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FFmpeg/libavcodec/raw.h
Andreas Rheinhardt 3d53cefb49 avcodec/raw: Reduce number of avpriv symbols
libavcodec currently exports four avpriv symbols that deal with
PixelFormatTags: avpriv_get_raw_pix_fmt_tags, avpriv_find_pix_fmt,
avpriv_pix_fmt_bps_avi and avpriv_pix_fmt_bps_mov. The latter two are
lists of PixelFormatTags, the former returns such a list and the second
searches a list for a pixel format that matches a given fourcc; only
one of the aforementioned three lists is ever searched.

Yet for avpriv_pix_fmt_bps_avi, avpriv_pix_fmt_bps_mov and
avpriv_find_pix_fmt the overhead of exporting these functions actually
exceeds the size of said objects (at least for ELF; the following numbers
are for x64 Ubuntu 20.10):
The code size of avpriv_find_pix_fmt is small (GCC 10.2 37B, Clang 11 41B),
yet exporting it adds a 20B string for the name alone to the exporting
as well as to each importing library; there is more: Four bytes in the
exporting libraries .gnu.hash; two bytes each for the exporting as well
as each importing libraries .gnu.version; 24B in the exporting as well
as each importing libraries .dynsym; 16B+24B for an entry in .plt as
well as the accompanying relocation entry in .rela.plt for each
importing library.

The overhead for the lists is similar: The strings are 23B and the
.plt+.rela.plt pair is replaced by 8B+24B for an entry in .got and
a relocation entry in .rela.dyn. These lists have a size of 80 resp.
72 bytes.

Yet for ff_raw_pix_fmt_tags, exporting it is advantageous compared to
duplicating it into libavformat and potentially libavdevice. Therefore
this commit replaces all library uses of the four symbols with a single
function that is exported for shared builds. It has an enum parameter
to choose the desired list besides the parameter for the fourcc. New
lists can be supported with new enum values.

Unfortunately, avpriv_get_raw_pix_fmt_tags could not be removed, as the
fourcc2pixfmt tool uses the table of raw pix fmts. No other user of this
function remains.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2022-01-04 13:16:49 +01:00

49 lines
1.3 KiB
C

/*
* Raw Video Codec
* Copyright (c) 2001 Fabrice Bellard
*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* Raw Video Codec
*/
#ifndef AVCODEC_RAW_H
#define AVCODEC_RAW_H
#include "libavutil/pixfmt.h"
typedef struct PixelFormatTag {
enum AVPixelFormat pix_fmt;
unsigned int fourcc;
} PixelFormatTag;
const struct PixelFormatTag *avpriv_get_raw_pix_fmt_tags(void);
enum PixelFormatTagLists {
PIX_FMT_LIST_RAW,
PIX_FMT_LIST_AVI,
PIX_FMT_LIST_MOV,
};
enum AVPixelFormat avpriv_pix_fmt_find(enum PixelFormatTagLists list,
unsigned fourcc);
#endif /* AVCODEC_RAW_H */