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/* nal_units.c
*
* Copyright (c) 2003-2019 HandBrake Team
* This file is part of the HandBrake source code.
* Homepage: <http://handbrake.fr/>.
* It may be used under the terms of the GNU General Public License v2.
* For full terms see the file COPYING file or visit http://www.gnu.org/licenses/gpl-2.0.html
*/
#include <stdint.h>
#include <string.h>
#include "handbrake/common.h"
#include "handbrake/nal_units.h"
static const uint8_t hb_annexb_startcode[] = { 0x00, 0x00, 0x00, 0x01, };
size_t hb_nal_unit_write_annexb(uint8_t *buf,
const uint8_t *nal_unit,
const size_t nal_unit_size)
{
if (buf != NULL)
{
memcpy(buf, hb_annexb_startcode, sizeof(hb_annexb_startcode));
memcpy(buf + sizeof(hb_annexb_startcode), nal_unit, nal_unit_size);
}
return sizeof(hb_annexb_startcode) + nal_unit_size;
}
size_t hb_nal_unit_write_isomp4(uint8_t *buf,
const uint8_t *nal_unit,
const size_t nal_unit_size)
{
int i;
uint8_t length[4]; // 4-byte length replaces Annex B start code prefix
if (buf != NULL)
{
for (i = 0; i < sizeof(length); i++)
{
length[i] = (nal_unit_size >> (8 * (sizeof(length) - 1 - i))) & 0xff;
}
memcpy(buf, &length[0], sizeof(length));
memcpy(buf + sizeof(length), nal_unit, nal_unit_size);
}
return sizeof(length) + nal_unit_size;
}
uint8_t* hb_annexb_find_next_nalu(const uint8_t *start, size_t *size)
{
uint8_t *nal = NULL;
uint8_t *buf = (uint8_t*)start;
uint8_t *end = (uint8_t*)start + *size;
/* Look for an Annex B start code prefix (3-byte sequence == 1) */
while (end - buf > 3)
{
if (!buf[0] && !buf[1] && buf[2] == 1)
{
nal = (buf += 3); // NAL unit begins after start code
break;
}
buf++;
}
if (nal == NULL)
{
*size = 0;
return NULL;
}
/*
* Start code prefix found, look for the next one to determine the size
*
* A 4-byte sequence == 1 is also a start code, so check for a 3-byte
* sequence == 0 too (start code emulation prevention will prevent such a
* sequence from occurring outside of a start code prefix)
*/
while (end - buf > 3)
{
if (!buf[0] && !buf[1] && (!buf[2] || buf[2] == 1))
{
end = buf;
break;
}
buf++;
}
*size = end - nal;
return nal;
}
hb_buffer_t* hb_nal_bitstream_annexb_to_mp4(const uint8_t *data,
const size_t size)
{
hb_buffer_t *out;
uint8_t *buf, *end;
size_t out_size, buf_size;
out_size = 0;
buf_size = size;
buf = (uint8_t*)data;
end = (uint8_t*)data + size;
while ((buf = hb_annexb_find_next_nalu(buf, &buf_size)) != NULL)
{
out_size += hb_nal_unit_write_isomp4(NULL, buf, buf_size);
buf_size = end - buf;
}
out = hb_buffer_init(out_size);
if (out == NULL)
{
hb_error("hb_nal_bitstream_annexb_to_mp4: hb_buffer_init failed");
return NULL;
}
out_size = 0;
buf_size = size;
buf = (uint8_t*)data;
end = (uint8_t*)data + size;
while ((buf = hb_annexb_find_next_nalu(buf, &buf_size)) != NULL)
{
out_size += hb_nal_unit_write_isomp4(out->data + out_size, buf, buf_size);
buf_size = end - buf;
}
return out;
}
static size_t mp4_nal_unit_length(const uint8_t *data,
const size_t nal_length_size,
size_t *nal_unit_length)
{
uint8_t i;
/* In MP4, NAL units are preceded by a 2-4 byte length field */
for (i = 0, *nal_unit_length = 0; i < nal_length_size; i++)
{
*nal_unit_length |= data[i] << (8 * (nal_length_size - 1 - i));
}
return nal_length_size;
}
hb_buffer_t* hb_nal_bitstream_mp4_to_annexb(const uint8_t *data,
const size_t size,
const uint8_t nal_length_size)
{
hb_buffer_t *out;
uint8_t *buf, *end;
size_t out_size, nal_size;
out_size = 0;
buf = (uint8_t*)data;
end = (uint8_t*)data + size;
while (end - buf > nal_length_size)
{
buf += mp4_nal_unit_length(buf, nal_length_size, &nal_size);
if (end - buf < nal_size)
{
hb_log("hb_nal_bitstream_mp4_to_annexb: truncated bitstream"
" (remaining: %lu, expected: %lu)", end - buf, nal_size);
return NULL;
}
out_size += hb_nal_unit_write_annexb(NULL, buf, nal_size);
buf += nal_size;
}
out = hb_buffer_init(out_size);
if (out == NULL)
{
hb_error("hb_nal_bitstream_mp4_to_annexb: hb_buffer_init failed");
return NULL;
}
out_size = 0;
buf = (uint8_t*)data;
end = (uint8_t*)data + size;
while (end - buf > nal_length_size)
{
buf += mp4_nal_unit_length(buf, nal_length_size, &nal_size);
out_size += hb_nal_unit_write_annexb(out->data + out_size, buf, nal_size);
buf += nal_size;
}
return out;
}
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