+/* header + layer + bitrate + freq + lsf/mpeg25 */
+#define SAME_HEADER_MASK \
+ (0xffe00000 | (3 << 17) | (0xf << 12) | (3 << 10) | (3 << 19))
+
+#define MP3_MASK 0xFFFE0CCF
+
+#if CONFIG_MPEGAUDIO_HP
+#define FRAC_BITS 23 /* fractional bits for sb_samples and dct */
+#define WFRAC_BITS 16 /* fractional bits for window */
+#else
+#define FRAC_BITS 15 /* fractional bits for sb_samples and dct */
+#define WFRAC_BITS 14 /* fractional bits for window */
+#endif
+
+#define FRAC_ONE (1 << FRAC_BITS)
+
+#define FIX(a) ((int)((a) * FRAC_ONE))
+
+#if CONFIG_MPEGAUDIO_HP && CONFIG_AUDIO_NONSHORT
+typedef int32_t OUT_INT;
+#define OUT_MAX INT32_MAX
+#define OUT_MIN INT32_MIN
+#define OUT_SHIFT (WFRAC_BITS + FRAC_BITS - 31)
+#define OUT_FMT SAMPLE_FMT_S32
+#else
+typedef int16_t OUT_INT;
+#define OUT_MAX INT16_MAX
+#define OUT_MIN INT16_MIN
+#define OUT_SHIFT (WFRAC_BITS + FRAC_BITS - 15)
+#define OUT_FMT SAMPLE_FMT_S16
+#endif
+
+#if FRAC_BITS <= 15
+typedef int16_t MPA_INT;
+#else
+typedef int32_t MPA_INT;
+#endif
+
+#define BACKSTEP_SIZE 512
+#define EXTRABYTES 24
+
+struct GranuleDef;
+
+#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;
+
+typedef struct MPADecodeContext {
+ MPA_DECODE_HEADER
+ uint8_t last_buf[2*BACKSTEP_SIZE + EXTRABYTES];
+ int last_buf_size;
+ /* next header (used in free format parsing) */
+ uint32_t free_format_next_header;
+ GetBitContext gb;
+ GetBitContext in_gb;
+ DECLARE_ALIGNED_16(MPA_INT, synth_buf[MPA_MAX_CHANNELS][512 * 2]);
+ int synth_buf_offset[MPA_MAX_CHANNELS];
+ DECLARE_ALIGNED_16(int32_t, sb_samples[MPA_MAX_CHANNELS][36][SBLIMIT]);
+ int32_t mdct_buf[MPA_MAX_CHANNELS][SBLIMIT * 18]; /* previous samples, for layer 3 MDCT */
+#ifdef DEBUG
+ int frame_count;
+#endif
+ void (*compute_antialias)(struct MPADecodeContext *s, struct GranuleDef *g);
+ int adu_mode; ///< 0 for standard mp3, 1 for adu formatted mp3
+ int dither_state;
+ int error_recognition;
+ AVCodecContext* avctx;
+} MPADecodeContext;
+
+/* layer 3 huffman tables */
+typedef struct HuffTable {
+ int xsize;
+ const uint8_t *bits;
+ const uint16_t *codes;
+} HuffTable;
+
+int ff_mpa_l2_select_table(int bitrate, int nb_channels, int freq, int lsf);
+int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate);
+void ff_mpa_synth_init(MPA_INT *window);
+void ff_mpa_synth_filter(MPA_INT *synth_buf_ptr, int *synth_buf_offset,
+ MPA_INT *window, int *dither_state,
+ OUT_INT *samples, int incr,
+ int32_t sb_samples[SBLIMIT]);
+
+/* fast header check for resync */
+static inline int ff_mpa_check_header(uint32_t header){
+ /* header */
+ if ((header & 0xffe00000) != 0xffe00000)
+ 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;
+}