Decodes and plays audio data using FFmpeg libraries in a separate thread. More...

#include <audio_decoder.h>

Inheritance diagram for AudioDecoder:

Collaboration diagram for AudioDecoder:

Signals
void	audioInfo (int sample_rate, int channels, double duration)
	Emitted after successful initialization, providing audio stream details.

void	error (const QString &message)
	Emitted when an error occurs during initialization or decoding.

void	playbackFinished ()
	Emitted when the decoder reaches the end of the audio stream.

void	positionChanged (double position)
	Emitted periodically during playback to indicate the current position.

Public Member Functions
	AudioDecoder (const QByteArray &audio_data, QObject *parent=nullptr)
	Constructs an AudioDecoder object. Initializes internal state, allocates memory for FFmpeg's custom I/O context, and copies the provided audio data into an internal buffer.

float	GetVolume () const
	Gets the current playback volume. This operation is thread-safe.

bool	Initialize ()
	Initializes the FFmpeg components and QAudioOutput for playback. Opens the input stream using the custom I/O context, finds the audio stream and codec, opens the codec, sets up the resampler (to convert to PCM S16LE stereo 44.1 kHz), configures and starts QAudioOutput. Emits audioInfo upon success. This operation is thread-safe and should be called before starting the thread.

bool	IsDecoderRunning () const
	Checks if the decoding thread is currently running.

bool	IsPaused () const
	Checks if the playback is currently paused. This operation is thread-safe.

void	Pause ()
	Toggles the paused state of the playback. If paused, playback stops; if unpaused, playback resumes. Wakes the thread if it was waiting due to being paused. This operation is thread-safe.

bool	Reinitialize ()
	Reinitializes the decoder after it has been stopped or encountered an error. Releases existing resources, resets state flags (paused, stopped, seeking, position), reallocates I/O buffer and context if necessary. Does not automatically start playback. This operation is thread-safe.

void	ReleaseResources ()
	Releases all FFmpeg and Qt Multimedia resources. Stops audio output, frees contexts (format, codec, resampler, I/O), frames, and buffers. Resets the initialization flag. This operation is thread-safe.

void	Reset ()
	Resets the playback position to the beginning (0 seconds). Seeks the FFmpeg format context, flushes codec buffers, resets the internal position counter, resets the audio output device, and emits positionChanged(0). This operation is thread-safe.

void	Seek (double position)
	Seeks to a specific position in the audio stream. The position is specified in seconds. Sets the seeking_ flag and wakes the thread. The actual seek operation happens within the run() loop. This operation is thread-safe.

void	SetVolume (float volume) const
	Sets the playback volume. The volume is a linear factor between 0.0 (silent) and 1.0 (full volume). This operation is thread-safe.

void	Stop ()
	Stops the decoding thread and playback gracefully. Sets the stopped_ flag and wakes the thread if it's waiting. The thread will then exit its run loop. This operation is thread-safe.

	~AudioDecoder () override
	Destructor. Stops the decoding thread, waits for it to finish, and releases all allocated resources.

Protected Member Functions
void	DecodeAudioFrame (const AVFrame *audio_frame) const
	Decodes a single audio frame using the FFmpeg resampler and writes the result to the audio device.

void	run () override
	The main function executed by the QThread. Contains the loop that reads packets, decodes frames, handles seeking/pausing, updates playback position, and sends decoded audio data to the output device.

Static Private Member Functions
static int	ReadPacket (void opaque, uint8_t buf, int buf_size)
	Custom read function for FFmpeg's AVIOContext. Reads data from the internal audio_data_ QByteArray buffer.

static int64_t	SeekPacket (void *opaque, int64_t offset, int whence)
	Custom seek function for FFmpeg's AVIOContext. Adjusts the internal read_position_ based on the offset and whence parameters. Supports SEEK_SET, SEEK_CUR, SEEK_END, and AVSEEK_SIZE.

Private Attributes
AVCodecContext *	audio_codec_context_ = nullptr
	FFmpeg context for the audio codec.

QByteArray	audio_data_
	The raw audio data provided in the constructor.

QIODevice *	audio_device_ = nullptr
	Qt I/O device associated with audio_output_, used for writing PCM data.

