FFmpeg: libavcodec/adx.c Source File

FFmpeg

libavcodec

adx.c

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1 /*

2 * Copyright (c) 2011 Justin Ruggles

3 *

4 * This file is part of FFmpeg.

5 *

6 * FFmpeg is free software; you can redistribute it and/or

7 * modify it under the terms of the GNU Lesser General Public

8 * License as published by the Free Software Foundation; either

9 * version 2.1 of the License, or (at your option) any later version.

10 *

11 * FFmpeg is distributed in the hope that it will be useful,

12 * but WITHOUT ANY WARRANTY; without even the implied warranty of

13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

14 * Lesser General Public License for more details.

15 *

16 * You should have received a copy of the GNU Lesser General Public

17 * License along with FFmpeg; if not, write to the Free Software

18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

19 */

20

21 #include "libavutil/common.h"

22 #include "libavutil/intreadwrite.h"

23 #include "libavutil/mathematics.h"

24 #include "adx.h"

25

26 void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff)

27 {

28 double a, b, c;

29

30 a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate);

31 b = M_SQRT2 - 1.0;

32 c = (a - sqrt((a + b) * (a - b))) / b;

33

34 coeff[0] = lrintf(c * 2.0 * (1 << bits));

35 coeff[1] = lrintf(-(c * c) * (1 << bits));

36 }

37

38 int ff_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf,

39 int bufsize, int *header_size, int *coeff)

40 {

41 int offset, cutoff, channels;

42

43 if (bufsize < 24)

44 return AVERROR_INVALIDDATA;

45

46 if (AV_RB16(buf) != 0x8000)

47 return AVERROR_INVALIDDATA;

48 offset = AV_RB16(buf + 2) + 4;

49

50 /* if copyright string is within the provided data, validate it */

51 if (bufsize >= offset && offset >= 6 && memcmp(buf + offset - 6, "(c)CRI", 6))

52 return AVERROR_INVALIDDATA;

53

54 /* check for encoding=3 block_size=18, sample_size=4 */

55 if (buf[4] != 3 || buf[5] != 18 || buf[6] != 4) {

56 avpriv_request_sample(avctx, "Support for this ADX format");

57 return AVERROR_PATCHWELCOME;

58 }

59

60 /* channels */

61 channels = buf[7];

62 if (channels <= 0 || channels > 2)

63 return AVERROR_INVALIDDATA;

64

65 if (avctx->ch_layout.nb_channels != channels) {

66 av_channel_layout_uninit(&avctx->ch_layout);

67 avctx->ch_layout.order = AV_CHANNEL_ORDER_UNSPEC;

68 avctx->ch_layout.nb_channels = channels;

69 }

70

71 /* sample rate */

72 avctx->sample_rate = AV_RB32(buf + 8);

73 if (avctx->sample_rate < 1 ||

74 avctx->sample_rate > INT_MAX / (channels * BLOCK_SIZE * 8))

75 return AVERROR_INVALIDDATA;

76

77 /* bit rate */

78 avctx->bit_rate = avctx->sample_rate * channels * BLOCK_SIZE * 8 / BLOCK_SAMPLES;

79

80 /* LPC coefficients */

81 if (coeff) {

82 cutoff = AV_RB16(buf + 16);

83 ff_adx_calculate_coeffs(cutoff, avctx->sample_rate, COEFF_BITS, coeff);

84 }

85

86 *header_size = offset;

87 return 0;

88 }

AVCodecContext::sample_rate

int sample_rate

samples per second

Definition: avcodec.h:998

b

#define b

Definition: input.c:34

AVChannelLayout::order

enum AVChannelOrder order

Channel order used in this layout.

Definition: channel_layout.h:295

AVChannelLayout::nb_channels

int nb_channels

Number of channels in this layout.

Definition: channel_layout.h:300

sample_rate

Definition: ffmpeg_filter.c:153

AVCodecContext::ch_layout

AVChannelLayout ch_layout

Audio channel layout.

Definition: avcodec.h:2056

AV_CHANNEL_ORDER_UNSPEC

@ AV_CHANNEL_ORDER_UNSPEC

Only the channel count is specified, without any further information about the channel order.

Definition: channel_layout.h:106

#define BLOCK_SAMPLES

Definition: adx.h:54

uint8_t bits

Definition: vp3data.h:141

channels

Definition: aptx.h:32

AVERROR_PATCHWELCOME

#define AVERROR_PATCHWELCOME

Not yet implemented in FFmpeg, patches welcome.

Definition: error.h:64

AVCodecContext::bit_rate

int64_t bit_rate

the average bitrate

Definition: avcodec.h:439

c

Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c

Definition: undefined.txt:32

av_channel_layout_uninit

void av_channel_layout_uninit(AVChannelLayout *channel_layout)

Free any allocated data in the channel layout and reset the channel count to 0.

Definition: channel_layout.c:630

ff_adx_calculate_coeffs

void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff)

Calculate LPC coefficients based on cutoff frequency and sample rate.

Definition: adx.c:26

uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_RB32

Definition: bytestream.h:96

a

The reader does not expect b to be semantically here and if the code is changed by maybe adding a a division or other the signedness will almost certainly be mistaken To avoid this confusion a new type was SUINT is the C unsigned type but it holds a signed int to use the same example SUINT a

Definition: undefined.txt:41

it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset

Definition: writing_filters.txt:86

#define M_PI

Definition: mathematics.h:52

#define lrintf(x)

Definition: libm_mips.h:72

main external API structure.

Definition: avcodec.h:389

#define COEFF_BITS

Definition: adx.h:51

avpriv_request_sample

#define avpriv_request_sample(...)

Definition: tableprint_vlc.h:36

#define M_SQRT2

Definition: mathematics.h:61

static const double coeff[2][5]

Definition: vf_owdenoise.c:78

AVERROR_INVALIDDATA

#define AVERROR_INVALIDDATA

Invalid data found when processing input.

Definition: error.h:61

#define BLOCK_SIZE

Definition: adx.h:53

ff_adx_decode_header

int ff_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf, int bufsize, int *header_size, int *coeff)

Decode ADX stream header.

Definition: adx.c:38

uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16

Definition: bytestream.h:98

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