Decodes video data frame by frame using FFmpeg libraries in a separate thread. More...

#include <video_decoder.h>

Inheritance diagram for VideoDecoder:

Collaboration diagram for VideoDecoder:

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

void	frameReady (const QImage &frame)
	Emitted for each decoded video frame.

void	playbackFinished ()
	Emitted when both video and audio (if present) streams reach the end.

void	positionChanged (double position)
	Emitted periodically during playback to indicate the current position (based on audio if available, otherwise estimated).

void	videoInfo (int width, int height, double fps, double duration, bool has_audio)
	Emitted after successful initialization, providing video stream details.

Public Member Functions
void	ExtractFirstFrame ()
	Synchronously extracts the first video frame from the data. Performs a separate, simplified FFmpeg initialization and decoding process to get the first frame quickly, typically for generating a thumbnail. Emits frameReady() with the first frame upon success. This method runs in the calling thread.

float	GetVolume () const
	Gets the current playback volume (from the internal AudioDecoder). Returns 0.0 if there is no audio stream. This operation is thread-safe.

bool	HasAudio () const
	Checks if the video file contains an audio stream.

bool	Initialize ()
	Initializes the FFmpeg components for decoding the video and potentially audio. Opens the input stream using the custom I/O context, finds video and audio streams, opens codecs, sets up the video scaler (to convert to RGB24), allocates frames/buffers. If audio is found, creates and connects to an internal AudioDecoder instance. Emits videoInfo upon success. This operation is thread-safe and should be called before starting the thread.

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. Also pauses/resumes the internal audio decoder (if present). Wakes the thread if it was waiting due to being paused. This operation is thread-safe.

void	ReleaseResources ()
	Releases all FFmpeg and internal AudioDecoder resources. Calls CleanupFFmpegResources(). This operation is thread-safe.

void	Reset ()
	Resets the playback position to the beginning of the video. Pauses playback, seeks both video and internal audio decoder (if present) to 0, resets internal state flags (finished, first frame), and wakes the thread. This operation is thread-safe.

void	Seek (double position)
	Seeks to a specific position in the video stream. Seeks the internal audio decoder (if present) and sets the seeking flag and target timestamp for the video stream. The actual video seek operation happens within the run() loop. This operation is thread-safe.

void	SetVolume (float volume) const
	Sets the playback volume (delegated to the internal AudioDecoder). Has no effect if there is no audio stream. This operation is thread-safe.

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

	VideoDecoder (const QByteArray &video_data, QObject *parent=nullptr)
	Constructs a VideoDecoder object. Initializes internal state, allocates memory for FFmpeg's custom I/O context, sets up the QBuffer for reading from the provided video data.

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

Protected Member Functions
void	run () override
	The main function executed by the QThread. Contains the loop that reads packets, decodes video frames, handles seeking/pausing, synchronizes with the internal audio decoder (if present) or uses frame timing, and emits decoded frames via the frameReady signal.

Private Slots
void	HandleAudioError (const QString &message)
	Slot connected to the internal AudioDecoder's error signal. Relays the audio error message via the main error() signal.

void	HandleAudioFinished ()
	Slot connected to the internal AudioDecoder's playbackFinished signal. Sets the audio_finished_ flag and emits the main playbackFinished() signal if the video stream has also finished.

void	UpdateAudioPosition (double position)
	Slot connected to the internal AudioDecoder's positionChanged signal. Updates the internal current_audio_position_ and emits the main positionChanged() signal.

Private Member Functions
void	CleanupFFmpegResources ()
	Releases all FFmpeg resources (contexts, frames, scaler) and deletes the internal AudioDecoder. Resets internal state variables related to FFmpeg and audio.

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 QBuffer (buffer_).

static int64_t	SeekPacket (void *opaque, int64_t offset, int whence)
	Custom seek function for FFmpeg's AVIOContext. Adjusts the position within the internal QBuffer (buffer_). Supports SEEK_SET and AVSEEK_SIZE.

Private Attributes
AudioDecoder *	audio_decoder_ = nullptr
	Pointer to the internal AudioDecoder instance (if audio stream exists).

bool	audio_finished_ = false
	Flag indicating if the internal AudioDecoder has finished playback. Access protected by mutex_.

bool	audio_initialized_ = false
	Flag indicating if the internal AudioDecoder has been successfully initialized.

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

QBuffer	buffer_
	QBuffer used by FFmpeg's custom I/O context to read video_data_.

