MP3: Support decode mp3 by FFmpeg natively. (#296) (#3340)

trunk/3rdparty/ffmpeg-4-fit/libavcodec/mpegaudiodecheader.h

@@ -0,0 +1,80 @@
+/*
+ * MPEG Audio header decoder
+ * Copyright (c) 2001, 2002 Fabrice Bellard
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * MPEG Audio header decoder.
+ */
+
+#ifndef AVCODEC_MPEGAUDIODECHEADER_H
+#define AVCODEC_MPEGAUDIODECHEADER_H
+
+#include "avcodec.h"
+
+#define MP3_MASK 0xFFFE0CCF
+
+#define MPA_DECODE_HEADER \
+    int frame_size; \
+    int error_protection; \
+    int layer; \
+    int sample_rate; \
+    int sample_rate_index; /* between 0 and 8 */ \
+    int bit_rate; \
+    int nb_channels; \
+    int mode; \
+    int mode_ext; \
+    int lsf;
+
+typedef struct MPADecodeHeader {
+  MPA_DECODE_HEADER
+} MPADecodeHeader;
+
+/* header decoding. MUST check the header before because no
+   consistency check is done there. Return 1 if free format found and
+   that the frame size must be computed externally */
+int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header);
+
+/* useful helper to get MPEG audio stream info. Return -1 if error in
+   header, otherwise the coded frame size in bytes */
+int ff_mpa_decode_header(uint32_t head, int *sample_rate,
+                         int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id);
+
+/* fast header check for resync */
+static inline int ff_mpa_check_header(uint32_t header){
+    /* header */
+    if ((header & 0xffe00000) != 0xffe00000)
+        return -1;
+    /* version check */
+    if ((header & (3<<19)) == 1<<19)
+        return -1;
+    /* layer check */
+    if ((header & (3<<17)) == 0)
+        return -1;
+    /* bit rate */
+    if ((header & (0xf<<12)) == 0xf<<12)
+        return -1;
+    /* frequency */
+    if ((header & (3<<10)) == 3<<10)
+        return -1;
+    return 0;
+}
+
+#endif /* AVCODEC_MPEGAUDIODECHEADER_H */