avcodec: add MI-SC4 audio decoder

Changelog

@@ -12,6 +12,7 @@ version <next>:
 - WBMP (Wireless Application Protocol Bitmap) image format
 - a3dscope filter
 - bonk decoder and demuxer
+- Micronas SC-4 audio decoder
 
 
 version 5.1:

doc/general_contents.texi

@@ -1256,6 +1256,7 @@ following image formats are supported:
 @item Interplay ACM            @tab     @tab  X
 @item MACE (Macintosh Audio Compression/Expansion) 3:1  @tab     @tab  X
 @item MACE (Macintosh Audio Compression/Expansion) 6:1  @tab     @tab  X
+@item MI-SC4 (Micronas SC-4 Audio)  @tab     @tab  X
 @item MLP (Meridian Lossless Packing)  @tab  X  @tab  X
     @tab Used in DVD-Audio discs.
 @item Monkey's Audio         @tab     @tab  X

libavcodec/Makefile

@@ -471,6 +471,7 @@ OBJS-$(CONFIG_METASOUND_DECODER)       += metasound.o metasound_data.o \
                                           twinvq.o
 OBJS-$(CONFIG_MICRODVD_DECODER)        += microdvddec.o ass.o
 OBJS-$(CONFIG_MIMIC_DECODER)           += mimic.o
+OBJS-$(CONFIG_MISC4_DECODER)           += misc4.o
 OBJS-$(CONFIG_MJPEG_DECODER)           += mjpegdec.o mjpegdec_common.o
 OBJS-$(CONFIG_MJPEG_QSV_DECODER)       += qsvdec.o
 OBJS-$(CONFIG_MJPEG_ENCODER)           += mjpegenc.o mjpegenc_common.o \

libavcodec/allcodecs.c

@@ -483,6 +483,7 @@ extern const FFCodec ff_interplay_acm_decoder;
 extern const FFCodec ff_mace3_decoder;
 extern const FFCodec ff_mace6_decoder;
 extern const FFCodec ff_metasound_decoder;
+extern const FFCodec ff_misc4_decoder;
 extern const FFCodec ff_mlp_encoder;
 extern const FFCodec ff_mlp_decoder;
 extern const FFCodec ff_mp1_decoder;

libavcodec/codec_desc.c

@@ -3297,6 +3297,13 @@ static const AVCodecDescriptor codec_descriptors[] = {
         .long_name = NULL_IF_CONFIG_SMALL("Bonk audio"),
         .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_INTRA_ONLY | AV_CODEC_PROP_LOSSLESS,
     },
+    {
+        .id        = AV_CODEC_ID_MISC4,
+        .type      = AVMEDIA_TYPE_AUDIO,
+        .name      = "misc4",
+        .long_name = NULL_IF_CONFIG_SMALL("Micronas SC-4 Audio"),
+        .props     = AV_CODEC_PROP_LOSSY | AV_CODEC_PROP_INTRA_ONLY,
+    },
 
     /* subtitle codecs */
     {

libavcodec/codec_id.h

@@ -528,6 +528,7 @@ enum AVCodecID {
     AV_CODEC_ID_MSNSIREN,
     AV_CODEC_ID_DFPWM,
     AV_CODEC_ID_BONK,
+    AV_CODEC_ID_MISC4,
 
     /* subtitle codecs */
     AV_CODEC_ID_FIRST_SUBTITLE = 0x17000,          ///< A dummy ID pointing at the start of subtitle codecs.