AVCodecContext *	codec_context_ = nullptr
	FFmpeg context for the video codec.

double	current_audio_position_ = 0.0
	Current playback position reported by the internal AudioDecoder. Access protected by mutex_.

double	current_position_ = 0.0
	Current estimated playback position in seconds (used if no audio).

double	duration_ = 0.0
	Total duration of the video in seconds.

bool	first_frame_ = true
	Flag indicating if the current frame is the first one after start/seek.

AVFormatContext *	format_context_ = nullptr
	FFmpeg context for handling the container format (e.g., MP4, WebM).

AVFrame *	frame_ = nullptr
	FFmpeg frame structure to hold decoded video data.

double	frame_rate_ = 0.0
	Calculated average frame rate of the video in frames per second.

QElapsedTimer	frame_timer_
	Timer used for frame timing synchronization when no audio is present.

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

int64_t	last_frame_pts_ = AV_NOPTS_VALUE
	Presentation timestamp (PTS) of the previously decoded frame (used for frame timing).

QMutex	mutex_
	Mutex protecting access to shared state variables (paused_, stopped_, seeking_, etc.).

bool	paused_ = false
	Flag indicating if playback is currently paused. Access protected by mutex_.

int64_t	seek_position_ = -1
	Target timestamp (in video stream timebase) for the pending seek operation. Access protected by mutex_.

bool	seeking_ = false
	Flag indicating if a seek operation is pending. Access protected by mutex_.

bool	stopped_ = false
	Flag indicating if the thread should stop execution. Access protected by mutex_.

SwsContext *	sws_context_ = nullptr
	FFmpeg context for image scaling and pixel format conversion (to RGB24).

QByteArray	video_data_
	The raw video data provided in the constructor.

bool	video_finished_ = false
	Flag indicating if the video stream has reached the end. Access protected by mutex_.

int	video_stream_ = -1
	Index of the video stream within the format context.

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

Detailed Description

Decodes video data frame by frame using FFmpeg libraries in a separate thread.

This class takes raw video data (e.g., MP4, WebM) as a QByteArray, uses FFmpeg (libavformat, libavcodec, libswscale) to decode the video stream, and emits each decoded frame as a QImage (Format_RGB888). If an audio stream is present, it uses an internal AudioDecoder instance to handle audio decoding and playback synchronization.

The decoding loop runs in a separate QThread to avoid blocking the main UI thread. It supports pausing, resuming, seeking, volume control (via the internal AudioDecoder), and provides signals for status updates (errors, info, position, frames, finish). It uses a custom AVIOContext to read data directly from the QByteArray in memory.

Constructor & Destructor Documentation

◆ VideoDecoder()

VideoDecoder::VideoDecoder	(	const QByteArray &	video_data,
		QObject *	parent = nullptr )

explicit

Constructs a VideoDecoder object. Initializes internal state, allocates memory for FFmpeg's custom I/O context, sets up the QBuffer for reading from the provided video data.

Parameters

video_data	The raw video data to be decoded.
parent	Optional parent QObject.

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◆ ~VideoDecoder()

VideoDecoder::~VideoDecoder ( )

override

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

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Member Function Documentation

◆ CleanupFFmpegResources()

void VideoDecoder::CleanupFFmpegResources ( )

private

Releases all FFmpeg resources (contexts, frames, scaler) and deletes the internal AudioDecoder. Resets internal state variables related to FFmpeg and audio.

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◆ error

void VideoDecoder::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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◆ ExtractFirstFrame()

void VideoDecoder::ExtractFirstFrame ( )

Synchronously extracts the first video frame from the data. Performs a separate, simplified FFmpeg initialization and decoding process to get the first frame quickly, typically for generating a thumbnail. Emits frameReady() with the first frame upon success. This method runs in the calling thread.

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◆ frameReady

void VideoDecoder::frameReady ( const QImage & frame )

signal

Emitted for each decoded video frame.

Parameters

frame The decoded frame as a QImage (Format_RGB888). A copy is emitted.

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◆ GetVolume()

float VideoDecoder::GetVolume ( ) const

Gets the current playback volume (from the internal AudioDecoder). Returns 0.0 if there is no audio stream. This operation is thread-safe.

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

◆ HandleAudioError

void VideoDecoder::HandleAudioError ( const QString & message )

inlineprivateslot

Slot connected to the internal AudioDecoder's error signal. Relays the audio error message via the main error() signal.

Parameters

message The error message from the AudioDecoder.

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◆ HandleAudioFinished

void VideoDecoder::HandleAudioFinished ( )

privateslot

Slot connected to the internal AudioDecoder's playbackFinished signal. Sets the audio_finished_ flag and emits the main playbackFinished() signal if the video stream has also finished.

