From a2d4b152f3c831daed4ddf61640c697afec664c3 Mon Sep 17 00:00:00 2001
From: Harishankar Kumar <hari01584@gmail.com>
Date: Fri, 23 Jun 2023 18:54:21 +0530
Subject: [PATCH] VIDEO: Implement non 0/1 rate with audio

Uses Mixer's setRate() function implemented in pr #4965 to set
video playback rates of movies that are not 0 or 1.

`undome` of 'mediaband' required this feature where the video can
have playback rates other than 0 or 1.
---
 video/video_decoder.cpp | 42 +++++++++++++++++++++++++++++++++++++----
 video/video_decoder.h   | 21 ++++++++++++++++++---
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/video/video_decoder.cpp b/video/video_decoder.cpp
index ebbc23599b5..e7d84497a7b 100644
--- a/video/video_decoder.cpp
+++ b/video/video_decoder.cpp
@@ -280,7 +280,7 @@ uint32 VideoDecoder::getTime() const {
 	if (useAudioSync()) {
 		for (TrackList::const_iterator it = _tracks.begin(); it != _tracks.end(); it++) {
 			if ((*it)->getTrackType() == Track::kTrackTypeAudio && !(*it)->endOfTrack()) {
-				uint32 time = ((const AudioTrack *)*it)->getRunningTime();
+				uint32 time = (((const AudioTrack *)*it)->getRunningTime() * _playbackRate).toInt();
 
 				if (time != 0)
 					return time + _lastTimeChange.msecs();
@@ -471,13 +471,14 @@ void VideoDecoder::setRate(const Common::Rational &rate) {
 	if (rate == 0) {
 		stop();
 		return;
-	} else if (rate != 1 && hasAudio()) {
-		warning("Cannot set custom rate in videos with audio");
-		return;
 	}
 
 	Common::Rational targetRate = rate;
 
+	if (hasAudio()) {
+		setAudioRate(targetRate);
+	}
+
 	// Attempt to set the reverse
 	if (!setReverse(rate < 0)) {
 		assert(rate < 0); // We shouldn't fail for forward.
@@ -633,6 +634,7 @@ Audio::Timestamp VideoDecoder::FixedRateVideoTrack::getDuration() const {
 VideoDecoder::AudioTrack::AudioTrack(Audio::Mixer::SoundType soundType) :
 		_volume(Audio::Mixer::kMaxChannelVolume),
 		_soundType(soundType),
+		_rate(0),
 		_balance(0),
 		_muted(false) {
 }
@@ -649,6 +651,23 @@ void VideoDecoder::AudioTrack::setVolume(byte volume) {
 		g_system->getMixer()->setChannelVolume(_handle, _muted ? 0 : _volume);
 }
 
+void VideoDecoder::AudioTrack::setRate(uint32 rate) {
+	_rate = rate;
+
+	if (g_system->getMixer()->isSoundHandleActive(_handle))
+		g_system->getMixer()->setChannelRate(_handle, _rate);
+}
+
+void VideoDecoder::AudioTrack::setRate(Common::Rational rate) {
+	Audio::AudioStream *stream = getAudioStream();
+	assert(stream);
+
+	// Convert rational rate to audio rate
+	uint32 convertedRate = (stream->getRate() * rate).toInt();
+
+	setRate(convertedRate);
+}
+
 void VideoDecoder::AudioTrack::setBalance(int8 balance) {
 	_balance = balance;
 
@@ -664,6 +683,10 @@ void VideoDecoder::AudioTrack::start() {
 
 	g_system->getMixer()->playStream(_soundType, &_handle, stream, -1, _muted ? 0 : getVolume(), getBalance(), DisposeAfterUse::NO);
 
+	// Set rate of audio
+	if (_rate != 0)
+		g_system->getMixer()->setChannelRate(_handle, _rate);
+
 	// Pause the audio again if we're still paused
 	if (isPaused())
 		g_system->getMixer()->pauseHandle(_handle, true);
@@ -683,6 +706,10 @@ void VideoDecoder::AudioTrack::start(const Audio::Timestamp &limit) {
 
 	g_system->getMixer()->playStream(_soundType, &_handle, stream, -1, _muted ? 0 : getVolume(), getBalance(), DisposeAfterUse::YES);
 
+	// Set rate of audio
+	if (_rate != 0)
+		g_system->getMixer()->setChannelRate(_handle, _rate);
+
 	// Pause the audio again if we're still paused
 	if (isPaused())
 		g_system->getMixer()->pauseHandle(_handle, true);
@@ -958,6 +985,13 @@ void VideoDecoder::stopAudio() {
 			((AudioTrack *)*it)->stop();
 }
 
+void VideoDecoder::setAudioRate(Common::Rational rate) {
+	for (TrackList::iterator it = _tracks.begin(); it != _tracks.end(); it++)
+		if ((*it)->getTrackType() == Track::kTrackTypeAudio) {
+			((AudioTrack *)*it)->setRate(rate);
+		}
+}
+
 void VideoDecoder::startAudioLimit(const Audio::Timestamp &limit) {
 	for (TrackList::iterator it = _tracks.begin(); it != _tracks.end(); it++)
 		if ((*it)->getTrackType() == Track::kTrackTypeAudio)
diff --git a/video/video_decoder.h b/video/video_decoder.h
index 379e7429f4f..bd9585cce17 100644
--- a/video/video_decoder.h
+++ b/video/video_decoder.h
@@ -120,9 +120,6 @@ public:
 	 * would play the video normally. Passing 2 to this function would
 	 * play the video at twice the normal speed.
 	 *
-	 * @note This function does not work for non-0/1 rates on videos that
-	 * have audio tracks.
-	 *
 	 * @todo This currently does not implement backwards playback, but will
 	 * be implemented soon.
 	 */
@@ -720,6 +717,22 @@ protected:
 		 */
 		void setVolume(byte volume);
 
+		/**
+		 * Get audio rate for this track (in Hz)
+		 */
+		uint32 getRate() const { return _rate; }
+
+		/**
+		 * Set audio rate for this track
+		 */
+		void setRate(uint32 rate);
+
+		/**
+		 * Set audio rate using relative playback rate wrt original rate
+		 * ie a rate of 2.0 will play the audio at twice the original rate
+		 */
+		void setRate(Common::Rational rate);
+
 		/**
 		 * Get the balance for this track
 		 */
@@ -763,6 +776,7 @@ protected:
 		Audio::SoundHandle _handle;
 		Audio::Mixer::SoundType _soundType;
 		byte _volume;
+		uint32 _rate;
 		int8 _balance;
 		bool _muted;
 	};
@@ -968,6 +982,7 @@ private:
 protected:
 	// Internal helper functions
 	void stopAudio();
+	void setAudioRate(Common::Rational rate);
 	void startAudio();
 	void startAudioLimit(const Audio::Timestamp &limit);
 	bool hasFramesLeft() const;