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Add True Peak calculation to EBU R128 loudness scanner. #48

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Add True Peak calculation to EBU R128 loudness scanner. #48

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81 changes: 78 additions & 3 deletions libavfilter/f_ebur128.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@
* EBU R.128 implementation
* @see http://tech.ebu.ch/loudness
* @see https://www.youtube.com/watch?v=iuEtQqC-Sqo "EBU R128 Introduction - Florian Camerer"
* @todo True Peak
* @todo implement start/stop/reset through filter command injection
* @todo support other frequencies to avoid resampling
*/
Expand All @@ -37,6 +36,7 @@
#include "libavutil/xga_font_data.h"
#include "libavutil/opt.h"
#include "libavutil/timestamp.h"
#include "libswresample/swresample.h"
#include "audio.h"
#include "avfilter.h"
#include "formats.h"
Expand Down Expand Up @@ -109,6 +109,13 @@ typedef struct {
double *ch_weighting; ///< channel weighting mapping
int sample_count; ///< sample count used for refresh frequency, reset at refresh

/* Helpers for peak calculation*/
struct SwrContext *swr; ///< up-sample context
uint8_t **peak_samples_buffer; ///< buffer for the up-sampled signal
int peak_samples_size; ///< buffer size
int sample_ratio; ///< sample frequency ratio
float peak; ///< total peak

/* Filter caches.
* The mult by 3 in the following is for X[i], X[i-1] and X[i-2] */
double x[MAX_CHANNELS * 3]; ///< 3 input samples cache for each channel
Expand Down Expand Up @@ -323,6 +330,7 @@ static int config_video_output(AVFilterLink *outlink)

static int config_audio_input(AVFilterLink *inlink)
{
int ret;
AVFilterContext *ctx = inlink->dst;
EBUR128Context *ebur128 = ctx->priv;

Expand All @@ -332,6 +340,28 @@ static int config_audio_input(AVFilterLink *inlink)
inlink->min_samples =
inlink->max_samples =
inlink->partial_buf_size = inlink->sample_rate / 10;

// init libswresample context
ebur128->sample_ratio = 4;
ebur128->swr = swr_alloc_set_opts(ebur128->swr,
inlink->channel_layout, inlink->format,
(inlink->sample_rate * ebur128->sample_ratio),
inlink->channel_layout, inlink->format, inlink->sample_rate,
0, ctx);
av_opt_set_sample_fmt(ebur128->swr, "internal_sample_fmt", AV_SAMPLE_FMT_S16P, 0);
if (!ebur128->swr)
return AVERROR(ENOMEM);
ret = swr_init(ebur128->swr);
if (ret < 0)
return ret;

//just set up peak_samples_buffer, keep it small, we'll throw it away...
ebur128->peak_samples_size = 0;
ret = av_samples_alloc_array_and_samples(&ebur128->peak_samples_buffer, NULL, 2,
2, AV_SAMPLE_FMT_DBL, 0);
if (ret < 0)
return ret;

return 0;
}

Expand Down Expand Up @@ -456,6 +486,27 @@ static av_cold int init(AVFilterContext *ctx)

#define HIST_POS(power) (int)(((power) - ABS_THRES) * HIST_GRAIN)

/*
* Update largest absolute sample value.
*/
static void calc_peak(const double *samples, int nb_samples, int nb_channels, float *peak_p)
{
float peak = 0.0;
assert(samples);

while (nb_samples--) {
for (int i = 0; i < nb_channels; i++){
if (samples[i] > peak)
peak = samples[i];
else if (-samples[i] > peak)
peak = -samples[i];
}
samples += nb_channels;
}

*peak_p = FFMAX(peak, *peak_p);
}

/* loudness and power should be set such as loudness = -0.691 +
* 10*log10(power), we just avoid doing that calculus two times */
static int gate_update(struct integrator *integ, double power,
Expand Down Expand Up @@ -490,6 +541,23 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)
const int nb_samples = insamples->nb_samples;
const double *samples = (double *)insamples->data[0];
AVFrame *pic = ebur128->outpicref;
const int nb_up_samples = nb_samples * ebur128->sample_ratio + 32;
int ret = 0;

if (ebur128->peak_samples_size < nb_up_samples){
av_free(ebur128->peak_samples_buffer[0]);
ret = av_samples_alloc(ebur128->peak_samples_buffer, NULL, nb_channels, nb_up_samples,
AV_SAMPLE_FMT_DBL, 1);
if (ret < 0)
return ret;
ebur128->peak_samples_size = nb_up_samples;
}
ret = swr_convert(ebur128->swr, ebur128->peak_samples_buffer, nb_up_samples,
(const uint8_t **)insamples->extended_data, nb_samples);
if (ret < 0)
return ret;

calc_peak((double *)ebur128->peak_samples_buffer[0], ret, nb_channels, &ebur128->peak);

for (idx_insample = 0; idx_insample < nb_samples; idx_insample++) {
const int bin_id_400 = ebur128->i400.cache_pos;
Expand Down Expand Up @@ -757,10 +825,15 @@ static av_cold void uninit(AVFilterContext *ctx)
" LRA: %5.1f LU\n"
" Threshold: %5.1f LUFS\n"
" LRA low: %5.1f LUFS\n"
" LRA high: %5.1f LUFS\n",
" LRA high: %5.1f LUFS\n\n"
" Peak:\n"
" Max peak: %5.1f TPFS\n"
" Max peak: %1.6f\n",
ebur128->integrated_loudness, ebur128->i400.rel_threshold,
ebur128->loudness_range, ebur128->i3000.rel_threshold,
ebur128->lra_low, ebur128->lra_high);
ebur128->lra_low, ebur128->lra_high,
20 * log10(ebur128->peak),
ebur128->peak);

av_freep(&ebur128->y_line_ref);
av_freep(&ebur128->ch_weighting);
Expand All @@ -773,6 +846,8 @@ static av_cold void uninit(AVFilterContext *ctx)
for (i = 0; i < ctx->nb_outputs; i++)
av_freep(&ctx->output_pads[i].name);
av_frame_free(&ebur128->outpicref);
swr_free(&ebur128->swr);
av_free(ebur128->peak_samples_buffer[0]);
}

static const AVFilterPad ebur128_inputs[] = {
Expand Down