@spec fourcc(char(), char(), char(), char()) :: integer() | {:error, String.t()}

Concatenates 4 chars to a fourcc code

Positional Arguments

• c1: char
• c2: char
• c3: char
• c4: char

Return

• retval: int

@return a fourcc code This static method constructs the fourcc code of the codec to be used in the constructor VideoWriter::VideoWriter or VideoWriter::open.

Python prototype (for reference only):

fourcc(c1, c2, c3, c4) -> retval

@spec get(t(), integer()) :: number() | {:error, String.t()}

Returns the specified VideoWriter property

Positional Arguments

• self: Evision.VideoWriter.t()

• propId: int.

  Property identifier from cv::VideoWriterProperties (eg. cv::VIDEOWRITER_PROP_QUALITY) or one of @ref videoio_flags_others

Return

• retval: double

@return Value for the specified property. Value 0 is returned when querying a property that is not supported by the backend used by the VideoWriter instance.

Python prototype (for reference only):

get(propId) -> retval

@spec getBackendName(t()) :: binary() | {:error, String.t()}

Returns used backend API name

Positional Arguments

• self: Evision.VideoWriter.t()

Return

• retval: String

Note: Stream should be opened.

Python prototype (for reference only):

getBackendName() -> retval

@spec isOpened(t()) :: boolean() | {:error, String.t()}

Returns true if video writer has been successfully initialized.

Positional Arguments

• self: Evision.VideoWriter.t()

Return

• retval: bool

Python prototype (for reference only):

isOpened() -> retval

@spec open(t(), binary(), integer(), number(), {number(), number()}) ::
  boolean() | {:error, String.t()}

Initializes or reinitializes video writer.

Positional Arguments

• self: Evision.VideoWriter.t()
• filename: String
• fourcc: int
• fps: double
• frameSize: Size

Keyword Arguments

• isColor: bool.

Return

• retval: bool

The method opens video writer. Parameters are the same as in the constructor VideoWriter::VideoWriter. @return true if video writer has been successfully initialized The method first calls VideoWriter::release to close the already opened file.

Python prototype (for reference only):

open(filename, fourcc, fps, frameSize[, isColor]) -> retval

@spec open(
  t(),
  binary(),
  integer(),
  number(),
  {number(), number()},
  [{atom(), term()}, ...] | nil
) ::
  boolean() | {:error, String.t()}

@spec open(t(), binary(), integer(), number(), {number(), number()}, [integer()]) ::
  boolean() | {:error, String.t()}

@spec open(t(), binary(), integer(), integer(), number(), {number(), number()}) ::
  boolean() | {:error, String.t()}

Variant 1:

open

Positional Arguments

• self: Evision.VideoWriter.t()
• filename: String
• fourcc: int
• fps: double
• frameSize: Size
• params: [int]

Return

• retval: bool

Has overloading in C++

Python prototype (for reference only):

open(filename, fourcc, fps, frameSize, params) -> retval

Variant 2:

open

Positional Arguments

• self: Evision.VideoWriter.t()
• filename: String
• apiPreference: int
• fourcc: int
• fps: double
• frameSize: Size

Keyword Arguments

• isColor: bool.

Return

• retval: bool

Has overloading in C++

Python prototype (for reference only):

open(filename, apiPreference, fourcc, fps, frameSize[, isColor]) -> retval

Variant 3:

Initializes or reinitializes video writer.

Positional Arguments

• self: Evision.VideoWriter.t()
• filename: String
• fourcc: int
• fps: double
• frameSize: Size

Keyword Arguments

• isColor: bool.

Return

• retval: bool

The method opens video writer. Parameters are the same as in the constructor VideoWriter::VideoWriter. @return true if video writer has been successfully initialized The method first calls VideoWriter::release to close the already opened file.

Python prototype (for reference only):

open(filename, fourcc, fps, frameSize[, isColor]) -> retval

@spec open(
  t(),
  binary(),
  integer(),
  integer(),
  number(),
  {number(), number()},
  [{atom(), term()}, ...] | nil
) :: boolean() | {:error, String.t()}

@spec open(t(), binary(), integer(), integer(), number(), {number(), number()}, [
  integer()
]) ::
  boolean() | {:error, String.t()}

Variant 1:

open

Positional Arguments

• self: Evision.VideoWriter.t()
• filename: String
• apiPreference: int
• fourcc: int
• fps: double
• frameSize: Size
• params: [int]

Return

• retval: bool

Has overloading in C++

Python prototype (for reference only):

open(filename, apiPreference, fourcc, fps, frameSize, params) -> retval

Variant 2:

open

Positional Arguments

• self: Evision.VideoWriter.t()
• filename: String
• apiPreference: int
• fourcc: int
• fps: double
• frameSize: Size

Keyword Arguments

• isColor: bool.

