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6147 | serge | 1 | /* |
2 | * Copyright (c) 2011 Justin Ruggles |
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3 | * |
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4 | * This file is part of FFmpeg. |
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5 | * |
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6 | * FFmpeg is free software; you can redistribute it and/or |
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7 | * modify it under the terms of the GNU Lesser General Public |
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8 | * License as published by the Free Software Foundation; either |
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9 | * version 2.1 of the License, or (at your option) any later version. |
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10 | * |
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11 | * FFmpeg is distributed in the hope that it will be useful, |
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12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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14 | * Lesser General Public License for more details. |
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15 | * |
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16 | * You should have received a copy of the GNU Lesser General Public |
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17 | * License along with FFmpeg; if not, write to the Free Software |
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18 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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19 | */ |
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20 | |||
21 | #include "libavutil/common.h" |
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22 | #include "libavutil/intreadwrite.h" |
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23 | #include "libavutil/mathematics.h" |
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24 | #include "adx.h" |
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25 | |||
26 | void ff_adx_calculate_coeffs(int cutoff, int sample_rate, int bits, int *coeff) |
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27 | { |
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28 | double a, b, c; |
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29 | |||
30 | a = M_SQRT2 - cos(2.0 * M_PI * cutoff / sample_rate); |
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31 | b = M_SQRT2 - 1.0; |
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32 | c = (a - sqrt((a + b) * (a - b))) / b; |
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33 | |||
34 | coeff[0] = lrintf(c * 2.0 * (1 << bits)); |
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35 | coeff[1] = lrintf(-(c * c) * (1 << bits)); |
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36 | } |
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37 | |||
38 | int ff_adx_decode_header(AVCodecContext *avctx, const uint8_t *buf, |
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39 | int bufsize, int *header_size, int *coeff) |
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40 | { |
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41 | int offset, cutoff; |
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42 | |||
43 | if (bufsize < 24) |
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44 | return AVERROR_INVALIDDATA; |
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45 | |||
46 | if (AV_RB16(buf) != 0x8000) |
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47 | return AVERROR_INVALIDDATA; |
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48 | offset = AV_RB16(buf + 2) + 4; |
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49 | |||
50 | /* if copyright string is within the provided data, validate it */ |
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51 | if (bufsize >= offset && offset >= 6 && memcmp(buf + offset - 6, "(c)CRI", 6)) |
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52 | return AVERROR_INVALIDDATA; |
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53 | |||
54 | /* check for encoding=3 block_size=18, sample_size=4 */ |
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55 | if (buf[4] != 3 || buf[5] != 18 || buf[6] != 4) { |
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56 | avpriv_request_sample(avctx, "Support for this ADX format"); |
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57 | return AVERROR_PATCHWELCOME; |
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58 | } |
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59 | |||
60 | /* channels */ |
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61 | avctx->channels = buf[7]; |
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62 | if (avctx->channels <= 0 || avctx->channels > 2) |
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63 | return AVERROR_INVALIDDATA; |
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64 | |||
65 | /* sample rate */ |
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66 | avctx->sample_rate = AV_RB32(buf + 8); |
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67 | if (avctx->sample_rate < 1 || |
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68 | avctx->sample_rate > INT_MAX / (avctx->channels * BLOCK_SIZE * 8)) |
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69 | return AVERROR_INVALIDDATA; |
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70 | |||
71 | /* bit rate */ |
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72 | avctx->bit_rate = avctx->sample_rate * avctx->channels * BLOCK_SIZE * 8 / BLOCK_SAMPLES; |
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73 | |||
74 | /* LPC coefficients */ |
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75 | if (coeff) { |
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76 | cutoff = AV_RB16(buf + 16); |
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77 | ff_adx_calculate_coeffs(cutoff, avctx->sample_rate, COEFF_BITS, coeff); |
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78 | } |
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79 | |||
80 | *header_size = offset; |
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81 | return 0; |
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82 | }>=>>><>><> |