QAudioFormat	audio_format_
	Qt audio format description (PCM S16LE stereo 44.1kHz).

AVFrame *	audio_frame_ = nullptr
	FFmpeg frame structure to hold decoded audio data.

QAudioOutput *	audio_output_ = nullptr
	Qt Multimedia object for audio output.

int	audio_stream_ = -1
	Index of the audio stream within the format context.

double	current_position_ = 0
	Current playback position in seconds.

AVFormatContext *	format_context_ = nullptr
	FFmpeg context for handling the container format.

bool	initialized_ = false
	Flag indicating if the Initialize() method has completed successfully.

unsigned char *	io_buffer_ = nullptr
	Buffer used by the custom I/O context to hold audio_data_.

AVIOContext *	io_context_ = nullptr
	FFmpeg context for custom I/O operations (reading from memory).

QMutex	mutex_
	Mutex protecting access to shared state variables from different threads.

bool	paused_ = true
	Flag indicating if playback is currently paused.

bool	reached_end_of_stream_ = false
	Flag indicating if the end of the audio stream has been reached.

int	read_position_ = 0
	Current read position within audio_data_ for the custom I/O context.

int64_t	seek_position_ = 0
	Target timestamp for the pending seek operation (in stream timebase).

bool	seeking_ = false
	Flag indicating if a seek operation is pending.

bool	stopped_ = false
	Flag indicating if the thread should stop execution.

SwrContext *	swr_context_ = nullptr
	FFmpeg context for audio resampling (format/rate/channel conversion).

QWaitCondition	wait_condition_
	Condition variable used to pause/resume the decoding thread.

Detailed Description

Decodes and plays audio data using FFmpeg libraries in a separate thread.

This class takes raw audio data (e.g., from a file) as a QByteArray, uses FFmpeg (libavformat, libavcodec, libswresample) to decode it, and plays the resulting PCM audio using Qt Multimedia (QAudioOutput). It runs the decoding and playback loop in a separate QThread to avoid blocking the main UI thread. It supports pausing, seeking, volume control, and provides signals for status updates (errors, position, finish).

Constructor & Destructor Documentation

◆ AudioDecoder()

AudioDecoder::AudioDecoder	(	const QByteArray &	audio_data,
		QObject *	parent = nullptr )

explicit

Constructs an AudioDecoder object. Initializes internal state, allocates memory for FFmpeg's custom I/O context, and copies the provided audio data into an internal buffer.

Parameters

audio_data	The raw audio data to be decoded.
parent	Optional parent QObject.

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◆ ~AudioDecoder()

AudioDecoder::~AudioDecoder ( )

override

Destructor. Stops the decoding thread, waits for it to finish, and releases all allocated resources.

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Member Function Documentation

◆ audioInfo

void AudioDecoder::audioInfo	(	int	sample_rate,
		int	channels,
		double	duration )

signal

Emitted after successful initialization, providing audio stream details.

Parameters

sample_rate	The sample rate of the audio in Hz.
channels	The number of audio channels.
duration	The total duration of the audio in seconds.

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◆ DecodeAudioFrame()

void AudioDecoder::DecodeAudioFrame ( const AVFrame * audio_frame ) const

protected

Decodes a single audio frame using the FFmpeg resampler and writes the result to the audio device.

Converts the input frame (audio_frame) to the target format (PCM S16LE stereo 44.1 kHz), allocates a buffer for the converted data, performs the conversion using swr_convert, and writes the resulting data to the QAudioOutput device (audio_device_). Includes logic to wait if the audio device buffer is nearly full. This method is thread-safe regarding access to shared decoder state via mutex_.

Parameters

audio_frame The raw audio frame received from the FFmpeg decoder.

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◆ error

void AudioDecoder::error ( const QString & message )

signal

Emitted when an error occurs during initialization or decoding.

Parameters

message A description of the error.

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◆ GetVolume()

float AudioDecoder::GetVolume ( ) const

Gets the current playback volume. This operation is thread-safe.

Returns: The current volume level (0.0 to 1.0).

