mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2026-11-06 05:17:42 +00:00
Romain Beauxis
fda85d16e0
MPADecodeHeader is allocated by callers in other libraries, on the stack among other places, so fields cannot be added to it. Add MPADecodeHeader2, which holds every field of the header and which libavcodec itself allocates, along with a packer turning it back into header bits. A test program walks the frames of a file, checks that every header encodes back to its original bits and prints the header fields.
128 lines
3.8 KiB
C
128 lines
3.8 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* Walks the MPEG audio frames of a file, checks that every frame header
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* encodes back to its original bits, and prints each distinct header.
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*/
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#include <inttypes.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <string.h>
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#include "libavutil/file.h"
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#include "libavutil/mem.h"
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#include "libavutil/intreadwrite.h"
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#include "libavcodec/mpegaudiodecheader.h"
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#define PADDING_BIT (1U << 9)
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static size_t id3v2_size(const uint8_t *buf, size_t size)
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{
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if (size < 10 || memcmp(buf, "ID3", 3))
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return 0;
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return 10 + (buf[5] & 0x10 ? 10 : 0) +
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((buf[6] & 0x7f) << 21 | (buf[7] & 0x7f) << 14 |
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(buf[8] & 0x7f) << 7 | (buf[9] & 0x7f));
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}
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static void print_header(size_t offset, unsigned frames, uint32_t bits,
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const MPADecodeHeader2 *header)
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{
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printf("offset=%zu frames=%u header=%08"PRIX32" layer=%d sample_rate=%d "
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"bit_rate=%d crc=%d mode=%d mode_ext=%d copyright=%d original=%d "
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"emphasis=%d private_bit=%d\n",
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offset, frames, bits, header->layer, header->sample_rate,
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header->bit_rate, header->error_protection, header->mode,
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header->mode_ext, header->copyright, header->original,
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header->emphasis, header->private_bit);
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}
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int main(int argc, char *argv[])
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{
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MPADecodeHeader2 run_header, *header = NULL;
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uint8_t *buf;
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size_t size, pos, run_offset = 0;
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uint32_t run_bits = 0;
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unsigned run_frames = 0, total_frames = 0;
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int ret = 1;
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if (argc != 2) {
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fprintf(stderr, "Usage: %s <file>\n", argv[0]);
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return 1;
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}
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if (av_file_map(argv[1], &buf, &size, 0, NULL) < 0) {
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fprintf(stderr, "Failed to open '%s'\n", argv[1]);
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return 1;
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}
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pos = id3v2_size(buf, size);
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while (pos + 4 <= size) {
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uint32_t bits = AV_RB32(buf + pos);
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uint32_t encoded;
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int decoded;
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if (ff_mpa_check_header(bits) < 0) {
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pos++;
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continue;
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}
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if (header)
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memset(header, 0, sizeof(*header));
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decoded = avpriv_mpegaudio_decode_header2(&header, bits);
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if (decoded < 0)
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goto end;
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encoded = ff_mpa_encode_header(header);
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if (encoded != bits) {
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printf("offset=%zu header=%08"PRIX32" encoded back as %08"PRIX32"\n",
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pos, bits, encoded);
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goto end;
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}
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if (run_frames && (bits & ~PADDING_BIT) != (run_bits & ~PADDING_BIT)) {
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print_header(run_offset, run_frames, run_bits, &run_header);
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run_frames = 0;
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}
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if (!run_frames) {
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run_offset = pos;
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run_bits = bits;
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run_header = *header;
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}
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run_frames++;
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total_frames++;
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pos += decoded == 0 ? header->frame_size : 1;
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}
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if (run_frames)
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print_header(run_offset, run_frames, run_bits, &run_header);
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printf("frames=%u\n", total_frames);
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ret = !total_frames;
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end:
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av_freep(&header);
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av_file_unmap(buf, size);
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return ret;
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}
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