[FFmpeg-devel] [PATCH] Implement AAC Long Term Prediction (LTP) decoding module
Alex Converse
alex.converse
Fri Feb 4 06:09:18 CET 2011
On Thu, Feb 3, 2011 at 3:37 AM, Young Han Lee <cpumaker at gmail.com> wrote:
> On Thu, Feb 3, 2011 at 2:18 PM, Alex Converse <alex.converse at gmail.com>wrote:
[...]
>
> please check again.
>
> diff --git a/libavcodec/aac.h b/libavcodec/aac.h
> index cff476a..1e300fb 100644
> --- a/libavcodec/aac.h
> +++ b/libavcodec/aac.h
[...]
> @@ -206,14 +220,16 @@ typedef struct {
> IndividualChannelStream ics;
> TemporalNoiseShaping tns;
> Pulse pulse;
> - enum BandType band_type[128]; ///< band types
> - int band_type_run_end[120]; ///< band type run end points
> - float sf[120]; ///< scalefactors
> - int sf_idx[128]; ///< scalefactor indices (used by encoder)
> - uint8_t zeroes[128]; ///< band is not coded (used by encoder)
> - DECLARE_ALIGNED(16, float, coeffs)[1024]; ///< coefficients for IMDCT
> - DECLARE_ALIGNED(16, float, saved)[1024]; ///< overlap
> - DECLARE_ALIGNED(16, float, ret)[2048]; ///< PCM output
> + enum BandType band_type[128]; ///< band types
> + int band_type_run_end[120]; ///< band type run end points
> + float sf[120]; ///< scalefactors
> + int sf_idx[128]; ///< scalefactor indices (used by encoder)
> + uint8_t zeroes[128]; ///< band is not coded (used by encoder)
> + DECLARE_ALIGNED(16, float, coeffs)[1024]; ///< coefficients for IMDCT
> + DECLARE_ALIGNED(16, float, saved)[1024]; ///< overlap
> + DECLARE_ALIGNED(16, float, saved_ltp)[1024]; ///< overlap for LTP
> + DECLARE_ALIGNED(16, float, ret)[2048]; ///< PCM output
> + int16_t ltp_state[3072];
I meant DECLARE_ALIGNED here
> PredictorState predictor_state[MAX_PREDICTORS];
> } SingleChannelElement;
>
> @@ -259,7 +275,7 @@ typedef struct {
> * @defgroup temporary aligned temporary buffers (We do not want to have these on the stack.)
> * @{
> */
> - DECLARE_ALIGNED(16, float, buf_mdct)[1024];
> + DECLARE_ALIGNED(16, float, buf_mdct)[2048];
> /** @} */
>
> /**
> @@ -268,6 +284,7 @@ typedef struct {
> */
> FFTContext mdct;
> FFTContext mdct_small;
> + FFTContext mdct_ltp;
> DSPContext dsp;
> FmtConvertContext fmt_conv;
> int random_state;
> diff --git a/libavcodec/aacdec.c b/libavcodec/aacdec.c
> index 411c1df..cc4ab6c 100644
> --- a/libavcodec/aacdec.c
> +++ b/libavcodec/aacdec.c
> @@ -478,6 +478,7 @@ static int decode_audio_specific_config(AACContext *ac,
> switch (m4ac->object_type) {
> case AOT_AAC_MAIN:
> case AOT_AAC_LC:
> + case AOT_AAC_LTP:
> if (decode_ga_specific_config(ac, avctx, &gb, m4ac, m4ac->chan_config))
> return -1;
> break;
> @@ -580,8 +581,9 @@ static av_cold int aac_decode_init(AVCodecContext *avctx)
> ff_aac_scalefactor_code, sizeof(ff_aac_scalefactor_code[0]), sizeof(ff_aac_scalefactor_code[0]),
> 352);
>
> - ff_mdct_init(&ac->mdct, 11, 1, 1.0);
> - ff_mdct_init(&ac->mdct_small, 8, 1, 1.0);
> + ff_mdct_init(&ac->mdct, 11, 1, 1.0);
> + ff_mdct_init(&ac->mdct_small, 8, 1, 1.0);
> + ff_mdct_init(&ac->mdct_ltp, 11, 0, 1.0);
> // window initialization
> ff_kbd_window_init(ff_aac_kbd_long_1024, 4.0, 1024);
> ff_kbd_window_init(ff_aac_kbd_short_128, 6.0, 128);
> @@ -631,6 +633,21 @@ static int decode_prediction(AACContext *ac, IndividualChannelStream *ics,
> }
>
> /**
> + * Decode Long Term Prediction data; reference: table 4.xx.
