stream->ci->curpos) {
DEBUGF("curpos=%ld, j=%d - Skipping %ld bytes\n",qtmovie->stream->ci->curpos,j,j-qtmovie->stream->ci->curpos);
stream_skip(qtmovie->stream,j-qtmovie->stream->ci->curpos);
}
got_codec_data = true;
entry_remaining-=sub_chunk_len;
} else {
DEBUGF("Error reading esds\n");
return false;
}
DEBUGF("entry_remaining=%ld\n",(long)entry_remaining);
stream_skip(qtmovie->stream,entry_remaining);
} else if (qtmovie->res->format==MAKEFOURCC('f','r','e','e')) {
/* Skip "filler" atom */
stream_skip(qtmovie->stream,entry_remaining);
} else {
DEBUGF("expecting 'alac', 'mp4a' or 'free' data format, got %c%c%c%c\n",
SPLITFOURCC(qtmovie->res->format));
return false;
}
}
return got_codec_data;
}
static bool read_chunk_stts(qtmovie_t *qtmovie, size_t chunk_len)
{
unsigned int i;
uint32_t numentries;
size_t size_remaining = chunk_len - 8;
/* version */
stream_read_uint8(qtmovie->stream);
size_remaining -= 1;
/* flags */
stream_read_uint8(qtmovie->stream);
stream_read_uint8(qtmovie->stream);
stream_read_uint8(qtmovie->stream);
size_remaining -= 3;
numentries = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
qtmovie->res->num_time_to_samples = numentries;
qtmovie->res->time_to_sample = malloc(numentries * sizeof(*qtmovie->res->time_to_sample));
if (!qtmovie->res->time_to_sample)
{
DEBUGF("stts too large\n");
return false;
}
for (i = 0; i < numentries; i++)
{
qtmovie->res->time_to_sample[i].sample_count = stream_read_uint32(qtmovie->stream);
qtmovie->res->time_to_sample[i].sample_duration = stream_read_uint32(qtmovie->stream);
size_remaining -= 8;
}
if (size_remaining)
{
DEBUGF("ehm, size remianing?\n");
stream_skip(qtmovie->stream, size_remaining);
}
return true;
}
static bool read_chunk_stsz(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
uint32_t numsizes, i;
/* version */
stream_read_uint8(qtmovie->stream);
size_remaining -= 1;
/* flags */
stream_read_uint8(qtmovie->stream);
stream_read_uint8(qtmovie->stream);
stream_read_uint8(qtmovie->stream);
size_remaining -= 3;
/* default sample size */
if (stream_read_uint32(qtmovie->stream) != 0)
{
DEBUGF("i was expecting variable samples sizes\n");
stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
return true;
}
size_remaining -= 4;
numsizes = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
/* Because this table can be really large and is only used to improve seek
* accuracy, it's optional. In that case the seek code will fall back to a
* less accurate seek method. */
qtmovie->res->num_sample_byte_sizes = numsizes;
if (numsizes * sizeof(uint32_t) < CODEC_SIZE * 1 / 2)
qtmovie->res->sample_byte_sizes = malloc(numsizes * sizeof(uint32_t));
else
qtmovie->res->sample_byte_sizes = NULL;
if (qtmovie->res->sample_byte_sizes)
{
for (i = 0; i < numsizes; ++i)
{
qtmovie->res->sample_byte_sizes[i] =
stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
}
if (size_remaining)
{
DEBUGF("extra bytes after stsz\n");
}
}
else
{
DEBUGF("stsz too large, ignoring it\n");
}
if (size_remaining)
{
stream_skip(qtmovie->stream, size_remaining);
}
return true;
}
static bool read_chunk_stsc(qtmovie_t *qtmovie, size_t chunk_len)
{
unsigned int i;
uint32_t numentries;
size_t size_remaining = chunk_len - 8;
/* version + flags */
stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
numentries = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
qtmovie->res->num_sample_to_chunks = numentries;
qtmovie->res->sample_to_chunk = malloc(numentries * sizeof(sample_to_chunk_t));
if (!qtmovie->res->sample_to_chunk)
{
DEBUGF("stsc too large\n");
return false;
}
for (i = 0; i < numentries; i++)
{
qtmovie->res->sample_to_chunk[i].first_chunk =
stream_read_uint32(qtmovie->stream);
qtmovie->res->sample_to_chunk[i].num_samples =
stream_read_uint32(qtmovie->stream);
stream_read_uint32(qtmovie->stream);
size_remaining -= 12;
}
if (size_remaining)
{
DEBUGF("ehm, size remianing?\n");
stream_skip(qtmovie->stream, size_remaining);
}
return true;
}
static bool read_chunk_stco(qtmovie_t *qtmovie, size_t chunk_len)
{
uint32_t i, k, old_i;
uint32_t numentries;
uint32_t idx = 0;
uint32_t frame;
uint32_t offset;
uint32_t old_first;
uint32_t new_first;
uint32_t old_frame;
size_t size_remaining = chunk_len - 8;
/* version + flags */
stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
numentries = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
qtmovie->res->num_lookup_table = numentries;
qtmovie->res->lookup_table = malloc(numentries * sizeof(*qtmovie->res->lookup_table));
if (!qtmovie->res->lookup_table)
{
DEBUGF("stco too large to allocate lookup_table[]\n");
return false;
}
/* read first offset */
offset = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
/* Build up lookup table. The lookup table contains the sample index and
* byte position in the file for each chunk. This table is used to seek
* and resume (see m4a_seek() and m4a_seek_raw() in libm4a/m4a.c) and
* to skip empty chunks (see m4a_check_sample_offset() in codecs/aac.c and
* libm4a/m4a.c).
* The seek/resume precision is lower than using sample_byte_size[] and
* depends on numentries. Typically the resolution is ~1/10 of all frames
* which equals about 1/4-1/2 seconds. The loss of seek precision is
* accepted to be able to avoid allocation of the large sample_byte_size[]
* table. This reduces the memory consumption by a factor of 2 or even
* more. */
i = 1;
old_i = 1;
frame = 0;
old_first = qtmovie->res->sample_to_chunk[0].first_chunk;
old_frame = qtmovie->res->sample_to_chunk[0].num_samples;
new_first = qtmovie->res->sample_to_chunk[1].first_chunk;
for (k = 1; k < numentries; ++k)
{
for (; i < qtmovie->res->num_sample_to_chunks; ++i)
{
if (i > old_i)
{
/* Only access sample_to_chunk[] if new data is required. */
old_first = qtmovie->res->sample_to_chunk[i-1].first_chunk;
old_frame = qtmovie->res->sample_to_chunk[i-1].num_samples;
new_first = qtmovie->res->sample_to_chunk[i ].first_chunk;
old_i = i;
}
if (new_first > k)
break;
frame += (new_first - old_first) * old_frame;
}
frame += (k - old_first) * old_frame;
qtmovie->res->lookup_table[idx].sample = frame;
qtmovie->res->lookup_table[idx].offset = offset;
idx++;
frame -= (k - old_first) * old_frame;
offset = stream_read_uint32(qtmovie->stream);
size_remaining -= 4;
}
/* zero-terminate the lookup table */
qtmovie->res->lookup_table[idx].sample = 0;
qtmovie->res->lookup_table[idx].offset = 0;
if (size_remaining)
{
DEBUGF("ehm, size remianing?\n");
stream_skip(qtmovie->stream, size_remaining);
}
return true;
