+++ /dev/null
-#ifndef _RESAMPLER_H
-#define _RESAMPLER_H 1
-
-// Takes in samples from an input source, possibly with jitter, and outputs a fixed number
-// of samples every iteration. Used to a) change sample rates if needed, and b) deal with
-// input sources that don't have audio locked to video. For every input video
-// frame, you call add_input_samples() with the pts (measured in seconds) of the video frame,
-// taken to be the start point of the frame's audio. When you want to _output_ a finished
-// frame with audio, you get_output_samples() with the number of samples you want, and will
-// get exactly that number of samples back. If the input and output clocks are not in sync,
-// the audio will be stretched for you. (If they are _very_ out of sync, this will come through
-// as a pitch shift.) Of course, the process introduces some delay; you specify a target delay
-// (typically measured in milliseconds, although more is fine) and the algorithm works to
-// provide exactly that.
-//
-// A/V sync is a much harder problem than one would intuitively assume. This implementation
-// is based on a 2012 paper by Fons Adriaensen, “Controlling adaptive resampling”
-// (http://kokkinizita.linuxaudio.org/papers/adapt-resamp.pdf). The paper gives an algorithm
-// that converges to jitter of <100 ns; the basic idea is to measure the _rate_ the input
-// queue fills and is drained (as opposed to the length of the queue itself), and smoothly
-// adjust the resampling rate so that it reaches steady state at the desired delay.
-//
-// Parts of the code is adapted from Adriaensen's project Zita-ajbridge (based on the same
-// algorithm), although it has been heavily reworked for this use case. Original copyright follows:
-//
-// Copyright (C) 2012-2015 Fons Adriaensen <fons@linuxaudio.org>
-//
-// This program is free software; you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation; either version 3 of the License, or
-// (at your option) any later version.
-//
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program. If not, see <http://www.gnu.org/licenses/>.
-
-#include <stdint.h>
-#include <stdlib.h>
-#include <sys/types.h>
-#include <zita-resampler/vresampler.h>
-#include <deque>
-#include <memory>
-
-class Resampler {
-public:
- Resampler(unsigned freq_in, unsigned freq_out, unsigned num_channels = 2);
-
- // Note: pts is always in seconds.
- void add_input_samples(double pts, const float *samples, ssize_t num_samples);
- bool get_output_samples(double pts, float *samples, ssize_t num_samples); // Returns false if underrun.
-
-private:
- void init_loop_filter(double bandwidth_hz);
-
- VResampler vresampler;
-
- unsigned freq_in, freq_out, num_channels;
-
- bool first_input = true, first_output = true;
- double last_input_pts; // Start of last input block, in seconds.
- double last_output_pts;
-
- ssize_t k_a0 = 0; // Total amount of samples inserted _before_ the last call to add_input_samples().
- ssize_t k_a1 = 0; // Total amount of samples inserted _after_ the last call to add_input_samples().
-
- ssize_t total_consumed_samples = 0;
-
- // Duration of last input block, in seconds.
- double last_input_len;
-
- // Filter state for the loop filter.
- double z1 = 0.0, z2 = 0.0, z3 = 0.0;
-
- // Ratio between the two frequencies.
- double ratio;
-
- // How much delay we are expected to have, in input samples.
- // If actual delay drifts too much away from this, we will start
- // changing the resampling ratio to compensate.
- double expected_delay = 4800.0;
-
- // Input samples not yet fed into the resampler.
- // TODO: Use a circular buffer instead, for efficiency.
- std::deque<float> buffer;
-};
-
-#endif // !defined(_RESAMPLER_H)
projects / nageru / blobdiff