#include "libavutil/lfg.h"
#include "ac3.h"
#include "ac3dsp.h"
#include "get_bits.h"
#include "dsputil.h"
#include "fft.h"
#include "fmtconvert.h"
Go to the source code of this file.
Data Structures | |
| struct | AC3DecodeContext |
Defines | |
| #define | AC3_OUTPUT_LFEON 8 |
| #define | SPX_MAX_BANDS 17 |
| #define | AC3_FRAME_BUFFER_SIZE 32768 |
| Large enough for maximum possible frame size when the specification limit is ignored. | |
Functions | |
| int | ff_eac3_parse_header (AC3DecodeContext *s) |
| Parse the E-AC-3 frame header. | |
| void | ff_eac3_decode_transform_coeffs_aht_ch (AC3DecodeContext *s, int ch) |
| Decode mantissas in a single channel for the entire frame. | |
| void | ff_eac3_apply_spectral_extension (AC3DecodeContext *s) |
| 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. | |
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
Definition in file ac3dec.h.
| #define AC3_FRAME_BUFFER_SIZE 32768 |
Large enough for maximum possible frame size when the specification limit is ignored.
Definition at line 66 of file ac3dec.h.
Referenced by ac3_decode_frame().
| #define AC3_OUTPUT_LFEON 8 |
| #define SPX_MAX_BANDS 17 |
| void ff_eac3_apply_spectral_extension | ( | AC3DecodeContext * | s | ) |
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.
Definition at line 66 of file eac3dec.c.
Referenced by decode_audio_block().
| void ff_eac3_decode_transform_coeffs_aht_ch | ( | AC3DecodeContext * | s, | |
| int | ch | |||
| ) |
Decode mantissas in a single channel for the entire frame.
This is used when AHT mode is enabled.
Definition at line 198 of file eac3dec.c.
Referenced by decode_transform_coeffs_ch().
| int ff_eac3_parse_header | ( | AC3DecodeContext * | s | ) |
Parse the E-AC-3 frame header.
This parses both the bit stream info and audio frame header.
Definition at line 291 of file eac3dec.c.
Referenced by parse_frame_header().
1.5.8