This class uses the FFmpeg libraries, to write and encode video files and audio files. More...

#include <FFmpegWriter.h>

Inheritance diagram for openshot::FFmpegWriter:

Collaboration diagram for openshot::FFmpegWriter:

Public Member Functions
void	Close ()
	Close the writer. More...

	FFmpegWriter (const std::string &path)
	Constructor for FFmpegWriter. Throws an exception on failure to open path. More...

bool	IsOpen ()
	Determine if writer is open or closed. More...

void	Open ()
	Open writer. More...

void	OutputStreamInfo ()
	Output the ffmpeg info about this format, streams, and codecs (i.e. dump format) More...

void	PrepareStreams ()
	Prepare & initialize streams and open codecs. This method is called automatically by the Open() method if this method has not yet been called. More...

void	RemoveScalers ()
	Remove & deallocate all software scalers. More...

void	ResampleAudio (int sample_rate, int channels)
	Set audio resample options. More...

void	SetAudioOptions (bool has_audio, std::string codec, int sample_rate, int channels, openshot::ChannelLayout channel_layout, int bit_rate)
	Set audio export options. More...

void	SetAudioOptions (std::string codec, int sample_rate, int bit_rate)
	Set audio export options. More...

void	SetOption (openshot::StreamType stream, std::string name, std::string value)
	Set custom options (some codecs accept additional params). This must be called after the PrepareStreams() method, otherwise the streams have not been initialized yet. More...

void	SetVideoOptions (bool has_video, std::string codec, openshot::Fraction fps, int width, int height, openshot::Fraction pixel_ratio, bool interlaced, bool top_field_first, int bit_rate)
	Set video export options. More...

void	SetVideoOptions (std::string codec, int width, int height, openshot::Fraction fps, int bit_rate)
	Set video export options. More...

void	WriteFrame (openshot::ReaderBase *reader, int64_t start, int64_t length)
	Write a block of frames from a reader. More...

void	WriteFrame (std::shared_ptr< openshot::Frame > frame)
	Add a frame to the stack waiting to be encoded. More...

void	WriteHeader ()
	Write the file header (after the options are set). This method is called automatically by the Open() method if this method has not yet been called. More...

void	WriteTrailer ()
	Write the file trailer (after all frames are written). This is called automatically by the Close() method if this method has not yet been called. More...

Public Member Functions inherited from openshot::WriterBase
void	CopyReaderInfo (openshot::ReaderBase *reader)
	This method copy's the info struct of a reader, and sets the writer with the same info. More...

void	DisplayInfo (std::ostream *out=&std::cout)
	Display file information in the standard output stream (stdout) More...

std::string	Json () const
	Generate JSON string of this object. More...

Json::Value	JsonValue () const
	Generate Json::Value for this object. More...

void	SetJson (const std::string value)
	Load JSON string into this object. More...

void	SetJsonValue (const Json::Value root)
	Load Json::Value into this object. More...

	WriterBase ()
	Constructor for WriterBase class, many things are initialized here. More...

virtual	~WriterBase ()=default

Static Public Member Functions
static bool	IsValidCodec (std::string codec_name)
	Determine if codec name is valid. More...

Additional Inherited Members
Public Attributes inherited from openshot::WriterBase
WriterInfo	info
	Information about the current media file. More...

Detailed Description

This class uses the FFmpeg libraries, to write and encode video files and audio files.

All FFmpeg options can be set using the SetOption() method, and any Reader may be used to generate openshot::Frame objects needed for writing. Be sure to use valid bit rates, frame rates, and sample rates (each format / codec has a limited # of valid options).

 SIMPLE EXAMPLE
 
// Create a reader for a video
openshot::FFmpegReader r("MyAwesomeVideo.webm");
r.Open(); // Open the target reader
 
// Create a writer (which will create a WebM video)
openshot::FFmpegWriter w("/home/jonathan/NewVideo.webm");
 
// Set options
 
// Sample Rate: 44100, Channels: 2, Bitrate: 128000
w.SetAudioOptions(true, "libvorbis", 44100, 2, openshot::ChannelLayout::LAYOUT_STEREO, 128000);
 
// FPS: 24, Size: 720x480, Pixel Ratio: 1/1, Bitrate: 300000
w.SetVideoOptions(true, "libvpx", openshot::Fraction(24,1), 720, 480, openshot::Fraction(1,1), false, false, 300000);
 
// Open the writer
w.Open();
 
// Write all frames from the reader
w.WriteFrame(&r, 1, r.info.video_length);
 
// Close the reader & writer
w.Close();
r.Close();

Here is a more advanced example, which sets some additional (and optional) encoding options.

