Decoder

H264Decoder Class

The H264Decoder class provides an H.264 decoder based on Cisco's OpenH264 library. It allows you to decode H.264 video streams into YUV or RGB images.

Table of Contents

• Overview
• Constructors
• Properties
• Methods
• Usage Examples
• DecodingState Enum

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Overview

The H264Decoder class wraps the Cisco OpenH264 library to provide efficient H.264 decoding capabilities. It supports various initialization modes, runtime configuration adjustments, and decoding to different output image formats.

Features:

• Decodes H.264 streams to YUV 420P or RGB images.
• Supports runtime configuration adjustments (options).
• Provides multiple decoding methods for different scenarios.
• Implements IDisposable for proper resource management.

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Constructors

Constructor	Description
H264Decoder()	Creates a new instance using the default Cisco DLL name.
H264Decoder(string ciscoDllPath)	Creates a new instance using the specified Cisco DLL path.

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Properties

Property	Type	Description
EnableDebugPrints	bool	Enables or disables debug prints during initialization.

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Methods

Method	Return Type	Description
Initialize()	int	Initializes decoder with default parameters.
Initialize(TagSVCDecodingParam param)	int	Initializes decoder with custom parameters.
GetOption<T>(DECODER_OPTION option, out T value)	bool	Gets a decoder option.
GetOptionRef<T>(DECODER_OPTION option, ref T value)	bool	Gets a decoder option, allowing reuse of the value.
SetOption<T>(DECODER_OPTION option, T value)	bool	Sets a decoder option.
Decode(byte[] encoded, int offset, int count, bool noDelay, out DecodingState state, out YUVImagePointer yuv)	bool	Decodes encoded data into YUV420Planar (YV12) image.
Decode(EncodedData data, bool noDelay, out DecodingState state, out YUVImagePointer yuv)	bool	Decodes encoded data into YUV420Planar (YV12) image.
Decode(EncodedData data, bool noDelay, out DecodingState state, ref YuvImage yuv)	bool	Decodes encoded data into provided YuvImage memory.
Decode(byte[] encoded, int offset, int count, bool noDelay, out DecodingState state, ref YuvImage yuv)	bool	Decodes encoded data into provided YuvImage memory.
Decode(EncodedData data, bool noDelay, out DecodingState state, ref RgbImage img)	bool	Decodes encoded data into an RGB image.
Decode(byte[] encoded, int offset, int count, bool noDelay, out DecodingState state, ref RgbImage img)	bool	Decodes encoded data into an RGB image.
Dispose()	void	Disposes of the decoder and releases native resources.

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Decoding State

Value	Name	Description	Category
0x00	dsErrorFree	bit stream error-free	Bitstream Parsing
0x01	dsFramePending	need more throughput to generate a frame output	Bitstream Parsing
0x02	dsRefLost	layer lost at reference frame with temporal id 0	Bitstream Parsing
0x04	dsBitstreamError	error bitstreams(maybe broken internal frame) the decoder cared	Bitstream Parsing
0x08	dsDepLayerLost	dependented layer is ever lost	Bitstream Parsing
0x10	dsNoParamSets	no parameter set NALs involved	Bitstream Parsing
0x20	dsDataErrorConcealed	current data error concealed specified	Bitstream Parsing
0x40	dsRefListNullPtrs	picure list contains null ptrs within uiRefCount range	Bitstream Parsing
0x1000	dsInvalidArgument	invalid argument specified	Logic Level
0x2000	dsInitialOptExpected	initializing operation is expected	Logic Level
0x4000	dsOutOfMemory	out of memory due to new request	Logic Level
0x8000	dsDstBufNeedExpan	actual picture size exceeds size of dst pBuffer feed in decoder, so need expand its size	Logic Level

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Usage Examples

Creating and Initializing a Decoder

using (var decoder = new H264Decoder())
{
    decoder.Initialize(); // Initialize with default parameters

    byte[] buffer // some encoded data located
    int offset = 0 ;
    int count = 256;
    YUVImagePointer yuvPtr;
    if (decoder.Decode(buffer, offset, count, noDelay: true, out DecodingState state, yuvPtr))
    {
        // Process YUV data
    }  
}

Decoding into RGB Image

using (var decoder = new H264Decoder())
{
    decoder.Initialize();

    byte[] buffer // encoded data located
    int offset = 0 ;
    int count = 256;
    RgbImage rgbImage = new RgbImage(ImageFormat.Rgb, 1280, 720); // Create an RgbImage
    if (decoder.Decode(buffer, offset, count, noDelay: true, out DecodingState state, ref rgbImage))
    {
        // Process RGB image
    }
}