◆ Initialize()

bool AudioDecoder::Initialize ( )

Initializes the FFmpeg components and QAudioOutput for playback. Opens the input stream using the custom I/O context, finds the audio stream and codec, opens the codec, sets up the resampler (to convert to PCM S16LE stereo 44.1 kHz), configures and starts QAudioOutput. Emits audioInfo upon success. This operation is thread-safe and should be called before starting the thread.

Returns: True if initialization was successful, false otherwise.

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◆ IsDecoderRunning()

bool AudioDecoder::IsDecoderRunning ( ) const

inline

Checks if the decoding thread is currently running.

Returns: True if the thread is running, false otherwise.

◆ IsPaused()

bool AudioDecoder::IsPaused ( ) const

Checks if the playback is currently paused. This operation is thread-safe.

Returns: True if paused, false otherwise.

◆ Pause()

void AudioDecoder::Pause ( )

Toggles the paused state of the playback. If paused, playback stops; if unpaused, playback resumes. Wakes the thread if it was waiting due to being paused. This operation is thread-safe.

◆ playbackFinished

void AudioDecoder::playbackFinished ( )

signal

Emitted when the decoder reaches the end of the audio stream.

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◆ positionChanged

void AudioDecoder::positionChanged ( double position )

signal

Emitted periodically during playback to indicate the current position.

Parameters

position The current playback position in seconds.

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◆ ReadPacket()

int AudioDecoder::ReadPacket	(	void *	opaque,
		uint8_t *	buf,
		int	buf_size )

staticprivate

Custom read function for FFmpeg's AVIOContext. Reads data from the internal audio_data_ QByteArray buffer.

Parameters

opaque	Pointer to the AudioDecoder instance.
buf	Buffer to read data into.
buf_size	Size of the buffer.

Returns: Number of bytes read, or AVERROR_EOF if the end of data is reached.

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◆ Reinitialize()

bool AudioDecoder::Reinitialize ( )

Reinitializes the decoder after it has been stopped or encountered an error. Releases existing resources, resets state flags (paused, stopped, seeking, position), reallocates I/O buffer and context if necessary. Does not automatically start playback. This operation is thread-safe.

Returns: True if reinitialization setup was successful, false otherwise.

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◆ ReleaseResources()

void AudioDecoder::ReleaseResources ( )

Releases all FFmpeg and Qt Multimedia resources. Stops audio output, frees contexts (format, codec, resampler, I/O), frames, and buffers. Resets the initialization flag. This operation is thread-safe.

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◆ Reset()

void AudioDecoder::Reset ( )

Resets the playback position to the beginning (0 seconds). Seeks the FFmpeg format context, flushes codec buffers, resets the internal position counter, resets the audio output device, and emits positionChanged(0). This operation is thread-safe.

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◆ run()

void AudioDecoder::run ( )

overrideprotected

The main function executed by the QThread. Contains the loop that reads packets, decodes frames, handles seeking/pausing, updates playback position, and sends decoded audio data to the output device.

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◆ Seek()

void AudioDecoder::Seek ( double position )

Seeks to a specific position in the audio stream. The position is specified in seconds. Sets the seeking_ flag and wakes the thread. The actual seek operation happens within the run() loop. This operation is thread-safe.

Parameters

position The target position in seconds from the beginning of the audio.

◆ SeekPacket()

int64_t AudioDecoder::SeekPacket	(	void *	opaque,
		int64_t	offset,
		int	whence )

staticprivate

Custom seek function for FFmpeg's AVIOContext. Adjusts the internal read_position_ based on the offset and whence parameters. Supports SEEK_SET, SEEK_CUR, SEEK_END, and AVSEEK_SIZE.

Parameters

opaque	Pointer to the AudioDecoder instance.
offset	The offset to seek to/by.
whence	The seeking mode (SEEK_SET, SEEK_CUR, SEEK_END, AVSEEK_SIZE).

Returns: The new read position, or the total size if whence is AVSEEK_SIZE, or -1 on error.

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◆ SetVolume()

void AudioDecoder::SetVolume ( float volume ) const

Sets the playback volume. The volume is a linear factor between 0.0 (silent) and 1.0 (full volume). This operation is thread-safe.

Parameters

volume The desired volume level (0.0 to 1.0).

◆ Stop()

void AudioDecoder::Stop ( )

Stops the decoding thread and playback gracefully. Sets the stopped_ flag and wakes the thread if it's waiting. The thread will then exit its run loop. This operation is thread-safe.

