AVCodecContext

public final class AVCodecContext

Undocumented

  • Creates an AVCodecContext and set its fields to default values.

    Declaration

    Swift

    public init(codec: AVCodec? = nil)

    Parameters

    codec

    codec

  • The codec’s media type.

    Declaration

    Swift

    public var mediaType: AVMediaType { get }

  • Undocumented

    Declaration

    Swift

    public var codec: AVCodec? { get set }

  • The codec’s id.

    Declaration

    Swift

    public var codecId: AVCodecID { get set }

  • fourcc (LSB first, so ABCD -> (‘D’<<24) + (‘C’<<16) + (‘B’<<8) + ‘A’).

    This is used to work around some encoder bugs. A demuxer should set this to what is stored in the field used to identify the codec. If there are multiple such fields in a container then the demuxer should choose the one which maximizes the information about the used codec. If the codec tag field in a container is larger than 32 bits then the demuxer should remap the longer ID to 32 bits with a table or other structure. Alternatively a new extra_codec_tag + size could be added but for this a clear advantage must be demonstrated first.

    • encoding: Set by user, if not then the default based on codecId will be used.
    • decoding: Set by user, will be converted to uppercase by libavcodec during init.

    Declaration

    Swift

    public var codecTag: UInt32 { get set }

  • Private data of the user, can be used to carry app specific stuff.

    • encoding: Set by user.
    • decoding: Set by user.

    Declaration

    Swift

    public var opaque: UnsafeMutableRawPointer? { get set }

  • The average bitrate.

    • encoding: Set by user, unused for constant quantizer encoding.
    • decoding: Set by user, may be overwritten by libavcodec if this info is available in the stream.

    Declaration

    Swift

    public var bitRate: Int64 { get set }

  • Number of bits the bitstream is allowed to diverge from the reference. The reference can be CBR (for CBR pass1) or VBR (for pass2).

    • encoding: Set by user, unused for constant quantizer encoding.
    • decoding: Unused.

    Declaration

    Swift

    public var bitRateTolerance: Int { get set }

  • AVCodecContext.Flag

    • encoding: Set by user.
    • decoding: Set by user.

    Declaration

    Swift

    public var flags: Flag { get set }

  • AVCodecContext.Flag2

    • encoding: Set by user.
    • decoding: Set by user.

    Declaration

    Swift

    public var flags2: Flag2 { get set }

  • Some codecs need / can use extradata like Huffman tables.

    • MJPEG: Huffman tables
    • rv10: additional flags
    • MPEG-4: global headers (they can be in the bitstream or here)

    The allocated memory should be AVConstant.inputBufferPaddingSize bytes larger than extradataSize to avoid problems if it is read with the bitstream reader. The bytewise contents of extradata must not depend on the architecture or CPU endianness. Must be allocated with the AVIO.malloc(size:) family of functions.

    • encoding: Set/allocated/freed by libavcodec.
    • decoding: Set/allocated/freed by user.

    Declaration

    Swift

    public var extradata: UnsafeMutablePointer<UInt8>? { get set }

  • The size of the extradata content in bytes.

    Declaration

    Swift

    public var extradataSize: Int { get set }

  • This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented. For fixed-fps content, timebase should be 1/framerate and timestamp increments should be identically 1. This often, but not always is the inverse of the frame rate or field rate for video. 1/timebase is not the average frame rate if the frame rate is not constant.

    Like containers, elementary streams also can store timestamps, 1/timebase is the unit in which these timestamps are specified. As example of such codec timebase see ISO/IEC 14496-2:2001(E) vop_time_increment_resolution and fixed_vop_rate (fixed_vop_rate == 0 implies that it is different from the framerate)

    • encoding: Must be set by user.
    • decoding: The use of this field for decoding is deprecated. Use framerate instead.

    Declaration

    Swift

    public var timebase: AVRational { get set }

  • Frame counter.

    • encoding: Total number of frames passed to the encoder so far.
    • decoding: Total number of frames returned from the decoder so far.

    Declaration

    Swift

    public var frameNumber: Int { get }

  • A reference to the AVHWFramesContext describing the input (for encoding) or output (decoding) frames. The reference is set by the caller and afterwards owned (and freed) by libavcodec - it should never be read by the caller after being set.

    This field should be set before openCodec(_:options:) is called.

    • decoding: This field should be set by the caller from the getFormat callback. The previous reference (if any) will always be unreffed by libavcodec before the getFormat call.

    If the default get_buffer2() is used with a hwaccel pixel format, then this AVHWFramesContext will be used for allocating the frame buffers.

    Declaration

    Swift

    public var hwFramesContext: AVHWFramesContext? { get set }

  • A reference to the AVHWDeviceContext describing the device which will be used by a hardware encoder/decoder. The reference is set by the caller and afterwards owned (and freed) by libavcodec.