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◆ HasAudio()

bool VideoDecoder::HasAudio ( ) const

inline

Checks if the video file contains an audio stream.

Returns: True if an audio stream was detected during initialization, false otherwise.

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◆ Initialize()

bool VideoDecoder::Initialize ( )

Initializes the FFmpeg components for decoding the video and potentially audio. Opens the input stream using the custom I/O context, finds video and audio streams, opens codecs, sets up the video scaler (to convert to RGB24), allocates frames/buffers. If audio is found, creates and connects to an internal AudioDecoder instance. Emits videoInfo 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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◆ IsPaused()

bool VideoDecoder::IsPaused ( ) const

inline

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

Returns: True if paused, false otherwise.

◆ Pause()

void VideoDecoder::Pause ( )

Toggles the paused state of the playback. If paused, playback stops; if unpaused, playback resumes. Also pauses/resumes the internal audio decoder (if present). Wakes the thread if it was waiting due to being paused. This operation is thread-safe.

◆ playbackFinished

void VideoDecoder::playbackFinished ( )

signal

Emitted when both video and audio (if present) streams reach the end.

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◆ positionChanged

void VideoDecoder::positionChanged ( double position )

signal

Emitted periodically during playback to indicate the current position (based on audio if available, otherwise estimated).

Parameters

position The current playback position in seconds.

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◆ ReadPacket()

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

staticprivate

Custom read function for FFmpeg's AVIOContext. Reads data from the internal QBuffer (buffer_).

Parameters

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

Returns: Number of bytes read, or 0 if the end of buffer is reached.

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◆ ReleaseResources()

void VideoDecoder::ReleaseResources ( )

inline

Releases all FFmpeg and internal AudioDecoder resources. Calls CleanupFFmpegResources(). This operation is thread-safe.

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◆ Reset()

void VideoDecoder::Reset ( )

Resets the playback position to the beginning of the video. Pauses playback, seeks both video and internal audio decoder (if present) to 0, resets internal state flags (finished, first frame), and wakes the thread. This operation is thread-safe.

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◆ run()

void VideoDecoder::run ( )

overrideprotected

The main function executed by the QThread. Contains the loop that reads packets, decodes video frames, handles seeking/pausing, synchronizes with the internal audio decoder (if present) or uses frame timing, and emits decoded frames via the frameReady signal.

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◆ Seek()

void VideoDecoder::Seek ( double position )

Seeks to a specific position in the video stream. Seeks the internal audio decoder (if present) and sets the seeking flag and target timestamp for the video stream. The actual video seek operation happens within the run() loop. This operation is thread-safe.

Parameters

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

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◆ SeekPacket()

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

staticprivate

Custom seek function for FFmpeg's AVIOContext. Adjusts the position within the internal QBuffer (buffer_). Supports SEEK_SET and AVSEEK_SIZE.

Parameters

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

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

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◆ SetVolume()

void VideoDecoder::SetVolume ( float volume ) const

Sets the playback volume (delegated to the internal AudioDecoder). Has no effect if there is no audio stream. This operation is thread-safe.

Parameters

volume The desired volume level (0.0 to 1.0).

◆ Stop()

void VideoDecoder::Stop ( )

Stops the decoding thread and playback gracefully. Sets the stopped_ flag, stops the internal audio decoder (if present), 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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◆ UpdateAudioPosition

void VideoDecoder::UpdateAudioPosition ( double position )

privateslot

Slot connected to the internal AudioDecoder's positionChanged signal. Updates the internal current_audio_position_ and emits the main positionChanged() signal.

Parameters

position The current audio playback position in seconds.

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◆ videoInfo

void VideoDecoder::videoInfo	(	int	width,
		int	height,
		double	fps,
		double	duration,
		bool	has_audio )

signal

Emitted after successful initialization, providing video stream details.

Parameters

width	The width of the video in pixels.
height	The height of the video in pixels.
fps	The calculated average frame rate in frames per second.
duration	The total duration of the video in seconds.
has_audio	True if an audio stream was detected, false otherwise.

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Member Data Documentation

◆ audio_decoder_

AudioDecoder* VideoDecoder::audio_decoder_ = nullptr

private

Pointer to the internal AudioDecoder instance (if audio stream exists).

◆ audio_finished_

bool VideoDecoder::audio_finished_ = false

private

Flag indicating if the internal AudioDecoder has finished playback. Access protected by mutex_.

◆ audio_initialized_

bool VideoDecoder::audio_initialized_ = false

private

Flag indicating if the internal AudioDecoder has been successfully initialized.