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Member Data Documentation

◆ audio_codec_context_

AVCodecContext* AudioDecoder::audio_codec_context_ = nullptr

private

FFmpeg context for the audio codec.

◆ audio_data_

QByteArray AudioDecoder::audio_data_

private

The raw audio data provided in the constructor.

◆ audio_device_

QIODevice* AudioDecoder::audio_device_ = nullptr

private

Qt I/O device associated with audio_output_, used for writing PCM data.

◆ audio_format_

QAudioFormat AudioDecoder::audio_format_

private

Qt audio format description (PCM S16LE stereo 44.1kHz).

◆ audio_frame_

AVFrame* AudioDecoder::audio_frame_ = nullptr

private

FFmpeg frame structure to hold decoded audio data.

◆ audio_output_

QAudioOutput* AudioDecoder::audio_output_ = nullptr

private

Qt Multimedia object for audio output.

◆ audio_stream_

int AudioDecoder::audio_stream_ = -1

private

Index of the audio stream within the format context.

◆ current_position_

double AudioDecoder::current_position_ = 0

private

Current playback position in seconds.

◆ format_context_

AVFormatContext* AudioDecoder::format_context_ = nullptr

private

FFmpeg context for handling the container format.

◆ initialized_

bool AudioDecoder::initialized_ = false

private

Flag indicating if the Initialize() method has completed successfully.

◆ io_buffer_

unsigned char* AudioDecoder::io_buffer_ = nullptr

private

Buffer used by the custom I/O context to hold audio_data_.

◆ io_context_

AVIOContext* AudioDecoder::io_context_ = nullptr

private

FFmpeg context for custom I/O operations (reading from memory).

◆ mutex_

QMutex AudioDecoder::mutex_

mutableprivate

Mutex protecting access to shared state variables from different threads.

◆ paused_

bool AudioDecoder::paused_ = true

private

Flag indicating if playback is currently paused.

◆ reached_end_of_stream_

bool AudioDecoder::reached_end_of_stream_ = false

private

Flag indicating if the end of the audio stream has been reached.

◆ read_position_

int AudioDecoder::read_position_ = 0

private

Current read position within audio_data_ for the custom I/O context.

◆ seek_position_

int64_t AudioDecoder::seek_position_ = 0

private

Target timestamp for the pending seek operation (in stream timebase).

◆ seeking_

bool AudioDecoder::seeking_ = false

private

Flag indicating if a seek operation is pending.

◆ stopped_

bool AudioDecoder::stopped_ = false

private

Flag indicating if the thread should stop execution.

◆ swr_context_

SwrContext* AudioDecoder::swr_context_ = nullptr

private

FFmpeg context for audio resampling (format/rate/channel conversion).

◆ wait_condition_

QWaitCondition AudioDecoder::wait_condition_

private

Condition variable used to pause/resume the decoding thread.

The documentation for this class was generated from the following files:

src/chat/files/audio/decoder/audio_decoder.h
src/chat/files/audio/decoder/audio_decoder.cpp

Signals

Public Member Functions

Protected Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ AudioDecoder()

◆ ~AudioDecoder()

Member Function Documentation

◆ audioInfo

◆ DecodeAudioFrame()

◆ error

◆ GetVolume()

◆ Initialize()

◆ IsDecoderRunning()

◆ IsPaused()

◆ Pause()

◆ playbackFinished

◆ positionChanged

◆ ReadPacket()

◆ Reinitialize()

◆ ReleaseResources()

◆ Reset()

◆ run()

◆ Seek()

◆ SeekPacket()

◆ SetVolume()

◆ Stop()

Member Data Documentation

◆ audio_codec_context_

◆ audio_data_

◆ audio_device_

◆ audio_format_

◆ audio_frame_

◆ audio_output_

◆ audio_stream_

◆ current_position_

◆ format_context_

◆ initialized_

◆ io_buffer_

◆ io_context_

◆ mutex_

◆ paused_

◆ reached_end_of_stream_

◆ read_position_

◆ seek_position_

◆ seeking_

◆ stopped_

◆ swr_context_

◆ wait_condition_