    This should be used if either the codec device does not require hardware frames or any that are used are to be allocated internally by libavcodec. If the user wishes to supply any of the frames used as encoder input or decoder output then hwFramesContext should be used instead. When hwFramesContext is set in getFormat for a decoder, this field will be ignored while decoding the associated stream segment, but may again be used on a following one after another getFormat call.

    For both encoders and decoders this field should be set before openCodec(_:options:) is called and must not be written to thereafter.

    Note that some decoders may require this field to be set initially in order to support hwFramesContext at all - in that case, all frames contexts used must be created on the same device.

    Declaration

    Swift

    public var hwDeviceContext: AVHWDeviceContext? { get set }

  • A Boolean value indicating whether the codec is open.

    Declaration

    Swift

    public var isOpen: Bool { get }

  • Fill the codec context based on the values from the supplied codec parameters.

    Declaration

    Swift

    public func setParameters(_ params: AVCodecParameters)

    Parameters

    params

    codec parameters

  • Initialize the AVCodecContext.

    Throws

    AVError

    Declaration

    Swift

    public func openCodec(_ codec: AVCodec? = nil, options: [String: String]? = nil) throws

    Parameters

    codec

    The codec to open this context for. If a non-NULL codec has been previously passed to init(codec:) or for this context, then this parameter MUST be either nil or equal to the previously passed codec.
    options

    A dictionary filled with AVCodecContext and codec-private options.

  • Supply raw packet data as input to a decoder.

    Throws

    • AVError.tryAgain if input is not accepted in the current state - user must read output with receiveFrame. (once all output is read, the packet should be resent, and the call will not fail with AVError.tryAgain).
    • AVError.eof if the decoder has been flushed, and no new packets can be sent to it. (also returned if more than 1 flush packet is sent)
    • AVError.invalidArgument if codec not opened, it is an encoder, or requires flush
    • AVError.outOfMemory if failed to add packet to internal queue, or similar.
    • legitimate decoding errors

    Declaration

    Swift

    public func sendPacket(_ packet: AVPacket?) throws

    Parameters

    packet

    The input AVPacket. Usually, this will be a single video frame, or several complete audio frames. It can be nil (or an AVPacket with data set to nil and size set to 0); in this case, it is considered a flush packet, which signals the end of the stream. Sending the first flush packet will return success. Subsequent ones are unnecessary and will throw AVError.eof. If the decoder still has frames buffered, it will return them after sending a flush packet.

  • Return decoded output data from a decoder.

    Throws

    • AVError.tryAgain if output is not available in this state - user must try to send new input.
    • AVError.eof if the decoder has been fully flushed, and there will be no more output frames.
    • AVError.invalidArgument if codec not opened, or it is an encoder.
    • legitimate decoding errors

    Declaration

    Swift

    public func receiveFrame(_ frame: AVFrame) throws

    Parameters

    frame

    This will be set to a reference-counted video or audio frame (depending on the decoder type) allocated by the decoder.

  • Supply a raw video or audio frame to the encoder.

    Throws

    • AVError.tryAgain if input is not accepted in the current state - user must read output with receivePacket. (once all output is read, the packet should be resent, and the call will not fail with AVError.tryAgain).
    • AVError.eof if the encoder has been flushed, and no new frames can be sent to it.
    • AVError.invalidArgument if codec not opened, refcounted_frames not set, it is a decoder, or requires flush.
    • AVError.outOfMemory if failed to add packet to internal queue, or similar.
    • legitimate decoding errors

    Declaration

    Swift

    public func sendFrame(_ frame: AVFrame?) throws

    Parameters

    frame

    AVFrame containing the raw audio or video frame to be encoded. It can be nil, in which case it is considered a flush packet. This signals the end of the stream. If the encoder still has packets buffered, it will return them after this call. Once flushing mode has been entered, additional flush packets are ignored, and sending frames will return AVError.eof.

  • Read encoded data from the encoder.

    Throws

    • AVError.tryAgain if output is not available in the current state - user must try to send input.
    • AVError.eof if the encoder has been fully flushed, and there will be no more output packets.
    • AVError.invalidArgument if codec not opened, or it is an encoder.
    • legitimate decoding errors

    Declaration

    Swift

    public func receivePacket(_ packet: AVPacket) throws

    Parameters

    packet

    This will be set to a reference-counted packet allocated by the encoder.

  • Reset the internal decoder state / flush internal buffers. Should be called e.g. when seeking or when switching to a different stream.

