SFBMusepackDecoder.m

//
// Copyright (c) 2006-2025 Stephen F. Booth <me@sbooth.org>
// Part of https://github.com/sbooth/SFBAudioEngine
// MIT license
//

@import os.log;

@import Accelerate;

// TODO: Figure out a way to selectively disable diagnostic warnings for module imports
@import mpc.dec;
@import AVFAudioExtensions;

#import "SFBMusepackDecoder.h"

#import "NSData+SFBExtensions.h"
#import "NSError+SFBURLPresentation.h"

SFBAudioDecoderName const SFBAudioDecoderNameMusepack = @"org.sbooth.AudioEngine.Decoder.Musepack";

SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackSampleFrequency = @"sample_freq";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackChannels = @"channels";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackStreamVersion = @"stream_version";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackBitrate = @"bitrate";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackAverageBitrate = @"average_bitrate";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackMaximumBandIndex = @"max_band";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackMidSideStereo = @"ms";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeystreamInfoMusepackFastSeek = @"fast_seek";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackBlockPower = @"block_pwr";

SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackTitleGain = @"gain_title";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackAlbumGain = @"gain_album";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackAlbumPeak = @"peak_album";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackTitlePeak = @"peak_title";

SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackIsTrueGapless = @"is_true_gapless";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackSamples = @"samples";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackBeginningSilence = @"beg_silence";

SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackEncoderVersion = @"encoder_version";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackEncoder = @"encoder";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackPNS = @"pns";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackProfile = @"profile";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackProfileName = @"profile_name";

SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackHeaderPosition = @"header_position";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackTagOffset = @"tag_offset";
SFBAudioDecodingPropertiesKey const SFBAudioDecodingPropertiesKeyMusepackTotalFileLength = @"total_file_length";

static mpc_int32_t read_callback(mpc_reader *p_reader, void *ptr, mpc_int32_t size)
{
	NSCParameterAssert(p_reader != NULL);

	SFBMusepackDecoder *decoder = (__bridge SFBMusepackDecoder *)p_reader->data;
	NSInteger bytesRead;
	if(![decoder->_inputSource readBytes:ptr length:size bytesRead:&bytesRead error:nil])
		return -1;
	return (mpc_int32_t)bytesRead;
}

static mpc_bool_t seek_callback(mpc_reader *p_reader, mpc_int32_t offset)
{
	NSCParameterAssert(p_reader != NULL);

	SFBMusepackDecoder *decoder = (__bridge SFBMusepackDecoder *)p_reader->data;
	return (mpc_bool_t)[decoder->_inputSource seekToOffset:offset error:nil];
}

static mpc_int32_t tell_callback(mpc_reader *p_reader)
{
	NSCParameterAssert(p_reader != NULL);

	SFBMusepackDecoder *decoder = (__bridge SFBMusepackDecoder *)p_reader->data;
	NSInteger offset;
	if(![decoder->_inputSource getOffset:&offset error:nil])
		return -1;
	return (mpc_int32_t)offset;
}

static mpc_int32_t get_size_callback(mpc_reader *p_reader)
{
	NSCParameterAssert(p_reader != NULL);

	SFBMusepackDecoder *decoder = (__bridge SFBMusepackDecoder *)p_reader->data;

	NSInteger length;
	if(![decoder->_inputSource getLength:&length error:nil])
		return -1;
	return (mpc_int32_t)length;
}

static mpc_bool_t canseek_callback(mpc_reader *p_reader)
{
	NSCParameterAssert(p_reader != NULL);

	SFBMusepackDecoder *decoder = (__bridge SFBMusepackDecoder *)p_reader->data;
	return (mpc_bool_t)decoder.supportsSeeking;
}

@interface SFBMusepackDecoder ()
{
@private
	mpc_reader _reader;
	mpc_demux *_demux;
	AVAudioFramePosition _framePosition;
	AVAudioFramePosition _frameLength;
	AVAudioPCMBuffer *_buffer;
}
@end

@implementation SFBMusepackDecoder

+ (void)load
{
	[SFBAudioDecoder registerSubclass:[self class]];
}

+ (NSSet *)supportedPathExtensions
{
	return [NSSet setWithObject:@"mpc"];
}

+ (NSSet *)supportedMIMETypes
{
	return [NSSet setWithArray:@[@"audio/musepack", @"audio/x-musepack"]];
}

+ (SFBAudioDecoderName)decoderName
{
	return SFBAudioDecoderNameMusepack;
}

+ (BOOL)testInputSource:(SFBInputSource *)inputSource formatIsSupported:(SFBTernaryTruthValue *)formatIsSupported error:(NSError **)error
{
	NSParameterAssert(inputSource != nil);
	NSParameterAssert(formatIsSupported != NULL);

