diff options
Diffstat (limited to 'libavcodec/ac3dec.h')
| -rw-r--r-- | libavcodec/ac3dec.h | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h index 78869b5e26..bd555bdde1 100644 --- a/libavcodec/ac3dec.h +++ b/libavcodec/ac3dec.h @@ -22,6 +22,29 @@ /** * @file libavcodec/ac3.h * Common code between the AC-3 and E-AC-3 decoders. + * + * Summary of MDCT Coefficient Grouping: + * The individual MDCT coefficient indices are often referred to in the + * (E-)AC-3 specification as frequency bins. These bins are grouped together + * into subbands of 12 coefficients each. The subbands are grouped together + * into bands as defined in the bitstream by the band structures, which + * determine the number of bands and the size of each band. The full spectrum + * of 256 frequency bins is divided into 1 DC bin + 21 subbands = 253 bins. + * This system of grouping coefficients is used for channel bandwidth, stereo + * rematrixing, channel coupling, enhanced coupling, and spectral extension. + * + * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+ + * |1| |12| | [12|12|12|12] | | | | | | | | | | | | |3| + * +-+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+-+ + * ~~~ ~~~~ ~~~~~~~~~~~~~ ~~~ + * | | | | + * | | | 3 unused frequency bins--+ + * | | | + * | | +--1 band containing 4 subbands + * | | + * | +--1 subband of 12 frequency bins + * | + * +--DC frequency bin */ #ifndef AVCODEC_AC3DEC_H @@ -43,6 +66,7 @@ #define AC3_MAX_COEFS 256 #define AC3_BLOCK_SIZE 256 #define MAX_BLOCKS 6 +#define SPX_MAX_BANDS 17 typedef struct { AVCodecContext *avctx; ///< parent context @@ -89,6 +113,22 @@ typedef struct { int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates (cplco) ///@} +///@defgroup spx spectral extension +///@{ + int spx_in_use; ///< spectral extension in use (spxinu) + uint8_t channel_uses_spx[AC3_MAX_CHANNELS]; ///< channel uses spectral extension (chinspx) + int8_t spx_atten_code[AC3_MAX_CHANNELS]; ///< spx attenuation code (spxattencod) + int spx_src_start_freq; ///< spx start frequency bin + int spx_dst_end_freq; ///< spx end frequency bin + int spx_dst_start_freq; ///< spx starting frequency bin for copying (copystartmant) + ///< the copy region ends at the start of the spx region. + int num_spx_bands; ///< number of spx bands (nspxbnds) + uint8_t spx_band_sizes[SPX_MAX_BANDS]; ///< number of bins in each spx band + uint8_t first_spx_coords[AC3_MAX_CHANNELS]; ///< first spx coordinates states (firstspxcos) + float spx_noise_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS]; ///< spx noise blending factor (nblendfact) + float spx_signal_blend[AC3_MAX_CHANNELS][SPX_MAX_BANDS];///< spx signal blending factor (sblendfact) +///@} + ///@defgroup aht adaptive hybrid transform int channel_uses_aht[AC3_MAX_CHANNELS]; ///< channel AHT in use (chahtinu) int pre_mantissa[AC3_MAX_CHANNELS][AC3_MAX_COEFS][MAX_BLOCKS]; ///< pre-IDCT mantissas @@ -182,4 +222,11 @@ void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch); void ff_ac3_downmix_c(float (*samples)[256], float (*matrix)[2], int out_ch, int in_ch, int len); +/** + * Apply spectral extension to each channel by copying lower frequency + * coefficients to higher frequency bins and applying side information to + * approximate the original high frequency signal. + */ +void ff_eac3_apply_spectral_extension(AC3DecodeContext *s); + #endif /* AVCODEC_AC3DEC_H */ |