| /* |
| * The simplest AC-3 encoder |
| * Copyright (c) 2000 Fabrice Bellard |
| * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com> |
| * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de> |
| * |
| * 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 |
| * fixed-point AC-3 encoder. |
| */ |
| |
| #define CONFIG_FFT_FLOAT 0 |
| #undef CONFIG_AC3ENC_FLOAT |
| #include "ac3enc.h" |
| |
| #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED |
| #include "ac3enc_opts_template.c" |
| static AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name, |
| ac3fixed_options, LIBAVUTIL_VERSION_INT }; |
| |
| #include "ac3enc_template.c" |
| |
| |
| /** |
| * Finalize MDCT and free allocated memory. |
| */ |
| av_cold void AC3_NAME(mdct_end)(AC3MDCTContext *mdct) |
| { |
| ff_mdct_end(&mdct->fft); |
| } |
| |
| |
| /** |
| * Initialize MDCT tables. |
| * @param nbits log2(MDCT size) |
| */ |
| av_cold int AC3_NAME(mdct_init)(AVCodecContext *avctx, AC3MDCTContext *mdct, |
| int nbits) |
| { |
| int ret = ff_mdct_init(&mdct->fft, nbits, 0, -1.0); |
| mdct->window = ff_ac3_window; |
| return ret; |
| } |
| |
| |
| /** |
| * Apply KBD window to input samples prior to MDCT. |
| */ |
| void AC3_NAME(apply_window)(DSPContext *dsp, int16_t *output, |
| const int16_t *input, const int16_t *window, |
| unsigned int len) |
| { |
| dsp->apply_window_int16(output, input, window, len); |
| } |
| |
| |
| /** |
| * Calculate the log2() of the maximum absolute value in an array. |
| * @param tab input array |
| * @param n number of values in the array |
| * @return log2(max(abs(tab[]))) |
| */ |
| static int log2_tab(AC3EncodeContext *s, int16_t *src, int len) |
| { |
| int v = s->ac3dsp.ac3_max_msb_abs_int16(src, len); |
| return av_log2(v); |
| } |
| |
| |
| /** |
| * Normalize the input samples to use the maximum available precision. |
| * This assumes signed 16-bit input samples. |
| * |
| * @return exponent shift |
| */ |
| int AC3_NAME(normalize_samples)(AC3EncodeContext *s) |
| { |
| int v = 14 - log2_tab(s, s->windowed_samples, AC3_WINDOW_SIZE); |
| if (v > 0) |
| s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v); |
| /* +6 to right-shift from 31-bit to 25-bit */ |
| return v + 6; |
| } |
| |
| |
| /** |
| * Scale MDCT coefficients to 25-bit signed fixed-point. |
| */ |
| void AC3_NAME(scale_coefficients)(AC3EncodeContext *s) |
| { |
| int blk, ch; |
| |
| for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { |
| AC3Block *block = &s->blocks[blk]; |
| for (ch = 1; ch <= s->channels; ch++) { |
| s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS, |
| block->coeff_shift[ch]); |
| } |
| } |
| } |
| |
| |
| static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx) |
| { |
| AC3EncodeContext *s = avctx->priv_data; |
| s->fixed_point = 1; |
| return ff_ac3_encode_init(avctx); |
| } |
| |
| |
| AVCodec ff_ac3_fixed_encoder = { |
| "ac3_fixed", |
| AVMEDIA_TYPE_AUDIO, |
| CODEC_ID_AC3, |
| sizeof(AC3EncodeContext), |
| ac3_fixed_encode_init, |
| ff_ac3_encode_frame, |
| ff_ac3_encode_close, |
| NULL, |
| .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, |
| .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"), |
| .priv_class = &ac3enc_class, |
| .channel_layouts = ff_ac3_channel_layouts, |
| }; |