	NSData *header = [inputSource readHeaderOfLength:SFBMusepackDetectionSize skipID3v2Tag:YES error:error];
	if(!header)
		return NO;

	if([header isMusepackHeader])
		*formatIsSupported = SFBTernaryTruthValueTrue;
	else
		*formatIsSupported = SFBTernaryTruthValueFalse;

	return YES;
}

- (BOOL)decodingIsLossless
{
	return NO;
}

- (BOOL)openReturningError:(NSError **)error
{
	if(![super openReturningError:error])
		return NO;

	_reader.read = read_callback;
	_reader.seek = seek_callback;
	_reader.tell = tell_callback;
	_reader.get_size = get_size_callback;
	_reader.canseek = canseek_callback;
	_reader.data = (__bridge void *)self;

	_demux = mpc_demux_init(&_reader);
	if(!_demux) {
		if(error)
			*error = [NSError SFB_errorWithDomain:SFBAudioDecoderErrorDomain
											 code:SFBAudioDecoderErrorCodeInvalidFormat
					descriptionFormatStringForURL:NSLocalizedString(@"The file “%@” is not a valid Musepack file.", @"")
											  url:_inputSource.url
									failureReason:NSLocalizedString(@"Not a valid Musepack file", @"")
							   recoverySuggestion:NSLocalizedString(@"The file's extension may not match the file's type.", @"")];

		return NO;
	}

	// Get input file information
	mpc_streaminfo streaminfo;
	mpc_demux_get_info(_demux, &streaminfo);

	_frameLength = mpc_streaminfo_get_length_samples(&streaminfo);

	AVAudioChannelLayout *channelLayout = nil;
	switch(streaminfo.channels) {
		case 1:		channelLayout = [AVAudioChannelLayout layoutWithLayoutTag:kAudioChannelLayoutTag_Mono];				break;
		case 2:		channelLayout = [AVAudioChannelLayout layoutWithLayoutTag:kAudioChannelLayoutTag_Stereo];			break;
			// FIXME: Is there a standard ordering for multichannel files? WAVEFORMATEX?
		default:
			channelLayout = [AVAudioChannelLayout layoutWithLayoutTag:(kAudioChannelLayoutTag_Unknown | streaminfo.channels)];
			break;
	}

	_processingFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32 sampleRate:streaminfo.sample_freq interleaved:NO channelLayout:channelLayout];

	// Set up the source format
	AudioStreamBasicDescription sourceStreamDescription = {0};

	sourceStreamDescription.mFormatID			= kSFBAudioFormatMusepack;

	sourceStreamDescription.mSampleRate			= streaminfo.sample_freq;
	sourceStreamDescription.mChannelsPerFrame	= (UInt32)streaminfo.channels;

	sourceStreamDescription.mFramesPerPacket	= (1 << streaminfo.block_pwr);

	_sourceFormat = [[AVAudioFormat alloc] initWithStreamDescription:&sourceStreamDescription channelLayout:channelLayout];

	// Populate codec properties
	_properties = @{
		SFBAudioDecodingPropertiesKeyMusepackSampleFrequency: @(streaminfo.sample_freq),
		SFBAudioDecodingPropertiesKeyMusepackChannels: @(streaminfo.channels),
		SFBAudioDecodingPropertiesKeyMusepackStreamVersion: @(streaminfo.stream_version),
		SFBAudioDecodingPropertiesKeyMusepackBitrate: @(streaminfo.bitrate),
		SFBAudioDecodingPropertiesKeyMusepackAverageBitrate: @(streaminfo.average_bitrate),
		SFBAudioDecodingPropertiesKeyMusepackMaximumBandIndex: @(streaminfo.max_band),
		SFBAudioDecodingPropertiesKeyMusepackMidSideStereo: streaminfo.ms ? (@YES) : (@NO),
		SFBAudioDecodingPropertiesKeystreamInfoMusepackFastSeek: streaminfo.fast_seek ? (@YES) : (@NO),
		SFBAudioDecodingPropertiesKeyMusepackBlockPower: @(streaminfo.block_pwr),

		SFBAudioDecodingPropertiesKeyMusepackTitleGain: @(streaminfo.gain_title),
		SFBAudioDecodingPropertiesKeyMusepackAlbumGain: @(streaminfo.gain_album),
		SFBAudioDecodingPropertiesKeyMusepackAlbumPeak: @(streaminfo.peak_album),
		SFBAudioDecodingPropertiesKeyMusepackTitlePeak: @(streaminfo.peak_title),

