From 6fd96d1a85f3b81a1dbf08b79ba395506471ded0 Mon Sep 17 00:00:00 2001
From: Justin Ruggles <justin.ruggles@gmail.com>
Date: Tue, 4 Jan 2011 11:53:44 +0000
Subject: Change the AC-3 encoder to use floating-point. Fixed-point AC-3
 encoder renamed to ac3_fixed. Regression test acodec-ac3 renamed to
 acodec-ac3_fixed. Regression test lavf-rm changed to use ac3_fixed encoder.

Originally committed as revision 26209 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/ac3enc_float.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)
 create mode 100644 libavcodec/ac3enc_float.c

(limited to 'libavcodec/ac3enc_float.c')

diff --git a/libavcodec/ac3enc_float.c b/libavcodec/ac3enc_float.c
new file mode 100644
index 0000000000..82d806bc06
--- /dev/null
+++ b/libavcodec/ac3enc_float.c
@@ -0,0 +1,117 @@
+/*
+ * 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
+ * floating-point AC-3 encoder.
+ */
+
+#define CONFIG_AC3ENC_FLOAT 1
+#include "ac3enc.c"
+
+
+/**
+ * Finalize MDCT and free allocated memory.
+ */
+static av_cold void mdct_end(AC3MDCTContext *mdct)
+{
+    ff_mdct_end(&mdct->fft);
+    av_freep(&mdct->window);
+}
+
+
+/**
+ * Initialize MDCT tables.
+ * @param nbits log2(MDCT size)
+ */
+static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
+                             int nbits)
+{
+    float *window;
+    int n, n2;
+
+    n  = 1 << nbits;
+    n2 = n >> 1;
+
+    window = av_malloc(n2 * sizeof(*window));
+    if (!window) {
+        av_log(avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
+        return AVERROR(ENOMEM);
+    }
+    ff_kbd_window_init(window, 5.0, n2);
+    mdct->window = window;
+
+    return ff_mdct_init(&mdct->fft, nbits, 0, -2.0 / n);
+}
+
+
+/**
+ * Calculate a 512-point MDCT
+ * @param out 256 output frequency coefficients
+ * @param in  512 windowed input audio samples
+ */
+static void mdct512(AC3MDCTContext *mdct, float *out, float *in)
+{
+    ff_mdct_calc(&mdct->fft, out, in);
+}
+
+
+/**
+ * Apply KBD window to input samples prior to MDCT.
+ */
+static void apply_window(float *output, const float *input,
+                         const float *window, int n)
+{
+    int i;
+    int n2 = n >> 1;
+
+    for (i = 0; i < n2; i++) {
+        output[i]     = input[i]     * window[i];
+        output[n-i-1] = input[n-i-1] * window[i];
+    }
+}
+
+
+/**
+ * Normalize the input samples to use the maximum available precision.
+ */
+static int normalize_samples(AC3EncodeContext *s)
+{
+    /* Normalization is not needed for floating-point samples, so just return 0 */
+    return 0;
+}
+
+
+AVCodec ac3_encoder = {
+    "ac3",
+    AVMEDIA_TYPE_AUDIO,
+    CODEC_ID_AC3,
+    sizeof(AC3EncodeContext),
+    ac3_encode_init,
+    ac3_encode_frame,
+    ac3_encode_close,
+    NULL,
+    .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_FLT,AV_SAMPLE_FMT_NONE},
+    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
+    .channel_layouts = ac3_channel_layouts,
+};
-- 
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