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avformat/avc: Add functions to split access unit into list of NALUs

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This will allow to avoid the temporary buffer and memcpys
when repacketing annex B to mp4-style H.264/H.265 without
searching twice for start codes.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2022-01-16 01:17:26 +01:00
parent f9b8b89b75
commit b177fca06b
2 changed files with 66 additions and 3 deletions
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40
libavformat/avc.c
View File

@ -70,7 +70,8 @@ const uint8_t *ff_avc_find_startcode(const uint8_t *p, const uint8_t *end){
return out;
}
int ff_avc_parse_nal_units(AVIOContext *pb, const uint8_t *buf_in, int size)
static int avc_parse_nal_units(AVIOContext *pb, NALUList *list,
const uint8_t *buf_in, int size)
{
const uint8_t *p = buf_in;
const uint8_t *end = p + size;
@ -79,19 +80,52 @@ int ff_avc_parse_nal_units(AVIOContext *pb, const uint8_t *buf_in, int size)
size = 0;
nal_start = ff_avc_find_startcode(p, end);
for (;;) {
const size_t nalu_limit = SIZE_MAX / sizeof(*list->nalus);
while (nal_start < end && !*(nal_start++));
if (nal_start == end)
break;
nal_end = ff_avc_find_startcode(nal_start, end);
avio_wb32(pb, nal_end - nal_start);
avio_write(pb, nal_start, nal_end - nal_start);
if (pb) {
avio_wb32(pb, nal_end - nal_start);
avio_write(pb, nal_start, nal_end - nal_start);
} else if (list->nb_nalus >= nalu_limit) {
return AVERROR(ERANGE);
} else {
NALU *tmp = av_fast_realloc(list->nalus, &list->nalus_array_size,
(list->nb_nalus + 1) * sizeof(*list->nalus));
if (!tmp)
return AVERROR(ENOMEM);
list->nalus = tmp;
tmp[list->nb_nalus++] = (NALU){ .offset = nal_start - p,
.size = nal_end - nal_start };
}
size += 4 + nal_end - nal_start;
nal_start = nal_end;
}
return size;
}
int ff_avc_parse_nal_units(AVIOContext *pb, const uint8_t *buf_in, int size)
{
return avc_parse_nal_units(pb, NULL, buf_in, size);
}
int ff_nal_units_create_list(NALUList *list, const uint8_t *buf, int size)
{
list->nb_nalus = 0;
return avc_parse_nal_units(NULL, list, buf, size);
}
void ff_nal_units_write_list(const NALUList *list, AVIOContext *pb,
const uint8_t *buf)
{
for (unsigned i = 0; i < list->nb_nalus; i++) {
avio_wb32(pb, list->nalus[i].size);
avio_write(pb, buf + list->nalus[i].offset, list->nalus[i].size);
}
}
int ff_avc_parse_nal_units_buf(const uint8_t *buf_in, uint8_t **buf, int *size)
{
AVIOContext *pb;

29
libavformat/avc.h
View File

@ -25,6 +25,35 @@
#include <stdint.h>
#include "avio.h"
typedef struct NALU {
int offset;
uint32_t size;
} NALU;
typedef struct NALUList {
NALU *nalus;
unsigned nalus_array_size;
unsigned nb_nalus; ///< valid entries in nalus
} NALUList;
/* This function will parse the given annex B buffer and create
* a NALUList from it. This list can be passed to ff_nal_units_write_list()
* to write the access unit reformatted to mp4.
*
* @param list A NALUList. The list->nalus and list->nalus_array_size
* must be valid when calling this function and may be updated.
* nb_nalus is set by this function on success.
* @param buf buffer containing annex B H.264 or H.265. Must be padded.
* @param size size of buf, excluding padding.
* @return < 0 on error, the size of the mp4-style packet on success.
*/
int ff_nal_units_create_list(NALUList *list, const uint8_t *buf, int size);
/* Writes a NALUList to the specified AVIOContext. The list must originate
* from ff_nal_units_create_list() with the same buf. */
void ff_nal_units_write_list(const NALUList *list, AVIOContext *pb,
const uint8_t *buf);
int ff_avc_parse_nal_units(AVIOContext *s, const uint8_t *buf, int size);
int ff_avc_parse_nal_units_buf(const uint8_t *buf_in, uint8_t **buf, int *size);
int ff_isom_write_avcc(AVIOContext *pb, const uint8_t *data, int len);