Implement audio sync foundations

app/codec/CMakeLists.txt

@@ -33,5 +33,7 @@ set(OLIVE_SOURCES
   codec/frame.h
   codec/planarfiledevice.cpp
   codec/planarfiledevice.h
+  codec/timecodemetadata.cpp
+  codec/timecodemetadata.h
   PARENT_SCOPE
 )

app/codec/ffmpeg/ffmpegdecoder.cpp

@@ -81,6 +81,7 @@ extern "C" {
 #include <QThread>
 
 #include "codec/planarfiledevice.h"
+#include "codec/timecodemetadata.h"
 #include "common/ffmpegutils.h"
 #include "common/filefunctions.h"
 #include "render/renderer.h"
@@ -128,6 +129,36 @@ void DiscardSubtitleStreams(AVFormatContext *ctx)
 	}
 }
 
+TimecodeMetadata::SourceTime ExtractSourceStartTime(
+	AVDictionary *metadata, const rational &timebase, int sample_rate)
+{
+	if (!metadata) {
+		return TimecodeMetadata::SourceTime();
+	}
+
+	if (AVDictionaryEntry *entry =
+			av_dict_get(metadata, "timecode", nullptr, AV_DICT_IGNORE_SUFFIX)) {
+		TimecodeMetadata::SourceTime parsed =
+			TimecodeMetadata::FromTimecodeString(
+				QString::fromUtf8(entry->value), timebase);
+		if (parsed.valid) {
+			return parsed;
+		}
+	}
+
+	if (AVDictionaryEntry *entry = av_dict_get(
+			metadata, "time_reference", nullptr, AV_DICT_IGNORE_SUFFIX)) {
+		TimecodeMetadata::SourceTime parsed =
+			TimecodeMetadata::FromBwfTimeReference(
+				QString::fromUtf8(entry->value), sample_rate);
+		if (parsed.valid) {
+			return parsed;
+		}
+	}
+
+	return TimecodeMetadata::SourceTime();
+}
+
 } // namespace
 
 FFmpegDecoder::FFmpegDecoder()
@@ -530,6 +561,9 @@ FootageDescription FFmpegDecoder::Probe(const QString &filename,
 		avformat_find_stream_info(fmt_ctx, nullptr);
 
 		int64_t footage_duration = fmt_ctx->duration;
+		TimecodeMetadata::SourceTime source_start_time =
+			ExtractSourceStartTime(fmt_ctx->metadata, rational(1, AV_TIME_BASE),
+								   0);
 
 		bool duration_guessed_from_bitrate =
 			(fmt_ctx->duration_estimation_method ==
@@ -545,6 +579,11 @@ FootageDescription FFmpegDecoder::Probe(const QString &filename,
 		for (unsigned int i = 0; i < fmt_ctx->nb_streams; i++) {
 			// FFmpeg AVStream
 			AVStream *avstream = fmt_ctx->streams[i];
+			if (!source_start_time.valid) {
+				source_start_time = ExtractSourceStartTime(
+					avstream->metadata, avstream->time_base,
+					avstream->codecpar->sample_rate);
+			}
 
 			// Find decoder for this stream, if it exists we can proceed
 			const AVCodec *decoder =
@@ -720,6 +759,10 @@ FootageDescription FFmpegDecoder::Probe(const QString &filename,
 		}
 
 		desc.SetStreamCount(fmt_ctx->nb_streams);
+		if (source_start_time.valid) {
+			desc.SetSourceStartTime(source_start_time.time,
+									source_start_time.source);
+		}
 
 		if (video_streams == 0 && audio_streams > 0 && still_streams > 0) {
 			// This footage has no video streams, but has audio and image streams. We've probably

app/codec/timecodemetadata.cpp

@@ -0,0 +1,88 @@
+/***
+
+  Oak - Non-Linear Video Editor
+  Copyright (C) 2026 Oak Team
+
+  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 "timecodemetadata.h"
+
+#include <limits>
+#include <numeric>
+
+#include "olive/core/util/timecodefunctions.h"
+
+namespace olive
+{
+
+TimecodeMetadata::SourceTime TimecodeMetadata::FromTimecodeString(
+	const QString &timecode, const core::rational &timebase)
+{
+	SourceTime result;
+	const QString trimmed = timecode.trimmed();
+	if (trimmed.isEmpty()) {
+		return result;
+	}
+
+	bool ok = false;
+	const core::Timecode::Display display =
+		trimmed.contains(';') ? core::Timecode::kTimecodeDropFrame
+							  : core::Timecode::kTimecodeNonDropFrame;
+	result.time = core::Timecode::timecode_to_time(trimmed.toStdString(),
+												   timebase, display, &ok);
+	result.valid = ok;
+	if (ok) {
+		result.source = QStringLiteral("timecode");
+	}
+	return result;
+}
+
+TimecodeMetadata::SourceTime TimecodeMetadata::FromBwfTimeReference(
+	const QString &time_reference, int sample_rate)
+{
+	SourceTime result;
+	if (sample_rate <= 0) {
+		return result;
+	}
+
+	bool ok = false;
+	const qulonglong samples = time_reference.trimmed().toULongLong(&ok);
+	if (!ok) {
+		return result;
+	}
+
+	qulonglong numerator = samples;
+	qulonglong denominator = static_cast<qulonglong>(sample_rate);
+	const qulonglong divisor = std::gcd(numerator, denominator);
+	numerator /= divisor;
+	denominator /= divisor;
+
+	const qulonglong rational_limit =
+		static_cast<qulonglong>(std::numeric_limits<int>::max());
+	if (numerator <= rational_limit && denominator <= rational_limit) {
+		result.time =
+			core::rational(static_cast<int>(numerator),
+						   static_cast<int>(denominator));
+	} else {
+		result.time = core::rational::fromDouble(
+			static_cast<double>(samples) / static_cast<double>(sample_rate));
+	}
+	result.source = QStringLiteral("bwf_time_reference");
+	result.valid = true;
+	return result;
+}
+
+}

app/codec/timecodemetadata.h

@@ -0,0 +1,48 @@
+/***
+
+  Oak - Non-Linear Video Editor
+  Copyright (C) 2026 Oak Team
+
+  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/>.
+
+***/
+
+#ifndef TIMECODEMETADATA_H
+#define TIMECODEMETADATA_H
+
+#include <QString>
+
+#include "olive/core/util/rational.h"
+
+namespace olive
+{
+
+class TimecodeMetadata {
+public:
+	struct SourceTime {
+		core::rational time;
+		QString source;
+		bool valid = false;
+	};
+
+	static SourceTime FromTimecodeString(const QString &timecode,
+										 const core::rational &timebase);
+
+	static SourceTime FromBwfTimeReference(const QString &time_reference,
+										   int sample_rate);
+};
+
+}
+
+#endif // TIMECODEMETADATA_H