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

Changelog

@@ -70,6 +70,7 @@ version <next>:
 - Windows Televison (WTV) demuxer
 - FFmpeg metadata format muxer and demuxer
 - SubRip (srt) subtitle decoder
+- floating-point AC-3 encoder added
 
 
 version 0.6:

configure

@@ -1193,6 +1193,7 @@ aac_decoder_select="mdct rdft"
 aac_encoder_select="mdct"
 aac_latm_decoder_select="aac_decoder aac_latm_parser"
 ac3_decoder_select="mdct ac3_parser"
+ac3_encoder_select="mdct"
 alac_encoder_select="lpc"
 amrnb_decoder_select="lsp"
 amrwb_decoder_select="lsp"
@@ -1453,7 +1454,6 @@ set_ne_test_deps(){
 }
 
 test_deps _encoder _decoder                                             \
-    ac3                                                                 \
     adpcm_g726=g726                                                     \
     adpcm_ima_qt                                                        \
     adpcm_ima_wav                                                       \
@@ -1525,6 +1525,7 @@ test_deps _muxer _demuxer                                               \
     wav                                                                 \
     yuv4mpegpipe=yuv4mpeg                                               \
 
+ac3_fixed_test_deps="ac3_fixed_encoder ac3_decoder rm_muxer rm_demuxer"
 mpg_test_deps="mpeg1system_muxer mpegps_demuxer"
 
 set_ne_test_deps pixdesc

libavcodec/Makefile

@@ -54,7 +54,8 @@ OBJS-$(CONFIG_AAC_ENCODER)             += aacenc.o aaccoder.o    \
                                           mpeg4audio.o
 OBJS-$(CONFIG_AASC_DECODER)            += aasc.o msrledec.o
 OBJS-$(CONFIG_AC3_DECODER)             += ac3dec.o ac3dec_data.o ac3.o
-OBJS-$(CONFIG_AC3_ENCODER)             += ac3enc_fixed.o ac3tab.o ac3.o
+OBJS-$(CONFIG_AC3_ENCODER)             += ac3enc_float.o ac3tab.o ac3.o
+OBJS-$(CONFIG_AC3_FIXED_ENCODER)       += ac3enc_fixed.o ac3tab.o ac3.o
 OBJS-$(CONFIG_ALAC_DECODER)            += alac.o
 OBJS-$(CONFIG_ALAC_ENCODER)            += alacenc.o
 OBJS-$(CONFIG_ALS_DECODER)             += alsdec.o bgmc.o mpeg4audio.o

libavcodec/ac3enc.c

@@ -37,6 +37,11 @@
 #include "audioconvert.h"
 
 
+#ifndef CONFIG_AC3ENC_FLOAT
+#define CONFIG_AC3ENC_FLOAT 0
+#endif
+
+
 /** Maximum number of exponent groups. +1 for separate DC exponent. */
 #define AC3_MAX_EXP_GROUPS 85
 
@@ -44,7 +49,11 @@
 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
 
 
+#if CONFIG_AC3ENC_FLOAT
+#include "ac3enc_float.h"
+#else
 #include "ac3enc_fixed.h"
+#endif
 
 
 /**
@@ -130,7 +139,7 @@ typedef struct AC3EncodeContext {
 } AC3EncodeContext;
 
 
-/* prototypes for functions in ac3enc_fixed.c */
+/* prototypes for functions in ac3enc_fixed.c and ac3_float.c */
 
 static av_cold void mdct_end(AC3MDCTContext *mdct);
 

libavcodec/ac3enc_fixed.c

@@ -26,6 +26,7 @@
  * fixed-point AC-3 encoder.
  */
 
+#undef CONFIG_AC3ENC_FLOAT
 #include "ac3enc.c"
 
 
@@ -413,8 +414,8 @@ int main(void)
 #endif /* TEST */
 
 
-AVCodec ac3_encoder = {
+AVCodec ac3_fixed_encoder = {
-    "ac3",
+    "ac3_fixed",
     AVMEDIA_TYPE_AUDIO,
     CODEC_ID_AC3,
     sizeof(AC3EncodeContext),

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,
+};

libavcodec/ac3enc_float.h

@@ -0,0 +1,46 @@
+/*
+ * 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 header.
+ */
+
+#ifndef AVCODEC_AC3ENC_FLOAT_H
+#define AVCODEC_AC3ENC_FLOAT_H
+
+#include "fft.h"
+
+
+typedef float SampleType;
+typedef float CoefType;
+
+#define SCALE_COEF(a) SCALE_FLOAT((a), 24)
+
+
+typedef struct AC3MDCTContext {
+    const float *window;    ///< MDCT window function
+    FFTContext fft;         ///< FFT context for MDCT calculation
+} AC3MDCTContext;
+
+#endif /* AVCODEC_AC3ENC_FLOAT_H */

libavcodec/allcodecs.c

@@ -222,6 +222,7 @@ void avcodec_register_all(void)
     REGISTER_ENCDEC  (AAC, aac);
     REGISTER_DECODER (AAC_LATM, aac_latm);
     REGISTER_ENCDEC  (AC3, ac3);
+    REGISTER_ENCODER (AC3_FIXED, ac3_fixed);
     REGISTER_ENCDEC  (ALAC, alac);
     REGISTER_DECODER (ALS, als);
     REGISTER_DECODER (AMRNB, amrnb);

libavcodec/avcodec.h

@@ -32,7 +32,7 @@
 #include "libavutil/cpu.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 52
-#define LIBAVCODEC_VERSION_MINOR 101
+#define LIBAVCODEC_VERSION_MINOR 102
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \

tests/codec-regression.sh

@@ -269,8 +269,8 @@ do_audio_decoding
 $tiny_psnr $pcm_dst $pcm_ref 2 1924 >> $logfile
 fi
 
-if [ -n "$do_ac3" ] ; then
+if [ -n "$do_ac3_fixed" ] ; then
-do_audio_encoding ac3.rm "" -vn
+do_audio_encoding ac3.rm "" "-vn -acodec ac3_fixed"
 # binaries configured with --disable-sse decode ac3 differently
 #do_audio_decoding
 #$tiny_psnr $pcm_dst $pcm_ref 2 1024 >> $logfile

tests/lavf-regression.sh

@@ -57,7 +57,7 @@ fi
 
 if [ -n "$do_rm" ] ; then
 file=${outfile}lavf.rm
-do_ffmpeg $file -t 1 -qscale 10 -f image2 -vcodec pgmyuv -i $raw_src -f s16le -i $pcm_src
+do_ffmpeg $file -t 1 -qscale 10 -f image2 -vcodec pgmyuv -i $raw_src -f s16le -i $pcm_src -acodec ac3_fixed
 # broken
 #do_ffmpeg_crc $file -i $target_path/$file
 fi