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author | Justin Ruggles <justin.ruggles@gmail.com> | 2007-03-19 00:43:20 +0300 |
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committer | Justin Ruggles <justin.ruggles@gmail.com> | 2007-03-19 00:43:20 +0300 |
commit | 575bf46f164092ca04565fa05637ec62b022cfdb (patch) | |
tree | b030fcc196a6a6fec599ce445311ce4d18dde42c /libavcodec/ac3.h | |
parent | f8b9830b6c48a44821bc623d5fc4673db76099a5 (diff) |
split ac3_parametric_bit_allocation into 3 separate functions
Originally committed as revision 8442 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/ac3.h')
-rw-r--r-- | libavcodec/ac3.h | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/libavcodec/ac3.h b/libavcodec/ac3.h index bd7e7b611b..ae53a80c3d 100644 --- a/libavcodec/ac3.h +++ b/libavcodec/ac3.h @@ -102,6 +102,68 @@ extern const int16_t ff_floortab[8]; extern const uint16_t ff_fgaintab[8]; void ac3_common_init(void); + +/** + * Calculates the log power-spectral density of the input signal. + * This gives a rough estimate of signal power in the frequency domain by using + * the spectral envelope (exponents). The psd is also separately grouped + * into critical bands for use in the calculating the masking curve. + * 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters + * determines the reference level. + * + * @param[in] exp frequency coefficient exponents + * @param[in] start starting bin location + * @param[in] end ending bin location + * @param[out] psd signal power for each frequency bin + * @param[out] bndpsd signal power for each critical band + */ +void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, + int16_t *bndpsd); + +/** + * Calculates the masking curve. + * First, the excitation is calculated using parameters in \p s and the signal + * power in each critical band. The excitation is compared with a predefined + * hearing threshold table to produce the masking curve. If delta bit + * allocation information is provided, it is used for adjusting the masking + * curve, usually to give a closer match to a better psychoacoustic model. + * + * @param[in] s adjustable bit allocation parameters + * @param[in] bndpsd signal power for each critical band + * @param[in] start starting bin location + * @param[in] end ending bin location + * @param[in] fgain fast gain (estimated signal-to-mask ratio) + * @param[in] is_lfe whether or not the channel being processed is the LFE + * @param[in] deltbae delta bit allocation exists (none, reuse, or new) + * @param[in] deltnseg number of delta segments + * @param[in] deltoffst location offsets for each segment + * @param[in] deltlen length of each segment + * @param[in] deltba delta bit allocation for each segment + * @param[out] mask calculated masking curve + */ +void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd, + int start, int end, int fgain, int is_lfe, + int deltbae, int deltnseg, uint8_t *deltoffst, + uint8_t *deltlen, uint8_t *deltba, + int16_t *mask); + +/** + * Calculates bit allocation pointers. + * The SNR is the difference between the masking curve and the signal. AC-3 + * uses this value for each frequency bin to allocate bits. The \p snroffset + * parameter is a global adjustment to the SNR for all bins. + * + * @param[in] mask masking curve + * @param[in] psd signal power for each frequency bin + * @param[in] start starting bin location + * @param[in] end ending bin location + * @param[in] snroffset SNR adjustment + * @param[in] floor noise floor + * @param[out] bap bit allocation pointers + */ +void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end, + int snroffset, int floor, uint8_t *bap); + void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap, int8_t *exp, int start, int end, int snroffset, int fgain, int is_lfe, |