 ADVANCED WRITER EXAMPLE
 
// Create a reader for a video
openshot::FFmpegReader r("MyAwesomeVideo.webm");
r.Open(); // Open the reader
 
// Create a writer (which will create a WebM video)
openshot::FFmpegWriter w("/home/jonathan/NewVideo.webm");
 
// Set options
 
// Sample Rate: 44100, Channels: 2, Bitrate: 128000
w.SetAudioOptions(true, "libvorbis", 44100, 2, openshot::ChannelLayout::LAYOUT_STEREO, 128000);
 
// FPS: 24, Size: 720x480, Pixel Ratio: 1/1, Bitrate: 300000
w.SetVideoOptions(true, "libvpx", openshot::Fraction(24,1), 720, 480, openshot::Fraction(1,1), false, false, 300000);
 
// Prepare Streams (Optional method that must be called before any SetOption calls)
w.PrepareStreams();
 
// Set some specific encoding options (Optional methods)
w.SetOption(VIDEO_STREAM, "qmin", "2" );
w.SetOption(VIDEO_STREAM, "qmax", "30" );
w.SetOption(VIDEO_STREAM, "crf", "10" );
w.SetOption(VIDEO_STREAM, "rc_min_rate", "2000000" );
w.SetOption(VIDEO_STREAM, "rc_max_rate", "4000000" );
w.SetOption(VIDEO_STREAM, "max_b_frames", "10" );
 
// Write the header of the video file
w.WriteHeader();
 
// Open the writer
w.Open();
 
// Write all frames from the reader
w.WriteFrame(&r, 1, r.info.video_length);
 
// Write the trailer of the video file
w.WriteTrailer();
 
// Close the reader & writer
w.Close();
r.Close();

Definition at line 116 of file FFmpegWriter.h.

Constructor & Destructor Documentation

◆ FFmpegWriter()

FFmpegWriter::FFmpegWriter ( const std::string & path )

Constructor for FFmpegWriter. Throws an exception on failure to open path.

Parameters

path	The file path of the video file you want to open and read

Definition at line 75 of file FFmpegWriter.cpp.

Member Function Documentation

◆ Close()

void FFmpegWriter::Close ( )

Close the writer.

Definition at line 967 of file FFmpegWriter.cpp.

Referenced by openshot::ChunkWriter::Close(), and openshot::ChunkWriter::WriteFrame().

◆ IsOpen()

bool openshot::FFmpegWriter::IsOpen ( )

inlinevirtual

Determine if writer is open or closed.

Implements openshot::WriterBase.

Definition at line 218 of file FFmpegWriter.h.

◆ IsValidCodec()

bool FFmpegWriter::IsValidCodec ( std::string codec_name )

static

Determine if codec name is valid.

Definition at line 603 of file FFmpegWriter.cpp.

◆ Open()

void FFmpegWriter::Open ( )

virtual

Open writer.

Implements openshot::WriterBase.

Definition at line 95 of file FFmpegWriter.cpp.

◆ OutputStreamInfo()

void FFmpegWriter::OutputStreamInfo ( )

Output the ffmpeg info about this format, streams, and codecs (i.e. dump format)

Definition at line 2297 of file FFmpegWriter.cpp.

◆ PrepareStreams()

void FFmpegWriter::PrepareStreams ( )

Prepare & initialize streams and open codecs. This method is called automatically by the Open() method if this method has not yet been called.

Definition at line 615 of file FFmpegWriter.cpp.

Referenced by Open(), and openshot::ChunkWriter::WriteFrame().

◆ RemoveScalers()

void FFmpegWriter::RemoveScalers ( )

Remove & deallocate all software scalers.

Definition at line 2336 of file FFmpegWriter.cpp.

Referenced by Close().

◆ ResampleAudio()

void FFmpegWriter::ResampleAudio	(	int	sample_rate,
		int	channels
	)

Set audio resample options.

Parameters

sample_rate	The number of samples per second of the audio
channels	The number of audio channels

Definition at line 2330 of file FFmpegWriter.cpp.

◆ SetAudioOptions() [1/2]

void FFmpegWriter::SetAudioOptions	(	bool	has_audio,
		std::string	codec,
		int	sample_rate,
		int	channels,
		openshot::ChannelLayout	channel_layout,
		int	bit_rate
	)

Set audio export options.

Parameters

has_audio	Does this file need an audio stream?
codec	The codec used to encode the audio for this file
sample_rate	The number of audio samples needed in this file
channels	The number of audio channels needed in this file
channel_layout	The 'layout' of audio channels (i.e. mono, stereo, surround, etc...)
bit_rate	The audio bit rate used during encoding

Note: This is an overloaded function.

Definition at line 286 of file FFmpegWriter.cpp.

Referenced by SetAudioOptions(), and openshot::ChunkWriter::WriteFrame().

◆ SetAudioOptions() [2/2]

void FFmpegWriter::SetAudioOptions	(	std::string	codec,
		int	sample_rate,
		int	bit_rate
	)

Set audio export options.

