33e8294fbfb11117b098f056d3992106399e23c8
[libav.git] / libavcodec / ac3enc_float.c
1 /*
2 * The simplest AC-3 encoder
3 * Copyright (c) 2000 Fabrice Bellard
4 * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
5 * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 /**
25 * @file
26 * floating-point AC-3 encoder.
27 */
28
29 #define CONFIG_AC3ENC_FLOAT 1
30 #include "ac3enc.c"
31
32
33 /**
34 * Finalize MDCT and free allocated memory.
35 */
36 static av_cold void mdct_end(AC3MDCTContext *mdct)
37 {
38 ff_mdct_end(&mdct->fft);
39 av_freep(&mdct->window);
40 }
41
42
43 /**
44 * Initialize MDCT tables.
45 * @param nbits log2(MDCT size)
46 */
47 static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
48 int nbits)
49 {
50 float *window;
51 int i, n, n2;
52
53 n = 1 << nbits;
54 n2 = n >> 1;
55
56 window = av_malloc(n * sizeof(*window));
57 if (!window) {
58 av_log(avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
59 return AVERROR(ENOMEM);
60 }
61 ff_kbd_window_init(window, 5.0, n2);
62 for (i = 0; i < n2; i++)
63 window[n-1-i] = window[i];
64 mdct->window = window;
65
66 return ff_mdct_init(&mdct->fft, nbits, 0, -2.0 / n);
67 }
68
69
70 /**
71 * Calculate a 512-point MDCT
72 * @param out 256 output frequency coefficients
73 * @param in 512 windowed input audio samples
74 */
75 static void mdct512(AC3MDCTContext *mdct, float *out, float *in)
76 {
77 ff_mdct_calc(&mdct->fft, out, in);
78 }
79
80
81 /**
82 * Apply KBD window to input samples prior to MDCT.
83 */
84 static void apply_window(DSPContext *dsp, float *output, const float *input,
85 const float *window, int n)
86 {
87 dsp->vector_fmul(output, input, window, n);
88 }
89
90
91 /**
92 * Normalize the input samples to use the maximum available precision.
93 */
94 static int normalize_samples(AC3EncodeContext *s)
95 {
96 /* Normalization is not needed for floating-point samples, so just return 0 */
97 return 0;
98 }
99
100
101 /**
102 * Scale MDCT coefficients from float to 24-bit fixed-point.
103 */
104 static void scale_coefficients(AC3EncodeContext *s)
105 {
106 int i;
107 for (i = 0; i < AC3_MAX_COEFS * AC3_MAX_BLOCKS * s->channels; i++)
108 s->fixed_coef_buffer[i] = SCALE_FLOAT(s->mdct_coef_buffer[i], 24);
109 }
110
111
112 AVCodec ac3_encoder = {
113 "ac3",
114 AVMEDIA_TYPE_AUDIO,
115 CODEC_ID_AC3,
116 sizeof(AC3EncodeContext),
117 ac3_encode_init,
118 ac3_encode_frame,
119 ac3_encode_close,
120 NULL,
121 .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_FLT,AV_SAMPLE_FMT_NONE},
122 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
123 .channel_layouts = ac3_channel_layouts,
124 };