Return

• retval: bool

Has overloading in C++

Python prototype (for reference only):

open(filename, apiPreference, fourcc, fps, frameSize[, isColor]) -> retval

@spec release(t()) :: t() | {:error, String.t()}

Closes the video writer.

Positional Arguments

• self: Evision.VideoWriter.t()

The method is automatically called by subsequent VideoWriter::open and by the VideoWriter destructor.

Python prototype (for reference only):

release() -> None

@spec set(t(), integer(), number()) :: boolean() | {:error, String.t()}

Sets a property in the VideoWriter.

Positional Arguments

• self: Evision.VideoWriter.t()

• propId: int.

  Property identifier from cv::VideoWriterProperties (eg. cv::VIDEOWRITER_PROP_QUALITY) or one of @ref videoio_flags_others

• value: double.

  Value of the property.

Return

• retval: bool

@return true if the property is supported by the backend used by the VideoWriter instance.

Python prototype (for reference only):

set(propId, value) -> retval

@spec videoWriter() :: t() | {:error, String.t()}

Default constructors

Return

• self: Evision.VideoWriter.t()

The constructors/functions initialize video writers.

• On Linux FFMPEG is used to write videos;
• On Windows FFMPEG or MSWF or DSHOW is used;
• On MacOSX AVFoundation is used.

Python prototype (for reference only):

VideoWriter() -> <VideoWriter object>

@spec videoWriter(binary(), integer(), number(), {number(), number()}) ::
  t() | {:error, String.t()}

VideoWriter

Positional Arguments

• filename: String.

  Name of the output video file.

• fourcc: int.

  4-character code of codec used to compress the frames. For example, VideoWriter::fourcc('P','I','M','1') is a MPEG-1 codec, VideoWriter::fourcc('M','J','P','G') is a motion-jpeg codec etc. List of codes can be obtained at MSDN page or with this page of the fourcc site for a more complete list). FFMPEG backend with MP4 container natively uses other values as fourcc code: see ObjectType, so you may receive a warning message from OpenCV about fourcc code conversion.

• fps: double.

  Framerate of the created video stream.

• frameSize: Size.

  Size of the video frames.

Keyword Arguments

• isColor: bool.

  If it is not zero, the encoder will expect and encode color frames, otherwise it will work with grayscale frames.

Return

• self: Evision.VideoWriter.t()

Has overloading in C++

@b Tips:

• With some backends fourcc=-1 pops up the codec selection dialog from the system.

• To save image sequence use a proper filename (eg. img_%02d.jpg) and fourcc=0 OR fps=0. Use uncompressed image format (eg. img_%02d.BMP) to save raw frames.

• Most codecs are lossy. If you want lossless video file you need to use a lossless codecs (eg. FFMPEG FFV1, Huffman HFYU, Lagarith LAGS, etc...)

• If FFMPEG is enabled, using codec=0; fps=0; you can create an uncompressed (raw) video file.

• If FFMPEG is used, we allow frames of odd width or height, but in this case we truncate the rightmost column/the bottom row. Probably, this should be handled more elegantly, but some internal functions inside FFMPEG swscale require even width/height.

Python prototype (for reference only):

VideoWriter(filename, fourcc, fps, frameSize[, isColor]) -> <VideoWriter object>

@spec videoWriter(
  binary(),
  integer(),
  number(),
  {number(), number()},
  [{atom(), term()}, ...] | nil
) ::
  t() | {:error, String.t()}

@spec videoWriter(binary(), integer(), number(), {number(), number()}, [integer()]) ::
  t() | {:error, String.t()}

@spec videoWriter(binary(), integer(), integer(), number(), {number(), number()}) ::
  t() | {:error, String.t()}

Variant 1:

VideoWriter

Positional Arguments

• filename: String
• fourcc: int
• fps: double
• frameSize: Size
• params: [int]

Return

• self: Evision.VideoWriter.t()

Has overloading in C++

The params parameter allows to specify extra encoder parameters encoded as pairs (paramId_1, paramValue_1, paramId_2, paramValue_2, ... .) see cv::VideoWriterProperties

Python prototype (for reference only):

VideoWriter(filename, fourcc, fps, frameSize, params) -> <VideoWriter object>

Variant 2:

VideoWriter

Positional Arguments

• filename: String
• apiPreference: int
• fourcc: int
• fps: double
• frameSize: Size

Keyword Arguments

• isColor: bool.

