From 230c1a90754860719b017a9ea4627dc81f67ff6e Mon Sep 17 00:00:00 2001 From: Nathan Caldwell Date: Wed, 5 Jan 2011 01:32:16 -0700 Subject: aacenc: Finish 3GPP psymodel analysis for non mid/side cases. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There is still are still a few sections missing relating to TNS (not present) and mid/side (contains other bugs). Overall this improves quality, and vastly improves rate-control. Signed-off-by: Martin Storsjö --- libavcodec/aacpsy.c | 305 +++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 300 insertions(+), 5 deletions(-) (limited to 'libavcodec/aacpsy.c') diff --git a/libavcodec/aacpsy.c b/libavcodec/aacpsy.c index 4250a5d763..98be176c0f 100644 --- a/libavcodec/aacpsy.c +++ b/libavcodec/aacpsy.c @@ -30,7 +30,6 @@ /*********************************** * TODOs: - * thresholds linearization after their modifications for attaining given bitrate * try other bitrate controlling mechanism (maybe use ratecontrol.c?) * control quality for quality-based output **********************************/ @@ -41,10 +40,51 @@ */ #define PSY_3GPP_THR_SPREAD_HI 1.5f // spreading factor for low-to-hi threshold spreading (15 dB/Bark) #define PSY_3GPP_THR_SPREAD_LOW 3.0f // spreading factor for hi-to-low threshold spreading (30 dB/Bark) +/* spreading factor for low-to-hi energy spreading, long block, > 22kbps/channel (20dB/Bark) */ +#define PSY_3GPP_EN_SPREAD_HI_L1 2.0f +/* spreading factor for low-to-hi energy spreading, long block, <= 22kbps/channel (15dB/Bark) */ +#define PSY_3GPP_EN_SPREAD_HI_L2 1.5f +/* spreading factor for low-to-hi energy spreading, short block (15 dB/Bark) */ +#define PSY_3GPP_EN_SPREAD_HI_S 1.5f +/* spreading factor for hi-to-low energy spreading, long block (30dB/Bark) */ +#define PSY_3GPP_EN_SPREAD_LOW_L 3.0f +/* spreading factor for hi-to-low energy spreading, short block (20dB/Bark) */ +#define PSY_3GPP_EN_SPREAD_LOW_S 2.0f #define PSY_3GPP_RPEMIN 0.01f #define PSY_3GPP_RPELEV 2.0f +#define PSY_3GPP_C1 3.0f /* log2(8) */ +#define PSY_3GPP_C2 1.3219281f /* log2(2.5) */ +#define PSY_3GPP_C3 0.55935729f /* 1 - C2 / C1 */ + +#define PSY_SNR_1DB 7.9432821e-1f /* -1dB */ +#define PSY_SNR_25DB 3.1622776e-3f /* -25dB */ + +#define PSY_3GPP_SAVE_SLOPE_L -0.46666667f +#define PSY_3GPP_SAVE_SLOPE_S -0.36363637f +#define PSY_3GPP_SAVE_ADD_L -0.84285712f +#define PSY_3GPP_SAVE_ADD_S -0.75f +#define PSY_3GPP_SPEND_SLOPE_L 0.66666669f +#define PSY_3GPP_SPEND_SLOPE_S 0.81818181f +#define PSY_3GPP_SPEND_ADD_L -0.35f +#define PSY_3GPP_SPEND_ADD_S -0.26111111f +#define PSY_3GPP_CLIP_LO_L 0.2f +#define PSY_3GPP_CLIP_LO_S 0.2f +#define PSY_3GPP_CLIP_HI_L 0.95f +#define PSY_3GPP_CLIP_HI_S 0.75f + +#define PSY_3GPP_AH_THR_LONG 0.5f +#define PSY_3GPP_AH_THR_SHORT 0.63f + +enum { + PSY_3GPP_AH_NONE, + PSY_3GPP_AH_INACTIVE, + PSY_3GPP_AH_ACTIVE +}; + +#define PSY_3GPP_BITS_TO_PE(bits) ((bits) * 1.18f) + /* LAME psy model constants */ #define PSY_LAME_FIR_LEN 21 ///< LAME psy model FIR order #define AAC_BLOCK_SIZE_LONG 1024 ///< long block size @@ -63,6 +103,12 @@ typedef struct AacPsyBand{ float energy; ///< band energy float thr; ///< energy threshold float thr_quiet; ///< threshold in quiet + float nz_lines; ///< number of