> + */
> +static void decode_ltp(AACContext *ac, LongTermPrediction *ltp,
> + GetBitContext *gb, uint8_t max_sfb)
> +{
> + int sfb;
> +
> + ltp->lag = get_bits(gb, 11);
> + ltp->coef = ltp_coef[get_bits(gb, 3)] * ac->sf_scale;
> + for (sfb = 0; sfb < FFMIN(max_sfb, MAX_LTP_LONG_SFB); sfb++)
> + ltp->used[sfb] = get_bits1(gb);
> +}
> +
> +
> +/**
> * Decode Individual Channel Stream info; reference: table 4.6.
> *
> * @param common_window Channels have independent [0], or shared [1], Individual Channel Stream information.
> @@ -684,9 +701,8 @@ static int decode_ics_info(AACContext *ac, IndividualChannelStream *ics,
> memset(ics, 0, sizeof(IndividualChannelStream));
> return -1;
> } else {
> - av_log_missing_feature(ac->avctx, "Predictor bit set but LTP is", 1);
> - memset(ics, 0, sizeof(IndividualChannelStream));
> - return -1;
> + if ((ics->ltp.present = get_bits(gb, 1)))
> + decode_ltp(ac, &ics->ltp, gb, ics->max_sfb);
> }
> }
> }
> @@ -1420,6 +1436,9 @@ static int decode_cpe(AACContext *ac, GetBitContext *gb, ChannelElement *cpe)
> i = cpe->ch[1].ics.use_kb_window[0];
> cpe->ch[1].ics = cpe->ch[0].ics;
> cpe->ch[1].ics.use_kb_window[1] = i;
> + if (cpe->ch[1].ics.predictor_present && (ac->m4ac.object_type != AOT_AAC_MAIN))
> + if ((cpe->ch[1].ics.ltp.present = get_bits(gb, 1)))
> + decode_ltp(ac, &cpe->ch[1].ics.ltp, gb, cpe->ch[1].ics.max_sfb);
> ms_present = get_bits(gb, 2);
> if (ms_present == 3) {
> av_log(ac->avctx, AV_LOG_ERROR, "ms_present = 3 is reserved.\n");
> @@ -1659,6 +1678,7 @@ static void apply_tns(float coef[1024], TemporalNoiseShaping *tns,
> int w, filt, m, i;
> int bottom, top, order, start, end, size, inc;
> float lpc[TNS_MAX_ORDER];
> + float tmp[TNS_MAX_ORDER];
>
> for (w = 0; w < ics->num_windows; w++) {
> bottom = ics->num_swb;
> @@ -1684,14 +1704,123 @@ static void apply_tns(float coef[1024], TemporalNoiseShaping *tns,
> }
> start += w * 128;
>
> - // ar filter
> - for (m = 0; m < size; m++, start += inc)
> - for (i = 1; i <= FFMIN(m, order); i++)
> - coef[start] -= coef[start - i * inc] * lpc[i - 1];
> + if (decode) {
> + // ar filter
> + for (m = 0; m < size; m++, start += inc)
> + for (i = 1; i <= FFMIN(m, order); i++)
> + coef[start] -= coef[start - i * inc] * lpc[i - 1];
> + } else {
> + // ma filter
> + for (m = 0; m < size; m++, start += inc) {
> + tmp[0] = coef[start];
> + for (i = 1; i <= FFMIN(m, order); i++)
> + coef[start] += tmp[i] * lpc[i - 1];
> + for (i = order; i > 0; i--)
> + tmp[i] = tmp[i - 1];
> + }
> + }
> }
> }
> }
>
> +
> +
> +/**
> + * Apply windowing and MDCT to obtain the spectral
> + * coefficient from the predicted sample by LTP.
> + */
> +static void windowing_and_mdct_ltp(AACContext *ac, float *out,
> + float *in, IndividualChannelStream *ics)
> +{
> + const float * lwindow = ics->use_kb_window[0] ? ff_aac_kbd_long_1024 : ff_sine_1024;
> + const float * swindow = ics->use_kb_window[0] ? ff_aac_kbd_short_128 : ff_sine_128;
> + const float * lwindow_prev = ics->use_kb_window[1] ? ff_aac_kbd_long_1024 : ff_sine_1024;
> + const float * swindow_prev = ics->use_kb_window[1] ? ff_aac_kbd_short_128 : ff_sine_128;
> + float * buf = ac->buf_mdct;
> +
> + if (ics->window_sequence[0] != LONG_STOP_SEQUENCE) {
> + ac->dsp.vector_fmul(buf, in, lwindow_prev, 1024);
> + } else {
> + memset(buf, 0, 448 * sizeof(float));
> + ac->dsp.vector_fmul(buf + 448, in + 448, swindow_prev, 128);
> + memcpy(buf + 576, in + 576, 448 * sizeof(float));
> + }
> + if (ics->window_sequence[0] != LONG_START_SEQUENCE) {
> + ac->dsp.vector_fmul_reverse(buf + 1024, in + 1024, lwindow, 1024);
> + } else {
> + memcpy(buf + 1024, in + 1024, 448 * sizeof(float));
> + ac->dsp.vector_fmul_reverse(buf + 1024 + 448, in + 1024 + 448, swindow, 128);
> + memset(buf + 1024 + 576, 0, 448 * sizeof(float));
> + }
> + ff_mdct_calc(&ac->mdct_ltp, out, buf);
> +}
> +
> +
> +/**
> + * Apply the long term prediction
> + */
> +static void apply_ltp(AACContext *ac, SingleChannelElement *sce)
> +{
> + const LongTermPrediction *ltp = &sce->ics.ltp;
> + const uint16_t *offsets = sce->ics.swb_offset;
> + int i, sfb;
> +
> + if (sce->ics.window_sequence[0] != EIGHT_SHORT_SEQUENCE) {
> + float x_est[2048], X_est[1024];
These are too big to use stack allocations.