Enables the stream and configures a default 2-channel stereo layout.

Parameters

codec	The codec used to encode the audio for this file
sample_rate	The number of audio samples needed in this file
bit_rate	The audio bit rate used during encoding

Note: This is an overloaded function.

Definition at line 323 of file FFmpegWriter.cpp.

◆ SetOption()

void FFmpegWriter::SetOption	(	openshot::StreamType	stream,
		std::string	name,
		std::string	value
	)

Set custom options (some codecs accept additional params). This must be called after the PrepareStreams() method, otherwise the streams have not been initialized yet.

Parameters

stream	The stream (openshot::StreamType) this option should apply to
name	The name of the option you want to set (i.e. qmin, qmax, etc...)
value	The new value of this option

Definition at line 333 of file FFmpegWriter.cpp.

◆ SetVideoOptions() [1/2]

void FFmpegWriter::SetVideoOptions	(	bool	has_video,
		std::string	codec,
		openshot::Fraction	fps,
		int	width,
		int	height,
		openshot::Fraction	pixel_ratio,
		bool	interlaced,
		bool	top_field_first,
		int	bit_rate
	)

Set video export options.

Parameters

has_video	Does this file need a video stream
codec	The codec used to encode the images in this video
fps	The number of frames per second
width	The width in pixels of this video
height	The height in pixels of this video
pixel_ratio	The shape of the pixels represented as a openshot::Fraction (1x1 is most common / square pixels)
interlaced	Does this video need to be interlaced?
top_field_first	Which frame should be used as the top field?
bit_rate	The video bit rate used during encoding

Note: This is an overloaded function.

Definition at line 163 of file FFmpegWriter.cpp.

Referenced by SetVideoOptions(), and openshot::ChunkWriter::WriteFrame().

◆ SetVideoOptions() [2/2]

void FFmpegWriter::SetVideoOptions	(	std::string	codec,
		int	width,
		int	height,
		openshot::Fraction	fps,
		int	bit_rate
	)

Set video export options.

Enables the stream and configures non-interlaced video with a 1:1 pixel aspect ratio.

Parameters

codec	The codec used to encode the images in this video
width	The width in pixels of this video
height	The height in pixels of this video
fps	The number of frames per second
bit_rate	The video bit rate used during encoding

Note: This is an overloaded function.

Warning: Observe the argument order, which is consistent with the openshot::Timeline constructor, but differs from the other signature.

Definition at line 276 of file FFmpegWriter.cpp.

◆ WriteFrame() [1/2]

void FFmpegWriter::WriteFrame	(	openshot::ReaderBase *	reader,
		int64_t	start,
		int64_t	length
	)

virtual

Write a block of frames from a reader.

Parameters

reader	A openshot::ReaderBase object which will provide frames to be written
start	The starting frame number of the reader
length	The number of frames to write

Note: This is an overloaded function.

Implements openshot::WriterBase.

Definition at line 737 of file FFmpegWriter.cpp.

◆ WriteFrame() [2/2]

void FFmpegWriter::WriteFrame ( std::shared_ptr< openshot::Frame > frame )

virtual

Add a frame to the stack waiting to be encoded.

Parameters

frame The openshot::Frame object to write to this image

Note: This is an overloaded function.

Implements openshot::WriterBase.

Definition at line 677 of file FFmpegWriter.cpp.

Referenced by openshot::ChunkWriter::Close(), openshot::ChunkWriter::WriteFrame(), and WriteFrame().

◆ WriteHeader()

void FFmpegWriter::WriteHeader ( )

Write the file header (after the options are set). This method is called automatically by the Open() method if this method has not yet been called.

Definition at line 632 of file FFmpegWriter.cpp.

Referenced by Open(), and openshot::ChunkWriter::WriteFrame().

◆ WriteTrailer()

void FFmpegWriter::WriteTrailer ( )

Write the file trailer (after all frames are written). This is called automatically by the Close() method if this method has not yet been called.

Definition at line 754 of file FFmpegWriter.cpp.

Referenced by openshot::ChunkWriter::Close(), Close(), and openshot::ChunkWriter::WriteFrame().

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

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ FFmpegWriter()

Member Function Documentation

◆ Close()

◆ IsOpen()

◆ IsValidCodec()

◆ Open()

◆ OutputStreamInfo()

◆ PrepareStreams()

◆ RemoveScalers()

◆ ResampleAudio()

◆ SetAudioOptions() [1/2]

◆ SetAudioOptions() [2/2]

◆ SetOption()

◆ SetVideoOptions() [1/2]

◆ SetVideoOptions() [2/2]

◆ WriteFrame() [1/2]

◆ WriteFrame() [2/2]

◆ WriteHeader()

◆ WriteTrailer()