154 typedef struct AC3EncodeContext {  struct
155     AVClass *av_class;                      ///< AVClass used for AVOption
156     AC3EncOptions options;                  ///< encoding options
157     AVCodecContext *avctx;                  ///< parent AVCodecContext
158     PutBitContext pb;                       ///< bitstream writer context
159     AudioDSPContext adsp;
161     AVFloatDSPContext *fdsp;
163     AVFixedDSPContext *fdsp;
165     MECmpContext mecc;
166     AC3DSPContext ac3dsp;                   ///< AC-3 optimized functions
167     FFTContext mdct;                        ///< FFT context for MDCT calculation
168     const SampleType *mdct_window;          ///< MDCT window function array
170     AC3Block blocks[AC3_MAX_BLOCKS];        ///< per-block info
172     int fixed_point;                        ///< indicates if fixed-point encoder is being used
173     int eac3;                               ///< indicates if this is E-AC-3 vs. AC-3
174     int bitstream_id;                       ///< bitstream id                           (bsid)
175     int bitstream_mode;                     ///< bitstream mode                         (bsmod)
177     int bit_rate;                           ///< target bit rate, in bits-per-second
178     int sample_rate;                        ///< sampling frequency, in Hz
180     int num_blks_code;                      ///< number of blocks code                  (numblkscod)
181     int num_blocks;                         ///< number of blocks per frame
182     int frame_size_min;                     ///< minimum frame size in case rounding is necessary
183     int frame_size;                         ///< current frame size in bytes
184     int frame_size_code;                    ///< frame size code                        (frmsizecod)
185     uint16_t crc_inv[2];
186     int64_t bits_written;                   ///< bit count    (used to avg. bitrate)
187     int64_t samples_written;                ///< sample count (used to avg. bitrate)
189     int fbw_channels;                       ///< number of full-bandwidth channels      (nfchans)
190     int channels;                           ///< total number of channels               (nchans)
191     int lfe_on;                             ///< indicates if there is an LFE channel   (lfeon)
192     int lfe_channel;                        ///< channel index of the LFE channel
193     int has_center;                         ///< indicates if there is a center channel
194 …  int has_surround;                       ///< indicates if there are one or more surround channels
195     int channel_mode;                       ///< channel mode                           (acmod)
196     const uint8_t *channel_map;             ///< channel map used to reorder channels
198     int center_mix_level;                   ///< center mix level code
199     int surround_mix_level;                 ///< surround mix level code
200     int ltrt_center_mix_level;              ///< Lt/Rt center mix level code
201     int ltrt_surround_mix_level;            ///< Lt/Rt surround mix level code
202     int loro_center_mix_level;              ///< Lo/Ro center mix level code
203     int loro_surround_mix_level;            ///< Lo/Ro surround mix level code
205     int cutoff;                             ///< user-specified cutoff frequency, in Hz
206     int bandwidth_code;                     ///< bandwidth code (0 to 60)               (chbwcod)
207     int start_freq[AC3_MAX_CHANNELS];       ///< start frequency bin                    (strtmant)
208     int cpl_end_freq;                       ///< coupling channel end frequency bin
210     int cpl_on;                             ///< coupling turned on for this frame
211     int cpl_enabled;                        ///< coupling enabled for all frames
212     int num_cpl_subbands;                   ///< number of coupling subbands            (ncplsubnd)
213     int num_cpl_bands;                      ///< number of coupling bands               (ncplbnd)
214     uint8_t cpl_band_sizes[AC3_MAX_CPL_BANDS];  ///< number of coeffs in each coupling band
216     int rematrixing_enabled;                ///< stereo rematrixing enabled
219     int slow_gain_code;                     ///< slow gain code                         (sgaincod)
220     int slow_decay_code;                    ///< slow decay code                        (sdcycod)
221     int fast_decay_code;                    ///< fast decay code                        (fdcycod)
222     int db_per_bit_code;                    ///< dB/bit code                            (dbpbcod)
223     int floor_code;                         ///< floor code                             (floorcod)
224     AC3BitAllocParameters bit_alloc;        ///< bit allocation parameters
225     int coarse_snr_offset;                  ///< coarse SNR offsets                     (csnroffst)
226     int fast_gain_code[AC3_MAX_CHANNELS];   ///< fast gain codes (signal-to-mask ratio) (fgaincod)
227     int fine_snr_offset[AC3_MAX_CHANNELS];  ///< fine SNR offsets                       (fsnroffst)
228     int frame_bits_fixed;                   ///< number of non-coefficient bits for fixed parameters
229     int frame_bits;                         ///< all frame bits except exponents and mantissas
230     int exponent_bits;                      ///< number of bits used for exponents
232     SampleType *windowed_samples;
233     SampleType **planar_samples;
257     void (*mdct_end)(struct AC3EncodeContext *s);  argument
258     int  (*mdct_init)(struct AC3EncodeContext *s);  argument
261     int  (*allocate_sample_buffers)(struct AC3EncodeContext *s);  argument
264     void (*output_frame_header)(struct AC3EncodeContext *s);  argument
265 } AC3EncodeContext;  typedef