avformat: add demuxer for Simon & Schuster Interactive's VAG format

Adds support for the custom VAG container used by some Simon & Schuster
Interactive games such as Real War, and Real War: Rogue States.

Signed-off-by: Zane van Iperen <zane@zanevaniperen.com>
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/Makefile

@@ -279,6 +279,7 @@ OBJS-$(CONFIG_JACOSUB_DEMUXER)           += jacosubdec.o subtitles.o
 OBJS-$(CONFIG_JACOSUB_MUXER)             += jacosubenc.o rawenc.o
 OBJS-$(CONFIG_JV_DEMUXER)                += jvdec.o
 OBJS-$(CONFIG_KUX_DEMUXER)               += flvdec.o
+OBJS-$(CONFIG_KVAG_DEMUXER)              += kvag.o
 OBJS-$(CONFIG_LATM_MUXER)                += latmenc.o rawenc.o
 OBJS-$(CONFIG_LMLM4_DEMUXER)             += lmlm4.o
 OBJS-$(CONFIG_LOAS_DEMUXER)              += loasdec.o rawdec.o

libavformat/allformats.c

@@ -214,6 +214,7 @@ extern AVInputFormat  ff_jacosub_demuxer;
 extern AVOutputFormat ff_jacosub_muxer;
 extern AVInputFormat  ff_jv_demuxer;
 extern AVInputFormat  ff_kux_demuxer;
+extern AVInputFormat  ff_kvag_demuxer;
 extern AVOutputFormat ff_latm_muxer;
 extern AVInputFormat  ff_lmlm4_demuxer;
 extern AVInputFormat  ff_loas_demuxer;

libavformat/kvag.c

@@ -0,0 +1,117 @@
+/*
+ * Simon & Schuster Interactive VAG demuxer
+ *
+ * Copyright (C) 2020 Zane van Iperen (zane@zanevaniperen.com)
+ *
+ * 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 "avformat.h"
+#include "internal.h"
+#include "libavutil/intreadwrite.h"
+
+#define KVAG_TAG            MKTAG('K', 'V', 'A', 'G')
+#define KVAG_HEADER_SIZE    14
+#define KVAG_MAX_READ_SIZE  4096
+
+typedef struct KVAGHeader {
+    uint32_t    magic;
+    uint32_t    data_size;
+    uint32_t    sample_rate;
+    uint16_t    stereo;
+} KVAGHeader;
+
+static int kvag_probe(const AVProbeData *p)
+{
+    if (AV_RL32(p->buf) != KVAG_TAG)
+        return 0;
+
+    return AVPROBE_SCORE_EXTENSION + 1;
+}
+
+static int kvag_read_header(AVFormatContext *s)
+{
+    int ret;
+    AVStream *st;
+    KVAGHeader hdr;
+    AVCodecParameters *par;
+    uint8_t buf[KVAG_HEADER_SIZE];
+
+    if (!(st = avformat_new_stream(s, NULL)))
+        return AVERROR(ENOMEM);
+
+    if ((ret = avio_read(s->pb, buf, KVAG_HEADER_SIZE)) < 0)
+        return ret;
+    else if (ret != KVAG_HEADER_SIZE)
+        return AVERROR(EIO);
+
+    hdr.magic                   = AV_RL32(buf +  0);
+    hdr.data_size               = AV_RL32(buf +  4);
+    hdr.sample_rate             = AV_RL32(buf +  8);
+    hdr.stereo                  = AV_RL16(buf + 12);
+
+    par                         = st->codecpar;
+    par->codec_type             = AVMEDIA_TYPE_AUDIO;
+    par->codec_id               = AV_CODEC_ID_ADPCM_IMA_SSI;
+    par->format                 = AV_SAMPLE_FMT_S16;
+
+    if (hdr.stereo) {
+        par->channel_layout     = AV_CH_LAYOUT_STEREO;
+        par->channels           = 2;
+    } else {
+        par->channel_layout     = AV_CH_LAYOUT_MONO;
+        par->channels           = 1;
+    }
+
+    par->sample_rate            = hdr.sample_rate;
+    par->bits_per_coded_sample  = 4;
+    par->bits_per_raw_sample    = 16;
+    par->block_align            = 1;
+    par->bit_rate               = par->channels *
+                                  par->sample_rate *
+                                  par->bits_per_coded_sample;
+
+    avpriv_set_pts_info(st, 64, 1, par->sample_rate);
+    st->start_time              = 0;
+    st->duration                = hdr.data_size *
+                                  (8 / par->bits_per_coded_sample) /
+                                  par->channels;
+
+    return 0;
+}
+
+static int kvag_read_packet(AVFormatContext *s, AVPacket *pkt)
+{
+    int ret;
+    AVCodecParameters *par = s->streams[0]->codecpar;
+
+    if ((ret = av_get_packet(s->pb, pkt, KVAG_MAX_READ_SIZE)) < 0)
+        return ret;
+
+    pkt->flags          &= ~AV_PKT_FLAG_CORRUPT;
+    pkt->stream_index   = 0;
+    pkt->duration       = ret * (8 / par->bits_per_coded_sample) / par->channels;
+
+    return 0;
+}
+
+AVInputFormat ff_kvag_demuxer = {
+    .name           = "kvag",
+    .long_name      = NULL_IF_CONFIG_SMALL("Simon & Schuster Interactive VAG"),
+    .read_probe     = kvag_probe,
+    .read_header    = kvag_read_header,
+    .read_packet    = kvag_read_packet
+};

libavformat/version.h

@@ -32,7 +32,7 @@
 // Major bumping may affect Ticket5467, 5421, 5451(compatibility with Chromium)
 // Also please add any ticket numbers that you believe might be affected here
 #define LIBAVFORMAT_VERSION_MAJOR  58
-#define LIBAVFORMAT_VERSION_MINOR  37
+#define LIBAVFORMAT_VERSION_MINOR  38
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \