This commit implements temporal noise shaping support in the encoder, along with an -aac_tns option to toggle it on or off (off by default for now). TNS will increase audio quality and reduce quantization noise by applying a multitap FIR filter across allowed coefficients and transmit side information to the decoder so it could create an inverse filter. Users are encouraged to test the new functionality by enabling -aac_tns 1 during encoding. No major bugs are observable at this time so after a while if no new problems appear and if the current implementation is deemed of high enough quality and stability it will be enabled by default, possibly at the same time the encoder has its experimental flag removed and becomes the standard aac encoder in ffmpeg.
Showing the changes to libavcodec/aaccoder.c (1 of 7 files). Show all
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| @@ -45,6 +45,7 @@ · 44 unmodified lines | ||
| 45 | 45 | #include "aac_tablegen_decl.h" |
| 46 | 46 | |
| 47 | 47 | #include "aacenc_is.h" |
| 48 | +#include "aacenc_tns.h" | |
| 48 | 49 | |
| 49 | 50 | /** Frequency in Hz for lower limit of noise substitution **/ |
| 50 | 51 | #define NOISE_LOW_LIMIT 4500 |
| @@ -958,8 +959,10 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = { · 907 unmodified lines | ||
| 958 | 959 | search_for_quantizers_faac, |
| 959 | 960 | encode_window_bands_info, |
| 960 | 961 | quantize_and_encode_band, |
| 962 | + encode_tns_info, | |
| 961 | 963 | set_special_band_scalefactors, |
| 962 | 964 | search_for_pns, |
| 965 | + search_for_tns, | |
| 963 | 966 | search_for_ms, |
| 964 | 967 | search_for_is, |
| 965 | 968 | }, |
| @@ -967,8 +970,10 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = { · 1 unmodified line | ||
| 967 | 970 | search_for_quantizers_anmr, |
| 968 | 971 | encode_window_bands_info, |
| 969 | 972 | quantize_and_encode_band, |
| 973 | + encode_tns_info, | |
| 970 | 974 | set_special_band_scalefactors, |
| 971 | 975 | search_for_pns, |
| 976 | + search_for_tns, | |
| 972 | 977 | search_for_ms, |
| 973 | 978 | search_for_is, |
| 974 | 979 | }, |
| @@ -976,8 +981,10 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = { · 1 unmodified line | ||
| 976 | 981 | search_for_quantizers_twoloop, |
| 977 | 982 | codebook_trellis_rate, |
| 978 | 983 | quantize_and_encode_band, |
| 984 | + encode_tns_info, | |
| 979 | 985 | set_special_band_scalefactors, |
| 980 | 986 | search_for_pns, |
| 987 | + search_for_tns, | |
| 981 | 988 | search_for_ms, |
| 982 | 989 | search_for_is, |
| 983 | 990 | }, |
| @@ -985,8 +992,10 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = { · 1 unmodified line | ||
| 985 | 992 | search_for_quantizers_fast, |
| 986 | 993 | encode_window_bands_info, |
| 987 | 994 | quantize_and_encode_band, |
| 995 | + encode_tns_info, | |
| 988 | 996 | set_special_band_scalefactors, |
| 989 | 997 | search_for_pns, |
| 998 | + search_for_tns, | |
| 990 | 999 | search_for_ms, |
| 991 | 1000 | search_for_is, |
| 992 | 1001 | }, |