non-zero spectral lines + float active_lines; ///< number of active spectral lines + float pe; ///< perceptual entropy + float pe_const; ///< constant part of the PE calculation + float norm_fac; ///< normalization factor for linearization + int avoid_holes; ///< hole avoidance flag }AacPsyBand; /** @@ -97,6 +143,15 @@ typedef struct AacPsyCoeffs{ * 3GPP TS26.403-inspired psychoacoustic model specific data */ typedef struct AacPsyContext{ + int chan_bitrate; ///< bitrate per channel + int frame_bits; ///< average bits per frame + int fill_level; ///< bit reservoir fill level + struct { + float min; ///< minimum allowed PE for bit factor calculation + float max; ///< maximum allowed PE for bit factor calculation + float previous; ///< allowed PE of the previous frame + float correction; ///< PE correction factor + } pe; AacPsyCoeffs psy_coef[2][64]; AacPsyChannel *ch; }AacPsyContext; @@ -235,16 +290,33 @@ static av_cold int psy_3gpp_init(FFPsyContext *ctx) { AacPsyContext *pctx; float bark; int i, j, g, start; - float prev, minscale, minath; + float prev, minscale, minath, minsnr, pe_min; + const int chan_bitrate = ctx->avctx->bit_rate / ctx->avctx->channels; + const int bandwidth = ctx->avctx->cutoff ? ctx->avctx->cutoff : ctx->avctx->sample_rate / 2; + const float num_bark = calc_bark((float)bandwidth); ctx->model_priv_data = av_mallocz(sizeof(AacPsyContext)); pctx = (AacPsyContext*) ctx->model_priv_data; + pctx->chan_bitrate = chan_bitrate; + pctx->frame_bits = chan_bitrate * AAC_BLOCK_SIZE_LONG / ctx->avctx->sample_rate; + pctx->pe.min = 8.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f); + pctx->pe.max = 12.0f * AAC_BLOCK_SIZE_LONG * bandwidth / (ctx->avctx->sample_rate * 2.0f); + ctx->bitres.size = 6144 - pctx->frame_bits; + ctx->bitres.size -= ctx->bitres.size % 8; + pctx->fill_level = ctx->bitres.size; minath = ath(3410, ATH_ADD); for (j = 0; j < 2; j++) { AacPsyCoeffs *coeffs = pctx->psy_coef[j]; const uint8_t *band_sizes = ctx->bands[j]; float line_to_frequency = ctx->avctx->sample_rate / (j ? 256.f : 2048.0f); + float avg_chan_bits = chan_bitrate / ctx->avctx->sample_rate * (j ? 128.0f : 1024.0f); + /* reference encoder uses 2.4% here instead of 60% like the spec says */ + float bark_pe = 0.024f * PSY_3GPP_BITS_TO_PE(avg_chan_bits) / num_bark; + float en_spread_low = j ? PSY_3GPP_EN_SPREAD_LOW_S : PSY_3GPP_EN_SPREAD_LOW_L; + /* High energy spreading for long blocks <= 22kbps/channel and short blocks are the same. */ + float en_spread_hi = (j || (chan_bitrate <= 22.0f)) ? PSY_3GPP_EN_SPREAD_HI_S : PSY_3GPP_EN_SPREAD_HI_L1; + i = 0; prev = 0.0; for (g = 0; g < ctx->num_bands[j]; g++) { @@ -258,6 +330,11 @@ static av_cold int psy_3gpp_init(FFPsyContext *ctx) { float bark_width = coeffs[g+1].barks - coeffs->barks; coeff->spread_low[0] = pow(10.0, -bark_width * PSY_3GPP_THR_SPREAD_LOW); coeff->spread_hi [0] = pow(10.0, -bark_width * PSY_3GPP_THR_SPREAD_HI); + coeff->spread_low[1] = pow(10.0, -bark_width * en_spread_low); + coeff->spread_hi [1] = pow(10.0, -bark_width * en_spread_hi); + pe_min = bark_pe * bark_width; + minsnr = pow(2.0f, pe_min / band_sizes[g]) - 1.5f; + coeff->min_snr = av_clipf(1.0f / minsnr, PSY_SNR_25DB, PSY_SNR_1DB); } start = 0; for (g = 0; g < ctx->num_bands[j]; g++) { @@ -385,6 +462,97 @@ static FFPsyWindowInfo psy_3gpp_window(FFPsyContext *ctx, return wi; } +/* 5.6.1.2 "Calculation of Bit Demand" */ +static int calc_bit_demand(AacPsyContext *ctx, float pe, int bits, int size, + int short_window) +{ + const float bitsave_slope = short_window ? PSY_3GPP_SAVE_SLOPE_S : PSY_3GPP_SAVE_SLOPE_L; + const float bitsave_add = short_window ? PSY_3GPP_SAVE_ADD_S : PSY_3GPP_SAVE_ADD_L; + const float bitspend_slope = short_window ? PSY_3GPP_SPEND_SLOPE_S : PSY_3GPP_SPEND_SLOPE_L; + const float bitspend_add = short_window ? PSY_3GPP_SPEND_ADD_S : PSY_3GPP_SPEND_ADD_L; + const float clip_low = short_window ? PSY_3GPP_CLIP_LO_S : PSY_3GPP_CLIP_LO_L; + const float clip_high = short_window ? PSY_3GPP_CLIP_HI_S : PSY_3GPP_CLIP_HI_L; + float clipped_pe, bit_save, bit_spend, bit_factor, fill_level; + + ctx->fill_level += ctx->frame_bits - bits; + ctx->fill_level = av_clip(ctx->fill_level, 0, size); + fill_level = av_clipf((float)ctx->fill_level / size, clip_low, clip_high); + clipped_pe = av_clipf(pe, ctx->pe.min, ctx->pe.max); + bit_save = (fill_level + bitsave_add) * bitsave_slope; + assert(bit_save <= 0.3f && bit_save >= -0.05000001f); + bit_spend = (fill_level + bitspend_add) * bitspend_slope; + assert(bit_spend <= 0.5f && bit_spend >= -0.1f); + /* The bit factor graph in the spec is obviously incorrect. + * bit_spend + ((bit_spend - bit_spend))... + * The reference encoder subtracts everything from 1, but also seems incorrect. + * 1 - bit_save + ((bit_spend + bit_save))... + * Hopefully below is correct. + */ + bit_factor = 1.0f - bit_save + ((bit_spend - bit_save) / (ctx->pe.max - ctx->pe.min)) * (clipped_pe - ctx->pe.min); + /* NOTE: The reference encoder attempts to center pe max/min around the current pe. */ + ctx->pe.max = FFMAX(pe, ctx->pe.max); + ctx->pe.min = FFMIN(pe, ctx->pe.min); + + return FFMIN(ctx->frame_bits * bit_factor, ctx->frame_bits + size - bits); +} + +static float calc_pe_3gpp(AacPsyBand *band) +{ + float pe, a; + + band->pe = 0.0f; + band->pe_const = 0.0f; + band->active_lines = 0.0f; + if (band->energy > band->thr) { + a = log2f(band->energy); + pe = a - log2f(band->thr); + band->active_lines = band->nz_lines; + if (pe < PSY_3GPP_C1) { + pe = pe * PSY_3GPP_C3 + PSY_3GPP_C2; + a = a * PSY_3GPP_C3 + PSY_3GPP_C2; + band->active_lines *= PSY_3GPP_C3; + } + band->pe = pe * band->nz_lines; + band->pe_const = a * band->nz_lines; + } + + return band->pe; +} + +static float calc_reduction_3gpp(float a, float desired_pe, float pe, + float active_lines) +{ + float thr_avg, reduction; + + thr_avg = powf(2.0f, (a - pe) / (4.0f * active_lines)); + reduction = powf(2.0f, (a - desired_pe) / (4.0f * active_lines)) - thr_avg; + + return FFMAX(reduction, 0.0f); +} + +static float calc_reduced_thr_3gpp(AacPsyBand *band, float min_snr, + float reduction) +{ + float thr = band->thr; + + if (band->energy > thr) { + thr = powf(thr, 0.25f) + reduction; + thr = powf(thr, 4.0f); + + /* This deviates from the 3GPP spec to match the reference encoder. + * It performs min(thr_reduced, max(thr, energy/min_snr)) only for bands + * that have hole avoidance on (active or inactive). It always reduces