}
static bool read_chunk_stbl(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
while (size_remaining)
{
size_t sub_chunk_len;
fourcc_t sub_chunk_id;
sub_chunk_len = stream_read_uint32(qtmovie->stream);
if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
{
DEBUGF("strange size (%lu) for chunk inside stbl\n",
(unsigned long)sub_chunk_len);
return false;
}
sub_chunk_id = stream_read_uint32(qtmovie->stream);
switch (sub_chunk_id)
{
case MAKEFOURCC('s','t','s','d'):
if (!read_chunk_stsd(qtmovie, sub_chunk_len)) {
return false;
}
break;
case MAKEFOURCC('s','t','t','s'):
if (!read_chunk_stts(qtmovie, sub_chunk_len))
{
return false;
}
break;
case MAKEFOURCC('s','t','s','z'):
if (!read_chunk_stsz(qtmovie, sub_chunk_len))
{
return false;
}
break;
case MAKEFOURCC('s','t','s','c'):
if (!read_chunk_stsc(qtmovie, sub_chunk_len))
{
return false;
}
break;
case MAKEFOURCC('s','t','c','o'):
if (!read_chunk_stco(qtmovie, sub_chunk_len))
{
return false;
}
break;
default:
/*DEBUGF("(stbl) unknown chunk id: %c%c%c%c\n",
SPLITFOURCC(sub_chunk_id));*/
stream_skip(qtmovie->stream, sub_chunk_len - 8);
}
size_remaining -= sub_chunk_len;
}
return true;
}
static bool read_chunk_minf(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
uint32_t i;
/* Check for smhd, only kind of minf we care about */
if ((i = stream_read_uint32(qtmovie->stream)) != 16)
{
DEBUGF("unexpected size in media info: %ld\n", (long)i);
stream_skip(qtmovie->stream, size_remaining-4);
return true;
}
if (stream_read_uint32(qtmovie->stream) != MAKEFOURCC('s','m','h','d'))
{
DEBUGF("not a sound header! can't handle this.\n");
return false;
}
/* now skip the rest of the atom */
stream_skip(qtmovie->stream, 16 - 8);
size_remaining -= 16;
while (size_remaining)
{
size_t sub_chunk_len;
fourcc_t sub_chunk_id;
sub_chunk_len = stream_read_uint32(qtmovie->stream);
if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
{
DEBUGF("strange size (%lu) for chunk inside minf\n",
(unsigned long)sub_chunk_len);
return false;
}
sub_chunk_id = stream_read_uint32(qtmovie->stream);
switch (sub_chunk_id)
{
case MAKEFOURCC('s','t','b','l'):
if (!read_chunk_stbl(qtmovie, sub_chunk_len)) {
return false;
}
break;
default:
/*DEBUGF("(minf) unknown chunk id: %c%c%c%c\n",
SPLITFOURCC(sub_chunk_id));*/
stream_skip(qtmovie->stream, sub_chunk_len - 8);
break;
}
size_remaining -= sub_chunk_len;
}
return true;
}
static bool read_chunk_mdia(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
while (size_remaining)
{
size_t sub_chunk_len;
fourcc_t sub_chunk_id;
sub_chunk_len = stream_read_uint32(qtmovie->stream);
if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
{
DEBUGF("strange size (%lu) for chunk inside mdia\n",
(unsigned long)sub_chunk_len);
return false;
}
sub_chunk_id = stream_read_uint32(qtmovie->stream);
switch (sub_chunk_id)
{
case MAKEFOURCC('m','i','n','f'):
if (!read_chunk_minf(qtmovie, sub_chunk_len)) {
return false;
}
break;
default:
/*DEBUGF("(mdia) unknown chunk id: %c%c%c%c\n",
SPLITFOURCC(sub_chunk_id));*/
stream_skip(qtmovie->stream, sub_chunk_len - 8);
break;
}
size_remaining -= sub_chunk_len;
}
return true;
}
/* 'trak' - a movie track - contains other atoms */
static bool read_chunk_trak(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
