correctly affect speed/reversing when shuttling audio
This commit is contained in:
itsmattkc
@@ -0,0 +1,252 @@
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#include "tempoprocessor.h"
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extern "C" {
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#include <libavfilter/buffersink.h>
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#include <libavfilter/buffersrc.h>
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#include <libavutil/opt.h>
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}
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#include <QDebug>
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#include "codec/ffmpeg/ffmpegcommon.h"
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TempoProcessor::TempoProcessor() :
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filter_graph_(nullptr),
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buffersrc_ctx_(nullptr),
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buffersink_ctx_(nullptr),
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open_(false)
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{
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}
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bool TempoProcessor::IsOpen() const
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{
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return open_;
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}
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const double &TempoProcessor::GetSpeed() const
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{
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return speed_;
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}
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bool TempoProcessor::Open(const AudioRenderingParams ¶ms, const double& speed)
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{
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if (open_) {
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return true;
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}
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params_ = params;
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speed_ = speed;
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// Create AVFilterGraph instance
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filter_graph_ = avfilter_graph_alloc();
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if (!filter_graph_) {
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qCritical() << "Failed to create AVFilterGraph";
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Close();
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return false;
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}
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// Set up audio buffer args
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char filter_args[200];
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snprintf(filter_args, 200, "time_base=%d/%d:sample_rate=%d:sample_fmt=%d:channel_layout=0x%" PRIx64,
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1,
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params_.sample_rate(),
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params_.sample_rate(),
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FFmpegCommon::GetFFmpegSampleFormat(params_.format()),
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params.channel_layout());
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// Create buffer and buffersink
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if (avfilter_graph_create_filter(&buffersrc_ctx_, avfilter_get_by_name("abuffer"), "in", filter_args, nullptr, filter_graph_) < 0) {
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qCritical() << "Failed to create audio buffer source";
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Close();
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return false;
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}
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if (avfilter_graph_create_filter(&buffersink_ctx_, avfilter_get_by_name("abuffersink"), "out", nullptr, nullptr, filter_graph_) < 0) {
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qCritical() << "Failed to create audio buffer sink";
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Close();
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return false;
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}
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// Create audio tempo filters: FFmpeg's atempo can only be set between 0.5 and 2.0. If the requested speed is outside
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// those boundaries, we need to daisychain more than one together.
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double base = (speed_ > 1.0) ? 2.0 : 0.5;
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double speed_log = log(speed_) / log(base);
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// This is the number of how many 0.5 or 2.0 tempos we need to daisychain
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int whole = qFloor(speed_log);
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// Set speed_log to the remainder
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speed_log -= whole;
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AVFilterContext* previous_filter = buffersrc_ctx_;
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for (int i=0;i<=whole;i++) {
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double filter_tempo = (i == whole) ? qPow(base, speed_log) : base;
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if (qFuzzyCompare(filter_tempo, 1.0)) {
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// This filter would do nothing
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continue;
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}
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previous_filter = CreateTempoFilter(filter_graph_,
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previous_filter,
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filter_tempo);
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if (!previous_filter) {
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qCritical() << "Failed to create audio tempo filter";
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Close();
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return false;
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}
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}
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// Link the last filter to the buffersink
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if (avfilter_link(previous_filter, 0, buffersink_ctx_, 0) != 0) {
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qCritical() << "Failed to link final filter and buffer sink";
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Close();
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return false;
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}
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// Config graph
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if (avfilter_graph_config(filter_graph_, nullptr) < 0) {
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qCritical() << "Failed to configure filter graph";
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Close();
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return false;
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}
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timestamp_ = 0;
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open_ = true;
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flushed_ = false;
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return true;
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}
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void TempoProcessor::Push(const char *data, int length)
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{
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if (flushed_) {
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if (length > 0) {
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qCritical() << "Tried to push" << length << "bytes after TempoProcessor was closed";
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}
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return;
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}
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AVFrame* src_frame;
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if (length == 0) {
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// No audio data, flush the last out of the filter graph
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src_frame = nullptr;
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flushed_ = true;
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} else {
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src_frame = av_frame_alloc();
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if (!src_frame) {
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qCritical() << "Failed to allocate source frame";
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return;
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}
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// Allocate a buffer for the number of samples we got
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src_frame->sample_rate = params_.sample_rate();
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src_frame->format = FFmpegCommon::GetFFmpegSampleFormat(params_.format());
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src_frame->channel_layout = params_.channel_layout();
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src_frame->nb_samples = params_.bytes_to_samples(length);
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src_frame->pts = timestamp_;
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timestamp_ += src_frame->nb_samples;
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if (av_frame_get_buffer(src_frame, 0) < 0) {
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qCritical() << "Failed to allocate buffer for source frame";
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av_frame_free(&src_frame);
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return;
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}
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// Copy buffer from data array to frame
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memcpy(src_frame->data[0], data, length);
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}
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int ret = av_buffersrc_add_frame_flags(buffersrc_ctx_, src_frame, AV_BUFFERSRC_FLAG_KEEP_REF);
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if (ret < 0) {
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qCritical() << "Failed to feed buffer source" << ret;
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}
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if (src_frame) {
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av_frame_free(&src_frame);
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}
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}
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int TempoProcessor::Pull(char *data, int max_length)
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{
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if (!processed_frame_) {
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processed_frame_ = av_frame_alloc();
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// Try to pull samples from the buffersink
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int ret = av_buffersink_get_frame(buffersink_ctx_, processed_frame_);
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if (ret < 0) {
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// We couldn't pull for some reason, if the error was EAGAIN, we just need to send more samples. Otherwise the
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// error might be fatal...
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if (ret != AVERROR(EAGAIN)) {
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qCritical() << "Failed to pull from buffersink" << ret;
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}
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av_frame_free(&processed_frame_);
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return 0;
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}
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processed_frame_byte_index_ = 0;
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processed_frame_max_bytes_ = params_.samples_to_bytes(processed_frame_->nb_samples);
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}
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// Determine how many bytes we should copy into the data array
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int copy_length = qMin(max_length, processed_frame_max_bytes_ - processed_frame_byte_index_);
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// Copy the bytes
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memcpy(data, processed_frame_->data[0] + processed_frame_byte_index_, copy_length);
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// Add the copied amount to the current index
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processed_frame_byte_index_ += copy_length;
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// If the index has reached the limit of this processed frame, we can dispose of the frame now
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if (processed_frame_byte_index_ == processed_frame_max_bytes_) {
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av_frame_free(&processed_frame_);
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processed_frame_ = nullptr;
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}
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return copy_length;
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}
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void TempoProcessor::Close()
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{
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open_ = false;
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if (filter_graph_) {
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avfilter_graph_free(&filter_graph_);
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filter_graph_ = nullptr;
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}
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if (processed_frame_) {
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av_frame_free(&processed_frame_);
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processed_frame_ = nullptr;
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}
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buffersrc_ctx_ = nullptr;
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buffersink_ctx_ = nullptr;
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}
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AVFilterContext *TempoProcessor::CreateTempoFilter(AVFilterGraph* graph, AVFilterContext* link, const double &tempo)
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{
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// Set up tempo param, which is taken as a C string
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char speed_param[20];
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snprintf(speed_param, 20, "%f", tempo);
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AVFilterContext* tempo_ctx = nullptr;
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if (avfilter_graph_create_filter(&tempo_ctx, avfilter_get_by_name("atempo"), "atempo", speed_param, nullptr, graph) >= 0
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&& avfilter_link(link, 0, tempo_ctx, 0) == 0) {
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return tempo_ctx;
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}
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return nullptr;
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}
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