Also these names are too similar.
Also any buffer being sent to an MDCT needs to be DECALRE_ALIGNED
> + int16_t num_samples = 2048;
> + if (ltp->lag < 1024)
> + num_samples = ltp->lag + 1024;
> + for (i = 0; i < num_samples; i++)
> + x_est[i] = sce->ltp_state[i + 2048 - ltp->lag] * ltp->coef;
> + for ( ; i < 2048; i++)
> + x_est[i] = 0.0f;
Let's use memset() for this last loop
> +
> + windowing_and_mdct_ltp(ac, X_est, x_est, &sce->ics);
> +
> + if (sce->tns.present)
> + apply_tns(X_est, &sce->tns, &sce->ics, 0);
> +
> + for (sfb = 0; sfb < FFMIN(sce->ics.max_sfb, MAX_LTP_LONG_SFB); sfb++)
> + if (ltp->used[sfb])
> + for (i = offsets[sfb]; i < offsets[sfb + 1]; i++)
> + sce->coeffs[i] += X_est[i];
> + }
> +}
> +
> +/**
> + * Update the LTP buffer for next frame
> + */
> +static void update_ltp(AACContext *ac, SingleChannelElement *sce)
> +{
> + IndividualChannelStream *ics = &sce->ics;
> + float *saved = sce->saved;
> + float *saved_ltp = sce->saved_ltp;
> + const float *lwindow = ics->use_kb_window[0] ? ff_aac_kbd_long_1024 : ff_sine_1024;
> + const float *swindow = ics->use_kb_window[0] ? ff_aac_kbd_short_128 : ff_sine_128;
> + float *buf = ac->buf_mdct;
> + int i;
> +
> + for (i = 0; i < 512; i++)
> + buf[1535 - i] = buf[512 + i];
> +
> + if (ics->window_sequence[0] == EIGHT_SHORT_SEQUENCE) {
> + memcpy(saved_ltp, saved, 512 * sizeof(float));
> + memset(saved_ltp + 576, 0, 448 * sizeof(float));
> + ac->dsp.vector_fmul_reverse(saved_ltp+448, buf + 960, swindow, 128);
> + } else if (ics->window_sequence[0] == LONG_START_SEQUENCE) {
> + memcpy(saved_ltp, buf + 512, 448 * sizeof(float));
> + memset(saved_ltp + 576, 0, 448 * sizeof(float));
> + ac->dsp.vector_fmul_reverse(saved_ltp+448, buf + 960, swindow, 128);
> + } else { // LONG_STOP or ONLY_LONG
> + ac->dsp.vector_fmul_reverse(saved_ltp, buf + 512, lwindow, 1024);
> + }
> +
> + memcpy(sce->ltp_state, &sce->ltp_state[1024], 1024 * sizeof(int16_t));
> + ac->fmt_conv.float_to_int16(&(sce->ltp_state[1024]), sce->ret, 1024);
> + ac->fmt_conv.float_to_int16(&(sce->ltp_state[2048]), sce->saved_ltp, 1024);
> +}
> +
> +
> /**
> * Conduct IMDCT and windowing.
> */
> @@ -1857,6 +1986,14 @@ static void spectral_to_sample(AACContext *ac)
> if (che) {
> if (type <= TYPE_CPE)
> apply_channel_coupling(ac, che, type, i, BEFORE_TNS, apply_dependent_coupling);
> + if (che->ch[0].ics.predictor_present) {
> + if (ac->m4ac.object_type == AOT_AAC_LTP) {
I would slightly prefer the order of these two ifs to be swapped.
> + if (che->ch[0].ics.ltp.present)
> + apply_ltp(ac, &che->ch[0]);
> + if (che->ch[1].ics.ltp.present && type == TYPE_CPE)
> + apply_ltp(ac, &che->ch[1]);
> + }
> + }
> if (che->ch[0].tns.present)
> apply_tns(che->ch[0].coeffs, &che->ch[0].tns, &che->ch[0].ics, 1);
> if (che->ch[1].tns.present)
[...]
Thanks,
Alex
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