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mpv/demux/ebml.h
wm4 9e1fbffc37 demux_mkv: rewrite packet reading to avoid 1 memcpy()
This directly reads individual mkv sub-packets (block laces) into a
dedicated AVBufferRefs, which can be directly used for creating packets
without a additional copy of the packet data. This also means we switch
parsing of block header fields and lacing metadata to read directly from
the stream, instead of a memory buffer.

This could have been much easier if libavcodec didn't require padding
the packet data with zero bytes. We could just have each packet
reference a slice of the block data. But as it is, the only way to get
padding without a copy is to read the laces into individually allocated
(and padded) memory block, which required a larger rewrite.

This probably makes recovering from broken mkv files slightly worse if
the transport is unseekable. We just read, and then check if we've
overread. But I think that shouldn't be a real concern.

No actual measureable performance change. Potential for some
regressions, as this is quite intrusive, and touches weird obscure shit
like mkv lacing. Still keeping it because I like how it removes some
redundant EBML parsing functions.
2017-11-05 18:13:34 +01:00

94 lines
2.6 KiB
C

/*
* This file is part of mpv.
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef MPLAYER_EBML_H
#define MPLAYER_EBML_H
#include <inttypes.h>
#include <stddef.h>
#include <stdbool.h>
#include "stream/stream.h"
#include "misc/bstr.h"
struct mp_log;
/* EBML version supported */
#define EBML_VERSION 1
enum ebml_elemtype {
EBML_TYPE_SUBELEMENTS,
EBML_TYPE_UINT,
EBML_TYPE_SINT,
EBML_TYPE_FLOAT,
EBML_TYPE_STR,
EBML_TYPE_BINARY,
EBML_TYPE_EBML_ID,
};
struct ebml_field_desc {
uint32_t id;
bool multiple;
int offset;
int count_offset;
const struct ebml_elem_desc *desc;
};
struct ebml_elem_desc {
char *name;
enum ebml_elemtype type;
int size;
int field_count;
const struct ebml_field_desc *fields;
};
struct ebml_parse_ctx {
struct mp_log *log;
void *talloc_ctx;
bool has_errors;
bool no_error_messages;
};
#include "ebml_types.h"
#define EBML_ID_INVALID 0xffffffff
/* matroska track types */
#define MATROSKA_TRACK_VIDEO 0x01 /* rectangle-shaped pictures aka video */
#define MATROSKA_TRACK_AUDIO 0x02 /* anything you can hear */
#define MATROSKA_TRACK_COMPLEX 0x03 /* audio+video in same track used by DV */
#define MATROSKA_TRACK_LOGO 0x10 /* overlay-pictures displayed over video*/
#define MATROSKA_TRACK_SUBTITLE 0x11 /* text-subtitles */
#define MATROSKA_TRACK_CONTROL 0x20 /* control-codes for menu or other stuff*/
#define EBML_UINT_INVALID UINT64_MAX
#define EBML_INT_INVALID INT64_MAX
bool ebml_is_mkv_level1_id(uint32_t id);
uint32_t ebml_read_id (stream_t *s);
uint64_t ebml_read_length (stream_t *s);
int64_t ebml_read_signed_length(stream_t *s);
uint64_t ebml_read_uint (stream_t *s);
int64_t ebml_read_int (stream_t *s);
int ebml_read_skip(struct mp_log *log, int64_t end, stream_t *s);
int ebml_resync_cluster(struct mp_log *log, stream_t *s);
int ebml_read_element(struct stream *s, struct ebml_parse_ctx *ctx,
void *target, const struct ebml_elem_desc *desc);
#endif /* MPLAYER_EBML_H */