Return

• self: Evision.VideoWriter.t()

Has overloading in C++

The apiPreference parameter allows to specify API backends to use. Can be used to enforce a specific reader implementation if multiple are available: e.g. cv::CAP_FFMPEG or cv::CAP_GSTREAMER.

Python prototype (for reference only):

VideoWriter(filename, apiPreference, fourcc, fps, frameSize[, isColor]) -> <VideoWriter object>

Variant 3:

VideoWriter

Positional Arguments

• filename: String.

  Name of the output video file.

• fourcc: int.

  4-character code of codec used to compress the frames. For example, VideoWriter::fourcc('P','I','M','1') is a MPEG-1 codec, VideoWriter::fourcc('M','J','P','G') is a motion-jpeg codec etc. List of codes can be obtained at MSDN page or with this page of the fourcc site for a more complete list). FFMPEG backend with MP4 container natively uses other values as fourcc code: see ObjectType, so you may receive a warning message from OpenCV about fourcc code conversion.

• fps: double.

  Framerate of the created video stream.

• frameSize: Size.

  Size of the video frames.

Keyword Arguments

• isColor: bool.

  If it is not zero, the encoder will expect and encode color frames, otherwise it will work with grayscale frames.

Return

• self: Evision.VideoWriter.t()

Has overloading in C++

@b Tips:

• With some backends fourcc=-1 pops up the codec selection dialog from the system.

• To save image sequence use a proper filename (eg. img_%02d.jpg) and fourcc=0 OR fps=0. Use uncompressed image format (eg. img_%02d.BMP) to save raw frames.

• Most codecs are lossy. If you want lossless video file you need to use a lossless codecs (eg. FFMPEG FFV1, Huffman HFYU, Lagarith LAGS, etc...)

• If FFMPEG is enabled, using codec=0; fps=0; you can create an uncompressed (raw) video file.

• If FFMPEG is used, we allow frames of odd width or height, but in this case we truncate the rightmost column/the bottom row. Probably, this should be handled more elegantly, but some internal functions inside FFMPEG swscale require even width/height.

Python prototype (for reference only):

VideoWriter(filename, fourcc, fps, frameSize[, isColor]) -> <VideoWriter object>

@spec videoWriter(
  binary(),
  integer(),
  integer(),
  number(),
  {number(), number()},
  [{atom(), term()}, ...] | nil
) :: t() | {:error, String.t()}

@spec videoWriter(binary(), integer(), integer(), number(), {number(), number()}, [
  integer()
]) ::
  t() | {:error, String.t()}

Variant 1:

VideoWriter

Positional Arguments

• filename: String
• apiPreference: int
• fourcc: int
• fps: double
• frameSize: Size
• params: [int]

Return

• self: Evision.VideoWriter.t()

Has overloading in C++

Python prototype (for reference only):

VideoWriter(filename, apiPreference, fourcc, fps, frameSize, params) -> <VideoWriter object>

Variant 2:

VideoWriter

Positional Arguments

• filename: String
• apiPreference: int
• fourcc: int
• fps: double
• frameSize: Size

Keyword Arguments

• isColor: bool.

Return

• self: Evision.VideoWriter.t()

Has overloading in C++

The apiPreference parameter allows to specify API backends to use. Can be used to enforce a specific reader implementation if multiple are available: e.g. cv::CAP_FFMPEG or cv::CAP_GSTREAMER.

Python prototype (for reference only):

VideoWriter(filename, apiPreference, fourcc, fps, frameSize[, isColor]) -> <VideoWriter object>

@spec write(t(), Evision.Mat.maybe_mat_in()) :: t() | {:error, String.t()}

Writes the next video frame

Positional Arguments

• self: Evision.VideoWriter.t()

• image: Evision.Mat.t().

  The written frame. In general, color images are expected in BGR format.

The function/method writes the specified image to video file. It must have the same size as has been specified when opening the video writer.

Python prototype (for reference only):

write(image) -> None