[FFmpeg-devel] [PATCH v15 4/9] avformat/evc_demuxer: Added demuxer to handle reading EVC video files

[Dawid Kozinski]

- Provided AVInputFormat structure describing EVC input format (ff_evc_demuxer)

Signed-off-by: Dawid Kozinski <d.kozinski at samsung.com>
---
 libavformat/Makefile     |   1 +
 libavformat/allformats.c |   1 +
 libavformat/evcdec.c     | 124 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 126 insertions(+)
 create mode 100644 libavformat/evcdec.c

diff --git a/libavformat/Makefile b/libavformat/Makefile
index a14a759c1f..af175d2097 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -251,6 +251,7 @@ OBJS-$(CONFIG_HCOM_DEMUXER)              += hcom.o pcm.o
 OBJS-$(CONFIG_HDS_MUXER)                 += hdsenc.o
 OBJS-$(CONFIG_HEVC_DEMUXER)              += hevcdec.o rawdec.o
 OBJS-$(CONFIG_HEVC_MUXER)                += rawenc.o
+OBJS-$(CONFIG_EVC_DEMUXER)               += evcdec.o rawdec.o
 OBJS-$(CONFIG_EVC_MUXER)                 += rawenc.o
 OBJS-$(CONFIG_HLS_DEMUXER)               += hls.o hls_sample_encryption.o
 OBJS-$(CONFIG_HLS_MUXER)                 += hlsenc.o hlsplaylist.o avc.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index aabc9b5f99..a963c0223d 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -153,6 +153,7 @@ extern const AVInputFormat  ff_ea_cdata_demuxer;
 extern const AVInputFormat  ff_eac3_demuxer;
 extern const AVOutputFormat ff_eac3_muxer;
 extern const AVInputFormat  ff_epaf_demuxer;
+extern const AVInputFormat  ff_evc_demuxer;
 extern const AVOutputFormat ff_evc_muxer;
 extern const AVOutputFormat ff_f4v_muxer;
 extern const AVInputFormat  ff_ffmetadata_demuxer;
diff --git a/libavformat/evcdec.c b/libavformat/evcdec.c
new file mode 100644
index 0000000000..7887f0b591
--- /dev/null
+++ b/libavformat/evcdec.c
@@ -0,0 +1,124 @@
+/*
+ * RAW EVC video demuxer
+ *
+ * Copyright (c) 2021 Dawid Kozinski <d.kozinski at samsung.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 "libavcodec/get_bits.h"
+#include "libavcodec/golomb.h"
+#include "libavcodec/internal.h"
+#include "libavcodec/evc.h"
+
+#include "rawdec.h"
+#include "avformat.h"
+
+typedef struct EVCParserContext {
+    int got_sps;
+    int got_pps;
+    int got_idr;
+    int got_nonidr;
+} EVCParserContext;
+
+static int get_nalu_type(const uint8_t *bits, int bits_size)
+{
+    int unit_type_plus1 = 0;
+
+    if (bits_size >= EVC_NALU_HEADER_SIZE) {
+        unsigned char *p = (unsigned char *)bits;
+        // forbidden_zero_bit
+        if ((p[0] & 0x80) != 0) { // Cannot get bitstream information. Malformed bitstream.
+            return -1;
+        }
+
+        // nal_unit_type
+        unit_type_plus1 = (p[0] >> 1) & 0x3F;
+    }
+
+    return unit_type_plus1 - 1;
+}
+
+static uint32_t read_nal_unit_length(const uint8_t *bits, int bits_size)
+{
+    uint32_t nalu_len = 0;
+
+    if (bits_size >= EVC_NALU_LENGTH_PREFIX_SIZE) {
+
+        int t = 0;
+        unsigned char *p = (unsigned char *)bits;
+
+        for (int i=0; i<EVC_NALU_LENGTH_PREFIX_SIZE; i++) {
+            t = (t << 8) | p[i];
+        }
+
+        nalu_len = t;
+        if (nalu_len == 0) { // Invalid bitstream size
+            return 0;
+        }
+    }
+
+    return nalu_len;
+}
+
+static int parse_nal_units(const AVProbeData *p, EVCParserContext *ev)
+{
+    int nalu_type;
+    size_t nalu_size;
+    unsigned char *bits = (unsigned char *)p->buf;
+    int bytes_to_read = p->buf_size;
+
+    while (bytes_to_read > EVC_NALU_LENGTH_PREFIX_SIZE) {
+
+        nalu_size = read_nal_unit_length(bits, EVC_NALU_LENGTH_PREFIX_SIZE);
+        if (nalu_size == 0) break;
+
+        bits += EVC_NALU_LENGTH_PREFIX_SIZE;
+        bytes_to_read -= EVC_NALU_LENGTH_PREFIX_SIZE;
+
+        if(bytes_to_read < nalu_size) break;
+
+        nalu_type = get_nalu_type(bits, bytes_to_read);
+
+        bits += nalu_size;
+        bytes_to_read -= nalu_size;
+
+        if (nalu_type == EVC_SPS_NUT)
+            ev->got_sps++;
+        else if (nalu_type == EVC_PPS_NUT)
+            ev->got_pps++;
+        else if (nalu_type == EVC_IDR_NUT )
+            ev->got_idr++;
+        else if (nalu_type == EVC_NOIDR_NUT)
+            ev->got_nonidr++;
+    }
+
+    return 0;
+}
+
+static int evc_probe(const AVProbeData *p)
+{
+    EVCParserContext ev = {0};
+    int ret = parse_nal_units(p, &ev);
+
+    if (ret == 0 && ev.got_sps && ev.got_pps && (ev.got_idr || ev.got_nonidr > 3))
+        return AVPROBE_SCORE_EXTENSION + 1;  // 1 more than .mpg
+
+    return 0;
+}
+
+FF_DEF_RAWVIDEO_DEMUXER(evc, "raw EVC video", evc_probe, "evc", AV_CODEC_ID_EVC)
-- 
2.17.1