the + * threshold of bands with hole avoidance off. + */ + if (thr > band->energy * min_snr && band->avoid_holes != PSY_3GPP_AH_NONE) { + thr = FFMAX(band->thr, band->energy * min_snr); + band->avoid_holes = PSY_3GPP_AH_ACTIVE; + } + } + + return thr; +} + /** * Calculate band thresholds as suggested in 3GPP TS26.403 */ @@ -395,18 +563,27 @@ static void psy_3gpp_analyze(FFPsyContext *ctx, int channel, AacPsyChannel *pch = &pctx->ch[channel]; int start = 0; int i, w, g; + float desired_bits, desired_pe, delta_pe, reduction, spread_en[128] = {0}; + float a = 0.0f, active_lines = 0.0f, norm_fac = 0.0f; + float pe = pctx->chan_bitrate > 32000 ? 0.0f : FFMAX(50.0f, 100.0f - pctx->chan_bitrate * 100.0f / 32000.0f); const int num_bands = ctx->num_bands[wi->num_windows == 8]; const uint8_t *band_sizes = ctx->bands[wi->num_windows == 8]; AacPsyCoeffs *coeffs = pctx->psy_coef[wi->num_windows == 8]; + const float avoid_hole_thr = wi->num_windows == 8 ? PSY_3GPP_AH_THR_SHORT : PSY_3GPP_AH_THR_LONG; //calculate energies, initial thresholds and related values - 5.4.2 "Threshold Calculation" for (w = 0; w < wi->num_windows*16; w += 16) { for (g = 0; g < num_bands; g++) { AacPsyBand *band = &pch->band[w+g]; + float form_factor = 0.0f; band->energy = 0.0f; - for (i = 0; i < band_sizes[g]; i++) + for (i = 0; i < band_sizes[g]; i++) { band->energy += coefs[start+i] * coefs[start+i]; + form_factor += sqrtf(fabs(coefs[start+i])); + } band->thr = band->energy * 0.001258925f; + band->nz_lines = form_factor / powf(band->energy / band_sizes[g], 0.25f); + start += band_sizes[g]; } } @@ -414,10 +591,15 @@ static void psy_3gpp_analyze(FFPsyContext *ctx, int channel, for (w = 0; w < wi->num_windows*16; w += 16) { AacPsyBand *bands = &pch->band[w]; //5.4.2.3 "Spreading" & 5.4.3 "Spreaded Energy Calculation" - for (g = 1; g < num_bands; g++) + spread_en[0] = bands[0].energy; + for (g = 1; g < num_bands; g++) { bands[g].thr = FFMAX(bands[g].thr, bands[g-1].thr * coeffs[g].spread_hi[0]); - for (g = num_bands - 2; g >= 0; g--) + spread_en[w+g] = FFMAX(bands[g].energy, spread_en[w+g-1] * coeffs[g].spread_hi[1]); + } + for (g = num_bands - 2; g >= 0; g--) { bands[g].thr = FFMAX(bands[g].thr, bands[g+1].thr * coeffs[g].spread_low[0]); + spread_en[w+g] = FFMAX(spread_en[w+g], spread_en[w+g+1] * coeffs[g].spread_low[1]); + } //5.4.2.4 "Threshold in quiet" for (g = 0; g < num_bands; g++) { AacPsyBand *band = &bands[g]; @@ -426,6 +608,119 @@ static void psy_3gpp_analyze(FFPsyContext *ctx, int channel, if (!(wi->window_type[0] == LONG_STOP_SEQUENCE || (wi->window_type[1] == LONG_START_SEQUENCE && !w))) band->thr = FFMAX(PSY_3GPP_RPEMIN*band->thr, FFMIN(band->thr, PSY_3GPP_RPELEV*pch->prev_band[w+g].thr_quiet)); + + /* 5.6.1.3.1 "Prepatory steps of the perceptual entropy calculation" */ + pe += calc_pe_3gpp(band); + a += band->pe_const; + active_lines += band->active_lines; + + /* 5.6.1.3.3 "Selection of the bands for avoidance of holes" */ + if (spread_en[w+g] * avoid_hole_thr > band->energy || coeffs[g].min_snr > 1.0f) + band->avoid_holes = PSY_3GPP_AH_NONE; + else + band->avoid_holes = PSY_3GPP_AH_INACTIVE; + } + } + + /* 5.6.1.3.2 "Calculation of the desired perceptual entropy" */ + ctx->pe[channel] = pe; + desired_bits = calc_bit_demand(pctx, pe, ctx->bitres.bits, ctx->bitres.size, wi->num_windows == 8); + desired_pe = PSY_3GPP_BITS_TO_PE(desired_bits); + /* NOTE: PE correction is kept simple. During initial testing it had very + * little effect on the final bitrate. Probably a good idea to come + * back and do more testing later. + */ + if (ctx->bitres.bits > 0) + desired_pe *= av_clipf(pctx->pe.previous / PSY_3GPP_BITS_TO_PE(ctx->bitres.bits), + 0.85f, 1.15f); + pctx->pe.previous = PSY_3GPP_BITS_TO_PE(desired_bits); + + if (desired_pe < pe) { + /* 5.6.1.3.4 "First Estimation of the reduction value" */ + for (w = 0; w < wi->num_windows*16; w += 16) { + reduction = calc_reduction_3gpp(a, desired_pe, pe, active_lines); + pe = 0.0f; + a = 0.0f; + active_lines = 0.0f; + for (g = 0; g < num_bands; g++) { + AacPsyBand *band = &pch->band[w+g]; + + band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction); + /* recalculate PE */ + pe += calc_pe_3gpp(band); + a += band->pe_const; + active_lines += band->active_lines; + } + } + + /* 5.6.1.3.5 "Second Estimation of the reduction value" */ + for (i = 0; i < 2; i++) { + float pe_no_ah = 0.0f, desired_pe_no_ah; + active_lines = a = 0.0f; + for (w = 0; w < wi->num_windows*16; w += 16) { + for (g = 0; g < num_bands; g++) { + AacPsyBand *band = &pch->band[w+g]; + + if (band->avoid_holes != PSY_3GPP_AH_ACTIVE) { + pe_no_ah += band->pe; + a += band->pe_const; + active_lines += band->active_lines; + } + } + } + desired_pe_no_ah = FFMAX(desired_pe - (pe - pe_no_ah), 0.0f); + if (active_lines > 0.0f) + reduction += calc_reduction_3gpp(a, desired_pe_no_ah, pe_no_ah, active_lines); + + pe = 0.0f; + for (w = 0; w < wi->num_windows*16; w += 16) { + for (g = 0; g < num_bands; g++) { + AacPsyBand *band = &pch->band[w+g]; + + if (active_lines > 0.0f) + band->thr = calc_reduced_thr_3gpp(band, coeffs[g].min_snr, reduction); + pe += calc_pe_3gpp(band); + band->norm_fac = band->active_lines / band->thr; + norm_fac += band->norm_fac; + } + } + delta_pe = desired_pe - pe; + if (fabs(delta_pe) > 0.05f * desired_pe) + break; + } + + if (pe < 1.15f * desired_pe) { + /* 6.6.1.3.6 "Final threshold modification by linearization" */ + norm_fac = 1.0f / norm_fac; + for (w = 0; w < wi->num_windows*16; w += 16) { + for (g = 0; g < num_bands; g++) { + AacPsyBand *band = &pch->band[w+g]; + + if (band->active_lines > 0.5f) { + float delta_sfb_pe = band->norm_fac * norm_fac * delta_pe; + float thr = band->thr; + + thr *= powf(2.0f, delta_sfb_pe / band->active_lines); + if (thr > coeffs[g].min_snr * band->energy && band->avoid_holes == PSY_3GPP_AH_INACTIVE) + thr = FFMAX(band->thr, coeffs[g].min_snr * band->energy); + band->thr = thr; + } + } + } + } else { + /* 5.6.1.3.7 "Further perceptual entropy reduction" */ + g = num_bands; + while (pe > desired_pe && g--) { + for (w = 0; w < wi->num_windows*16; w+= 16) { + AacPsyBand *band = &pch->band[w+g]; + if (band->avoid_holes != PSY_3GPP_AH_NONE && coeffs[g].min_snr < PSY_SNR_1DB) { + coeffs[g].min_snr = PSY_SNR_1DB; + band->thr = band->energy * PSY_SNR_1DB; + pe += band->active_lines * 1.5f - band->pe; + } + } + } + /* TODO: allow more holes (unused without mid/side) */ } } -- cgit v1.2.3