OpenShot Library | libopenshot  0.2.5
Public Member Functions | Static Public Member Functions | List of all members
openshot::FFmpegWriter Class Reference

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

#include <FFmpegWriter.h>

Inheritance diagram for openshot::FFmpegWriter:
openshot::WriterBase

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...
 
int GetCacheSize ()
 Get the cache size (number of frames to queue before writing) 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 SetCacheSize (int new_size)
 Set the cache size. 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 (std::shared_ptr< openshot::Frame > frame)
 Add a frame to the stack waiting to be encoded. More...
 
void WriteFrame (openshot::ReaderBase *reader, int64_t start, int64_t length)
 Write a block of frames from a reader. 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 ()
 Display file information in the standard output stream (stdout) More...
 
std::string Json () const
 Get and Set JSON methods. 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 149 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
pathThe file path of the video file you want to open and read

Definition at line 88 of file FFmpegWriter.cpp.

Member Function Documentation

◆ Close()

void FFmpegWriter::Close ( )

Close the writer.

Definition at line 1033 of file FFmpegWriter.cpp.

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

◆ GetCacheSize()

int openshot::FFmpegWriter::GetCacheSize ( )
inline

Get the cache size (number of frames to queue before writing)

Definition at line 262 of file FFmpegWriter.h.

◆ IsOpen()

bool openshot::FFmpegWriter::IsOpen ( )
inlinevirtual

Determine if writer is open or closed.

Implements openshot::WriterBase.

Definition at line 265 of file FFmpegWriter.h.

◆ IsValidCodec()

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

Determine if codec name is valid.

Definition at line 617 of file FFmpegWriter.cpp.

Referenced by IsOpen().

◆ Open()

void FFmpegWriter::Open ( )
virtual

Open writer.

Implements openshot::WriterBase.

Definition at line 114 of file FFmpegWriter.cpp.

Referenced by IsOpen().

◆ OutputStreamInfo()

void FFmpegWriter::OutputStreamInfo ( )

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

Definition at line 2220 of file FFmpegWriter.cpp.

Referenced by IsOpen().

◆ 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 629 of file FFmpegWriter.cpp.

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

◆ RemoveScalers()

void FFmpegWriter::RemoveScalers ( )

Remove & deallocate all software scalers.

Definition at line 2259 of file FFmpegWriter.cpp.

Referenced by Close(), and IsOpen().

◆ ResampleAudio()

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

Set audio resample options.

Parameters
sample_rateThe number of samples per second of the audio
channelsThe number of audio channels

Definition at line 2253 of file FFmpegWriter.cpp.

Referenced by IsOpen().

◆ 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_audioDoes this file need an audio stream?
codecThe codec used to encode the audio for this file
sample_rateThe number of audio samples needed in this file
channelsThe number of audio channels needed in this file
channel_layoutThe 'layout' of audio channels (i.e. mono, stereo, surround, etc...)
bit_rateThe audio bit rate used during encoding
Note
This is an overloaded function.

Definition at line 299 of file FFmpegWriter.cpp.

Referenced by IsOpen(), 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
codecThe codec used to encode the audio for this file
sample_rateThe number of audio samples needed in this file
bit_rateThe audio bit rate used during encoding
Note
This is an overloaded function.

Definition at line 339 of file FFmpegWriter.cpp.

◆ SetCacheSize()

void openshot::FFmpegWriter::SetCacheSize ( int  new_size)
inline

Set the cache size.

Parameters
new_sizeThe number of frames to queue before writing to the file

Definition at line 312 of file FFmpegWriter.h.

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

Definition at line 349 of file FFmpegWriter.cpp.

Referenced by SetCacheSize().

◆ 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_videoDoes this file need a video stream
codecThe codec used to encode the images in this video
fpsThe number of frames per second
widthThe width in pixels of this video
heightThe height in pixels of this video
pixel_ratioThe shape of the pixels represented as a openshot::Fraction (1x1 is most common / square pixels)
interlacedDoes this video need to be interlaced?
top_field_firstWhich frame should be used as the top field?
bit_rateThe video bit rate used during encoding
Note
This is an overloaded function.

Definition at line 177 of file FFmpegWriter.cpp.

Referenced by SetCacheSize(), 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
codecThe codec used to encode the images in this video
widthThe width in pixels of this video
heightThe height in pixels of this video
fpsThe number of frames per second
bit_rateThe 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 289 of file FFmpegWriter.cpp.

◆ WriteFrame() [1/2]

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

Add a frame to the stack waiting to be encoded.

Parameters
frameThe openshot::Frame object to write to this image
Note
This is an overloaded function.

Implements openshot::WriterBase.

Definition at line 687 of file FFmpegWriter.cpp.

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

◆ WriteFrame() [2/2]

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

Write a block of frames from a reader.

Parameters
readerA openshot::ReaderBase object which will provide frames to be written
startThe starting frame number of the reader
lengthThe number of frames to write
Note
This is an overloaded function.

Implements openshot::WriterBase.

Definition at line 816 of file FFmpegWriter.cpp.

◆ 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 643 of file FFmpegWriter.cpp.

Referenced by Open(), SetCacheSize(), 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 830 of file FFmpegWriter.cpp.

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


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