		SFBAudioDecodingPropertiesKeyMusepackIsTrueGapless: streaminfo.is_true_gapless ? (@YES) : (@NO),
		SFBAudioDecodingPropertiesKeyMusepackSamples: @(streaminfo.samples),
		SFBAudioDecodingPropertiesKeyMusepackBeginningSilence: @(streaminfo.beg_silence),

		SFBAudioDecodingPropertiesKeyMusepackEncoderVersion: @(streaminfo.encoder_version),
		SFBAudioDecodingPropertiesKeyMusepackEncoder: @(streaminfo.encoder),
		SFBAudioDecodingPropertiesKeyMusepackPNS: @(streaminfo.pns),
		SFBAudioDecodingPropertiesKeyMusepackProfile: @(streaminfo.profile),
		SFBAudioDecodingPropertiesKeyMusepackProfileName: @(streaminfo.profile_name),

		SFBAudioDecodingPropertiesKeyMusepackHeaderPosition: @(streaminfo.header_position),
		SFBAudioDecodingPropertiesKeyMusepackTagOffset: @(streaminfo.tag_offset),
		SFBAudioDecodingPropertiesKeyMusepackTotalFileLength: @(streaminfo.total_file_length),
	};

	_buffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:_processingFormat frameCapacity:MPC_FRAME_LENGTH];
	_buffer.frameLength = 0;

	return YES;
}

- (BOOL)closeReturningError:(NSError **)error
{
	if(_demux) {
		mpc_demux_exit(_demux);
		_demux = NULL;
	}

	return [super closeReturningError:error];
}

- (BOOL)isOpen
{
	return _demux != NULL;
}

- (AVAudioFramePosition)framePosition
{
	return _framePosition;
}

- (AVAudioFramePosition)frameLength
{
	return _frameLength;
}

- (BOOL)decodeIntoBuffer:(AVAudioPCMBuffer *)buffer frameLength:(AVAudioFrameCount)frameLength error:(NSError **)error
{
	NSParameterAssert(buffer != nil);
	NSParameterAssert([buffer.format isEqual:_processingFormat]);

	// Reset output buffer data size
	buffer.frameLength = 0;

	if(frameLength > buffer.frameCapacity)
		frameLength = buffer.frameCapacity;

	if(frameLength == 0)
		return YES;

	AVAudioFrameCount framesProcessed = 0;

	for(;;) {
		AVAudioFrameCount framesRemaining = frameLength - framesProcessed;
		AVAudioFrameCount framesCopied = [buffer appendFromBuffer:_buffer readingFromOffset:0 frameLength:framesRemaining];
		[_buffer trimAtOffset:0 frameLength:framesCopied];

		framesProcessed += framesCopied;

		// All requested frames were read
		if(framesProcessed == frameLength)
			break;

		// Decode one frame of MPC data
		MPC_SAMPLE_FORMAT buf [MPC_DECODER_BUFFER_LENGTH];
		mpc_frame_info frame;
		frame.buffer = buf;

		if(mpc_demux_decode(_demux, &frame)) {
			os_log_error(gSFBAudioDecoderLog, "Musepack decoding error");
			if(error)
				*error = [NSError errorWithDomain:SFBAudioDecoderErrorDomain code:SFBAudioDecoderErrorCodeInternalError userInfo:@{ NSURLErrorKey: _inputSource.url }];
			return NO;
		}

		// End of input
		if(frame.bits == -1)
			break;

#ifdef MPC_FIXED_POINT
#error "Fixed point not yet supported"
#else
		// Clip the samples to [-1, 1)
		float minValue = -1.f;
		float maxValue = 8388607.f / 8388608.f;

		AVAudioChannelCount channelCount = _buffer.format.channelCount;
		vDSP_vclip((float *)frame.buffer, 1, &minValue, &maxValue, (float *)frame.buffer, 1, frame.samples * channelCount);

		// Deinterleave the normalized samples
		float * const *floatChannelData = _buffer.floatChannelData;
		for(AVAudioChannelCount channel = 0; channel < channelCount; ++channel) {
			const float *input = (float *)frame.buffer + channel;
			float *output = floatChannelData[channel] + _buffer.frameLength;
			for(uint32_t sample = 0; sample < frame.samples; ++sample) {
				*output++ = *input;
				input += channelCount;
			}
		}

		_buffer.frameLength = frame.samples;
#endif /* MPC_FIXED_POINT */
	}

	_framePosition += framesProcessed;

	return YES;
}

- (BOOL)seekToFrame:(AVAudioFramePosition)frame error:(NSError **)error
{
	NSParameterAssert(frame >= 0);

	if(mpc_demux_seek_sample(_demux, (mpc_uint64_t)frame))
		return NO;
	_framePosition = frame;
	return YES;
}

@end