while (size_remaining)
{
size_t sub_chunk_len;
fourcc_t sub_chunk_id;
sub_chunk_len = stream_read_uint32(qtmovie->stream);
if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
{
DEBUGF("strange size (%lu) for chunk inside trak\n",
(unsigned long)sub_chunk_len);
return false;
}
sub_chunk_id = stream_read_uint32(qtmovie->stream);
switch (sub_chunk_id)
{
case MAKEFOURCC('m','d','i','a'):
if (!read_chunk_mdia(qtmovie, sub_chunk_len)) {
return false;
}
break;
default:
/*DEBUGF("(trak) unknown chunk id: %c%c%c%c\n",
SPLITFOURCC(sub_chunk_id));*/
stream_skip(qtmovie->stream, sub_chunk_len - 8);
break;
}
size_remaining -= sub_chunk_len;
}
return true;
}
/* 'moov' movie atom - contains other atoms */
static bool read_chunk_moov(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
while (size_remaining)
{
size_t sub_chunk_len;
fourcc_t sub_chunk_id;
sub_chunk_len = stream_read_uint32(qtmovie->stream);
if (sub_chunk_len <= 1 || sub_chunk_len > size_remaining)
{
DEBUGF("strange size (%lu) for chunk inside moov\n",
(unsigned long)sub_chunk_len);
return false;
}
sub_chunk_id = stream_read_uint32(qtmovie->stream);
switch (sub_chunk_id)
{
case MAKEFOURCC('t','r','a','k'):
if (!read_chunk_trak(qtmovie, sub_chunk_len)) {
return false;
}
break;
default:
/*DEBUGF("(moov) unknown chunk id: %c%c%c%c\n",
SPLITFOURCC(sub_chunk_id));*/
stream_skip(qtmovie->stream, sub_chunk_len - 8);
break;
}
size_remaining -= sub_chunk_len;
}
return true;
}
static void read_chunk_mdat(qtmovie_t *qtmovie, size_t chunk_len)
{
size_t size_remaining = chunk_len - 8;
qtmovie->res->mdat_len = size_remaining;
}
int qtmovie_read(stream_t *file, demux_res_t *demux_res)
{
qtmovie_t qtmovie;
/* construct the stream */
qtmovie.stream = file;
qtmovie.res = demux_res;
/* read the chunks */
while (1)
{
size_t chunk_len;
fourcc_t chunk_id;
chunk_len = stream_read_uint32(qtmovie.stream);
if (stream_eof(qtmovie.stream))
{
if(qtmovie.res->mdat_offset == 0 || qtmovie.res->format == 0)
return 0;
stream_seek(qtmovie.stream, qtmovie.res->mdat_offset);
return 1;
}
if (chunk_len == 1)
{
//DEBUGF("need 64bit support\n");
return 0;
}
chunk_id = stream_read_uint32(qtmovie.stream);
//DEBUGF("Found a chunk %c%c%c%c, length=%d\n",SPLITFOURCC(chunk_id),chunk_len);
switch (chunk_id)
{
case MAKEFOURCC('f','t','y','p'):
read_chunk_ftyp(&qtmovie, chunk_len);
break;
case MAKEFOURCC('m','o','o','v'):
if (!read_chunk_moov(&qtmovie, chunk_len)) {
return 0;
}
break;
case MAKEFOURCC('m','d','a','t'):
/* There can be empty mdats before the real one. If so, skip them */
if (chunk_len == 8)
break;
read_chunk_mdat(&qtmovie, chunk_len);
qtmovie.res->mdat_offset=stream_tell(qtmovie.stream);
/* If we've already seen the format, assume there's nothing
interesting after the mdat chunk (the file is "streamable").
This avoids having to seek, which might cause rebuffering. */
if(qtmovie.res->format > 0)
return 1;
stream_skip(qtmovie.stream, chunk_len - 8);
break;
/* these following atoms can be skipped !!!! */
case MAKEFOURCC('f','r','e','e'):
stream_skip(qtmovie.stream, chunk_len - 8);
break;
default:
//DEBUGF("(top) unknown chunk id: %c%c%c%c\n",SPLITFOURCC(chunk_id));
return 0;
}
}
return 0;
}
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