libavcodec/misc4.c

@@ -0,0 +1,186 @@
+/*
+ * Micronas SC-4 audio decoder
+ * Copyright (c) 2022 Paul B Mahol
+ *
+ * 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
+ */
+
+#include "libavutil/internal.h"
+#include "libavutil/intreadwrite.h"
+#include "avcodec.h"
+#include "codec_internal.h"
+#include "decode.h"
+#include "bytestream.h"
+#include "mathops.h"
+
+static const int16_t steps[16] = {
+    4084, 18, 41, 64, 112, 198, 355, 1122,
+    1122, 355, 198, 112, 64, 41, 18, 4084,
+};
+
+static const int16_t diffs[16] = {
+    2048, 4, 135, 213, 273, 323, 373, 425,
+    425, 373, 323, 273, 213, 135, 4, 2048,
+};
+
+typedef struct ChannelContext {
+    unsigned last_step;
+    int64_t new_pred;
+    int64_t pred;
+    int64_t weights_tab[6];
+    int32_t diffs_tab[6];
+} ChannelContext;
+
+typedef struct MISC4Context {
+    GetByteContext gb;
+
+    uint32_t marker;
+
+    ChannelContext ch[2];
+} MISC4Context;
+
+static av_cold int misc4_init(AVCodecContext *avctx)
+{
+    MISC4Context *s = avctx->priv_data;
+
+    avctx->sample_fmt = AV_SAMPLE_FMT_S16;
+    switch (avctx->sample_rate) {
+    case 8000:
+    case 11025:
+        s->marker = 0x11b;
+        break;
+    case 16000:
+    case 32000:
+        s->marker = 0x2b2;
+        break;
+    }
+
+    return 0;
+}
+
+#define FRACBITS 12
+#define WEIGHTSBITS 26
+
+static int64_t prediction(int delta, ChannelContext *c)
+{
+    const int isign = FFDIFFSIGN(delta, 0);
+    int64_t dotpr = 0;
+
+    c->new_pred = delta * (1LL << FRACBITS) + c->pred;
+
+    for (int i = 0; i < 6; i++) {
+        const int sign = FFSIGN(c->diffs_tab[i]);
+        c->weights_tab[i] = (c->weights_tab[i] * 255LL) / 256;
+        c->weights_tab[i] += (1LL << (WEIGHTSBITS + 1)) * sign * isign;
+    }
+
+    memmove(&c->diffs_tab[1], &c->diffs_tab[0], 5 * sizeof(int32_t));
+
+    c->diffs_tab[0] = -delta * (1 << (FRACBITS-8));
+    c->pred = c->new_pred;
+
+    dotpr = 0;
+    for (int i = 0; i < 6; i++)
+        dotpr += ((int64_t)c->diffs_tab[i] * c->weights_tab[i]) >> WEIGHTSBITS;
+
+    c->pred += dotpr;
+    c->pred = av_clip64(c->pred, -16383 * (1 << FRACBITS), 16383 * (1 << FRACBITS));
+    c->pred = c->pred * 9 / 10;
+
+    return c->new_pred;
+}
+
+static int16_t decode(ChannelContext *c, unsigned nibble)
+{
+    int diff, diff_sign, adiff = 0, delta;
+    uint32_t step, newstep;
+    int64_t pred;
+
+    diff_sign = nibble >> 3;
+    diff = diffs[nibble];
+    step = diff + (c->last_step >> 2);
+    newstep = step & 0xfff;
+    if (newstep >> 11 == 0)
+        adiff = (((step & 0x7f) + 0x80) * 128) >>
+                 (14 - (newstep >> 7));
+    delta = diff_sign ? -adiff : adiff;
+    delta = av_clip_intp2(delta, 15);
+    pred = prediction(delta, c);
+    nibble = steps[nibble];
+    newstep = nibble * 32 - c->last_step & 0x1ffff;
+    newstep = ((newstep >> 5) + (newstep & 0x10000 ? 0x1000 : 0) + c->last_step) & 0x1fff;
+    c->last_step = av_clip(newstep, 544, 5120);
+
+    return av_clip_int16(pred >> (FRACBITS - 3));
+}
+
+static int misc4_decode(AVCodecContext *avctx, AVFrame *frame,
+                       int *got_frame_ptr, AVPacket *pkt)
+{
+    MISC4Context *s = avctx->priv_data;
+    GetByteContext *gb = &s->gb;
+    uint32_t hdr;
+    int ret;
+
+    bytestream2_init(gb, pkt->data, pkt->size);
+
+    frame->nb_samples = 29 * (1 + (avctx->ch_layout.nb_channels == 1));
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
+    hdr = bytestream2_peek_be32(gb);
+    if (hdr == s->marker) {
+        bytestream2_skip(gb, 5);
+    } else if ((hdr >> 16) == s->marker) {
+        bytestream2_skip(gb, 3);
+    }
+
+    {
+        int16_t *samples = (int16_t *)frame->data[0];
+        const int st = avctx->ch_layout.nb_channels == 2;
+        int n;
+
+        for (n = 0; n < 29; n++) {
+            int nibble = bytestream2_get_byte(gb);
+            samples[2*n+0] = decode(&s->ch[0 ], nibble >> 4);
+            samples[2*n+1] = decode(&s->ch[st], nibble & 15);
+            if (bytestream2_get_bytes_left(gb) <= 0)
+                break;
+        }
+
+        if (n == 29 && bytestream2_get_byte(gb) != 0x55)
+            return AVERROR_INVALIDDATA;
+    }
+
+    *got_frame_ptr = 1;
+
+    return bytestream2_tell(gb);
+}
+
+const FFCodec ff_misc4_decoder = {
+    .p.name           = "misc4",
+    CODEC_LONG_NAME("Micronas SC-4 Audio"),
+    .p.type           = AVMEDIA_TYPE_AUDIO,
+    .p.id             = AV_CODEC_ID_MISC4,
+    .priv_data_size   = sizeof(MISC4Context),
+    .init             = misc4_init,
+    FF_CODEC_DECODE_CB(misc4_decode),
+    .p.capabilities   = AV_CODEC_CAP_DR1 | AV_CODEC_CAP_SUBFRAMES |
+                        AV_CODEC_CAP_CHANNEL_CONF,
+    .p.sample_fmts    = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_S16,
+                                                        AV_SAMPLE_FMT_NONE },
+};

libavcodec/version.h

@@ -29,7 +29,7 @@
 
 #include "version_major.h"
 
-#define LIBAVCODEC_VERSION_MINOR  43
+#define LIBAVCODEC_VERSION_MINOR  44
 #define LIBAVCODEC_VERSION_MICRO 100
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \

libavformat/riff.c

@@ -564,6 +564,7 @@ const AVCodecTag ff_codec_wav_tags[] = {
     { AV_CODEC_ID_ATRAC3,          0x0270 },
     { AV_CODEC_ID_MSNSIREN,        0x028E },
     { AV_CODEC_ID_ADPCM_G722,      0x028F },
+    { AV_CODEC_ID_MISC4,           0x0350 },
     { AV_CODEC_ID_IMC,             0x0401 },
     { AV_CODEC_ID_IAC,             0x0402 },
     { AV_CODEC_ID_ON2AVC,          0x0500 },