avcodec: add HCOM decoder

1 files changed, 140 insertions, 0 deletions

diff --git a/libavcodec/hcom.c b/libavcodec/hcom.c
new file mode 100644
index 0000000000..aab1001dd2
--- /dev/null
+++ b/libavcodec/hcom.c
@@ -0,0 +1,140 @@
+/*
+ * HCOM audio decoder
+ *
+ * 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/intreadwrite.h"
+
+#include "avcodec.h"
+#include "get_bits.h"
+#include "internal.h"
+
+typedef struct HEntry {
+    int16_t l, r;
+} HEntry;
+
+typedef struct HCOMContext {
+    AVCodecContext *avctx;
+
+    uint8_t first_sample;
+    uint8_t sample;
+    int dict_entries;
+    int dict_entry;
+    int delta_compression;
+
+    HEntry *dict;
+} HCOMContext;
+
+static av_cold int hcom_init(AVCodecContext *avctx)
+{
+    HCOMContext *s = avctx->priv_data;
+
+    if (avctx->channels != 1) {
+        av_log(avctx, AV_LOG_ERROR, "invalid number of channels\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (avctx->extradata_size <= 7)
+        return AVERROR_INVALIDDATA;
+    s->dict_entries = AV_RB16(avctx->extradata);
+    if (avctx->extradata_size < s->dict_entries * 4 + 7)
+        return AVERROR_INVALIDDATA;
+    s->delta_compression = AV_RB32(avctx->extradata + 2);
+    s->sample = s->first_sample = avctx->extradata[avctx->extradata_size - 1];
+
+    s->dict = av_calloc(s->dict_entries, sizeof(*s->dict));
+    if (!s->dict)
+        return AVERROR(ENOMEM);
+    for (int i = 0; i < s->dict_entries; i++) {
+        s->dict[i].l = AV_RB16(avctx->extradata + 6 + 4 * i);
+        s->dict[i].r = AV_RB16(avctx->extradata + 6 + 4 * i + 2);
+    }
+
+    avctx->sample_fmt = AV_SAMPLE_FMT_U8;
+    s->dict_entry = 0;
+
+    return 0;
+}
+
+static int hcom_decode(AVCodecContext *avctx, void *data,
+                       int *got_frame, AVPacket *pkt)
+{
+    HCOMContext *s = avctx->priv_data;
+    AVFrame *frame = data;
+    GetBitContext gb;
+    int ret, n = 0;
+
+    if (pkt->size > INT16_MAX)
+        return AVERROR_INVALIDDATA;
+
+    frame->nb_samples = pkt->size * 8;
+    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
+        return ret;
+
+    if ((ret = init_get_bits8(&gb, pkt->data, pkt->size)) < 0)
+        return ret;
+
+    while (get_bits_left(&gb) > 0) {
+        if (get_bits1(&gb)) {
+            s->dict_entry = s->dict[s->dict_entry].r;
+        } else {
+            s->dict_entry = s->dict[s->dict_entry].l;
+        }
+
+        if (s->dict[s->dict_entry].l < 0) {
+            int16_t datum;
+
+            datum = s->dict[s->dict_entry].r;
+
+            if (!s->delta_compression)
+                s->sample = 0;
+            s->sample = (s->sample + datum) & 0xFF;
+
+            frame->data[0][n++] = s->sample;
+
+            s->dict_entry = 0;
+        }
+    }
+
+    frame->nb_samples = n;
+
+    *got_frame = 1;
+
+    return pkt->size;
+}
+
+static av_cold int hcom_close(AVCodecContext *avctx)
+{
+    HCOMContext *s = avctx->priv_data;
+
+    av_freep(&s->dict);
+
+    return 0;
+}
+
+AVCodec ff_hcom_decoder = {
+    .name           = "hcom",
+    .long_name      = NULL_IF_CONFIG_SMALL("HCOM Audio"),
+    .type           = AVMEDIA_TYPE_AUDIO,
+    .id             = AV_CODEC_ID_HCOM,
+    .priv_data_size = sizeof(HCOMContext),
+    .init           = hcom_init,
+    .close          = hcom_close,
+    .decode         = hcom_decode,
+    .capabilities   = AV_CODEC_CAP_DR1,
+};