◆ audio_stream_index_

int VideoDecoder::audio_stream_index_ = -1

private

Index of the audio stream within the format context.

◆ buffer_

QBuffer VideoDecoder::buffer_

private

QBuffer used by FFmpeg's custom I/O context to read video_data_.

◆ codec_context_

AVCodecContext* VideoDecoder::codec_context_ = nullptr

private

FFmpeg context for the video codec.

◆ current_audio_position_

double VideoDecoder::current_audio_position_ = 0.0

private

Current playback position reported by the internal AudioDecoder. Access protected by mutex_.

◆ current_position_

double VideoDecoder::current_position_ = 0.0

private

Current estimated playback position in seconds (used if no audio).

◆ duration_

double VideoDecoder::duration_ = 0.0

private

Total duration of the video in seconds.

◆ first_frame_

bool VideoDecoder::first_frame_ = true

private

Flag indicating if the current frame is the first one after start/seek.

◆ format_context_

AVFormatContext* VideoDecoder::format_context_ = nullptr

private

FFmpeg context for handling the container format (e.g., MP4, WebM).

◆ frame_

AVFrame* VideoDecoder::frame_ = nullptr

private

FFmpeg frame structure to hold decoded video data.

◆ frame_rate_

double VideoDecoder::frame_rate_ = 0.0

private

Calculated average frame rate of the video in frames per second.

◆ frame_timer_

QElapsedTimer VideoDecoder::frame_timer_

private

Timer used for frame timing synchronization when no audio is present.

◆ io_context_

AVIOContext* VideoDecoder::io_context_ = nullptr

private

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

◆ last_frame_pts_

int64_t VideoDecoder::last_frame_pts_ = AV_NOPTS_VALUE

private

Presentation timestamp (PTS) of the previously decoded frame (used for frame timing).

◆ mutex_

QMutex VideoDecoder::mutex_

mutableprivate

Mutex protecting access to shared state variables (paused_, stopped_, seeking_, etc.).

◆ paused_

bool VideoDecoder::paused_ = false

private

Flag indicating if playback is currently paused. Access protected by mutex_.

◆ seek_position_

int64_t VideoDecoder::seek_position_ = -1

private

Target timestamp (in video stream timebase) for the pending seek operation. Access protected by mutex_.

◆ seeking_

bool VideoDecoder::seeking_ = false

private

Flag indicating if a seek operation is pending. Access protected by mutex_.

◆ stopped_

bool VideoDecoder::stopped_ = false

private

Flag indicating if the thread should stop execution. Access protected by mutex_.

◆ sws_context_

SwsContext* VideoDecoder::sws_context_ = nullptr

private

FFmpeg context for image scaling and pixel format conversion (to RGB24).

◆ video_data_

QByteArray VideoDecoder::video_data_

private

The raw video data provided in the constructor.

◆ video_finished_

bool VideoDecoder::video_finished_ = false

private

Flag indicating if the video stream has reached the end. Access protected by mutex_.

◆ video_stream_

int VideoDecoder::video_stream_ = -1

private

Index of the video stream within the format context.

◆ wait_condition_

QWaitCondition VideoDecoder::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/video/decoder/video_decoder.h
src/chat/files/video/decoder/video_decoder.cpp

Signals

Public Member Functions

Protected Member Functions

Private Slots

Private Member Functions

Static Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ VideoDecoder()

◆ ~VideoDecoder()

Member Function Documentation

◆ CleanupFFmpegResources()

◆ error

◆ ExtractFirstFrame()

◆ frameReady

◆ GetVolume()

◆ HandleAudioError

◆ HandleAudioFinished

◆ HasAudio()

◆ Initialize()

◆ IsPaused()

◆ Pause()

◆ playbackFinished

◆ positionChanged

◆ ReadPacket()

◆ ReleaseResources()

◆ Reset()

◆ run()

◆ Seek()

◆ SeekPacket()

◆ SetVolume()

◆ Stop()

◆ UpdateAudioPosition

◆ videoInfo

Member Data Documentation

◆ audio_decoder_

◆ audio_finished_

◆ audio_initialized_

◆ audio_stream_index_

◆ buffer_

◆ codec_context_

◆ current_audio_position_

◆ current_position_

◆ duration_

◆ first_frame_

◆ format_context_

◆ frame_

◆ frame_rate_

◆ frame_timer_

◆ io_context_

◆ last_frame_pts_

◆ mutex_

◆ paused_

◆ seek_position_

◆ seeking_

◆ stopped_

◆ sws_context_

◆ video_data_

◆ video_finished_

◆ video_stream_

◆ wait_condition_