    Note

    when refcounted frames are not used (i.e. avctx->refcounted_frames is 0), this invalidates the frames previously returned from the decoder. When refcounted frames are used, the decoder just releases any references it might keep internally, but the caller’s reference remains valid.

    Declaration

    Swift

    public func flush()

AVCodecContext.Flag

AVCodecContext.Flag2

Video

  • The width of the picture.

    • encoding: Must be set by user.
    • decoding: May be set by the user before opening the decoder if known e.g. from the container. Some decoders will require the dimensions to be set by the caller. During decoding, the decoder may overwrite those values as required while parsing the data.

    Declaration

    Swift

    public var width: Int { get set }

  • The height of the picture.

    • encoding: Must be set by user.
    • decoding: May be set by the user before opening the decoder if known e.g. from the container. Some decoders will require the dimensions to be set by the caller. During decoding, the decoder may overwrite those values as required while parsing the data.

    Declaration

    Swift

    public var height: Int { get set }

  • Bitstream width, may be different from width e.g. when the decoded frame is cropped before being output or lowres is enabled.

    • encoding: Unused.
    • decoding: May be set by the user before opening the decoder if known e.g. from the container. During decoding, the decoder may overwrite those values as required while parsing the data.

    Declaration

    Swift

    public var codedWidth: Int { get set }

  • Bitstream height, may be different from height e.g. when the decoded frame is cropped before being output or lowres is enabled.

    • encoding: Unused.
    • decoding: May be set by the user before opening the decoder if known e.g. from the container. During decoding, the decoder may overwrite those values as required while parsing the data.

    Declaration

    Swift

    public var codedHeight: Int { get set }

  • The number of pictures in a group of pictures, or 0 for intra_only.

    • encoding: Set by user.
    • decoding: Unused.

    Declaration

    Swift

    public var gopSize: Int { get set }

  • The pixel format of the picture.

    • encoding: Set by user.
    • decoding: Set by user if known, overridden by codec while parsing the data.

    Declaration

    Swift

    public var pixelFormat: AVPixelFormat { get set }

  • The callback used to negotiate the pixel format.

    Note

    The callback may be called again immediately if initialization for the selected (hardware-accelerated) pixel format failed.

    Warning

    Behavior is undefined if the callback returns a value not in the fmt list of formats.

  • encoding: Unused.

  • decoding: Set by user, if not set the native format will be chosen.

    • Declaration

    Swift

    public var getFormat: AVGetFormatHandler? { get set }

  • Maximum number of B-frames between non-B-frames.

    Note

    The output will be delayed by max_b_frames+1 relative to the input.

  • encoding: Set by user.

  • decoding: Unused.

    • Declaration

    Swift

    public var maxBFrames: Int { get set }

  • Macroblock decision mode.

    • encoding: Set by user.
    • decoding: Unused.

    Declaration

    Swift

    public var mbDecision: Int { get set }

  • Sample aspect ratio (0/0 if unknown).

    That is the width of a pixel divided by the height of the pixel. Numerator and denominator must be relatively prime and smaller than 256 for some video standards.

    • encoding: Set by user.
    • decoding: Set by codec.

    Declaration

    Swift

    public var sampleAspectRatio: AVRational { get set }

  • low resolution decoding, 1->½ size, 2->¼ size

    • encoding: Unused.
    • decoding: Set by user.

    Declaration

    Swift

    public var lowres: Int { get }

  • The framerate of the video.

    • encoding: May be used to signal the framerate of CFR content to an encoder.
    • decoding: For codecs that store a framerate value in the compressed bitstream, the decoder may export it here. 0/1 when unknown.

    Declaration

    Swift

    public var framerate: AVRational { get set }

Audio

  • Samples per second.

    Declaration

    Swift

    public var sampleRate: Int { get set }

  • Number of audio channels.

    Declaration

    Swift

    public var channelCount: Int { get set }

  • Audio sample format.

    • encoding: Set by user.
    • decoding: Set by libavcodec.

    Declaration

    Swift

    public var sampleFormat: AVSampleFormat { get set }

  • Number of samples per channel in an audio frame.

    Declaration

    Swift

    public var frameSize: Int { get set }

  • Audio channel layout.

    • encoding: Set by user.
    • decoding: Set by user, may be overwritten by codec.

    Declaration

    Swift

    public var channelLayout: AVChannelLayout { get set }

Audio

  • Undocumented

    Declaration

    Swift

    public static let `class`: AVClass

  • Undocumented

    Declaration

    Swift

    public func withUnsafeClassObjectPointer<T>(_ body: (UnsafeMutableRawPointer) throws -> T) rethrows -> T

Audio

  • Undocumented

    Declaration

    Swift

    public func withUnsafeObjectPointer<T>(_ body: (UnsafeMutableRawPointer) throws -> T) rethrows -> T