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qtmux: Make sure to write 64-bit STCO table when needed.

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qtmux attempts to choose between writing a 32-bit stco chunk offset table
when it can, but switch to a 64-bit co64 table when file offsets go over
4GB.

This patch fixes a problem where the atom handling code was checking
mdat-relative offsets instead of the final file offset (computed by
adding the mdat position plus the mdat-relative offset) - leading to
problems where files with a size between 4GB and 4GB+offset-of-the-mdat
would write incorrect STCO tables with some samples having truncated
32-bit offsets.

Smaller files write STCO correctly, larger files would switch to
co64 and also output correctly.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/970>
This commit is contained in:
Jan Schmidt 2021-04-30 08:12:47 +10:00
parent 5e932395a4
commit 7c5f2185a9
2 changed files with 24 additions and 7 deletions
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25
gst/isomp4/atoms.c
View file

@ -850,6 +850,9 @@ atom_co64_init (AtomSTCO64 * co64)
guint8 flags[3] = { 0, 0, 0 };
atom_full_init (&co64->header, FOURCC_stco, 0, 0, 0, flags);
co64->chunk_offset = 0;
co64->max_offset = 0;
atom_array_init (&co64->entries, 256);
}
@ -2422,7 +2425,17 @@ atom_stco64_copy_data (AtomSTCO64 * stco64, guint8 ** buffer, guint64 * size,
{
guint64 original_offset = *offset;
guint i;
gboolean trunc_to_32 = stco64->header.header.type == FOURCC_stco;
/* If any (mdat-relative) offset will by over 32-bits when converted to an
* absolute file offset then we need to write a 64-bit co64 atom, otherwise
* we can write a smaller stco 32-bit table */
gboolean write_stco64 =
(stco64->max_offset + stco64->chunk_offset) > G_MAXUINT32;
if (write_stco64)
stco64->header.header.type = FOURCC_co64;
else
stco64->header.header.type = FOURCC_stco;
if (!atom_full_copy_data (&stco64->header, buffer, size, offset)) {
return 0;
@ -2438,10 +2451,10 @@ atom_stco64_copy_data (AtomSTCO64 * stco64, guint8 ** buffer, guint64 * size,
guint64 value =
atom_array_index (&stco64->entries, i) + stco64->chunk_offset;
if (trunc_to_32) {
prop_copy_uint32 ((guint32) value, buffer, size, offset);
} else {
if (write_stco64) {
prop_copy_uint64 (value, buffer, size, offset);
} else {
prop_copy_uint32 ((guint32) value, buffer, size, offset);
}
}
@ -3171,8 +3184,8 @@ atom_stco64_add_entry (AtomSTCO64 * stco64, guint64 entry)
return FALSE;
atom_array_append (&stco64->entries, entry, 256);
if (entry > G_MAXUINT32)
stco64->header.header.type = FOURCC_co64;
if (entry > stco64->max_offset)
stco64->max_offset = entry;
return TRUE;
}

6
gst/isomp4/atoms.h
View file

@ -548,13 +548,17 @@ typedef struct _AtomTREF
/*
* used for both STCO and CO64
* if used as STCO, entries should be truncated to use only 32bits
* The table will be written out as STCO automatically when
* the offsets being written will fit in a 32-bit table,
* otherwise it is written as CO64
*/
typedef struct _AtomSTCO64
{
AtomFull header;
/* Global offset to add to entries when serialising */
guint32 chunk_offset;
/* Maximum offset stored in the table */
guint64 max_offset;
ATOM_ARRAY (guint64) entries;
} AtomSTCO64;