[FFmpeg-devel] [PATCH 2/3] avformat: add raw AC-4 demuxer

[Paul B Mahol]

Signed-off-by: Paul B Mahol <onemda at gmail.com>
---
 libavformat/Makefile     |   1 +
 libavformat/ac4dec.c     | 104 +++++++++++++++++++++++++++++++++++++++
 libavformat/allformats.c |   1 +
 3 files changed, 106 insertions(+)
 create mode 100644 libavformat/ac4dec.c

diff --git a/libavformat/Makefile b/libavformat/Makefile
index e0681058a2..b4e8d20e65 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -70,6 +70,7 @@ OBJS-$(CONFIG_AA_DEMUXER)                += aadec.o
 OBJS-$(CONFIG_AAC_DEMUXER)               += aacdec.o apetag.o img2.o rawdec.o
 OBJS-$(CONFIG_AC3_DEMUXER)               += ac3dec.o rawdec.o
 OBJS-$(CONFIG_AC3_MUXER)                 += rawenc.o
+OBJS-$(CONFIG_AC4_DEMUXER)               += ac4dec.o
 OBJS-$(CONFIG_ACM_DEMUXER)               += acm.o rawdec.o
 OBJS-$(CONFIG_ACT_DEMUXER)               += act.o
 OBJS-$(CONFIG_ADF_DEMUXER)               += bintext.o sauce.o
diff --git a/libavformat/ac4dec.c b/libavformat/ac4dec.c
new file mode 100644
index 0000000000..8c6e539409
--- /dev/null
+++ b/libavformat/ac4dec.c
@@ -0,0 +1,104 @@
+/*
+ * RAW AC-4 demuxer
+ * Copyright (c) 2019 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/avassert.h"
+#include "libavutil/crc.h"
+#include "avformat.h"
+#include "rawdec.h"
+
+static int ac4_probe(const AVProbeData *p)
+{
+    const uint8_t *buf = p->buf;
+    int left = p->buf_size;
+    int max_frames = 0;
+
+    while (left > 7) {
+        int size;
+
+        if (buf[0] == 0xAC &&
+            (buf[1] == 0x40 ||
+             buf[1] == 0x41)) {
+            size = (buf[2] << 8) | buf[3];
+            if (size == 0xFFFF)
+                size = 3 + (buf[4] << 16) | (buf[5] << 8) | buf[6];
+            size += 4;
+            if (buf[1] == 0x41)
+                size += 2;
+            max_frames++;
+            left -= size;
+            buf += size;
+        } else {
+            break;
+        }
+    }
+
+    return FFMIN(AVPROBE_SCORE_MAX, max_frames * 7);
+}
+
+static int ac4_read_header(AVFormatContext *s)
+{
+    AVStream *st;
+
+    st = avformat_new_stream(s, NULL);
+    if (!st)
+        return AVERROR(ENOMEM);
+
+    st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
+    st->codecpar->codec_id   = AV_CODEC_ID_AC4;
+
+    return 0;
+}
+
+static int ac4_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    AVIOContext *pb = s->pb;
+    int64_t pos;
+    uint16_t sync;
+    int ret, size;
+
+    if (avio_feof(s->pb))
+        return AVERROR_EOF;
+
+    pos   = avio_tell(s->pb);
+    sync = avio_rb16(pb);
+    size = avio_rb16(pb);
+    if (size == 0xffff)
+        size = avio_rb24(pb);
+
+    ret = av_get_packet(pb, pkt, size);
+    pkt->pos = pos;
+    pkt->stream_index = 0;
+
+    if (sync == 0xAC41)
+        avio_skip(pb, 2);
+
+    return ret;
+}
+
+AVInputFormat ff_ac4_demuxer = {
+    .name           = "ac4",
+    .long_name      = NULL_IF_CONFIG_SMALL("raw AC-4"),
+    .read_probe     = ac4_probe,
+    .read_header    = ac4_read_header,
+    .read_packet    = ac4_read_packet,
+    .flags          = AVFMT_GENERIC_INDEX,
+    .extensions     = "ac4",
+};
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 0209bf0e30..d2afcb2bdd 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -33,6 +33,7 @@ extern AVInputFormat  ff_aa_demuxer;
 extern AVInputFormat  ff_aac_demuxer;
 extern AVInputFormat  ff_ac3_demuxer;
 extern AVOutputFormat ff_ac3_muxer;
+extern AVInputFormat  ff_ac4_demuxer;
 extern AVInputFormat  ff_acm_demuxer;
 extern AVInputFormat  ff_act_demuxer;
 extern AVInputFormat  ff_adf_demuxer;
-- 
2.17.1